Display device

Abstract

To provide a display device with a low manufacturing cost, to provide a display device with low power consumption, to provide a display device that can be manufactured on a large-area substrate, to provide a display device with a high numerical aperture of pixels, and to provide a display device with a high reliability.SOLUTION: A display device comprises: a transistor electrically connected with a pixel electrode having light transmissivity; and a capacitive element. The transistor includes: a gate electrode; a gate insulating film provided on the gate electrode; and a first multilayer film provided on the gate insulating film and that includes an oxide semiconductor layer. The capacitive element has: the pixel electrode; and a second multilayer film overlapped with and arranged at a predetermined interval from the pixel electrode, and that has the same layer structure as the first multilayer film. A channel formation region of the transistor is at least one layer not contacted with the gate insulating film, of the first multilayer film.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The invention disclosed in this specification and elsewhere relates to a display device and an electronic device. [Background technology]

[0002] In recent years, flat panel displays such as liquid crystal displays and organic EL displays have In display devices such as flat panel displays, In addition, in the pixels arranged in the column direction, a transistor serving as a switching element and a A display element electrically connected to the transistor and a capacitance element connected to the display element are provided. It is being done.

[0003] The silicon semiconductor film used in transistors is either amorphous silicon or polycrystalline silicon depending on the application. For example, when manufacturing a display device on a large-area substrate, In particular, a transistor using an amorphous silicon film, for which a film formation technique for a large-area substrate has been established, is preferred. By manufacturing a display device on a large-area substrate, the manufacturing cost of the display device can be reduced. However, the field effect mobility of a transistor using an amorphous silicon film is low. Therefore, the area of ​​the transistor must be large to obtain a sufficient on-current. The larger the area of ​​the transistor, the lower the pixel aperture ratio and the higher the power consumption of the display device. It becomes like this.

[0004] On the other hand, transistors using polycrystalline silicon films have high field effect mobility, so they can be used in small A sufficient on-state current can be obtained even with a transistor of this size. This allows the display device to consume less power. However, the polycrystalline silicon film The amorphous silicon film is formed by subjecting the film to a high-temperature heat treatment or a laser beam treatment. Therefore, it is difficult to form the display device on a large substrate. This makes it difficult to manufacture the display device, which increases the manufacturing cost.

[0005] In addition, oxides that exhibit semiconductor characteristics (also called oxide semiconductors) are used as semiconductors for transistors. It is a semiconductor material that can be applied to thin films. For example, zinc oxide or In-Ga-Zn oxide is used. Techniques for fabricating transistors using the above-mentioned method have been disclosed (see Patent Documents 1 and 2). Light. ).

[0006] Since the oxide semiconductor film can be formed by a sputtering method, it is possible to form a display device on a large-area substrate. By fabricating a display device on a large-area substrate, the fabrication of the display device becomes easier. In addition, a transistor including an oxide semiconductor film has a high Because of its field-effect mobility, even a small-area transistor can achieve sufficient on-state current. This makes it possible to increase the aperture ratio of the pixel and reduce the power consumption of the display device. In addition, some of the production equipment for transistors using amorphous silicon films can be improved and used. This also has the advantage of reducing capital investment.

[0007] In addition, as display devices become more highly detailed, the area occupied by wiring, electrodes, etc. increases. The aperture ratio of the pixel is reduced, and the power consumption of the display device increases. If the width of the wiring is narrowed to increase the efficiency, delays will occur in the operation of the display device, and the In addition, the display quality may be reduced. Even if the pixel size is reduced, the display quality of the display device may be reduced.

[0008] The oxide semiconductor film has a wide energy gap of about 3 eV to 4 eV. It is known that the film has a light-transmitting property. The channel layer of the transistor and one of the capacitance electrodes used in the capacitance element are made of a transparent oxide semiconductor. It is disclosed that the capacitance electrode is formed on the same plane as the conductive film. Since the other side is formed of a pixel electrode having light transmitting properties, the entire capacitance element can be made transparent. Cut. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2007-123861 A [Patent Document 2] JP 2007-96055 A [Patent Document 3] U.S. Patent No. 8,102,476 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide a display device with low manufacturing cost. It is an object of the present invention to provide a display device that can be manufactured on a large-area substrate. Another object of the present invention is to provide a display device having a high pixel aperture ratio. An object of the present invention is to provide a highly reliable display device. [Means for solving the problem]

[0011] One embodiment of the present invention is a semiconductor device including a transistor electrically connected to a light-transmitting pixel electrode and a capacitor. The transistor has a gate electrode and a gate insulating film provided on the gate electrode. a first multilayer film including an oxide semiconductor layer provided on the gate insulating film; The first multilayer film is disposed on the pixel electrode and overlaps the pixel electrode with a predetermined gap therebetween. and a second multilayer film having the same layer structure as the first multilayer film, and a channel forming region of the transistor is formed in the first multilayer film. In the display device, at least one of the layers is not in contact with the gate insulating film.

