Electronic book

Abstract

To provide an electronic book including a display panel having a thin film transistor with stable electrical characteristics, an electronic book capable having the high holding property of an image, a high-resolution electronic book, and an electronic book with low power consumption.SOLUTION: Display on a display panel of an electronic book is controlled by a thin film transistor whose channel formation region is formed using an oxide semiconductor which is an intrinsic or substantially intrinsic semiconductor by removal of an impurity that might be an electron donor in the oxide semiconductor and has a larger energy gap than a silicon semiconductor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] One embodiment of the present invention is a display including a field-effect transistor using an oxide semiconductor. The present invention relates to an electronic book having a panel. [Background technology]

[0002] Thin film transistors (TFTs) are fabricated using semiconductor thin films formed on substrates with insulating surfaces. Thin-film transistors are used in displays such as LCD TVs. Silicon-based semiconductors are used as semiconductor thin films that can be applied to thin-film transistors. Although semiconductor materials are well known, oxide semiconductors are attracting attention as other materials.

[0003] As oxide semiconductor materials, for example, zinc oxide or materials containing zinc oxide as a component are known. And the carrier (electron) concentration is 10 18 / cm 3 Amorphous oxide (oxide Thin film transistors formed of a compound semiconductor are disclosed (Patent Documents 1 to 3). ). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-165527 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-165528 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-165529 Summary of the Invention [Problem to be solved by the invention]

[0005] However, oxide semiconductors tend to deviate from the stoichiometric composition during the thin film formation process. For example, the electrical conductivity of an oxide semiconductor changes depending on whether there is an excess or deficiency of oxygen. In addition, hydrogen mixed in during the formation of oxide semiconductor thin films forms oxygen (O)-hydrogen (H) bonds. The OH bond acts as an electron donor, causing changes in electrical conductivity. Because of this bond, it is possible to achieve functions such as thin film transistors made of oxide semiconductors. This can cause fluctuations in the characteristics of dynamic devices.

[0006] Carrier (electron) concentration is 10 18 / cm 3 Even if it is less than 100%, it is practically The thin film transistor disclosed in the patent document is n-type, and the on-off ratio is 10 3 death The reason for the low on-off ratio of such thin film transistors is that the off-current This is due to the high cost.

[0007] In view of such a problem, one embodiment of the present invention provides a semiconductor device having stable electrical characteristics (for example, an extremely low off-state current). The electronic book is provided with a display panel having thin film transistors (which are reduced in Another object of the present invention is to provide an electronic book with high image retention. Another object of the present invention is to provide a high-resolution electronic book. Another object of one embodiment of the present invention is to provide an electronic book with low power consumption. The title is: [Means for solving the problem]

[0008] One embodiment of the present invention is to remove impurities that can serve as electron donors (donors) in an oxide semiconductor. Therefore, it is an intrinsic or substantially intrinsic semiconductor that has a higher energy gap than silicon semiconductors. A thin film transistor in which a channel formation region is formed using an oxide semiconductor with a large gap It controls the display of the display panel of an electronic book. It controls the voltage applied to the pixel electrode in the display.

[0009] That is, in one embodiment of the present invention, the concentration of hydrogen contained in the oxide semiconductor is 5×10 19 / cm 3 Less than or equal to 5 x 10 18 / cm 3 Less than or equal to 5 × 10 17 / cm 3 Below The hydrogen or OH bond contained in the oxide semiconductor is removed, and the carrier concentration is reduced to 5 x10 14 / cm 3 Less than or equal to 5 x 10 12 / cm 3 The oxide semiconductor film is The thin film transistor in which the channel formation region is formed controls the display of the display panel of the electronic book. Typically, the voltage applied to the pixel electrode of the pixel of the display panel is controlled. It controls the following:

[0010] The energy gap of the oxide semiconductor is 2 eV or more, preferably 2.5 eV or more, and more preferably or 3 eV or more, and impurities such as hydrogen that form donors are reduced as much as possible, and the carrier concentration 1×10 14 / cm 3 Less than 1 × 10 12 / cm 3 Make it so that it is as follows.

[0011] Such a highly purified oxide semiconductor is used in the channel formation region of a thin film transistor. By doing so, even when the channel width is 10 mm, the drain voltage is 1 V and 10 V. In the gate voltage range of -20V to -5V, the drain current is 1×10 - 13 It acts to keep it below A.

[0012] In addition, the electronic book according to one embodiment of the present invention may include a primary battery or a storage battery as a power supply device. The electronic book of one aspect of the present invention is further provided with a secondary battery or a capacitor having the same. The display panel has a pair of electrodes and a display medium provided between the pair of electrodes. The display panel includes a display element. In addition to electrophoretic panels using the electrophoretic method, there are also other types such as particle movement, particle rotation, liquid crystal display, and electrophoretic panels. The image can be displayed once and saved using methods such as analytical printing, electrochromic, and film transfer. It is a display panel that can be held. [Effects of the Invention]

[0013] According to one embodiment of the present invention, a thin film transistor using a highly purified oxide semiconductor having a low hydrogen concentration can be By controlling the display of the display panel of an e-book using a transistor, This reduces the number of times the pixel is scanned and also improves the retention of the potential of the pixel electrode. Since the driving frequency of the driving circuit can be lowered, the power consumption of the e-book can be reduced. In addition, the off-current is 1×10 - 13 A or less, reducing the capacitance that holds the signal voltage applied to the pixel. This makes it possible to reduce the area of ​​the screen. can be increased. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are a top view and a cross-sectional view illustrating an electronic book. [Figure 2] 2A and 2B are a top view and a cross-sectional view of a display panel. [Figure 3] FIG. 1 is a longitudinal cross-sectional view of an inverted staggered thin film transistor using an oxide semiconductor. [Figure 4] Energy band diagram (schematic diagram) at the A-A' cross section shown in Figure 3. [Figure 5] (A) shows a state in which a positive potential (+VG) is applied to the gate (G1), and (B) shows a state in which a negative potential (-VG) is applied to the gate (G1). [Figure 6] A diagram showing the relationship between the vacuum level, the work function of a metal (φM), and the electron affinity of an oxide semiconductor (χ). [Figure 7] FIG. 2 is a block diagram of a display panel. [Figure 8] FIG. 2 is a cross-sectional view illustrating the structure of a display medium. [Figure 9] 1A and 1B are diagrams illustrating a display method of a conventional display panel. [Figure 10] 1A to 1C illustrate a display method of a display panel according to one embodiment of the present invention. [Figure 11] 1A and 1B are a top view and a cross-sectional view illustrating a power storage device. [Figure 12] 1A to 1C illustrate a thin film transistor. [Figure 13] 1A to 1C illustrate a method for manufacturing a thin film transistor. [Figure 14] 1A to 1C illustrate a thin film transistor. [Figure 15] 1A to 1C illustrate a method for manufacturing a thin film transistor. [Figure 16] 1A to 1C illustrate a thin film transistor. [Figure 17] 1A to 1C illustrate a method for manufacturing a thin film transistor. [Figure 18] 1A to 1C illustrate a method for manufacturing a thin film transistor. [Figure 19] 1A to 1C illustrate a method for manufacturing a thin film transistor. [Figure 20] 1A to 1C illustrate a method for manufacturing a thin film transistor. [Figure 21] 1A to 1C illustrate a thin film transistor. [Figure 22] FIG. 2 is a cross-sectional view illustrating a display panel. [Figure 23] 1A and 1B are a perspective view illustrating an electronic book and a block diagram illustrating a semiconductor device. [Figure 24] FIG. [Figure 25] FIG. 2 is an equivalent circuit diagram illustrating a boost circuit. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the above, and various modifications and variations in form and detail are possible without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that the present invention can be modified in the following manner. It should be noted that the present invention is not limited to the following description. In the structure, the same parts or parts having similar functions are designated by the same reference numerals in different drawings. It will be used throughout and repeated explanations will be omitted.

[0016] In each drawing described in this specification, the size of each component, the thickness of a layer, or the area is not clearly indicated. The figures may be exaggerated for clarity and are not necessarily limited to that scale. .

[0017] In this specification, the terms "first," "second," "third," etc. are used to avoid confusion of components. Therefore, for example, "first" can be changed to "second" This can be explained by replacing it with "second" or "third" as appropriate.

[0018] (Embodiment 1) In this embodiment, a structure of an electronic book according to one embodiment of the present invention will be described with reference to FIG. do.

[0019] FIG. 1(A) is a plan view of the electronic book, and FIG. 1(B) is a cross-sectional view of the electronic book taken along the dashed line AB in FIG. 1(A). This corresponds to a plan view.

[0020] As shown in FIG. 1(A), the electronic book 01 includes a display unit 05 surrounded by a housing 03 and operation keys. Although not shown in FIG. 1(A), the back and sides of the housing have external Connection terminal (connects to various cables such as earphone terminal, USB terminal, or USB cable) It may also be equipped with a terminal for connecting a recording medium, a recording medium insertion section, a speaker, a volume control button, etc. Keys 07 and 09 are used to turn pages, input characters, zoom in and out on the display, and perform other operations. is possible.

[0021] Next, the inside of the housing 03 of the electronic book 01 will be described with reference to FIG. 1(B).

[0022] The housing 03 contains a display panel 10, a wiring board 31, and a display panel 10 and a wiring board 32. FPC (Flexible Printed Circuits) 33 that connects 31 and The semiconductor device 35 is mounted on the wiring board 31 , and the power supply device 37 is mounted on the wiring board 31 .

[0023] The display panel 10 includes a first substrate 11, an element layer 13, a display medium 21, and a second electrode 17. , the second substrate 15, the third substrate 27, and the first substrate 11, the second substrate 15, and the third substrate 27. The display device further includes a sealing material 23 for fixing the substrate 27 to the element layer 13. adhesive 19 for bonding the second substrate 15 and the third substrate 27; It has.

[0024] The first substrate 11 is a substrate for forming the element layer 13. The first substrate 11 may be: At the very least, it is necessary for the material to have heat resistance sufficient to withstand the subsequent heat treatment. The substrate 11 is made of glass such as barium borosilicate glass or aluminoborosilicate glass. A substrate can be used.

[0025] In addition, for glass substrates, if the temperature of the subsequent heat treatment is high, the distortion point will be 730°C or higher. The glass substrate may be made of, for example, aluminosilicate glass, aluminum Glass materials such as lumino borosilicate glass and barium borosilicate glass are used. By containing more barium oxide (BaO) than boron oxide, more practical resistance is achieved. Thermal glass is obtained. For this reason, a glass substrate containing more BaO than B2O3 is used. is preferred.

[0026] Instead of the glass substrate, an insulating substrate such as a ceramic substrate, a quartz substrate, or a sapphire substrate may be used. Alternatively, a substrate made of an insulating material may be used. Alternatively, a crystallized glass substrate or the like may be used.

[0027] In addition, polyethylene terephthalate may be used as long as it has heat resistance sufficient to withstand the subsequent heat treatment. Polyimide, acrylic resin, polycarbonate, polypropylene, polyester, A plastic film such as polyvinyl chloride can be used.

[0028] The element layer 13 includes active elements, passive elements, and pixel electrodes for driving the display medium 21. It includes a functional first electrode. Examples of active elements include thin film transistors and diodes. Passive elements include resistors and capacitors.

[0029] Here, one embodiment of the structure of the element layer 13 will be described with reference to FIG.

[0030] In FIG. 2, thin film transistors (hereinafter also referred to as TFTs) included in pixels in the element layer 13 are shown. ) and a first electrode (also simply referred to as a pixel electrode) that functions as a pixel electrode connected to the TFT. The pixel functions as a thin film transistor and a pixel electrode. An element consisting of an electrode and an element for controlling the display by electrical signals such as wiring. The pixel may include a color filter, etc., and each pixel Therefore, it may be one color element whose brightness can be controlled. In the case of a color display device consisting of four color elements, the smallest unit of an image is an R pixel, a G pixel, and A pixel is composed of three pixels, and a pixel of B, and an image can be obtained using multiple pixels. It will be possible.

[0031] When it is stated that A and B are connected, it means that A and B are electrically connected. This includes the case where A and B are directly connected, and the case where A and B are directly connected. Assume that the object is an object (for example, a device, an element, a circuit, a wiring, an electrode, a terminal, a conductive film, etc.).

[0032] 2A is a top view of a pixel. The TFT structure shown in FIG. 2A is an example. , a bottom gate structure is shown, which becomes the source electrode and drain electrode of the TFT. The wiring is an oxide semiconductor film that serves as a channel region and is formed by overlapping the wiring that serves as a gate electrode. 1 shows a so-called inverted staggered structure in which the upper surface of the substrate is in contact with a part of the upper surface of the substrate.

[0033] The pixel 100 shown in FIG. 2A includes a first wiring 101 functioning as a scan line, a second wiring 102 functioning as a signal line, and a third wiring 103 functioning as a signal line. The functional second wiring 102A, the oxide semiconductor film 103, the capacitance line 104, and the pixel electrode 105 are In addition, a third insulating film for electrically connecting the oxide semiconductor film 103 and the pixel electrode 105 is provided. The first wiring 101 has a thin film The second wiring 102A also functions as the gate of the transistor 106. It is also a wiring that functions as one of the source electrode or drain electrode and one of the electrodes of the storage capacitor. The third wiring 102B may also function as the other of the source electrode and the drain electrode. The capacitor line 104 is a wiring that functions as the other electrode of the storage capacitor. The line 101 and the capacitance line 104 are provided in the same layer, and the second wiring 102A and the third wiring 10 The third wiring 102B and the capacitor line 104 are provided in the same layer. The pixel electrodes 105 are provided to form a storage capacitor of the display medium. In order to increase the area to which pressure is applied, the first wiring 101 and the second wiring 102A are overlapped. Note that the oxide semiconductor film 103 included in the thin film transistor 106 is It is provided on a wiring branched from 101 via a gate insulating film (not shown). In FIG. 2(A), the hatching pattern of the pixel electrode 105 is not given.

[0034] 2B is a cross-sectional view taken along the dashed line AB in FIG. Above the first wiring 101, which is a gate, and the capacitance line 104 are provided via an underlayer film 112. A gate insulating film 113 is provided so as to cover the first wiring 101 and the capacitance line 104. The oxide semiconductor film 103 is provided over the gate insulating film 113. On the compound semiconductor film 103, a second wiring 102A and a third wiring 102B are provided. In addition, a pad is formed on the oxide semiconductor film 103, the second wiring 102A, and the third wiring 102. An oxide insulating film 114 functioning as an oxidization film is provided. A planarization insulating film 115 is provided over the oxide insulating film 114. An opening is formed in the film 115, and the pixel electrode 105 and the third wiring 10 are connected to each other through the opening. 2B. The third wiring 102B and the capacitance line 104 are connected to each other through the gate insulating film 104B. The capacitance element is formed with the base film 112 and the pixel electrode 113 as a dielectric. The stack of layers up to 05 is referred to as element layer 13.

[0035] A thin film transistor has at least three terminals including a gate, a drain, and a source. The element has a channel forming region between the drain region and the source region. A current can flow through the drain region, the channel forming region, and the source region. The source and drain are different depending on the structure and operating conditions of the transistor. It is difficult to determine whether the deviation is in the source or the drain. The region that functions as a drain may not be called a source or drain. In this case, for example, they may be referred to as the first terminal and the second terminal, respectively. These may be referred to as the first electrode and the second electrode, respectively. Alternatively, they may be referred to as the first region and the second region. This may be noted.

[0036] Next, the oxide semiconductor film 103 included in the thin film transistor 106 of this embodiment will be described. Reveal.

[0037] The oxide semiconductor used in this embodiment has a hydrogen concentration of 5×10 1 9 / cm 3 Less than or equal to 5 x 10 18 / cm 3 Less than or equal to 5 × 10 17 / cm 3 As shown below, hydrogen or OH bonds contained in the oxide semiconductor are removed. In addition, the carrier concentration is 5×10 14 / cm 3 Less than 1 × 10 14 / cm 3 below , preferably 5 x 10 12 / cm 3 Less than 1 × 10 12 / cm 3 The following is the result. That is, the carrier concentration of the oxide semiconductor film is close to zero. The voltage is 2 eV or more, preferably 2.5 eV or more, and more preferably 3 eV or more. The hydrogen concentration in the oxide semiconductor film was measured using secondary ion mass spectrometry (SIMS). This can be done using ion mass spectroscopy (Ion Mass Spectroscopy).

[0038] Next, a thin film transistor including the oxide semiconductor film 103 is The operation of the controller will now be described.

[0039] FIG. 3 shows a vertical cross section of an inverted staggered thin film transistor using an oxide semiconductor according to this embodiment. A cross-sectional view is shown. An oxide semiconductor film is formed on a gate electrode (GE1) via a gate insulating film (GI). An OS is provided on which a source electrode (S) and a drain electrode (D) are provided. do.

[0040] FIG. 4 shows an energy band diagram (schematic diagram) in the cross section A-A' shown in FIG. A) shows the case where the voltage between the source and drain is equipotential (VD=0V), and Fig. 4 (B) shows the case where a positive potential (VD>0V) is applied to the drain.

[0041] FIG. 5 is an energy band diagram (schematic diagram) in the cross section taken along line B-B' in FIG. 5(A) shows the state where a positive potential (+VG) is applied to the gate (G1), and the source and The figure shows the on-state where carriers (electrons) flow between the gate and drain. A negative potential (-VG) is applied to the gate (G1), and the gate is in the off state (minority carriers are This indicates the case where the current does not flow.

[0042] Figure 6 shows the relationship between the vacuum level, the work function of a metal (φM), and the electron affinity of an oxide semiconductor (χ). show.

[0043] At room temperature, electrons in metals are degenerate, and the Fermi level is located within the conduction band. Conventional oxide semiconductors are generally n-type, and the Fermi level (E F ) is a band The intrinsic Fermi level (E i ) and is located closer to the conduction band. In addition, some hydrogen atoms in oxide semiconductors act as donors, which is one of the reasons why they become n-type. It is known that:

[0044] In contrast, the oxide semiconductor according to this embodiment does not absorb hydrogen, which is an n-type impurity, into the oxide semiconductor. The oxide semiconductor is then highly purified to minimize the amount of impurities contained therein other than the main component. This makes it intrinsic (type i) or intrinsic. High purity achieved by removing impurities such as hydrogen and water as much as possible, rather than adding them to make it i-type. The feature is that it is an i-type (intrinsic semiconductor) or close to it. Therefore, the Fermi level (E F ) is the intrinsic Fermi level (E i ) to the same level as can.

[0045] When the band gap (Eg) of an oxide semiconductor is 3.15 eV, the electron affinity (χ) is The titanium (Ti) that makes up the source and drain electrodes is said to be 4.3 eV. The electron affinity function is approximately equal to the electron affinity (χ) of the oxide semiconductor. At the interface between the layers, no Schottky barrier is formed for electrons.

[0046] That is, when the work function (φM) of the metal and the electron affinity (χ) of the oxide semiconductor are equal, When a person comes into contact with the material, an energy band diagram (schematic diagram) such as that shown in Figure 4(A) is displayed.

[0047] In Figure 4(B), black circles (●) represent electrons, and when a positive potential is applied to the drain, the breakdown voltage is The line indicates the case where a positive potential (VG>0V) is applied to the gate. When the electrode is not electrically connected to the oxide semiconductor, the high ohmic contact resistance prevents carriers (electrons) from flowing from the electrode to the oxide semiconductor. On the other hand, when a positive potential is applied to the gate, an ohmic The contact resistance decreases, indicating an ON state in which current flows.

[0048] At this time, the electrons pass through the gate insulating film and the highly purified oxide semiconductor as shown in FIG. At the interface, the electrons move through the lowest energetically stable part on the oxide semiconductor side.

[0049] In addition, in FIG. 5(B), when a negative potential is applied to the gate (G1), Since the number of holes is essentially zero, the current is close to zero.

[0050] For example, if the channel width W of a thin-film transistor is 1×10 4 μm and the channel length L is 3 μm Even if the off-state current is 10 -13 A or less, and the subthreshold swing value (S The gate insulating film thickness is 100 nm.

[0051] In this way, it is possible to purify the oxide semiconductor to the greatest extent possible so that it contains as few impurities as possible other than the main component. As a result, the operation of the thin film transistor can be improved. can be reduced.

[0052] In FIG. 2B, the first electrode (pixel electrode 105) formed in the element layer 13 is a typical These include aluminum, copper, titanium, tantalum, tungsten, molybdenum, chromium, and neodymium. A simple substance consisting of an element selected from zinc and scandium, an alloy containing the above elements, Conductive materials with reflective or opaque properties, such as compounds containing elements (oxides and nitrides) Indium tin oxide (hereinafter referred to as ITO), tin oxide, Indium oxide containing tungsten, indium zinc oxide containing tungsten oxide, oxide Indium oxide containing titanium, indium tin oxide containing titanium oxide, indium zinc Conductive materials with transparency such as indium tin oxide or silicon oxide are used. A laminated structure containing these materials can also be used. The first electrode formed on the layer 13 is made of a conductive material having reflectivity, so that external light is reflected. This allows the light to be reflected, thereby improving the light reflection efficiency.

[0053] A first electrode (pixel electrode 105) is formed in each pixel on the element layer 13. The electrode (pixel electrode 105) is connected to a thin film transistor 106. This controls the voltage applied to the first electrode (pixel electrode 105) of each pixel.

[0054] The pixels shown in FIGS. 2A and 2B are formed by disposing a plurality of pixels on the first substrate 120 as shown in FIG. 7, a number of pixels 121 are arranged in a matrix on the first substrate 120. The display device has a pixel section 122, a scanning line driver circuit 123, and a signal line driver circuit 124. The pixel 121 has a first wiring 101 connected to a scanning line driver circuit 123. The selected or unselected state of each row is determined by the scanning signal supplied by The pixel 121 selected by the scanning signal is connected to a signal line driving circuit 124. The wiring 102A is connected to the video signal (image signal, video voltage, video (also called data) is provided.

[0055] In FIG. 7, the pixel section 122 has a plurality of pixels 121 arranged in a matrix (stripe). The pixels 121 are not necessarily arranged in a matrix. For example, the pixels 121 may be arranged in a delta arrangement or a Bayer arrangement. The display method in the pixel section 122 may be a progressive method or an interlace method. In addition, the color elements controlled by pixels when displaying colors are: The color is not limited to three colors, RGB (R is red, G is green, B is blue), but may be more than three. For example, RGBW (W is white), or RGB plus one or more colors such as yellow, cyan, or magenta Even if the size of the display area for each dot of a color element is different, good.

[0056] In FIG. 7, the first wiring 101 and the second wiring 102A are arranged in the row and column directions of the pixels. The first wiring 101 and the second wiring 102A constitute a pixel. The number of sub-pixels (also called sub-pixels or sub-sub-pixels) that make up a pixel, or the number of transistors in a pixel In addition, the number of the first wiring 101 and the second wiring 102 may be increased depending on the pixel. The pixel 121 may be driven by sharing the line 102A.

[0057] In FIG. 2A, the opposing portions of the second wiring 102A and the third wiring 102B are linear. The structure shown is such that the second wiring 102A surrounds the third wiring 102B (specifically, The area of ​​the region through which carriers move is increased, resulting in a thin-film transistor. Alternatively, the amount of current (also called ON current) that flows when the capacitor is conductive may be increased.

[0058] Note that the on-state current described in this specification refers to the current that flows when a thin film transistor is in an on-state (also called a conductive state). ) refers to the current that flows between the source and drain when n-channel thin-film transistors In a transistor, when the voltage applied between the gate and source is greater than the threshold voltage (Vth), This refers to the current that flows between the source and drain.

[0059] One of the scanning line driver circuit 123 and the signal line driver circuit 124 shown in FIG. 7 is the same as that shown in FIG. 1(B). In this case, the scanning line driver circuit 123 or the signal line driver circuit 1 24 is provided on the first substrate 120 by COG (Chip on Glass). However, both the scanning line driver circuit 123 and the signal line driver circuit 124 are Alternatively, only the pixel section 122 may be provided on the first substrate 120. 20, and the scanning line driver circuit 123 or the signal line driver circuit 124 is provided on the substrate ... It may also be provided on the wiring board 31.

[0060] In addition, one or both of the scanning line driver circuit 123 and the signal line driver circuit 124 may be formed on the element layer 13. In this case, a thin film transistor formed in the same manner as the thin film transistor connected to the pixel electrode may be provided. One or both of the scanning line driver circuit 123 and the signal line driver circuit 124 are formed using a film transistor. It is possible to create a method.

[0061] The second substrate 15 shown in FIG. 1(B) functions as a sealing substrate for the display medium 21. Since the plate 15 side is the viewing surface, the second substrate 15 is preferably a substrate having light-transmitting properties. The substrates having such properties include glass substrates, polyethylene terephthalate, polyimide, and acrylic. Plastics such as polyethylene terephthalate, ... There are also stick films.

[0062] A second electrode 17 is formed on the second substrate 15. The second electrode 17 has light-transmitting properties. The conductive film is formed of a conductive film. Typical examples of the conductive film having light-transmitting properties include indium tin oxide and oxide. Tungsten-containing indium oxide, tungsten oxide-containing indium zinc oxide, Indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium Examples include zinc oxide and indium tin oxide with added silicon oxide.

[0063] The second electrode 17 corresponds to a common electrode (opposite electrode) and is formed on the first substrate 11. It is electrically connected to the position line.

[0064] The display medium 21 may be an electrophoretic type, a particle migration type, a particle rotation type, a liquid crystal display type, an electrolytic deposition type, or the like. This structure can be displayed using various methods such as electrochromic, film moving, etc. In the embodiments, the electrophoresis method, the particle movement method, and the particle rotation method will be described in detail. However, liquid crystal display method, electrolytic deposition method, electrochromic method, film transfer method, etc. are suitable. It can be used as appropriate.

[0065] Representative examples of electrophoresis methods include microcapsule electrophoresis, horizontal migration electrophoresis, and vertical migration electrophoresis. There are various types of particle rotation methods, such as the spherical twist ball method and the magnetic twist method. There are ball type, cylindrical twist ball type, etc. In the particle movement type, charged toner (charged toner The method using toner is also called the charged toner display method. The method using electrophoretic particles is also called the magnetophoretic method. 8 shows the structure of the display element of the display panel. In addition, in FIG. 8, the adhesive material 19 shown in FIG. is omitted.

[0066] FIG. 8A is a cross-sectional view of a display medium 21 using an electrophoretic system and its vicinity. An organic EL element is disposed between the electrode 41 (corresponding to the pixel electrode 105 in FIG. 2B) and the second electrode 17. The display medium 21 is filled with a filler 51 such as resin and has microcapsules 53. In the microcapsules 53, negatively charged black particles 55 and positively charged white particles The color particles 57 are dispersed in a transparent dispersion medium 59. The microcapsules 53 have a diameter of about 10 μm to 200 μm. It is formed from resin etc.

[0067] The microcapsules 53 provided between the first electrode 41 and the second electrode 17 When a voltage is applied by the electrode 41 and the second electrode 17, the first particles, the black particles 55 The first particle and the second particle, the white particle 57, move in opposite directions, and a white or It is possible to display black. A display element that applies this principle is an electrophoretic display element.

[0068] The first particles and the second particles contained in the microcapsules 53 are made of a conductive material and an insulating material. materials, semiconductor materials, magnetic materials, liquid crystal materials, ferroelectric materials, electrochromic materials, magnetic A material selected from electrophoretic materials or a composite material thereof may be used.

[0069] The colors of the first particles and the second particles are not limited to black and white, but may be different colors (colorless). Therefore, the dye may be added to one or both of the first particles and the second particles. By using particles having such a property, color display is possible.

[0070] FIG. 8B shows a cross-sectional view of the particle movement type display medium 21 and its vicinity. The electrode 41 (corresponding to the pixel electrode 105 in FIG. 2B), the second electrode 17, and the rib 61 In a space 63 surrounded by the positively charged black powder particles 65 and the negatively charged white powder particles 67, The space 63 is filled with a gas such as air, nitrogen, or a rare gas. The diameter of the black powder particles 65 and the white powder particles 67 is 0.1 to 20 μm.

[0071] When a voltage is applied between the first electrode 41 and the second electrode 17, the black powder particles 65 and the white powder particles 66 are The color particles 67 move in opposite directions to each other, allowing the pixel to display white or black. By using colored powders such as red, yellow, and blue, color display is possible. do.

[0072] FIG. 8C shows a cross-sectional view of a display medium 21 using the particle rotation method and its vicinity. The switching method is as follows: the first electrode 41 (corresponding to the pixel electrode 105 in FIG. 2B) and the second electrode The first electrode 41 and the second electrode 17 are arranged with spherical particles painted in black and white. This method displays images by controlling the orientation of spherical particles using the potential difference between the electrodes 17. Here, we will show an example using a spherical twist ball as a representative example of a particle rotation type.

[0073] The spherical twist ball is filled with a filler 71 such as an organic resin. The microcapsule 73 has a black area 75 and a black area 76 formed in the microcapsule 73. A ball having a white area 77 and a liquid 7 filling the space between the ball and the microcapsule 73. 9. The diameter of the spherical twist ball is 50 to 100 μm.

[0074] Electrophoresis method, particle migration method, particle rotation method, liquid crystal display method, electrolytic deposition method, electro Display elements that can display using chromic methods, film movement methods, etc. have high reflectivity, so they are No light source is required, and power consumption is low. In addition, when no voltage is applied, electrophoresis, There is no particle movement or rotation, so once an image is displayed it can be maintained. do.

[0075] In this embodiment, an adhesive 19 is provided between the display medium 21 and the element layer 13 (see FIG. 1(B)). This is done by fixing the second substrate 15 having the display medium 21 on the element layer 13. When the display medium 21 is formed directly on the element layer 13, The adhesive 19 is not necessary. The second substrate 15 protects the display medium 21 and also reduces reflection and If the function of reducing reflection is provided, the third substrate 27 does not need to be provided.

[0076] The third substrate 27 has functions such as anti-glare, anti-reflection, protection, and ultraviolet absorption. The third substrate 27 has an uneven surface to scatter external light. It is preferable that the optical element is made of a layer, and the interference of reflected light at the interface of the layer is utilized to reduce reflected light. Furthermore, by forming the third substrate 27 from a high-hardness organic resin, scratches can be reduced. In addition, the third substrate 27 is made of a material that absorbs ultraviolet light. This reduces the deterioration of particles in the microcapsules due to ultraviolet rays. The substrate 27 can be made of any known material having these functions. The second substrate 15 and the third substrate 27 are bonded together by an adhesive 25 .

[0077] The sealant 23 seals the first substrate 11 and the third substrate 27. Visible light curable resin, ultraviolet curable resin, or thermosetting resin can be used. Generally, visible light curing, ultraviolet light curing, or heat curing acrylic resins, methacrylic resins resins, epoxy resins, etc.

[0078] Here, a display method of the display panel shown in this embodiment mode will be described with reference to FIG.

[0079] First, as a comparative example, a conventional method for displaying an electronic book will be described with reference to FIG.

[0080] 9A shows a timing chart for pixels in the first to nth rows. In 131, one writing period 133 for pixels in the first to nth rows is indicated by diagonal lines. In addition, during the image rewriting period 131, a non-writing period 133 is included in one writing period 133. In electronic paper, the pixels in the first to nth rows are written multiple times. can be.

[0081] 9B shows the potential of the gate signal input to the gate line of the i-th row. In 3, the potential of the gate signal is V High and in the non-writing period 135, V Low is.

[0082] FIG. 9(C) shows the potential of the video signal input to the source line of an arbitrary column, and Any potential can be taken.

[0083] 9(D) shows the potential of the pixel electrode in the pixel in the i-th row. The potential of the pixel electrode is the same as the potential of the video signal. The potential of the pixel electrode in the image sensor is the same as that of the pixel electrode in the image sensor. However, the potential can be changed arbitrarily depending on the video signal written. In the final writing period 137 of the image rewriting period 131, the pixel voltage The electrode has the same potential as the common electrode, V com By applying a voltage of 0V to the display medium, This stops the electrophoresis, particle movement, and particle rotation of the display medium, thereby maintaining the image.

[0084] Since the conventional thin film transistor has a high leakage current, the pixel electrode The potential of the pixel is not maintained, and the potential fluctuates. Therefore, the period T1 until the next write operation starts must be shortened. The number of times increases, and the driving frequency (clock frequency) of the scanning line driving circuit becomes higher, so power consumption The power consumption will increase.

[0085] Next, a display method of the display panel shown in this embodiment mode is shown in FIG. 10. 1 shows a timing chart of pixels from the first row to the nth row. In addition, one writing period 143 for pixels in the first to nth rows is indicated by diagonal lines. The write period 141 includes a non-write period 145 between each write period 143 .

[0086] FIG. 10(B) shows the potential of the gate signal input to the gate line of the i-th row, and FIG. 10(C) indicates the potential of a video signal input to a source line of an arbitrary column, and FIG. 10(D) indicates the potential of a video signal input to a source line of the i-th row. 14 shows the potential of the pixel electrode in the pixel. In the interval 147, the pixel electrode is applied with the same potential V as the common electrode. com is applied.

[0087] In the display panel described in this embodiment, a thin film transistor connected to a pixel electrode is The thin film transistor has a channel width of 1000 nm to 1000 nm. The W is a thin-film transistor with a width of several tens to several hundreds of μm, and the off-current is 1×10 -16 A and below Therefore, as shown in FIG. 10(D), the non-writing period The potential fluctuation of the pixel electrode 145 is small. In a transistor, the off-state current is 1×10 -12 Design etc. should be carried out with an estimate equivalent to A. Therefore, thin film transistors with oxide semiconductors are When the storage capacitance is the same (about 0.1 pF) as that of a thin film transistor having a The voltage holding period can be extended by about 10,000 times. This allows the time period (T2) from when the next write operation begins to be extended. This reduces the number of times pixels are scanned and also makes it possible to lower the driving frequency of the scanning line driving circuit. Therefore, power consumption can be reduced.

[0088] In addition, the thin film having a highly purified oxide semiconductor with a reduced hydrogen concentration described in this embodiment Since the transistor can reduce the off-state current, the The flat surface area can be reduced. Electrophoresis method, particle movement method, particle rotation method, liquid crystal display Display method, electrolytic deposition method, electrochromic method, film transfer method, etc. Display panels that can hold images require high driving voltages (several tens of volts). ) When conventional thin film transistors are used, the leakage current becomes high and the printed Therefore, the storage capacitance is increased, that is, the planar area of ​​the capacitance element is increased. The planar area of ​​the capacitance element in the pixel is large, and the pixel area needs to be reduced. However, if the off-current of the thin film transistor is small, the voltage applied to the pixel electrode Since the fluctuation of the applied voltage is small, it is possible to reduce the planar area of ​​the capacitance element. As a result, as shown in this embodiment, a highly purified oxide semiconductor having a reduced hydrogen concentration can be obtained. By using thin film transistors, it is possible to reduce the capacitance element and pixel area. The resolution of the display panel can be increased.

[0089] Furthermore, when the off-current of the thin film transistor is low, the fluctuation of the potential applied to the pixel electrode is small. Therefore, the voltages of the pixel electrodes and the common electrode are kept constant. It is possible to keep the voltage applied to the display medium provided between the electrodes constant. Therefore, it is possible to reduce the movement of charged particles and maintain the gradation of each pixel. That is, the image retention characteristics of the display panel can be improved.

[0090] A semiconductor device 35 is provided on the wiring board 31 shown in FIG. is a controller that controls the display content of the display panel, typically a CPU, a memory unit, a power supply There are supply circuits, etc.

[0091] The element layer 13 and the wiring board 31 are connected by an FPC 33. The light is transmitted to the element layer 13 via the FPC 33, and an image is displayed on the display panel 10.

[0092] The power supply device 37 is connected to the semiconductor device 35 via the wiring board 31. The power of the device 37 drives the controller, causing the display panel 10 to display an image.