[0012] Stable electrical characteristics in transistors in which the channel is formed in a multilayer film including an oxide semiconductor layer In order to provide this, it is effective to reduce the impurity concentration in the layer in which the channel is formed. For example, silicon in an oxide semiconductor may form an impurity level. The impurity levels can become traps and degrade the electrical characteristics of a transistor. The gate insulating film of a transistor is a silicon oxide film, a silicon oxynitride film, a silicon nitride film, Since insulating films containing silicon, such as silicon oxide and silicon oxynitride films, are widely used, The layer in which the channel of the multilayer film including the semiconductor layer is formed is formed in a layer that is not in contact with the gate insulating film. It is preferable.

[0013] In addition, when a channel is formed at the interface between the gate insulating film and the multilayer film including the oxide semiconductor layer, In such a case, interface scattering occurs at the interface, and the field effect mobility of the transistor decreases. From the viewpoint of the above, the channel of the transistor is formed by a multilayer film including an oxide semiconductor layer and a gate insulating film. It is preferable that the layer is not in contact with the

[0014] Therefore, the channel of the transistor is connected to the gate insulating film of the multilayer film including the oxide semiconductor layer. By forming the transistor in a layer that does not have a high field effect mobility and stable electrical characteristics, The transistor can be used as a switching element of a display device. Since the transistor has stable electrical characteristics, a highly reliable display device can be obtained. In addition, the transistor can obtain a sufficient on-state current even in a small area. Therefore, the aperture ratio of the pixel can be increased, and the power consumption of the display device can be reduced.

[0015] In order to separate the channel formation region of the transistor from the gate insulating film, for example, an oxide semiconductor The multilayer film including the conductor layer may have the following structure.

[0016] The multilayer film including an oxide semiconductor layer includes at least an oxide semiconductor layer (for convenience, a second oxide layer ) and a first oxide layer provided between the second oxide layer and the gate insulating film; The first oxide layer is composed of at least one element other than oxygen that composes the second oxide layer. The first oxide layer is an oxide film having an electron affinity smaller than that of the second oxide layer by 0.2 eV or more. When an electric field is applied to the gate electrode, the electron affinity of the multilayer film including the oxide semiconductor layer increases. A channel is formed in the second oxide layer having a large capacitance. By having a first oxide layer between the gate insulating film and the transistor channel, It can be formed on a layer (here, the second oxide layer) that is not in contact with the second oxide layer. Since the first oxide layer is composed of one or more elements other than oxygen, the second oxide layer At the interface between the insulating layer and the first oxide layer, interfacial scattering is unlikely to occur. Since the movement of carriers is not hindered in the This can be done.

[0017] The first oxide layer may be, for example, aluminum, silicon, titanium, gallium, germanium, or the like. Cr, yttrium, zirconium, tin, lanthanum, cerium or hafnium in the second The oxide film may be one containing the element at a higher concentration than the oxide layer. The second oxide layer has a concentration of the above-mentioned elements that is 1.5 times or more, preferably 2 times or more, more preferably 1.5 times or more, more preferably 1.5 times or more, more preferably 2 times or more, more preferably 1.5 times or more, more preferably 2 times or more, more preferably 2.5 ... The oxide film containing the above elements at a concentration three times higher than that of the above elements is used. The first oxide layer has a function of suppressing the occurrence of oxygen vacancies in the oxide film. This oxide film is less susceptible to oxygen vacancies than the oxide layer in 2.