[0093] The power supply device 37 may be a primary battery, a secondary battery with a storage function, or a capacitor. Typical examples of primary batteries include manganese batteries and alkaline manganese batteries. There are gun batteries, nickel batteries, lithium batteries, etc. Typical examples of secondary batteries are lithium There are various types of batteries, such as ion batteries, nickel-metal hydride batteries, and lithium-ion polymer batteries. Typical examples include double layer capacitors and lithium ion capacitors.

[0094] Here, the structure of the power supply device 37 will be described with reference to FIG. In this embodiment, when a secondary battery and a capacitor having a power storage function are used as the power supply device 37, This section explains the case.

[0095] FIG. 11(A) is a plan view of the power supply device 37, and is a cross-sectional view taken along the dashed line AB in FIG. 11(A). The plan view is shown in FIG. 11(B).

[0096] The power supply device 37 shown in FIG. 11(A) has a storage cell 155 inside an exterior member 153. The exterior member 153 also has terminals 157 and 159 that are connected to the storage cell 155. , laminated film, polymer film, or metal film, metal case, plastic A case or the like can be used.

[0097] As shown in FIG. 11(B), the storage cell 155 includes a negative electrode 163, a positive electrode 165, and a negative electrode and A separator 167 is provided between the positive electrode and the exterior member 153 and the separator 167. The negative electrode 163 is composed of a negative electrode current collector 171 and a negative electrode active material 169. The positive electrode 165 is composed of a positive electrode current collector 175 and a positive electrode active material 177. The negative electrode active material 173 is formed on one surface or two opposing surfaces of the negative electrode current collector 171. The positive electrode active material 177 is formed on one surface or two opposing surfaces of the positive electrode current collector 175. is formed.

[0098] The negative electrode current collector 171 is connected to the terminal portion 159. The positive electrode current collector 175 is connected to the terminal The terminal portions 157 and 159 are connected to the outer casing 153. It is led outwards.

[0099] In this embodiment, the power supply device 37 (see FIG. 1(B)) is a pouched thin Although a type of power storage device is shown, power storage devices of various shapes such as cylindrical, square, and button types can also be used. In this embodiment, a structure in which a positive electrode, a negative electrode, and a separator are stacked is shown. However, the positive electrode, the negative electrode, and the separator may be wound together.

[0100] In a secondary battery, which is one form of the storage cell 155, a lithium-containing metal oxide such as LiCoO2 is used. Lithium-ion batteries using lithium ions have high capacity and are highly safe. The structure of a lithium ion battery, which is a typical example, will be described with reference to FIG. 11(B).

[0101] The negative electrode current collector 171 is made of stainless steel, copper, nickel, or the like. Shapes such as plate-like and net-like can be used as appropriate.

[0102] The negative electrode active material 173 is a material capable of reversibly absorbing lithium ions, a conductive material, and a barrier material. A typical example of a material that can reversibly store lithium ions is black Contains lead, non-graphitizable carbon, polyacenic semiconductor (PAS), etc., and has phosphorus absorbed PAS is also preferred because it can provide high capacity. Examples include fluororesins such as polytetrafluoroethylene and polyvinylidene fluoride, and polypropylene. Thermoplastic resins such as polyethylene and ethylene are also used. Examples include polyethylene black, graphite, and metal powder.

[0103] The positive electrode current collector 175 is made of aluminum, stainless steel, or the like. Shapes such as plate-like and net-like can be used as appropriate.

[0104] The positive electrode active material 177 may be LiFeO2, LiCoO2, LiNiO2, or LiMn2O 4, LiFePO4, LiCoPO4, LiNiPO4, LiMn2PO4, V2O5, There are Cr2O5, MnO2 and other materials.

[0105] The solute of the electrolyte 169 is capable of transporting lithium ions and is stable in the lithium ions. Typical examples of electrolyte solutes are LiClO4, LiAsF6, Li Lithium salts include BF4, LiPF6, and Li(C2F5SO2)2N.

[0106] The solvent of the electrolyte 169 is a material that can transport lithium ions. As the solvent for the substance 169, an aprotic organic solvent is preferable. Examples include ethylene carbonate, propylene carbonate, and dimethyl carbonate. , diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetramethylpropional tetrahydrofuran, etc., and one or more of these can be used. By using a polymer material that gels as a solvent for the substance 169, safety, including leakage, is improved. Furthermore, it is possible to reduce the thickness and weight of the electricity storage device 151. Typical examples of materials include silicone gel, acrylic gel, acrylonitrile gel, and polyethylene gel. Polypropylene oxide, polypropylene oxide, fluorine-based polymers, etc. As 69, a solid electrolyte such as Li3PO4 can be used.

[0107] The separator 167 is made of an insulating porous material. , nonwoven fabric, glass fiber, synthetic resin material or ceramic material. It is necessary to select a material that does not dissolve in

[0108] Lithium-ion batteries have a small memory effect, high energy density, and a large capacity. The operating voltage is also high. These factors make it possible to reduce the size and weight. There is little deterioration due to repeated charging and discharging, so it can be used for a long period of time and costs can be reduced. be.

[0109] Next, in a capacitor, which is another form of the storage cell 155, a lithium ion capacitor Here, we will look at a typical example of a capacitor, a lithium-ion battery, which has a high energy density and excellent charge / discharge characteristics. The structure of the lithium ion capacitor will be described with reference to FIG. 11(B).

[0110] The negative electrode current collector 171, the negative electrode active material 173, and the positive electrode current collector 175 are The same as that explained for the secondary battery can be used.

[0111] The positive electrode active material 177 is a material that can reversibly absorb lithium ions and / or anions. Representative examples of the positive electrode active material 177 include activated carbon, conductive polymers, and polyacene semiconducting materials. There is a conductor (PAS).

[0112] The solute of the electrolyte 169, the solvent of the electrolyte 169, and the separator 167 are the lithium ion The same as that described for the ON secondary battery can be used.

[0113] Lithium-ion capacitors have high charge / discharge efficiency, can be charged and discharged rapidly, and can be used repeatedly. The display panel has a high writing voltage and requires no power after writing. To avoid this, it is preferable to use a lithium ion capacitor that is capable of rapid discharge.

[0114] As described above, the electronic book described in this embodiment uses a highly purified oxide semiconductor with a low hydrogen concentration. The thin film transistors used in electronic books are used to scan pixels to control the display of the display panel. This reduces the number of times the scanning line is read and also reduces the driving frequency of the scanning line driving circuit. This can reduce power consumption and improve image retention characteristics. In addition, the off-state current of a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration was 1×10 -13 A or less, the capacitance that holds the signal voltage applied to the pixel is It is possible to reduce the area of ​​the capacitance element and the pixel. This allows for a higher resolution for e-books.

[0115] (Embodiment 2) The present embodiment is a thin film transistor that can be applied to the display panel disclosed in the first embodiment. The thin film transistor 410 shown in this embodiment is the same as the thin film transistor of Embodiment 1. It can be used as register 106 (see FIG. 2).

[0116] One mode of the thin film transistor and the manufacturing method of the thin film transistor of this embodiment is shown in FIGS. This will be explained with reference to FIG.

[0117] 12(A) and 12(B) show a plan view and a cross-sectional view of a thin film transistor. The thin film transistor 410 shown in (A) and (B) is a thin film transistor with a top gate structure. It is one.

[0118] FIG. 12(A) is a plan view of a thin film transistor 410 having a top gate structure, and FIG. 12(B) is a plan view of a thin film transistor 410 having a top gate structure. ) is a cross-sectional view taken along the dashed line AB in FIG. 12(A).

[0119] 12A and 12B, the thin film transistor 410 is formed on a first substrate 400. an insulating film 407, an oxide semiconductor film 412, one of a source electrode and a drain electrode 415a, and the other of the source electrode and the drain electrode 415b, the gate insulating film 402, the gate electrode 4 11, one of the source electrode or drain electrode 415a, The other electrode 415b is connected to the wiring 414a and the wiring 414b, respectively, and electrically connected. It continues.

[0120] The thin film transistor 410 is described using a thin film transistor with a single gate structure. However, if necessary, a thin-film transistor with a multi-gate structure having multiple channel forming regions may be used. It is also possible to create a

[0121] 13A to 13E, the thin film transistor 4 is formed on the first substrate 400. The process for producing 10 will be described.

[0122] First, an insulating film 407 serving as a base film is formed over a first substrate 400. The insulating film 407 may be a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or An oxide insulating film such as an aluminum oxynitride film is preferably used as the insulating film 407. As a method, a plasma CVD method or a sputtering method can be used. In order to prevent a large amount of hydrogen from being contained in the insulating film 407, the insulating film is formed by sputtering. It is preferable to form 407.

[0123] In this embodiment, a silicon oxide film is formed as the insulating film 407 by a sputtering method. The first substrate 400 is transferred to a processing chamber, and a high-purity oxygen gas containing hydrogen and moisture is added. Sputtering gas is introduced and a silicon target is used to form an insulating film 407 on the first substrate 400. The first substrate 400 may be at room temperature or may be heated. It's fine.

[0124] For example, quartz (preferably synthetic quartz) is used, the substrate temperature is 108° C., and the distance between the substrate and the target is 108° C. The distance between the two (TS distance) was 60 mm, the pressure was 0.4 Pa, the high frequency power supply was 1.5 kW, and oxygen and and argon (oxygen flow rate 25 sccm: argon flow rate 25 sccm = 1:1) atmosphere. A silicon oxide film is formed by F sputtering. The film thickness is 100 nm. Instead of quartz (preferably synthetic quartz), a silicon target is used to form a silicon oxide film. It can be used as a target for sputtering. and argon gas mixture.

[0125] In this case, it is preferable to form the insulating film 407 while removing the remaining moisture in the processing chamber. This is to prevent the insulating film 407 from containing hydrogen, hydroxyl groups, or moisture.

[0126] To remove residual moisture from the processing chamber, it is preferable to use an adsorption type vacuum pump. For example, a cryopump, an ion pump, or a titanium sublimation pump can be used. The exhaust means is preferably a turbo pump with a cold trap added. The processing chamber evacuated using a cryopump may contain, for example, hydrogen atoms and water (H 2O) and other compounds containing hydrogen atoms (and more preferably compounds containing carbon atoms) are exhausted. Therefore, the concentration of impurities contained in the insulating film 407 formed in the processing chamber can be reduced. .

[0127] The sputtering gas used to form the insulating film 407 is hydrogen, water, a hydroxyl group, or a hydride. Use high-purity gas in which impurities have been removed to concentrations of ppm or ppb. is preferred.

[0128] There are two types of sputtering methods: RF sputtering, which uses a high frequency power supply, and DC sputtering. DC sputtering using a power supply, and pulsed DC sputtering using a pulsed bias. The RF sputtering method is mainly used to form insulating films, and The C sputtering method is mainly used to form metal films.

[0129] There are also multi-target sputtering devices that can accommodate multiple targets of different materials. The equipment can deposit layers of different materials in the same chamber, or multiple types of materials in the same chamber. It is also possible to simultaneously discharge and deposit the same materials.

[0130] In addition, a magnetron sputtering method using a magnet mechanism inside the chamber is used. The ECR device uses a plasma generated by microwaves without glow discharge. There is a sputtering device that uses the sputtering method.

[0131] In addition, as a film formation method using a sputtering method, a target material and a sputtering gas are mixed during film formation. Reactive sputtering method to form compound thin films by chemically reacting the silicon dioxide and silicon dioxide components. There is also a bias sputtering method in which a voltage is applied to the substrate during film formation.

[0132] The insulating film 407 may have a laminated structure. For example, the insulating film 407 may have a silicon nitride layer on the first substrate 400 side. film, silicon nitride oxide film, aluminum nitride film, or aluminum nitride oxide film The insulating film may have a laminated structure of a nitride insulating film and the oxide insulating film.

[0133] For example, a spat containing high-purity nitrogen from which hydrogen and moisture have been removed is placed between the silicon oxide film and the substrate. A target gas is introduced and a silicon nitride film is formed using a silicon target. In the case of a silicon oxide film, the remaining moisture in the processing chamber is removed while the silicon nitride film is being processed. It is preferable to form a film.

[0134] When forming a silicon nitride film, the substrate may also be heated during film formation.

[0135] When a silicon nitride film and a silicon oxide film are laminated as the insulating film 407, the silicon nitride film The silicon oxide film and the silicon dioxide film are formed in the same processing chamber using a common silicon target. First, a sputtering gas containing nitrogen is introduced to the silicon wafer mounted in the processing chamber. A silicon nitride film is formed using a cone target, and then the film is sputtered in an oxygen-containing sputtering gas. The silicon oxide film is then formed using the same silicon target. Since the silicon nitride film and the silicon oxide film can be formed successively without exposure to the atmosphere, This can prevent impurities such as hydrogen and moisture from being adsorbed onto the silicon film surface.

[0136] Next, an oxide semiconductor film is formed over the insulating film 407 to a thickness of 2 nm to 200 nm.

[0137] In order to prevent hydrogen, hydroxyl groups, and moisture from being contained in the oxide semiconductor film as much as possible, As a pretreatment for film formation, the first insulating film 407 is formed in the preheating chamber of the sputtering device. The substrate 400 is preheated to remove impurities such as hydrogen and moisture adsorbed on the first substrate 400. It is preferable that the exhaust means provided in the preheating chamber is a cryopump. This preheating process can be omitted. This may be performed on the first substrate 400 before the formation of the gate insulating film 402 to be formed, or after the formation of the gate insulating film 402. One of the source electrode or the drain electrode 415a and the other of the source electrode or the drain electrode The same process may be carried out on the first substrate 400 on which the layers up to 415b have been formed.

[0138] Note that before the oxide semiconductor film is formed by a sputtering method, argon gas is introduced. Reverse sputtering is performed to generate plasma, and the dust adhering to the surface of the gate insulating film 402 is removed. It is preferable to remove the argon from the target. In a nitrogen atmosphere, a voltage is applied to the substrate side using a high frequency power supply to form plasma near the substrate. This is a method for modifying the surface. Note that nitrogen, helium, oxygen, etc. can be used instead of argon atmosphere. It may be used.

[0139] The oxide semiconductor film is formed by a sputtering method. nO series, In-Sn-Zn-O series, In-Al-Zn-O series, Sn-Ga-Zn-O series , Al-Ga-Zn-O system, Sn-Al-Zn-O system, In-Zn-O system, Sn-Zn- O-based, Al-Zn-O-based, In-O-based, Sn-O-based, and Zn-O-based oxide semiconductor films are used. In this embodiment, the oxide semiconductor film is formed using an In—Ga—Zn—O-based oxide semiconductor target. The oxide semiconductor film is formed by a sputtering method using a rare gas (typically In an atmosphere of noble gas (typically argon), oxygen, or a mixture of noble gas (typically argon) and oxygen, The film can be formed by sputtering in a mixed atmosphere. When using the ring method, a target containing 2% to 10% by weight of SiO2 is used. Film formation may also be performed.

[0140] The sputtering gas used in forming the oxide semiconductor film is hydrogen, water, a hydroxyl group, or a hydride. Use high-purity gas in which impurities have been removed to concentrations of ppm or ppb. is preferred.

[0141] A target for forming an oxide semiconductor film by a sputtering method is a substrate containing zinc oxide as the main component. A metal oxide target can be used. Another example is an oxide semiconductor target containing In, Ga, and Zn (composition ratio: , In2O3:Ga2O3:ZnO=1:1:1 [molar ratio], In:Ga:Zn=1 :1:0.5 [molar ratio]) can be used. As an oxide semiconductor target, In:Ga:Zn=1:1:1 [molar ratio], A target having a composition ratio of In:Ga:Zn=1:1:2 [molar ratio] was used. The filling rate of the oxide semiconductor target is 90% or more and 100% or less, preferably 90% or less. The filling rate is 5% or more and 99.9% or less. By using an oxide semiconductor target with a high filling rate, Therefore, the formed oxide semiconductor film becomes a dense film.

[0142] The oxide semiconductor film is formed by holding the substrate in a treatment chamber maintained in a reduced pressure state and removing residual moisture in the treatment chamber. While removing the hydrogen and moisture, a sputtering gas from which hydrogen and moisture have been removed is introduced to form a metal oxide. An oxide semiconductor film is formed on the first substrate 400 as a get. To remove the gas, it is preferable to use an adsorption type vacuum pump. For example, a cryopump It is preferable to use an ion pump or a titanium sublimation pump. The stage may be a turbopump plus a cold trap. The processing chamber evacuated using a pump contains, for example, hydrogen atoms, water (H2O), and other gases containing hydrogen atoms. Compounds (more preferably compounds containing carbon atoms) and the like are exhausted. The concentration of impurities contained in the oxide semiconductor film formed by the method can be reduced. The substrate may be heated during film formation.

[0143] An example of the film formation conditions is as follows: the substrate temperature is room temperature, the distance between the substrate and the target is 110 mm, Pressure 0.4 Pa, DC power 0.5 kW, oxygen and argon (oxygen flow rate 15 scc The conditions are as follows: argon flow rate 30 sccm; pulsed direct current (DC ) power supply, powdery substances (also called particles or dust) generated during film formation can be reduced. The oxide semiconductor film is preferably 5 nm or more and 30 nm or more in thickness. The appropriate thickness varies depending on the oxide semiconductor material used. The thickness can be selected appropriately depending on the application.

[0144] Next, the oxide semiconductor film is covered with a resist mask formed by a first photolithography process. The oxide semiconductor film 412 is then etched using the insulating film 412a to form an island-shaped oxide semiconductor film 412 (see FIG. 13A). In addition, a resist mask for forming the island-shaped oxide semiconductor film 412 was formed by an ink-jet method. If the resist mask is formed by the inkjet method, a photomask can be used. Therefore, the manufacturing cost can be reduced.

[0145] The etching of the oxide semiconductor film here can be performed by either dry etching or wet etching. Either one or both may be used.

[0146] The etching gas used in dry etching is a gas containing chlorine (chlorine-based gas, for example For example, chlorine (Cl2), boron chloride (BCl3), silicon chloride (SiCl4), carbon tetrachloride (CC l4) etc.) are preferred.

[0147] In addition, gases containing fluorine (fluorine-based gases, such as carbon tetrafluoride (CF4) and sulfur hexafluoride (S F6), nitrogen trifluoride (NF3), trifluoromethane (CHF3), etc.), hydrogen bromide (H Br), oxygen (O2), and rare gases such as helium (He) and argon (Ar) A gas containing added sulfur or the like can be used.

[0148] As a dry etching method, parallel plate type RIE (Reactive Ion Etch) ing) method and ICP (Inductively Coupled Plasma) A combined plasma etching method can be used. It is possible to etch into the desired processed shape. The etching conditions (the amount of power applied to the coil-type electrode, the amount of power applied to the electrode on the substrate side) were determined as follows: The amount of power used, the temperature of the electrode on the substrate, etc. are adjusted appropriately.

[0149] The etching solution used for wet etching is a mixture of phosphoric acid, acetic acid, and nitric acid. Ammonia peroxide solution (31% by weight hydrogen peroxide solution: 28% by weight ammonia solution = 5:2) was used. Alternatively, ITO07N (manufactured by Kanto Chemical Co., Ltd.) may be used.

[0150] In addition, after wet etching, the etching solution is washed away together with the etched material. The waste etching solution containing the removed material is purified to remove the contained material. The indium and the like contained in the oxide semiconductor film may be recycled from the waste liquid after etching. By recovering and reusing materials, resources can be used more effectively and costs can be reduced. .

[0151] In order to form the oxide semiconductor film 412 in a desired shape, etching conditions ( The etching solution, etching time, temperature, etc. are adjusted appropriately.

[0152] In this embodiment, a wet etching solution is used, which is a mixture of phosphoric acid, acetic acid, and nitric acid. The oxide semiconductor film is processed into an island-shaped oxide semiconductor film 412 by etching.

[0153] In this embodiment, first heat treatment is performed on the oxide semiconductor film 412. The temperature is set to 400° C. or higher and 750° C. or lower, preferably 400° C. or higher and lower than the strain point of the substrate. Here, the substrate is placed in an electric furnace, which is a type of heat treatment apparatus, and the oxide semiconductor film is heated to a nitrogen atmosphere. After heat treatment at 450°C for 1 hour in a nitrogen atmosphere, The oxide semiconductor film is obtained by preventing water and hydrogen from entering the oxide semiconductor film. The oxide semiconductor film 412 can be dehydrated or dehydrogenated by the heat treatment.

[0154] The heat treatment device is not limited to an electric furnace, and may be a heat treatment device using heat conduction or heat from a heat source such as a resistance heating element. A device for heating the object to be treated by radiation may be provided. For example, a GRTA (Gas Rapid Thermal Annealing) equipment, LRTA (Lamp Ra RTA (Rapid Thermal Annealing) equipment, etc. The LRTA device can be used with a halogen laser. lamps, metal halide lamps, xenon arc lamps, carbon arc lamps, high-pressure nato The radiation of light (electromagnetic waves) emitted from lamps such as sodium lamps and high-pressure mercury lamps can cause The GRTA device is a device that uses high-temperature gas to heat food. The gases include rare gases such as argon, or nitrogen, which can be treated by heat treatment. An inert gas that hardly reacts with the material is used.

[0155] For example, as the first heat treatment, a base is placed in an inert gas heated to a high temperature of 650°C to 700°C. The plate is moved and placed in the oven, heated for several minutes, and then the substrate is moved and placed in an inert gas atmosphere heated to a high temperature. GRTA can be used to heat the food at high temperatures in a short time. become.

[0156] In the first heat treatment, nitrogen or a rare gas such as helium, neon, or argon is used. It is preferable that the nitrogen introduced into the heat treatment device does not contain water, hydrogen, etc. Or the purity of rare gases such as helium, neon, and argon must be 6N (99.9999%) or higher. Preferably, the impurity concentration is 7N (99.99999%) or more (i.e., the impurity concentration is 1 ppm or less, It is preferable to set the concentration to 0.1 ppm or less.

[0157] Depending on the conditions of the first heat treatment or the material of the oxide semiconductor film, the oxide semiconductor film In some cases, the film crystallizes to become a microcrystalline or polycrystalline film. For example, if the crystallization rate is 90% or more, In some cases, the oxide semiconductor film is microcrystalline, or 80% or more of the crystallinity is high. Depending on the conditions or the material of the oxide semiconductor film, an amorphous oxide semiconductor film containing no crystalline components may be obtained. In some cases, it becomes a conductive film. In addition, microcrystalline parts (grain size 1 nm or more) are present in the amorphous oxide semiconductor. In the case where an oxide semiconductor film having a thickness of 20 nm or less (typically, 2 nm or more and 4 nm or less) is formed, There are also cases where this is the case.

[0158] In addition, the first heat treatment of the oxide semiconductor film is performed on the oxide semiconductor film before the island-shaped oxide semiconductor film is formed. In this case, after the first heat treatment, the substrate is removed from the heating device. The substrate is taken out and subjected to a photolithography process.

[0159] Note that the heat treatment which has the effect of dehydrating and dehydrogenating the oxide semiconductor film is performed After forming the oxide semiconductor film, a source electrode and a drain electrode are laminated on the oxide semiconductor film. The deposition may be performed either after forming a gate insulating film on the gate electrode or after forming a gate insulating film on the drain electrode.

[0160] Next, a conductive film is formed over the insulating film 407 and the oxide semiconductor film 412. The conductive film may be formed by a deposition method or a vacuum deposition method. an element selected from aluminum, copper, tantalum, titanium, molybdenum, and tungsten, or Examples of the alloy include an alloy containing the above elements as a component, and an alloy film made up of a combination of the above elements. One or more of manganese, magnesium, zirconium, beryllium, and thorium The metal conductive film may have a single layer structure or a laminate of two or more layers. For example, a single layer structure of an aluminum film containing silicon, an aluminum A two-layer structure in which a titanium film is laminated on top of a titanium film, and an aluminum film is laminated on top of the titanium film. A three-layer structure is possible, in which a Ti film is formed on top of the Al film. Tantalum (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), chromium ( One or more elements selected from the group consisting of neodymium (Nd), scandium (Sc) Combination films, alloy films, or nitride films may also be used.

[0161] Next, a resist mask is formed over the conductive film by a second photolithography process. 415a, the source electrode or the drain electrode, After forming the other drain electrode 415b, the resist mask is removed (see FIG. 13(B)). (Refer to Fig. 1). If the edges of the formed source and drain electrodes are tapered, This is preferable because it improves the coverage of the gate insulating film.

[0162] In this embodiment, one of the source electrode and the drain electrode 415a, A titanium film with a thickness of 150 nm is formed by sputtering as the other electrode 415b. do.

[0163] Note that when the conductive film is etched, the oxide semiconductor film 412 is removed, and the insulating film thereunder is removed. The materials and etching conditions are adjusted appropriately so that 407 is not exposed.

[0164] In this embodiment, a Ti film is used as the conductive film, and an In-Ga -Zn-O based oxide semiconductor is used, and ammonia hydrogen peroxide (ammonia, A mixture of water and hydrogen peroxide is used.

[0165] Note that in the etching step after the second photolithography step, the oxide semiconductor film 412 In some cases, only a part of the oxide semiconductor film is etched, resulting in an oxide semiconductor film having a groove (depression). In addition, one of the source electrode and the drain electrode 415a, On the other hand, the resist mask for forming 415b may be formed by an ink-jet method. When a resist mask is formed using the inkjet method, no photomask is used, reducing manufacturing costs. This can reduce the

[0166] The exposure to light when forming the resist mask in the second photolithography process is done using ultraviolet light or KrF laser. The lower ends of the adjacent source electrodes on the oxide semiconductor film 412 are The width of the gap between the lower end of the drain electrode and the channel of the thin film transistor to be formed later is determined by the width of the gap between the lower end of the drain electrode and the channel of the thin film transistor to be formed later. When exposure is performed for a channel length L of less than 25 nm, the channel length L is determined by the Extreme ultraviolet rays have extremely short wavelengths of up to several tens of nanometers. The exposure is performed when forming a resist mask in the second photolithography process. Line exposure has high resolution and a large depth of focus. It is also possible to set the channel length L of the transistor to 10 nm or more and 1000 nm or less, and the operation of the circuit is This allows for faster operation speeds, and the extremely small off-state current also allows for lower power consumption. can.

[0167] Next, the insulating film 407, the oxide semiconductor film 412, and one of the source electrode and the drain electrode 41 5a, forming a gate insulating film 402 on the other of the source electrode and the drain electrode 415b (See Figure 13(C)).

[0168] By removing impurities, an oxide semiconductor that has been made i-type or substantially i-type (highly purified) Since the gate insulating film (oxide semiconductor) is extremely sensitive to the interface state and the interface charge, The interface with the gate insulating film 402 is important. The film 402 is required to have high quality.

[0169] For example, high density plasma CVD using microwaves (2.45 GHz) produces dense, high dielectric strength films. This is preferable because it allows the formation of a high-quality insulating film. By closely contacting the insulating film, the interface state is reduced and the interface characteristics are improved. Because it is possible.

[0170] Of course, if a good quality insulating film can be formed as a gate insulating film, sputtering is also possible. Other film formation methods such as the plasma CVD method and the like can also be applied. Even if the insulating film is one in which the film quality of the gate insulating film and the interface characteristics with the oxide semiconductor are modified by In any case, it is important that the quality of the gate insulating film is good, and that the oxidation Any material may be used as long as it can reduce the interface state density with the compound semiconductor and form a good interface.

[0171] Furthermore, at 85°C, 2 × 10 6V / cm, 12-hour gate bias thermal stress test (B In the T test, when impurities are added to an oxide semiconductor, the impurities and the oxide semiconductor The bond with the main component of is broken by a strong electric field (B: bias) and high temperature (T: temperature), and The dangling bonds induce a shift in the threshold voltage (Vth).

[0172] In response to this, impurities in the oxide semiconductor, especially hydrogen and water, are removed as much as possible, and the gate electrode is formed as described above. By improving the interface characteristics with the insulating film, the thin film transistor is stable even in BT tests. This makes it possible to obtain stars.

[0173] The gate insulating film 402 may be a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride film. A silicon oxide film or an aluminum oxide film can be formed as a single layer or a laminated layer. Note that the gate insulating film 402 is formed by sputtering. The hydrogen concentration can be reduced by forming a silicon oxide film by sputtering. In this case, a silicon target or a quartz target is used as the target, and the sputtering The gas used is oxygen or a mixed gas of oxygen and argon.

[0174] The gate insulating film 402 is formed on one of the source and drain electrodes 415a, The other side of the drain electrode 415b has a structure in which a silicon oxide film and a silicon nitride film are stacked. For example, the first gate insulating film may have a thickness of 5 nm to 300 nm. Silicon oxide film (SiO x (x>0)), and a second gate insulating film is formed on the first gate insulating film. Silicon nitride film with a thickness of 50 nm to 200 nm is used as an insulating film by sputtering. (SiNy (y>0)) to form a gate insulating film with a total thickness of 55 nm to 500 nm. In this embodiment, the pressure is 0.4 Pa, the high frequency power supply is 1.5 kW, and oxygen and and argon (oxygen flow rate 25 sccm: argon flow rate 25 sccm = 1:1) atmosphere. A silicon oxide film with a thickness of 100 nm is formed by F sputtering.

[0175] Next, a resist mask is formed by a third photolithography process, and selective etching is performed. A part of the gate insulating film 402 is removed by etching, and one of the source electrode and the drain electrode is removed. 415a, and openings 421a and 421b reaching the other of the source and drain electrodes 415b. b is formed (see FIG. 13(D)).

[0176] Next, a conductive film is formed on the gate insulating film 402 and the openings 421a and 421b, and then a fourth The gate electrode 411 and wirings 414a and 414b are formed by the photolithography process. The resist mask may be formed by an ink-jet method. When formed by the jet method, no photomask is used, which reduces manufacturing costs.

[0177] The gate electrode 411 and the wirings 414a and 414b are made of molybdenum, titanium, chromium, or titanium. Metallic materials such as tantalum, tungsten, aluminum, copper, neodymium, scandium, etc. The conductive film can be formed as a single layer or a multilayer using an alloy material containing these as a main component.

[0178] For example, the gate electrode 411 and the wirings 414a and 414b may have a two-layer laminate structure. Two-layer structure with molybdenum film stacked on aluminum film, or molybdenum film stacked on copper film Two-layer structure, or two-layer structure with titanium nitride or tantalum nitride film laminated on copper film Preferably, the structure is a two-layer structure in which a titanium nitride film and a molybdenum film are laminated. The laminated structure is composed of a tungsten film or a tungsten nitride film, and a layer of aluminum and silicon. A titanium nitride film or titanium film is laminated on an alloy of aluminum or an alloy of aluminum and titanium. It is preferable to form a gate electrode using a light-transmitting conductive film. Examples of the conductive film having light-transmitting properties include a light-transmitting conductive oxide. It is possible.

[0179] In this embodiment, the gate electrode 411 and the wirings 414a and 414b are formed by sputtering. A titanium film having a thickness of 150 nm is formed.

[0180] Next, a second heat treatment (preferably 20 The heating temperature is 0°C or higher and 400°C or lower, for example, 250°C or higher and 350°C or lower. A second heat treatment is carried out at 250°C for 1 hour in a nitrogen atmosphere. This may be performed after forming a protective insulating film or a planarizing insulating film on the film transistor 410 .

[0181] Furthermore, heat treatment is carried out in the atmosphere at 100°C to 200°C for 1 hour to 30 hours. It is also possible.

[0182] Through the above steps, the oxide semiconductor film 41 in which the concentrations of hydrogen, moisture, hydride, and hydroxide are reduced is formed. 13E, a thin film transistor 410 having the above structure can be fabricated.

[0183] Next, although not shown, the oxide insulating film 114 and the like shown in FIG. 2 are formed on the thin film transistor 410. A planarization insulating film 115 is provided for planarization. For example, the planarization insulating film may be a polyimide film. Heat-resistant organic compounds such as amide, acrylic, benzocyclobutene, polyamide, and epoxy. In addition to the above organic materials, low-k materials can also be used. , siloxane resin, PSG (phosphorus glass), BPSG (borophosphorus glass), etc. Furthermore, by stacking multiple insulating films made of these materials, it is possible to achieve flattening. An insulating film 115 may be formed.

[0184] Siloxane-based resin is a Si-OS compound formed using siloxane-based materials as starting materials. The siloxane resin corresponds to a resin containing an i bond. The organic group may have a fluoro group.

[0185] The method for forming the planarizing insulating film is not particularly limited, and may be a sputtering method, a SO G method, spin coating, dip coating, spray coating, droplet ejection method (inkjet method, screen Printing methods such as inkjet printing, offset printing, doctor knife, roll coater, Next, a protective insulating film and a planarizing film can be formed. An opening is formed in the insulating film to reach the wiring 414b that functions as a source electrode or a drain electrode. The opening is electrically connected to the wiring 414b which functions as a source electrode or a drain electrode. A connecting pixel electrode is formed (not shown).

[0186] When forming the oxide semiconductor film as described above, it is necessary to remove residual moisture in the reaction atmosphere. Therefore, the concentrations of hydrogen and hydride in the oxide semiconductor film can be reduced, and the oxide semiconductor film can be highly purified. This makes it possible to stabilize the oxide semiconductor film.

[0187] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0188] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0189] (Embodiment 3) In this embodiment, in addition to the thin film transistor that can be applied to the display panel disclosed in the first embodiment, The embodiment shows the same parts as those in the second embodiment or parts having similar functions, and steps. The same as in the second embodiment, and the repeated explanation will be omitted. The thin film transistor 460 described in this embodiment is the same as that described in Embodiment 1. It can be used as a thin film transistor 106 (see FIG. 2).

[0190] One mode of the thin film transistor and the manufacturing method of the thin film transistor of this embodiment is shown in FIGS. This will be explained with reference to FIG.

[0191] 14(A) and 14(B) show a plan view and a cross-sectional view of a thin film transistor. The thin film transistor 460 shown in (A) and (B) is a thin film transistor with a top gate structure. It is one.

[0192] FIG. 14(A) is a plan view of a thin film transistor 460 having a top gate structure, and FIG. 14(B) is a plan view of a thin film transistor 460 having a top gate structure. ) is a cross-sectional view taken along the dashed line AB in FIG. 14(A).

[0193] 14(A) and 14(B), the thin film transistor 460 is formed on the first substrate 45 0, an insulating film 457, source or drain electrodes 465a1 and 465a2, and an oxide The semiconductor film 462, the source electrode or the drain electrode 465b, the wiring 468, the gate insulating film 4 52, including a gate electrode 461 (461a, 461b), a source electrode or a drain electrode 465a1 and 465a2 are electrically connected to the wiring 464 via the wiring 468. Although not shown, a source electrode or a drain electrode 465b is also provided on the gate insulating film 452. The opening is electrically connected to the wiring.

[0194] 15(A) to 15(E), the thin film transistor 4 is formed on the first substrate 450. The process for producing 60 will be described.

[0195] First, an insulating film 457 serving as a base film is formed over a first substrate 450 .

[0196] In this embodiment, the insulating film 457 is formed in a manner similar to that of the insulating film 407 described in Embodiment 2. It is possible.

[0197] Next, a conductive film is formed over the insulating film 457 and is then subjected to a first photolithography process. A resist mask is formed on the surface, and selective etching is performed to form a source electrode or a drain electrode. After the electrodes 465a1 and 465a2 are formed, the resist mask is removed (see FIG. 15(A)). The source and drain electrodes 465a1 and 465a2 are shown separated in the cross-sectional view. Although the film is continuous, the edges of the source and drain electrodes are A tapered shape is preferable because it improves the coverage of the gate insulating film to be laminated thereon.

[0198] The source or drain electrodes 465a1 and 465a2 are the same as those of the source electrode shown in the second embodiment. The gate electrode or drain electrode 415a, 415b can be formed in the same manner.

[0199] Next, an oxide semiconductor film having a thickness of 2 nm to 200 nm is formed over the gate insulating film 452. Then, etching is performed using a resist mask formed by a second photolithography process. Thus, an island-shaped oxide semiconductor film 462 is formed (see FIG. 15B). The oxide semiconductor film to be the oxide semiconductor film 62 is the oxide semiconductor film to be the oxide semiconductor film 412 described in Embodiment 2. It can be formed in the same manner as the conductive film.

[0200] In this embodiment, similarly to Embodiment 2, the oxide semiconductor film 462 is subjected to first heat treatment. Depending on the conditions of the first heat treatment or the material of the oxide semiconductor film, the oxide semiconductor film In some cases, the film crystallizes to form a microcrystalline or polycrystalline film.

[0201] In addition, the first heat treatment of the oxide semiconductor film is performed on the oxide semiconductor film before it is processed into the island-shaped oxide semiconductor film. In this case, after the first heat treatment, the substrate is removed from the heating device. The substrate is taken out and subjected to a photolithography process.

[0202] The heat treatment that has the effect of dehydrating and dehydrogenating the oxide semiconductor film is performed after the oxide semiconductor film formation. After the formation of the oxide semiconductor film, a source electrode and a drain electrode are further laminated on the oxide semiconductor film. The deposition may be performed either after forming a gate insulating film on the gate electrode or after forming a gate insulating film on the drain electrode.

[0203] Next, a conductive film is formed over the insulating film 457 and the oxide semiconductor film 462, and then a third photolithography A resist mask is formed on the conductive film by a photolithography process, and selective etching is performed to form a thin film. After forming the source or drain electrode 465b and the wiring 468, the resist mask is removed. (See FIG. 15C.) The source or drain electrode 465b and the wiring 468 are The source and drain electrodes 465a1 and 465a2 may be formed using the same material and process. good.

[0204] In this embodiment, the source electrode or drain electrode 465b and the wiring 468 are formed by sputtering. A titanium film having a thickness of 150 nm is formed by a ring method. The source or drain electrodes 465a1 and 465a2 and the source or drain electrode 465b are connected to the same In this example, the same titanium film is used, and the source electrode or drain electrode 465a1, 465a2 The source electrode or the drain electrode 465b cannot be selectively etched. The source or drain electrodes 465a1 and 465a2 are connected to the source or drain electrodes 465a1 and 465a2. The oxide semiconductor film 462 is covered with the insulating film 464 so as not to be etched when the insulating film 464b is etched. A wiring 468 is provided on the source electrode or drain electrode 465a2 that is not separated. Electrodes or drain electrodes 465a1, 465a2 and source or drain electrodes 465 When different materials having high selectivity in the etching process are used, The wiring 468 for protecting the source electrode or the drain electrode 465a2 during welding is not necessarily provided. It's not necessary.

[0205] Note that the conductive film is etched so that the oxide semiconductor film 462 is not removed. The material and etching conditions are adjusted appropriately.

[0206] In this embodiment, a Ti film is used as the conductive film, and an In-Ga -Zn-O based oxide semiconductor is used, and ammonia hydrogen peroxide (ammonia, A mixture of water and hydrogen peroxide is used.

[0207] Note that in the etching after the second photolithography step, the oxide semiconductor film 462 is In some cases, only the portion is etched, resulting in an oxide semiconductor film having a groove (depression). , a resist mask for forming the source or drain electrode 465b, and the wiring 468. The resist mask may be formed by an ink-jet method. Since no photomask is used, manufacturing costs can be reduced.

[0208] Next, the insulating film 457, the oxide semiconductor film 462, the source or drain electrode 465a1 , 465a2, and the gate insulating film 452 is formed on the source electrode or the drain electrode 465b. do.

[0209] The gate insulating film 452 can be formed in a manner similar to that of the gate insulating film 402 described in Embodiment 2. can.

[0210] Next, a resist mask is formed by a fourth photolithography process, and selective etching is performed. A part of the gate insulating film 452 is removed by etching to form an opening 423 reaching the wiring 468. (See FIG. 15(D)). Although not shown, when the opening 423 is formed, the source electrode or the drain electrode In this embodiment, an opening reaching the source electrode or the inner electrode 465b may be formed. An opening to the drain electrode 465b is formed after laminating an interlayer insulating film. Alternatively, a wiring electrically connected to the drain electrode 465b is formed in the opening.

[0211] Next, after forming a conductive film on the gate insulating film 452 and the opening 423, a fifth photolithography is performed. Etching is performed using a resist mask formed by a lithography process to form a gate electrode 46. 1 (461a, 461b), and wiring 464 are formed. If the resist mask is formed by the ink-jet method, the photomask Since no additional materials are used, the manufacturing cost can be reduced.

[0212] The gate electrode 461 (461a, 461b) and the wiring 464 are the same as those of the gate electrode shown in Embodiment 2. The port electrode 411 can be formed in the same manner as the wirings 414a and 414b.

[0213] Next, similarly to the second embodiment, a second heating process is carried out in an inert gas atmosphere or an oxygen gas atmosphere. Heat treatment (preferably at 200°C or higher and 400°C or lower, for example, at 250°C or higher and 350°C or lower) is carried out. cormorant.

[0214] Furthermore, similarly to the second embodiment, the heating is carried out in the atmosphere at 100°C or higher and 200°C or lower for 1 hour or higher and 30 hours or lower. Heat treatment may be carried out for 1 hour or less.

[0215] Through the above steps, the oxide semiconductor film 46 in which the concentrations of hydrogen, moisture, hydride, and hydroxide are reduced is formed. 15E, a thin film transistor 460 having the same structure as in FIG.

[0216] Next, although not shown, the oxide insulating film 114 and the like shown in FIG. 2 are formed on the thin film transistor 460. Next, a planarization insulating film 115 is provided for planarization. An opening is formed that reaches the source electrode or drain electrode 465b, and the opening is The pixel electrode electrically connected to the drain electrode 465b is formed (not shown).

[0217] When forming the oxide semiconductor film as described above, it is necessary to remove residual moisture in the reaction atmosphere. Therefore, the concentrations of hydrogen and hydride in the oxide semiconductor film can be reduced, and the oxide semiconductor film can be highly purified. This makes it possible to stabilize the oxide semiconductor film.

[0218] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0219] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0220] (Fourth embodiment) In this embodiment, in addition to the thin film transistor that can be applied to the display panel disclosed in the first embodiment, The embodiment shows the same parts as those in the second embodiment or parts having similar functions, and steps. The same as in the second embodiment, and the repeated explanation will be omitted. Detailed description is omitted. It can be used as the thin film transistor 106 of form 1 (see FIG. 2).

[0221] The thin film transistor of this embodiment mode will be described with reference to FIG.

[0222] 16(A) and 16(B) show one example of a cross-sectional structure of a thin film transistor. Thin film transistors 425 and 426 shown in B) each have an oxide semiconductor film as a conductive film and a gate electrode. It is a type of thin film transistor that has a structure in which a film is sandwiched between two electrodes.

[0223] 16(A) and 16(B), the first substrate 450 is the same as the substrate 4 shown in the second embodiment. 00 can be used. Alternatively, a silicon wafer can be used as the first substrate 450. Thin film transistors 425 and 426 are formed on an insulating film 422 provided on a first substrate 450. are provided respectively.

[0224] In FIG. 16A, the insulating film 422 and the insulating film 407 are formed on the first substrate 450. A conductive film 427 is provided between the oxide semiconductor film 412 and the conductive film 427 so as to overlap with at least the entire oxide semiconductor film 412. .

[0225] 16B, the conductive film between the insulating film 422 and the insulating film 407 is the conductive film 424. At least a part of the oxide semiconductor film 412 including the channel formation region is etched so as to It overlaps with.

[0226] The conductive films 427 and 424 can be made of any metal material that can withstand the heat treatment temperature in the subsequent process. Titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), An element selected from chromium (Cr), neodymium (Nd), scandium (Sc), or An alloy containing the above elements as components, an alloy film containing a combination of the above elements, or an alloy film containing the above elements as components Nitrides containing silicon as a component can be used. In addition, either a single layer structure or a laminated structure can be used. For example, a single layer of tungsten film or a laminated structure of a tungsten nitride film and a tungsten film. etc. can be used.

[0227] The conductive films 427 and 424 have a potential that is different from that of the gate electrodes 424 of the thin film transistors 425 and 426. 11 may be the same as or different from 11 and may function as a second gate electrode. In addition, the potential of the conductive films 427 and 424 is a fixed potential such as GND or 0V. Good too.

[0228] The conductive films 427 and 424 control the electrical characteristics of the thin film transistors 425 and 426. It is possible.

[0229] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0230] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0231] (Embodiment 5) This embodiment relates to a thin film transistor type that can be applied to the display panel disclosed in the first embodiment. Indicates attitude.

[0232] One mode of the thin film transistor and the manufacturing method of the thin film transistor of this embodiment mode will be described with reference to FIGS. This will be used to explain.

[0233] 17A to 17E show one mode of a cross-sectional structure of a thin film transistor. The thin film transistor 390 shown in (E) is one of the bottom gate structures, and has an inverted staggered structure. It is also called a thin film transistor.

[0234] The thin film transistor 390 will be described using a thin film transistor with a single gate structure. However, if necessary, a multi-channel structure having a plurality of channel forming regions may be used. A thin film transistor with a gate structure can also be formed.

[0235] 17A to 17E, a thin film transistor 390 is formed on a first substrate 394. The manufacturing process will be described.

[0236] First, a conductive film is formed on a first substrate 394, and then a first photolithography process is performed. The formed resist mask is used to perform etching to form a gate electrode 391. If the end of the gate electrode is tapered, the coverage of the gate insulating film to be laminated later is improved. The resist mask may be formed by an ink-jet method. When the inkjet method is used to form the mask, no photomask is required, which reduces manufacturing costs. Cut.

[0237] There is no significant limitation on the substrate that can be used for the first substrate 394. Among the substrates that can be used as the first substrate 11 shown in the first embodiment, In addition, it is preferable to use a substrate that has at least a heat resistance sufficient to withstand the subsequent heat treatment. This can be done.

[0238] An insulating film serving as a base film may be provided between the first substrate 394 and the gate electrode 391. The film has a function of preventing the diffusion of impurity elements from the first substrate 394. The insulating film 407 can be formed in the same manner as the insulating film 407 serving as a base film shown in FIG.

[0239] The gate electrode 391 is formed in the same manner as the gate electrode 411 shown in Embodiment 2. can be done.

[0240] Next, a gate insulating film 397 is formed on the gate electrode 391 .

[0241] The gate insulating film 397 can be formed in a manner similar to that of the gate insulating film 402 described in Embodiment 2. can.

[0242] The gate insulating film 397 is formed by stacking a silicon nitride film and a silicon oxide film from the gate electrode 391 side. For example, a structure in which a first gate insulating film is formed by sputtering can be used. Silicon nitride film (SiN) with a thickness of 50 nm or more and 200 nm or less y (y>0) A second gate insulating film is formed on the first gate insulating film with a thickness of 5 nm to 300 nm. Silicon film (SiO x (x>0)) to form a gate having a thickness of 55 nm to 500 nm. The insulating film can be formed of a thin film.

[0243] In addition, the gate insulating film 397 and the oxide semiconductor film 393 contain hydrogen, a hydroxyl group, and moisture as much as possible. In order to prevent this, a gate electrode is placed in the preheating chamber of the sputtering equipment as a pretreatment for film formation. The first substrate 394 on which the gate electrode 391 is formed or the gate insulating film 397 is formed. The first substrate 394 is preheated to remove impurities such as hydrogen and moisture adsorbed on the first substrate 394. It is preferable to desorb and exhaust the substances. The temperature is 0°C or less, preferably 150°C to 300°C. A cryopump is preferably used for the first stage. However, this preheating process can be omitted. This preheating is performed before the oxide insulating film 396 is formed. The same process may be carried out on the first substrate 394 on which the pole 395b has been formed.

[0244] Next, an oxide semiconductor film 393 having a thickness of 2 nm to 200 nm is formed over the gate insulating film 397. (See FIG. 17(A)).

[0245] Note that before the oxide semiconductor film 393 is formed by a sputtering method, argon gas is introduced. The reverse sputtering is performed by introducing the silicon dioxide into the silicon dioxide particles to generate plasma, and the silicon dioxide particles adhere to the surface of the gate insulating film 397. It is preferable to remove any dust particles that may be present in the atmosphere. etc. may also be used.

[0246] The oxide semiconductor film 393 can be formed in a manner similar to that of the oxide semiconductor film described in Embodiment 2. do.

[0247] Next, the oxide semiconductor film is covered with a resist mask formed by a second photolithography process. Etching is performed using the oxide semiconductor film 396 to form an island-shaped oxide semiconductor film 396 (see FIG. 17B). In addition, a resist mask for forming the island-shaped oxide semiconductor film 396 is formed by inkjet printing. If the resist mask is formed by the ink-jet method, the photomask Since no external power supply is used, manufacturing costs can be reduced.

[0248] In addition, when a contact hole is formed in the gate insulating film 397, the process is performed using an oxide semiconductor This can be done when the membrane 399 is formed.

[0249] Note that the oxide semiconductor film 393 is etched in this case by etching the oxide semiconductor film 393 described in Embodiment 2. Any suitable film etching method can be used.

[0250] Note that reverse sputtering is performed before forming a conductive film in the next step, and the oxide semiconductor film 399 and the gate electrode 396 are formed. It is preferable to remove resist residues and the like adhering to the surface of the photoinsulating film 397.

[0251] Next, a source electrode 395 a and a drain electrode 395 b are formed on the gate insulating film 397 and the oxide semiconductor film 399 . A source electrode 395a and a drain electrode 395b are formed (see FIG. 17(C)). The electrode 395b is the same as the source electrode and the drain electrode 415a and 415b shown in the second embodiment. It can be formed into.

[0252] During etching in the process of manufacturing the source electrode 395a and the drain electrode 395b, The materials and etching conditions are appropriately adjusted so that the oxide semiconductor film 399 is not removed. Adjust.

[0253] Next, the exposed surface is treated with a plasma using gases such as N2O, N2, or Ar. Water or the like attached or adsorbed on the surface of the oxide semiconductor film may be removed. Alternatively, the plasma treatment may be performed using a gas mixture of argon and argon.

[0254] When plasma treatment is performed, the protective layer in contact with a part of the oxide semiconductor film is not exposed to the air. An oxide insulating film 396 is formed as an oxide insulating film functioning as an insulating film (FIG. 17(D)). In this embodiment, the oxide semiconductor film 399 serves as the source electrode 395a and the drain electrode 395b. In a region not overlapping with the electrode 395b, the oxide semiconductor film 399 and the oxide insulating film 396 Form it so that it touches.

[0255] In this embodiment, the oxide insulating film 396 is an island-shaped oxide semiconductor film 399, a source electrode The first substrate 394, on which the electrode 395a and the drain electrode 395b have been formed, is heated at room temperature or 100 A sputtering gas containing high-purity oxygen from which hydrogen and moisture have been removed is introduced. A silicon oxide film containing defects is formed using a silicon target.

[0256] For example, the purity of the sputtering gas is 6N, and a boron-doped silicon target ( Resistance value 0.01Ωcm) and set the distance between the substrate and the target (TS distance) to 89 mm, pressure 0.4 Pa, direct current (DC) power supply 6 kW, oxygen (oxygen flow rate 100%) atmosphere A silicon oxide film is formed by pulse DC sputtering under the SiO2 layer. The film thickness is 300 nm. In place of the silicon target, quartz (preferably synthetic quartz) is used to form a silicon oxide film. It can be used as a target for forming a film. Alternatively, a mixed gas of oxygen and argon may be used.

[0257] In this case, the oxide insulating film 396 is formed while removing the remaining moisture in the processing chamber. It is preferable that hydrogen, a hydroxyl group, or moisture be contained in the oxide semiconductor film 399 and the oxide insulating film 396. To remove residual moisture in the processing chamber, an adsorption type It is preferable to use an empty pump.

[0258] Note that as the oxide insulating film 396, a silicon oxynitride film or an oxide An aluminum film, an aluminum oxynitride film, or the like can also be used.

[0259] Further, the oxide insulating film 396 was heated at 100° C. or higher while being in contact with part of the oxide semiconductor film 399. Heat treatment may be performed at temperatures up to 400° C. In this embodiment, the oxide insulating film 396 has a defect-free structure. Since the oxide semiconductor film 399 contains a large amount of hydrogen, moisture, and Impurities such as hydroxyl groups or hydrides are diffused into the oxide insulating film 396, and the oxide semiconductor film 3 The impurities contained in the hydrogen 99 can be further reduced by the above heat treatment. Thus, an oxide semiconductor film 392 in which the concentration of moisture, hydroxyl groups, or hydrides is reduced is formed.

[0260] The oxide semiconductor film 3 in which the concentration of hydrogen, moisture, hydroxyl groups, or hydrides is reduced through the above steps is obtained. A thin film transistor 390 having the gate insulating film 92 can be fabricated (see FIG. 17(E)).

[0261] When forming the oxide semiconductor film as described above, it is necessary to remove residual moisture in the reaction atmosphere. As a result, the concentrations of hydrogen and hydride in the oxide semiconductor film can be reduced. The oxide semiconductor film can be stabilized.

[0262] A protective insulating film may be provided over the oxide insulating film. The protective insulating film 398 is formed on the oxide insulating film 396. The protective insulating film 398 is formed of a silicon nitride film, a nitride oxide film, or the like. A silicon film, an aluminum nitride film, an aluminum nitride oxide film, or the like is used.

[0263] The first substrate 394 on which the oxide insulating film 396 was formed was then heated to 100°C. Sputtering gas containing high-purity nitrogen heated to a temperature of ℃ to 400℃ and from which hydrogen and moisture have been removed In this case, too, a silicon nitride film is formed using a silicon target. Similarly to the oxide insulating film 396, a protective insulating film 398 is formed while removing moisture remaining in the treatment chamber. It is preferable to do so.

[0264] When forming the protective insulating film 398, the temperature is set to 100° C. to 400° C. during the formation of the protective insulating film 398. The substrate 394 is heated to oxidize hydrogen or moisture contained in the oxide semiconductor film. In this case, after the oxide insulating film 396 is formed, a heat treatment is performed. There is no need to carry out the theory.

[0265] A silicon oxide film is formed as the oxide insulating film 396, and a silicon nitride film is formed as the protective insulating film 398. When stacking silicon oxide and silicon nitride films, the silicon oxide film and silicon nitride film are processed in the same processing chamber using a common sintering process. A silicon target can be used for film formation. A silicon oxide film is formed using a silicon target installed in the processing chamber, and then the The sputtering gas was changed to one containing nitrogen, and the same silicon target was used. The silicon oxide film and the silicon nitride film are formed continuously without being exposed to the atmosphere. Therefore, impurities such as hydrogen and moisture are adsorbed on the surface of the silicon oxide film. In this case, a silicon oxide film is formed as the oxide insulating film 396. After a silicon nitride film is stacked as a protective insulating film 398, A heat treatment (at a temperature of 100° C. to 400° C.) is performed to diffuse hydrogen or moisture into the oxide insulating film. 00℃).

[0266] After the formation of the protective insulating film, similarly to the second embodiment, the substrate is heated in the atmosphere at a temperature of 100° C. to 200° C. In this case, heat treatment may be carried out for 1 hour to 30 hours. This allows for the production of thin film transistors that are turned off, thereby improving the reliability of the display panel. It can be done.

[0267] In addition, when an oxide semiconductor film serving as a channel formation region is formed on a gate insulating film, a reaction By removing residual moisture in the atmosphere, the concentrations of hydrogen and hydride in the oxide semiconductor film are reduced. can be reduced.

[0268] Next, although not shown, a planarizing insulating film for planarization as shown in FIG. 2 is formed on the protective insulating film 398. Next, a source electrode or a drain electrode may be formed on the protective insulating film or the planarizing insulating film. An opening is formed in the opening, reaching the source electrode or the drain electrode 395b. A pixel electrode (not shown) is formed to electrically connect to the

[0269] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0270] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0271] (Embodiment 6) In this embodiment, in addition to the thin film transistor that can be applied to the display panel disclosed in the first embodiment, The thin film transistor 310 shown in this embodiment is the same as the thin film transistor of Embodiment 1. The transistor 106 (see FIG. 2) can be used.

[0272] One embodiment of the thin film transistor and the manufacturing method of the thin film transistor of this embodiment will be described with reference to FIG. and explain.

[0273] 18A to 18E show one mode of a cross-sectional structure of a thin film transistor. The thin film transistor 310 shown in (E) is one of the bottom gate structures and is an inverted stagger type. Also called a thin film transistor.

[0274] The thin film transistor 310 is described using a thin film transistor with a single gate structure. However, if necessary, a thin-film transistor with a multi-gate structure having multiple channel forming regions may be used. A data can also be formed.

[0275] 18A to 18E, a thin film transistor 310 is formed on a first substrate 300. The manufacturing process will be described.

[0276] First, a conductive film is formed on a first substrate 300, and then a first photolithography process is performed. The formed resist mask is used to perform etching to form a gate electrode 311. The resist mask may be formed by an inkjet method. When the film is formed by the method described above, no photomask is used, and therefore the manufacturing cost can be reduced.

[0277] The first substrate 11 described in Embodiment 1 can be used as the first substrate 300 as appropriate.

[0278] An insulating film serving as a base film may be provided between the first substrate 300 and the gate electrode 311. The film has a function of preventing the diffusion of impurity elements from the first substrate 300. The insulating film 407 can be formed in the same manner as the insulating film 407 serving as a base film shown in FIG.

[0279] The gate electrode 311 is formed in the same manner as the gate electrode 411 shown in Embodiment 2. can be done.

[0280] Next, a gate insulating film 302 is formed on the gate electrode 311 .

[0281] The gate insulating film 302 can be formed in a manner similar to that of the gate insulating film 402 described in Embodiment 2. can.

[0282] Next, an oxide semiconductor film 330 having a thickness of 2 nm to 200 nm is formed on the gate insulating film 302. Form.

[0283] Before the oxide semiconductor film 330 was formed by a sputtering method, argon gas was introduced. The reverse sputtering is performed by introducing the silicon dioxide into the gate insulating film 302 to generate plasma. It is preferable to remove any dust particles that may be present in the atmosphere. etc. may also be used.

[0284] The oxide semiconductor film 330 can be formed in a manner similar to that of the oxide semiconductor film described in Embodiment 2. In this embodiment, the oxide semiconductor film 330 is an In—Ga—Zn—O-based oxide film. The cross section at this stage is shown in Figure 18(A). is equivalent to

[0285] The substrate is held in a processing chamber maintained in a reduced pressure state, and the substrate temperature is maintained at 100°C or higher and 600°C or higher. The temperature is preferably 200°C or higher and 400°C or lower. This allows the concentration of impurities contained in the formed oxide semiconductor film to be reduced. Damage caused by tarring is reduced. A sputtering gas from which moisture has been removed is introduced, and a metal oxide is used as a target to sputter the first substrate 30. In order to remove residual moisture in the processing chamber, an oxide semiconductor film 330 is formed on the surface of the processing chamber. It is preferable to use a vacuum pump of this type. For example, a cryopump, an ion pump, a titanium It is preferable to use a sublimation pump. A cryopump with a cold trap may be used. The treatment chamber is filled with, for example, hydrogen atoms, compounds containing hydrogen atoms such as water (H2O) (more preferably Since the exhaust gas (including compounds containing carbon atoms) is exhausted, the oxide semiconductor film formed in the treatment chamber is The concentration of impurities contained can be reduced.

[0286] Next, the oxide semiconductor film 330 is subjected to a second photolithography process to form an island-shaped oxide semiconductor film. The oxide semiconductor film 331 is then processed into an island-shaped oxide semiconductor film 331. The resist mask may be formed by an ink-jet method. Since no photomask is used, manufacturing costs can be reduced.

[0287] Next, the oxide semiconductor film is subjected to first heat treatment in a manner similar to that of Embodiment 2. The oxide semiconductor film can be dehydrated or dehydrogenated by the treatment (FIG. 18(B)). )reference.).

[0288] The first heat treatment of the oxide semiconductor film is performed after the oxide semiconductor film is processed into the island-shaped oxide semiconductor film 331. The oxide semiconductor film 330 can also be subjected to the first heat treatment. The substrate is removed from the device and subjected to a photolithography process.

[0289] The heat treatment that has the effect of dehydrating and dehydrogenating the oxide semiconductor film is performed after the oxide semiconductor film formation. After the oxide semiconductor film is formed, a source electrode and a drain electrode are laminated on the oxide semiconductor film. After forming a protective insulating film on the drain electrode, the step may be performed at any time.

[0290] In addition, when forming a contact hole in the gate insulating film 302, the process is performed using an oxide semiconductor. This may be done before or after the membrane is subjected to a dehydration or dehydrogenation treatment.

[0291] Note that the etching of the oxide semiconductor film here is not limited to wet etching, but may be dry etching. Etching may be used. The etching conditions (etchant, etching time, temperature, etc.) are adjusted appropriately according to the material. do.

[0292] Next, a source electrode 315a and a drain electrode 315b are formed on the gate insulating film 302 and the oxide semiconductor film 331. A source electrode 315a and a drain electrode 315b are formed (see FIG. 18(C)). The electrode 315b is the same as the source electrode and the drain electrode 415a and 415b shown in the second embodiment. It can be formed into.

[0293] In addition, when etching is performed to form the source electrode 315a and the drain electrode 315b, an acid The materials and etching conditions are appropriately adjusted so that the nitride semiconductor film 331 is not removed. do.

[0294] In addition, an oxide conductive film may be formed between the oxide semiconductor film and the source electrode and the drain electrode. The oxide conductive film and the metal film for forming the source and drain electrodes are successively formed. The oxide conductive film can function as a source region and a drain region.

[0295] The oxide conductive film is formed as a source region and a drain region, and the oxide semiconductor film is formed as a source electrode and a drain electrode. By providing it between the source and drain electrodes, it is possible to reduce the resistance of the source and drain regions. This allows the transistor to operate at high speed.

[0296] Next, plasma treatment is performed using gas such as N2O, N2, or Ar. The treatment removes water or the like attached or adsorbed on the exposed surface of the oxide semiconductor film. Alternatively, the plasma treatment may be performed using a mixed gas of oxygen and argon.

[0297] After the plasma treatment, the protective insulating film in contact with a part of the oxide semiconductor film was An oxide insulating film 316 serving as an insulating film is formed.

[0298] The oxide insulating film 316 has a thickness of at least 1 nm and is formed by an oxide method such as a sputtering method. The insulating film 316 can be formed by using an appropriate method that does not allow impurities such as water and hydrogen to be mixed in. When hydrogen is contained in the oxide insulating film 316, the hydrogen can penetrate into the oxide semiconductor film or The oxygen in the oxide semiconductor film is extracted by hydrogen or the back-channel of the oxide semiconductor film. The panel may become N-type (low resistance), which may result in the formation of a parasitic channel. The oxide insulating film 316 is formed using a method that does not use hydrogen so that the oxide insulating film 316 contains as little hydrogen as possible. It is important that there is no

[0299] In this embodiment, the oxide insulating film 316 is formed by a sputtering method to a thickness of 200 nm. The substrate temperature during film formation should be between room temperature and 300°C. In this embodiment, the temperature is set to 100° C. The silicon oxide film is formed by sputtering using a rare gas ( In an atmosphere of oxygen, or in a rare gas atmosphere (typically argon) The target can be a silicon oxide target. For example, a silicon target can be used to form an oxide film. Silicon oxide can be formed by sputtering in a hydrogen or nitrogen atmosphere. The oxide insulating film 316 formed in contact with the oxide semiconductor film is resistant to moisture, hydrogen ions, and , O.H. - Inorganic insulation that does not contain impurities such as Typically, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or For example, an aluminum oxide nitride film is used.

[0300] In this case, the oxide insulating film 316 is formed while removing the remaining moisture in the processing chamber. It is preferable that hydrogen, a hydroxyl group, or moisture be contained in the oxide semiconductor film 331 and the oxide insulating film 316. To remove residual moisture in the processing chamber, an adsorption type It is preferable to use an empty pump.

[0301] The oxide insulating film 316 is formed using a sputtering gas containing hydrogen, water, a hydroxyl group, or a hydrogen atom. High-purity gas is used, in which impurities such as chlorine have been removed to concentrations of ppm or ppb. It is preferable that

[0302] Next, similarly to the second embodiment, a second heating process is carried out in an inert gas atmosphere or an oxygen gas atmosphere. Heat treatment (preferably at 200°C or higher and 400°C or lower, for example, at 250°C or higher and 350°C or lower) is carried out. In the second heat treatment, part of the oxide semiconductor film (channel formation region) is covered with the oxide insulating film 3. It is heated in contact with 16.

[0303] Through the above steps, the oxide semiconductor film 312 after deposition is dehydrated or dehydrogenated. After the heat treatment for reducing the resistance, a part of the oxide semiconductor film 312 is selectively treated with an oxygen-excess solution. As a result, the channel forming region 313 overlapping with the gate electrode 311 becomes I-shaped. The source electrode 315a and the drain electrode 315b are made of titanium (Ti). a high-resistance source region in contact with the source electrode 315a, and a high-resistance source region in contact with the drain electrode 315b. The resistive drain region is formed in a self-aligned manner. (See FIG. 18(D)).

[0304] Furthermore, similarly to the second embodiment, the heating is carried out in the atmosphere at 100°C or higher and 200°C or lower for 1 hour or higher and 30 hours or lower. In this embodiment, the heat treatment is performed at 150° C. for 10 hours. By this heat treatment, hydrogen is taken into the oxide insulating film from the oxide semiconductor film, and Therefore, the reliability of the display panel can be improved. Furthermore, if a silicon oxide film containing many defects is used as the oxide insulating film, the heating The treatment reduces impurities such as hydrogen, moisture, a hydroxyl group, or hydride contained in the oxide semiconductor film. The impurities contained in the oxide semiconductor film are diffused into the oxide insulating film, and the impurities are further reduced. To bear fruit.

[0305] If the source electrode 315a and the drain electrode 315b are made of titanium (Ti), At the interface between the drain electrode 315b (and the source electrode 315a) and the oxide semiconductor film, By forming a high-resistance drain region (or a high-resistance source region) in Specifically, the high-resistance drain region is formed. As a result, the drain electrode 315b, the high-resistance drain region, and the channel forming region 313 Therefore, the drain electrode can be made to have a structure in which the conductivity can be changed stepwise. When the electrode 315b is connected to a wiring that supplies a high power supply potential, the gate electrode 311 Even if a high voltage is applied between the drain electrode 315b and the high-resistance drain region, the high-resistance drain region acts as a buffer. This makes it difficult for local electric field concentration to occur, and the breakdown voltage of the transistor can be improved. can.

[0306] The high-resistance source region or the high-resistance drain region in the oxide semiconductor film is formed by using an oxide semiconductor. When the thickness of the conductive film is thin, 15 nm or less, it is formed throughout the film thickness direction. When the thickness of the semiconductor film is greater than 30 nm and less than 50 nm, a part of the oxide semiconductor film, The region in contact with the source electrode or drain electrode and its vicinity become highly resistive, resulting in a high-resistance source region. A high-resistance drain region or a high-resistance drain region is formed in the oxide semiconductor film, and a region close to the gate insulating film is formed in the oxide semiconductor film. The region can also be type I.

[0307] A protective insulating film may be further formed on the oxide insulating film 316. For example, RF sputtering The RF sputtering method is suitable for mass production, so it is suitable for protection. This is a preferred method for forming an insulating film. The protective insulating film is formed by absorbing moisture, hydrogen ions, and OH - etc. It does not contain impurities and uses an inorganic insulating film that blocks the penetration of these substances from the outside. Silicon film, aluminum nitride film, silicon nitride oxide film, aluminum nitride oxide film, etc. In this embodiment, a silicon nitride film is used as the protective insulating film 303. (See FIG. 18(E)).

[0308] In this embodiment, the protective insulating film 303 is formed from a first insulating film including the oxide insulating film 316. The substrate 300 is heated to a temperature of 100 to 400° C., and high-purity nitrogen from which hydrogen and moisture have been removed is used. A sputtering gas containing the compound is introduced, and a silicon nitride film is formed using a silicon target. In this case, similarly to the oxide insulating film 316, the remaining moisture in the treatment chamber is removed and the protection film is formed. It is preferable to form an insulating film 303 .

[0309] Next, although not shown, a planarizing insulating film for planarization as shown in FIG. 2 is formed on the protective insulating film 303. Next, a source electrode or a drain electrode 31 is formed on the protective insulating film or the planarizing insulating film. 5b, and the source electrode or drain electrode 315b is electrically connected to the opening. Then, pixel electrodes are formed to electrically connect the electrodes (not shown).

[0310] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0311] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0312] (Embodiment 7) In this embodiment, in addition to the thin film transistor that can be applied to the display panel disclosed in the first embodiment, The thin film transistor 360 shown in this embodiment is the same as the thin film transistor of Embodiment 1. The transistor 106 (see FIG. 2) can be used.

[0313] One mode of the thin film transistor and the manufacturing method of the thin film transistor of this embodiment will be described with reference to FIGS. This will be used to explain.

[0314] 19A to 19D show one mode of a cross-sectional structure of a thin film transistor. The thin film transistor 360 shown in (D) is a channel protection type (also called a channel stop type). It is one of the bottom gate structures known as inverted staggered thin film transistors. .

[0315] The thin film transistor 360 is described using a thin film transistor with a single gate structure. However, if necessary, a thin-film transistor with a multi-gate structure having multiple channel forming regions may be used. A data can also be formed.

[0316] 19A to 19D, a thin film transistor 360 is formed on a first substrate 320. The manufacturing process will be described.

[0317] First, a conductive film is formed on a first substrate 320, and then a first photolithography process is performed. The formed resist mask is used to perform etching to form a gate electrode 361. The resist mask may be formed by an inkjet method. When the film is formed by the method described above, no photomask is used, and therefore the manufacturing cost can be reduced.

[0318] The gate electrode 361 can be formed in a manner similar to that of the gate electrode 411 described in Embodiment 2. do.

[0319] Next, the gate insulating film 322 is formed on the gate electrode 361 .

[0320] The gate insulating film 322 can be formed in a manner similar to that of the gate insulating film 402 described in Embodiment 2. can.

[0321] Next, an oxide semiconductor film having a thickness of 2 nm to 200 nm is formed over the gate insulating film 322. The oxide semiconductor film is then processed into an island-shaped oxide semiconductor film by a second photolithography process. The oxide semiconductor film can be formed in a manner similar to that of the oxide semiconductor film described in Embodiment 2. In this study, we used an In-Ga-Zn-O oxide semiconductor target to form an oxide semiconductor film. It is formed by a sputtering method.

[0322] In this case, it is preferable to form the oxide semiconductor film while removing residual moisture in the treatment chamber. This is preferable in order to prevent hydrogen, a hydroxyl group, or moisture from being contained in the oxide semiconductor film. To remove residual moisture from the processing chamber, it is preferable to use an adsorption type vacuum pump.

[0323] Next, the oxide semiconductor film is dehydrated or dehydrogenated. The temperature of the heat treatment is 400°C or higher and 750°C or lower, preferably 400°C or higher and lower than the strain point of the substrate. Here, the substrate is introduced into an electric furnace, which is one of heat treatment devices, and an oxide semiconductor The film was heat-treated at 450°C for 1 hour in a nitrogen atmosphere, and then exposed to the air. The oxide semiconductor film 332 is obtained without any problem, preventing water or hydrogen from re-entering the oxide semiconductor film (FIG. See 19(A). ).

[0324] Next, plasma treatment is performed using gas such as N2O, N2, or Ar. The treatment removes adsorbed water and the like attached to the exposed surface of the oxide semiconductor film. Alternatively, the plasma treatment may be performed using a mixed gas of oxygen and argon.

[0325] Next, an oxide insulating film is formed over the gate insulating film 322 and the oxide semiconductor film 332. A resist mask is formed by a third photolithography process, and selective etching is performed. After the oxide insulating film 366 is formed, the resist mask is removed.

[0326] The oxide insulating film 366 can be formed in a manner similar to that of the oxide insulating film 316 described in Embodiment 6. When the oxide insulating film 366 is formed, the oxide insulating film 366 is formed by removing moisture remaining in the treatment chamber. It is preferable to form an insulating film. This is to prevent the inclusion of hydroxyl groups or moisture. For this purpose, it is preferable to use an adsorption type vacuum pump.

[0327] Next, the second heating is carried out in an inert gas atmosphere or an oxygen gas atmosphere in the same manner as in the second embodiment. Heat treatment (preferably at 200°C or higher and 400°C or lower, for example, at 250°C or higher and 350°C or lower) is carried out. It is also possible.

[0328] In this embodiment, an oxide insulating film 366 is further provided over the oxide semiconductor film 332. The oxide semiconductor film 332 where the surface is exposed is heated under a nitrogen or inert gas atmosphere or under reduced pressure. The exposed oxide semiconductor film 3 that is not covered with the oxide insulating film 366 is then subjected to heat treatment. In the region 32, when heat treatment is performed under nitrogen, an inert gas atmosphere, or reduced pressure, the resistance becomes low. For example, heat treatment can be performed at 250° C. for 1 hour in a nitrogen atmosphere.

[0329] Heat treatment in a nitrogen atmosphere on the oxide semiconductor film 332 provided with the oxide insulating film 366 As a result, the exposed region of the oxide semiconductor film 332 has a low resistance, and the region with a different resistance (FIG. 19( In B), the oxide semiconductor film 362 has a region indicated by hatched areas and a white region.

[0330] Next, a conductive film was formed over the gate insulating film 322, the oxide semiconductor film 362, and the oxide insulating film 366. After forming the film, a resist mask is formed by a fourth photolithography process. After etching the surface to form a source electrode 365a and a drain electrode 365b, The mask is removed (see FIG. 19(C)).

[0331] The source electrode 365a and the drain electrode 365b are the same as those shown in the second embodiment. The conductive layer 415 can be formed in the same manner as the conductive electrodes 415a and 415b.

[0332] Through the above steps, the oxide semiconductor film after deposition is dehydrated or dehydrogenated. After the first heat treatment for reducing the resistance, a part of the oxide semiconductor film is selectively oxidized. As a result, the channel forming region 363 overlapping the gate electrode 361 is in an excessive state. The source electrode 365a and the drain electrode 365b are made of titanium (Ti). When the semiconductor device is fabricated, a high-resistance source region contacting the source electrode 365a and a high-resistance source region contacting the drain electrode 365b are formed. The high-resistance drain region is formed in a self-aligned manner. 60 will be produced.

[0333] Furthermore, similarly to the second embodiment, the heating is carried out in the atmosphere at 100°C or higher and 200°C or lower for 1 hour or higher and 30 hours or lower. By this heat treatment, the oxide semiconductor film is converted into an oxide film. Hydrogen is taken into the insulating film, and a normally-off thin film transistor can be obtained. This improves the reliability of the display panel.

[0334] If the source electrode 365a and the drain electrode 365b are made of titanium (Ti), At the interface between the drain electrode 365b (and the source electrode 365a) and the oxide semiconductor film, By forming a high-resistance drain region (or a high-resistance source region) in Specifically, the high-resistance drain region is formed. As a result, the drain electrode, the high resistance drain region, and the channel forming region 363 are electrically conductive. Therefore, the drain electrode 36 can be made to have a structure in which the property can be changed stepwise. When the gate electrode 361 and the gate electrode 5b are connected to a wiring that supplies a high power supply potential VDD, Even if a high voltage is applied between the drain electrode 365b and the high resistance drain region, the high resistance drain region acts as a buffer. This makes it difficult for local electric field concentration to occur, and improves the breakdown voltage of the transistor. Cut.

[0335] A protective insulating film 323 is formed on the source electrode 365a, the drain electrode 365b, and the oxide insulating film 366. In this embodiment, the protective insulating film 323 is formed using a silicon nitride film (see FIG. See 19(D). ).

[0336] Next, although not shown, a planarizing insulating film for planarization as shown in FIG. 2 is formed on the protective insulating film 323. Next, a protective insulating film or a planarizing insulating film is formed on the drain electrode 365b. An opening is formed in the opening, and a pixel electrode electrically connected to the drain electrode 365b is formed in the opening. (not shown).

[0337] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0338] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0339] (Embodiment 8) In this embodiment, in addition to the thin film transistor that can be applied to the display panel disclosed in the first embodiment, The thin film transistor 350 shown in this embodiment is the same as the thin film transistor of Embodiment 1. It can be used as the transistor 106.

[0340] One mode of the thin film transistor and the manufacturing method of the thin film transistor of this embodiment mode will be described with reference to FIGS. This will be used to explain.

[0341] The thin film transistor 350 is described using a thin film transistor with a single gate structure. However, if necessary, a thin-film transistor with a multi-gate structure having multiple channel forming regions may be used. A data can also be formed.

[0342] 20(A) to 20(D), the thin film transistor 3 is formed on the first substrate 340. The process for producing 50 will be described.

[0343] First, a conductive film is formed on a first substrate 340, and then a first photolithography process is performed. The formed resist mask is used to perform etching to form a gate electrode 351. The electrode 351 can be formed in a manner similar to that of the gate electrode 411 described in Embodiment 2.

[0344] Next, a gate insulating film 342 is formed on the gate electrode 351. The gate insulating film 342 is It can be formed in the same manner as the gate insulating film 402 shown in the second embodiment.

[0345] Next, a conductive film is formed on the gate insulating film 342, and a conductive film is formed by a second photolithography process. A resist mask is formed on the conductive film, and selective etching is performed to form the source electrode 355a and the drain electrode 355b. After the rain electrode 355b is formed, the resist mask is removed (see FIG. 20(A)).

[0346] Next, an oxide semiconductor film 345 is formed (see FIG. 20B). The oxide semiconductor film can be formed in a manner similar to that of the oxide semiconductor film described in Embodiment 2. As the oxide semiconductor film 345, an In-Ga-Zn-O-based oxide semiconductor target was used. The oxide semiconductor film 345 is formed by a third photolithography process. The oxide semiconductor film is processed into an island shape by this process.

[0347] In this case, the oxide semiconductor film 345 is formed while removing residual moisture in the treatment chamber. It is preferable to prevent hydrogen, a hydroxyl group, or moisture from being contained in the oxide semiconductor film 345. To remove residual moisture from the processing chamber, an adsorption type vacuum pump is used. is preferred.

[0348] Next, the oxide semiconductor film is dehydrated or dehydrogenated. The temperature of the heat treatment is 400°C or higher and 750°C or lower, preferably 400°C or higher and lower than the strain point of the substrate. Here, the substrate is introduced into an electric furnace, which is one of heat treatment devices, and an oxide semiconductor The film was heat-treated at 450°C for 1 hour in a nitrogen atmosphere, and then exposed to the air. The oxide semiconductor film 346 is obtained without any problem, preventing water or hydrogen from re-entering the oxide semiconductor film (FIG. See 20(C). ).

[0349] In the first heat treatment, the substrate is immersed in an inert gas heated to a high temperature of 650°C to 700°C. After heating for several minutes, the substrate is removed from the inert gas atmosphere heated to a high temperature. GRTA can be used to heat the food at high temperatures in a short time. do.

[0350] An oxide insulating film 356 serving as a protective insulating film in contact with the oxide semiconductor film 346 is formed.

[0351] The oxide insulating film 356 can be formed in a manner similar to that of the oxide insulating film 316 described in Embodiment 6. Here, the oxide insulating film 356 is formed while removing moisture remaining in the treatment chamber. It is preferable that hydrogen, a hydroxyl group, or moisture be contained in the oxide semiconductor film 346 and the oxide insulating film 356. To remove residual moisture in the processing chamber, an adsorption type It is preferable to use an empty pump.

[0352] Next, similarly to the second embodiment, a second heating process is carried out in an inert gas atmosphere or an oxygen gas atmosphere. Heat treatment (preferably at 200°C or higher and 400°C or lower, for example, at 250°C or higher and 350°C or lower) is carried out. In the second heat treatment, the channel formation region of the oxide semiconductor film is in contact with the oxide insulating film 356. It is heated in this state.

[0353] Through the above steps, the oxide semiconductor film after deposition is dehydrated or dehydrogenated. After the first heat treatment is performed to reduce the resistance, the oxide semiconductor is The film is made to have an oxygen-excess state, and as a result, an i-type oxide semiconductor film 352 is formed. In this process, the thin film transistor 350 is formed.

[0354] Furthermore, heat treatment is carried out in the atmosphere at 100°C to 200°C for 1 hour to 30 hours. In this embodiment, heat treatment is performed at 150° C. for 10 hours. Hydrogen is taken into the oxide insulating film from the oxide semiconductor film, and a thin film transistor that becomes normally off is formed. This makes it possible to obtain a transistor, thereby improving the reliability of the display panel.

[0355] A protective insulating film may be further formed over the oxide insulating film 356. For example, a protective insulating film may be formed by RF sputtering. In this embodiment, a silicon nitride film is formed as a protective insulating film. The film 43 is formed using a silicon nitride film (see FIG. 20(D)).

[0356] Next, although not shown, the oxide insulating film 114 as shown in FIG. 2 or a flat film is formed on the protective insulating film 343. Next, a planarization insulating film 115 is formed on the protective insulating film and the planarization insulating film. An opening is formed in the opening, which reaches the drain electrode 355b, and a conductive film is formed in the opening, which is electrically connected to the drain electrode 355b. A pixel electrode is formed (not shown).

[0357] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0358] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0359] (Embodiment 9) In this embodiment, in addition to the thin film transistor that can be applied to the display panel disclosed in the first embodiment, The thin film transistor 380 shown in this embodiment is the same as the thin film transistor of Embodiment 1. The transistor 106 (see FIG. 2) can be used.

[0360] In this embodiment mode, an example in which a part of the manufacturing process of a thin film transistor is different from that in Embodiment Mode 6 is shown in FIG. 1. Figure 21 is the same as Figure 18 except for some differences in the process, so the same parts are The same reference numerals are used and detailed explanations of the same parts are omitted.

[0361] According to the sixth embodiment, a gate electrode 381 is formed on a first substrate 370. An insulating film 372a and a second gate insulating film 372b are laminated. The insulating film has a two-layer structure, with a nitride insulating film as the first gate insulating film 372a and a nitride insulating film as the second gate insulating film. The film 372b is an oxide insulating film.

[0362] The oxide insulating film may be a silicon oxide film, a silicon oxynitride film, or an aluminum oxide film. An aluminum oxynitride film or an aluminum nitride film can be used as the nitride insulating film. , silicon nitride film, silicon oxynitride film, aluminum nitride film, or aluminum oxynitride film A film or the like can be used.

[0363] Next, an oxide semiconductor film is formed, and the oxide semiconductor film is patterned by a photolithography process. The oxide semiconductor film is then etched using the resist mask formed thereon to form an island-shaped oxide semiconductor film. The semiconductor film can be formed in a manner similar to that of the oxide semiconductor film described in Embodiment 2. In this example, an In-Ga-Zn-O oxide semiconductor target is used as the oxide semiconductor film. The film is formed by sputtering.

[0364] In this case, it is preferable to form the oxide semiconductor film while removing residual moisture in the treatment chamber. This is preferable in order to prevent hydrogen, a hydroxyl group, or moisture from being contained in the oxide semiconductor film. To remove residual moisture from the processing chamber, it is preferable to use an adsorption type vacuum pump.

[0365] Next, the oxide semiconductor film is dehydrated or dehydrogenated. The temperature of the heat treatment is 400°C or higher and 750°C or lower, preferably 425°C or higher and 750°C or lower. If the temperature is 425°C or higher, the heat treatment time can be 1 hour or less. If the temperature is less than 100°C, the heat treatment time is longer than 1 hour. The substrate is placed in an electric furnace, which is a type of processing equipment, and the oxide semiconductor film is heated in a nitrogen atmosphere. After the heat treatment, the oxide semiconductor film is kept free from exposure to the air to prevent water and hydrogen from re-entering the oxide semiconductor film. After that, high-purity oxygen gas and high-purity NO gas are added to the same furnace. Alternatively, ultra-dry air (dew point below -40°C, preferably below -60°C) can be introduced to cool the It is preferable that the oxygen gas or N2O gas does not contain water, hydrogen, etc. The purity of oxygen gas or NO gas introduced into the heat treatment device is set to 6N (99.9999%). ) or more, preferably 7N (99.99999%) or more (i.e., oxygen gas or N2O gas It is preferable to keep the impurity concentration in the solution at 1 ppm or less, preferably 0.1 ppm or less.

[0366] The heat treatment device is not limited to an electric furnace, and may be, for example, a RT such as a GRTA device or an LRTA device. A device can be used.

[0367] After the first heat treatment for dehydration or dehydrogenation, the temperature is preferably 200° C. or higher and 400° C. or lower. Or heat treatment at a temperature between 200°C and 300°C in an oxygen gas or N2O gas atmosphere. The theory may also be carried out.

[0368] In addition, the first heat treatment of the oxide semiconductor film is performed on the oxide semiconductor film before it is processed into the island-shaped oxide semiconductor film. In this case, after the first heat treatment, the substrate is removed from the heating device. The substrate is taken out and subjected to a photolithography process.

[0369] By going through the above steps, the entire oxide semiconductor film is made into an oxygen-excess state, and thus a high resistance Thus, the oxide semiconductor film 382 is entirely i-type.

[0370] Next, a resist mask is formed over the oxide semiconductor film 382 by a photolithography process. Then, selective etching is performed to form a source electrode 385a and a drain electrode 385b. An oxide insulating film 386 is formed by sputtering.

[0371] In this case, the oxide insulating film 386 is formed while removing the remaining moisture in the processing chamber. It is preferable that hydrogen, a hydroxyl group, or moisture be contained in the oxide semiconductor film 382 and the oxide insulating film 386. To remove residual moisture in the processing chamber, an adsorption type It is preferable to use an empty pump.

[0372] Through the above steps, the thin film transistor 380 can be formed.

[0373] Next, in order to reduce the variation in the electrical characteristics of the thin film transistors, Alternatively, heat treatment (preferably at 150°C or higher but lower than 350°C) can be performed under a nitrogen gas atmosphere. For example, heat treatment is carried out at 250°C for 1 hour in a nitrogen atmosphere.

[0374] As in the second embodiment, the heating is carried out in the atmosphere at 100°C or higher and 200°C or lower for 1 hour to 30 hours. By this heat treatment, the oxide insulating film is removed from the oxide semiconductor film. Hydrogen is absorbed into the insulating film, resulting in a normally-off thin-film transistor. This improves the reliability of the display panel.

[0375] The protective insulating film 373 is formed over the oxide insulating film 386. As the film 73, a silicon nitride film having a thickness of 100 nm is formed by sputtering.

[0376] The protective insulating film 373 and the first gate insulating film 372a made of a nitride insulating film are resistant to moisture and water. It does not contain impurities such as hydrogen, hydrides, or hydroxides, and blocks these from entering from the outside. It has the effect of checking.

[0377] Therefore, in the manufacturing process after the formation of the protective insulating film 373, impurities such as moisture from the outside This also prevents the intrusion of dust and other foreign matter into the display panel after the device is completed. This prevents the intrusion of impurities such as moisture from the outside, improving the long-term reliability of the device. It is possible.

[0378] In addition, between the protective insulating film 373 made of a nitride insulating film and the first gate insulating film 372a The insulating film to be provided is removed, and the protective insulating film 373 and the first gate insulating film 372a are in contact with each other. The structure may be such that:

[0379] Therefore, impurities such as moisture, hydrogen, hydrides, and hydroxides in the oxide semiconductor film can be removed as much as possible. and the re-mixing of the impurities is prevented, thereby maintaining the impurity concentration in the oxide semiconductor film low. It is possible.

[0380] Next, although not shown, a planarizing insulating film for planarization as shown in FIG. 2 is formed on the protective insulating film 373. Next, an opening reaching the drain electrode 385b is formed in the protective insulating film and the planarizing insulating film. In the opening, a pixel electrode electrically connected to the drain electrode 385b is formed ( Not shown.

[0381] As shown in this embodiment, a thin film transistor using a highly purified oxide semiconductor with a low hydrogen concentration is By using transistors to control the display of the e-book display panel, the number of times pixels are scanned is reduced, In addition, the driving frequency of the scanning line driving circuit can be lowered, which reduces the power consumption of the electronic book. The hydrogen concentration can be reduced and the image retention characteristics can be improved. The off-state current of a thin film transistor using a highly purified oxide semiconductor with low -1 3 A or less, the capacitance that holds the signal voltage applied to the pixel can be reduced. This makes it possible to reduce the area of ​​the capacitance element and the pixel. The resolution of the book can be increased.

[0382] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0383] (Embodiment 10) In this embodiment mode, the electronic book reader shown in the above embodiment mode has a touch panel function. The format of the electronic book will be explained with reference to FIG.

[0384] FIG. 22 is a cross-sectional view of a display medium 21 of an electronic book having a touch panel function and its vicinity. The touch sensor unit 80 is provided on the second substrate 15. The touch sensor unit 80 includes a resistor A membrane type, a surface type electrostatic capacitance type, a projected type electrostatic capacitance type, or the like can be used as appropriate. In this embodiment, a resistive touch sensor is used as the touch sensor unit 80. I will explain.

[0385] The touch sensor unit 80 includes a third electrode 81 formed on the second substrate 15 and a fourth electrode 8 The second substrate 15 is provided with a fourth electrode 85 formed on the second substrate 15. and a spacer 83 are formed. Also, a fourth substrate 87 on which a fourth electrode 85 is formed, The second substrate 15 is sealed with a sealing material (not shown). The third substrate 27 shown in Embodiment Mode 1 may be provided over the substrate 87 .

[0386] The fourth substrate 87 can be the same as the second substrate 15. The first electrode 81 and the fourth electrode 85 can be formed using the same material as the second electrode 17. do.

[0387] When a predetermined position is pressed from the outside with a pen or a finger, the fourth substrate is deformed, and the third electrode 81 When the first electrode 82 and the fourth electrode 85 come into contact with each other, electricity flows, and the pressed position information can be detected. It is possible.

[0388] According to this embodiment, in an electronic book having a function of a touch panel, the hydrogen concentration in the element layer is By using a thin film transistor having a highly purified oxide semiconductor film with reduced power consumption, It is possible to reduce power consumption and improve image retention characteristics. In addition, the resolution of e-books can be increased.

[0389] Note that this embodiment mode can be combined with other embodiment modes as appropriate.

[0390] (Embodiment 11) In this embodiment, an electronic book that can wirelessly charge and discharge a power storage device will be described with reference to FIG. explain.

[0391] 23A is a diagram showing a cross-sectional structure of the electronic book according to this embodiment. In the electronic book shown in FIG. 1, an antenna 90 is attached to a wiring board 31, and a power storage device 39 can be wirelessly charged. The present invention is characterized by the provision of a semiconductor device 36.

[0392] As a method for wirelessly charging the power storage device 39, an external power supply device 91 and an electronic book are used. Electromagnetic induction type that uses electromotive force generated by changes in the magnetic field that penetrates between the coils installed in the The radio waves received by the antenna installed in the electronic book are converted into a DC voltage by a resonant circuit and a rectifier circuit. Radio wave receiving type that converts and uses it, external power supply device 91 and electronic book electric field or magnetic field There are resonance types that can be used, and they can be used appropriately.

[0393] In this embodiment, a charging method using electromagnetic induction will be described.

[0394] The semiconductor device 36 that wirelessly charges the power storage device receives a wireless signal from the external power supply device 91. 23B shows one example of a block diagram of the semiconductor device 36. The semiconductor device 36 includes an antenna circuit 93, It has a rectifier circuit 95, a charging circuit 97, and a stabilized power supply circuit 99.

[0395] When communication is performed using a magnetic field, the antenna circuit 93 includes at least a coil antenna, The rectifier circuit 95 has a diode and a smoothing capacitor. When communication with the supply device 91 is performed using an electric field instead of a magnetic field, the antenna is coil-shaped. There is no need.

[0396] The external power supply device 91 is composed of a power transmission control unit and an antenna circuit. The antenna circuit of the power supply device 91 has a coil-shaped antenna and a resonant capacitor. , modulates the electric signal for power transmission transmitted to the semiconductor device 36 of the electronic book and induces it in the antenna circuit A current is supplied and a signal for power transmission is output to the semiconductor device 36 from the antenna.

[0397] An antenna included in the antenna circuit of the external power supply device 91 and a semiconductor device 36 of the electronic book When the antenna included in the antenna circuit is brought close to the external power supply device 91, If the antenna included in the tena circuit is coil-shaped, an AC magnetic field is generated from the antenna. The magnetic field penetrates the antenna circuit 93 in the semiconductor device 36 of the electronic book, and the electronic book A voltage is applied between the terminals of the antenna circuit 93 in the semiconductor device 36 (between one end and the other end of the antenna). The voltage is half-wave rectified by the diodes in the rectifier circuit 95 and then smoothed by the smoothing capacitor. The charging circuit 97 operates using this smoothed voltage, and charges the storage device 39. Charge the battery.

[0398] The output voltage of the power storage device 39 is stabilized by the stabilized power supply circuit 99. The stabilized voltage are supplied to semiconductor devices 29 and 35 that drive the display panel.

[0399] When the power storage device 39 is a capacitor, typically a lithium ion capacitor, Since it is possible to charge and discharge, power can be charged to the power storage device 39 via the antenna 90 in a short time. It is possible.

[0400] According to this embodiment mode, in an electronic book that can be charged without contact, the hydrogen concentration in the element layer is reduced. By using a thin film transistor having a highly purified oxide semiconductor film, power consumption can be reduced. It is possible to reduce the electric charge and improve the image retention characteristics. The resolution of the child book can be increased.

[0401] Note that this embodiment mode can be combined with other embodiment modes as appropriate.

[0402] (Embodiment 12) In this embodiment mode, a form of an electronic book having a flexible display panel is shown in FIG. This will be explained using:

[0403] FIG. 24 is a perspective view of an electronic book 201 having two flexible display panels. The book 201 has display panels 205 and 207 sandwiched in a binding portion 203. The display panel 205 has a display unit 209. Although not shown, the back surface of the display panel 207 That is, the display unit is provided on the surface facing the display unit 209.

[0404] The flexible display panels 205 and 207 are the same as those in the display panel shown in the first embodiment. The first to third substrates can all be manufactured using flexible substrates. In addition, by laminating a glass substrate and a plastic film, a display panel The mechanical strength of the product can be improved by using a prepreg containing a fibrous body in a semi-cured organic resin. This can increase the mechanical strength of the display panel.

[0405] The binding portion 203 is formed of a hollow pillar-shaped or cylindrical housing. The hollow space contains a wiring board connected to the display panel by an FPC. A semiconductor device that controls the display of the display panels 205 and 207 is mounted on the wiring board. The plate is electrically connected to a power storage device. Also, the binding portion 203 is provided with operation keys.

[0406] According to this embodiment, in a flexible electronic book, the hydrogen concentration in the element layer is reduced and high purity is obtained. By using a thin film transistor having a highly-tuned oxide semiconductor film, power consumption can be reduced. It is possible to improve the image retention characteristics. The resolution can be increased.

[0407] Note that this embodiment mode can be combined with other embodiment modes as appropriate.

[0408] (Embodiment 13) In this embodiment, a semiconductor device that adjusts the voltage from a power supply device 37 included in an electronic book is used. A booster circuit will be described as one type of voltage regulator circuit that can supply power to the above.

[0409] One mode of the circuit configuration of the booster circuit of this embodiment will be described with reference to FIG. 1 is a circuit diagram showing one example of a circuit configuration of a booster circuit according to an embodiment of the present invention.

[0410] The booster circuit shown in FIG. 25 includes unit booster circuits 211_1 to 211_n (n is an integer). each of the unit boosting circuits 211_1 to 211_n is connected in series. It is constructed using n-stage unit boost circuits electrically connected in series.

[0411] Each of the unit boost circuits 211_1 to 211_n includes a thin film transistor 2 31 and a capacitance element 232.

[0412] The thin film transistor 231 is a thin film transistor having a reduced hydrogen concentration as described in the first embodiment. A thin film transistor including a highly purified oxide semiconductor film can be used.

[0413] In each of the unit boost circuits 211_1 to 211_n, a thin film transistor The gate of the thin film transistor 231 is electrically connected to one of the source and drain of the thin film transistor 231. That is, the thin film transistor 231 is diode-connected. The first electrode of the element 232 is electrically connected to the other of the source and drain of the thin film transistor 231. are connected to the network.

[0414] Furthermore, the Kth stage (K is a natural number from 2 to n) unit boost circuit has a thin film transistor 231 One of the source and drain of the thin film transistor 231 in the unit boost circuit of the (K-1)th stage The thin film in the K-1th stage unit boost circuit is electrically connected to the other of the source and drain. The other of the source and drain of the thin film transistor 231 and the thin film transistor The connection point of the membrane transistor 231 with one of the source and drain is a node N_M (M is 1 (a natural number from n to n-1).

[0415] Furthermore, in the unit booster circuit of the 2M-1th stage, the second electrode of the capacitance element 232 is connected to the clock signal line 2 21, and the second electrode of the capacitance element 232 of the 2Mth stage unit booster circuit is connected to the The clock signal line 221 is electrically connected to the clock signal line 222. The clock signal CK 1 is input to the clock signal line 222, and the clock signal CKB1 is input to the clock signal line 223. The signal CK1 and the clock signal CKB1 are in a phase-reversed relationship. For example, When CK1 is at a high level, the clock signal CKB1 is at a low level. For example, an inverted signal of the clock signal CK1 can be used as KB1. The voltage state of the clock signal CK1 is calculated by using a NOT circuit such as an inverter. It can be generated by inverting the state.

[0416] Furthermore, the thin film transistor in the first-stage unit booster circuit, that is, the unit booster circuit 211_1 The signal IN1 is input to one of the source and drain of the transistor 231.

[0417] Furthermore, the thin-film transistor in the final-stage unit boost circuit, that is, the unit boost circuit 211_n The voltage at the other of the source and drain of the capacitor 231 is the signal OUT1, which is the output signal of the boost circuit. The capacitance element 232 in the unit boost circuit 211_n has a voltage of The voltage Vc1 may be any value, for example, the voltage V H or voltage V L Same as In addition, the capacitance element 23 in the unit boost circuit 211_n can be The capacitance of the capacitor 232 in the other unit boosting circuits is preferably set to be larger than that of the capacitor 232 in the other unit boosting circuits. As a result, the output signal of the unit boosting circuit 211_n, that is, the output signal of the boosting circuit This makes it possible to make the voltage state of the signal OUT1 more stable.

[0418] As described above, one example of the booster circuit of this embodiment has n-stage unit booster circuits, each of which has The unit boost circuit has a diode-connected thin film transistor and a capacitance element. As a diode-connected thin film transistor, the hydrogen concentration is reduced and the transistor is highly purified. A thin film transistor having an oxide semiconductor film is used. It is possible to extend the holding time and shorten the time it takes to reach the target voltage. The voltage conversion efficiency can be improved.

[0419] Next, one mode of operation of the booster circuit shown in FIG. 25 will be described.

[0420] The operation of the boost circuit shown in FIG. 25 can be explained by dividing it into several periods. The operation of the boost circuit shown in FIG. In this configuration, a high-level signal is input as signal IN1, and the clock signal CK1 is set to high. The clock signal CKB1 is a clock signal that periodically changes between high and low levels. The inverted clock signal CK1 is used as the clock signal of the thin film transistor 23 in each unit boost circuit. 1 is an N-type thin film transistor, and the threshold voltage of the thin film transistor 231 in each unit boost circuit is The explanation will be given assuming that the voltages are the same value.

[0421] First, in the first period, the clock signal CK1 goes to a low level, and the clock signal CKB1 goes to a high level. Become a high level.

[0422] At this time, in the unit boosting circuit 211_1, the diode-connected thin film transistor 23 1 becomes conductive, and the voltage at node N_1 begins to rise. N1 (also called) is V IN1 (Voltage of signal IN1) -V th231 (Thin-film transistor 2 The voltage at node N_1 rises to voltage V IN1 -V th231 Nina Then, the diode-connected thin film transistor 231 in the unit boosting circuit 211_1 It becomes non-conductive and the node N_1 becomes floating.

[0423] Next, in the second period, the clock signal CK1 goes high, and the clock signal CKB1 goes low. become low level.

[0424] At this time, in the unit boosting circuit 211_1, the thin film transistor 231 is maintained in a non-conductive state. The node N_1 is in a floating state, and the capacitance element in the unit boosting circuit 211_1 is The voltage applied to the second electrode of the element 232 is V H , the second capacitance of the capacitance element 232 changes to The voltage of the first electrode of the capacitor 232 also starts to change in accordance with the change in the electrode. is V IN1 -V th231 +V H At this time, the first electrode of the capacitor 232 The voltage applied between the first electrode and the second electrode is V IN -V th231 In this way, the second During the first period, the voltage of the node N_1 is increased by the voltage of the node N_1 during the second period. The value is calculated as follows:

[0425] Furthermore, the voltage at node N_1 is V IN -V th231 +V H This results in a unit boost In the circuit 211_2, the diode-connected thin film transistor 231 is turned on. The voltage at node N_2 starts to rise. N2 (also called) is V N1 -V th231 The voltage at node N_2 rises to V N1 -V th231 When it comes to The diode-connected thin film transistor 231 in the unit boosting circuit 211_2 is non-conductive. The node N_1 is in the ON state, and the node N_2 is in the floating state.

[0426] Next, in the third period, the clock signal CK1 goes to a low level, and the clock signal CKB1 goes to a high level. Become a high level.

[0427] At this time, in the unit boosting circuit 211_2, the thin film transistor 231 is maintained in a non-conductive state. The node N_2 is in a floating state, and the capacitance element in the unit boosting circuit 211_2 The voltage applied to the second electrode of the element 232 is V L From V H Therefore, the capacitance element 232 The voltage of the first electrode of the capacitor 232 also starts to change in accordance with the voltage of the second electrode of the node N_ The voltage at 2 is V N1 -Vth 231 +V H At this time, the first capacitance of the capacitance element 232 The voltage applied between the first electrode and the second electrode is V N1 -V th231 Like this. In the third period, the voltage of the node N_2 is The boosted value is obtained.

[0428] Furthermore, the voltage at node N_2 is V N1 -V th231 +V H This results in a unit boost In the circuit 211_3, the diode-connected thin film transistor 231 is turned on. The voltage at node N_3 starts to rise. N3 (also called) is V N2 -V th231 The voltage at node N_3 rises to V N2 -V th231 When it comes to , the diode-connected thin film transistor 231 in the unit boosting circuit 211_3 is non-conductive. The node N_3 is in a floating state.

[0429] Furthermore, in each unit boost circuit from the third stage onwards, the clock signal CK1 or the clock signal CK As B1 periodically changes to high level or low level, the same The operation is performed sequentially, and the voltage of each node N_M rises to a maximum of V IN1 +M(V H -V t h231 ), and the voltage of the signal OUT1 is boosted to a maximum of V IN1 +n(V H -V th23 1). In this way, the boost circuit shown in FIG. 25 boosts the voltage of the signal IN1. The compressed voltage signal OUT1 is output as an output signal.

[0430] As described above, in one aspect of the booster circuit of this embodiment, the boosting operation is performed in each unit booster circuit. By performing this, a signal with a voltage higher than the voltage of the input signal is output as the output signal. It is possible.

[0431] In addition, one embodiment of the boost circuit of this embodiment is a diode-connected boost circuit in each unit boost circuit. The thin film transistor is a thin film transistor using an oxide semiconductor film with a reduced hydrogen concentration and high purity. This reduces the leakage current of the thin film transistors, The node voltage can be held for a longer period of time, and the voltage boost operation can be performed until the target voltage is reached. This can speed up the arrival speed.

[0432] Note that this embodiment mode can be combined with other embodiment modes as appropriate. [Explanation of symbols]

[0433] 01 E-books 03 Housing 05 Display section 07 Operation keys 09 Operation keys 11 First substrate 29 Semiconductor Devices 23 Sealing material 13 Device layer 19 Adhesive 21 Display media 17 Second electrode 15 Second board 25 Adhesive 27 Third Board 10 Display panel 33 FPC 35 Semiconductor Devices 31 Wiring board 37 Power supply equipment 102A Second Wiring 103 Oxide semiconductor film 106 Thin-film transistor 101 First Wiring 102B Third Wire 105 pixel electrode 100 pixels 104 Capacitance Line 123 Scanning line driving circuit 124 Signal line driver circuit 122 pixel section 121 pixels 120 first substrate 21 Display media 57 White particles 51 Filling material 53 Microcapsules 41 First electrode 55 Black particles 59 Dispersion medium 67 White powder 61 Ribs 63 Space 65 Black powder 71 Filling material 77 White area 73 Microcapsules 79 Liquid 75 black area 111 first substrate 112 Base film 113 Gate insulating film 114 Oxide insulating film 115 Planarization insulating film 133 Writing Period 135 Non-writing period 131 Image rewrite period 137 Writing Period 143 Writing Period 145 Non-writing period 141 Image rewrite period 147 Writing Period 155 Energy Storage Cells 157 Terminal section 159 Terminal section 151 Electricity storage device 153 Exterior materials 171 Negative electrode current collector 173 Negative electrode active material 163 Negative electrode 167 Separator 177 Cathode active material 175 Positive electrode current collector 165 Positive electrode 169 Electrolytes 414a Wiring 415a Source electrode or drain electrode 411 Gate electrode 412 Oxide semiconductor film 415b Source electrode or drain electrode 414b Wiring 410 Thin Film Transistor 407 Insulating Film 400 first substrate 402 Gate insulating film 460 Thin Film Transistor 465b Source or drain electrode 461 Gate electrode 462 Oxide semiconductor film 468 Wiring 452 Gate insulating film 461a Gate electrode 461b Gate electrode 468 Wiring 464 Wiring 465a2 Source or drain electrode 457 Insulating Film 465a1 Source electrode or drain electrode 450 First Substrate 422 insulating film 412 Oxide semiconductor film 425 Thin-film transistor 411 Gate electrode 427 Conductive Film 424 Conductive Film 426 Thin Film Transistor 394 First Substrate 393 Oxide Semiconductor Film 391 Gate electrode 397 Gate insulating film 399 Oxide Semiconductor Film 395a Source electrode 395b Drain electrode 396 Oxide insulating film 390 Thin-Film Transistors 392 Oxide semiconductor layer 398 Protective insulating film 300 first substrate 311 Gate electrode 330 Oxide semiconductor film 302 Gate insulating film 331 Oxide semiconductor film 315a Source electrode 315b Drain electrode 316 Oxide insulating film 310 Thin-film transistor 313 Channel formation region 312 Oxide semiconductor film 303 Protective insulating film 322 Gate insulating film 361 Gate electrode 332 Oxide semiconductor film 320 first substrate 366 Oxide insulating film 362 Oxide semiconductor film 365a Source electrode 365b Drain electrode 323 Protective insulating film 363 Channel formation region 362 Oxide semiconductor film 360 Thin Film Transistor 340 First Substrate 355a Source electrode 351 Gate electrode 342 Gate insulating film 355b Drain electrode 345 Oxide semiconductor film 346 Oxide semiconductor film 343 Protective insulating film 356 Oxide insulating film 352 Oxide semiconductor film 350 Thin-Film Transistors 385a Source electrode 386 Oxide insulating film 373 Protective insulating film 385b Drain electrode 372b Second gate insulating film 372a First gate insulating film 382 Oxide semiconductor film 380 Thin Film Transistors 381 Gate electrode 370 First Substrate 80 Touch sensor section 81 Third electrode 83 Spacer 85 Fourth Electrode 87 Fourth Board 90 Antenna 91 External power supply device 93 Antenna Circuit 95 Rectifier circuit 97 Charging circuit 99 Stabilized power supply circuit 201 e-books 203 Binding 205 Display Panel 207 Display Panel 209 Display section 221 Signal Line 222 Clock signal line 231 Thin-film transistor 232 Capacitor

Claims

[Claim 1] The hydrogen concentration detected by secondary ion mass spectrometry is 5 x 10 １９ / cm ３ and the carrier concentration is 5×10 １４ / cm ３ a thin film transistor including an oxide semiconductor film overlapping with a gate electrode, a pixel electrode connected to the thin film transistor; a common electrode facing the pixel electrode; a display panel having a display medium between the pixel electrodes and the common electrode.

Images