[0018] Alternatively, the second oxide layer is an In-Ga-Zn oxide and the first oxide layer is also an In-Ga When the first oxide layer is a-Zn oxide, the first oxide layer is In:Ga:Zn=x1:y1:z1 [original The second oxide layer is In:Ga:Zn=x2:y2:z2 [atomic ratio]. , select the first oxide layer and the second oxide layer such that y1 / x1 is greater than y2 / x2. Preferably, the first oxide has y1 / x1 1.5 times or more larger than y2 / x2. layer and the second oxide layer. More preferably, y1 / x1 is greater than y2 / x2. The first and second oxide layers are selected to be at least two times larger. More preferably, A first oxide layer and a second oxide layer in which y1 / x1 is at least three times larger than y2 / x2. Select .

[0019] In addition, the multilayer film including the oxide semiconductor layer has a second oxide layer on the side not in contact with the gate insulating film. and the second oxide layer is made of one or more elements other than oxygen, The third oxide layer may have an electron affinity smaller than that of the first oxide layer by 0.2 eV or more. Even if an electric field is applied to the gate electrode, no channel is formed in the third oxide layer. Since the third oxide layer is composed of one or more elements other than oxygen that composes the second oxide layer, The interface between the second oxide layer and the third oxide layer is unlikely to form an interface state. When the second transistor has a different threshold voltage, the interface serves as a channel forming region. This can cause the apparent threshold voltage of the transistor to vary. By providing the oxide layer 3, the variation of the electrical characteristics such as the threshold voltage of the transistor is reduced. This can reduce the amount of

[0020] For example, the third oxide layer may be made of aluminum, silicon, titanium, gallium, germanium, or the like. Cr, yttrium, zirconium, tin, lanthanum, cerium or hafnium in the second The oxide film may be one containing a higher concentration of ZnO than the oxide layer. The second oxide layer has a concentration of the above-mentioned elements that is 1.5 times or more, preferably 2 times or more, more preferably 1.5 times or more, more preferably 1.5 times or more, more preferably 2 times or more, more preferably 1.5 times or more, more preferably 2 times or more, more preferably 2.5 ... The oxide film containing the above elements at a concentration three times higher than that of the above elements is used. The third oxide layer has a function of suppressing the occurrence of oxygen vacancies in the oxide film. This oxide film is less susceptible to oxygen vacancies than the oxide layer in 2.

[0021] Alternatively, the second oxide layer is an In-Ga-Zn oxide film, and the third oxide layer is also an In- When the Ga-Zn oxide film is used, the second oxide layer is In:Ga:Zn=x2:y2:z2 [Atomic ratio], the third oxide layer is In:Ga:Zn=x 3:y 3: z3 [atomic ratio] Then, the second oxide layer and the third oxide layer in which y3 / x3 is larger than y2 / x2 are formed. Preferably, the second acid is selected such that y3 / x3 is 1.5 times greater than y2 / x2. Preferably, y3 / x3 is greater than y2 / x2. Preferably, the second and third oxide layers are selected to be at least twice as large as the first oxide layer. The second oxide layer and the third oxide layer have y3 / x3 three times larger than y2 / x2. Select the object layer.

[0022] In addition, the display device according to one embodiment of the present invention includes a multilayer film including an oxide semiconductor layer (for convenience, the first The first multilayer film has the same layer structure as the first multilayer film and is transparent to light. The second multilayer film has a light-transmitting property, and thus the capacitance element is formed. By using a capacitive element having light transmission properties, This increases the aperture ratio, and the power consumption of the display device can be reduced.

[0023] If the second multilayer film is formed in the same process as the first multilayer film, the number of manufacturing steps of the display device is reduced. By reducing the number of manufacturing steps of the display device, the manufacturing cost of the display device can be reduced. It can be lowered.

[0024] The second multilayer film is at least as thick as the second oxide layer by an electric field applied from the pixel electrode. Since carriers are induced in the layer formed in one step, it functions as a part of the electrode. The layer formed in the same process as the first oxide layer and the layer formed in the same process as the third oxide layer are also Since the carrier density is sufficiently high compared to the insulating film such as the gate insulating film, It functions as: Effect of the Invention

[0025] According to one embodiment of the present invention, a multilayer film including an oxide semiconductor layer is provided in a transistor and a capacitor. By using the above, it is possible to manufacture a display device on a large-area substrate, and therefore the manufacturing cost is low. In addition, since the multilayer film used in the capacitor element has a light transmitting property, the aperture ratio of the pixel can be increased. In addition, a display device with low power consumption can be provided. The channel is formed in the layer that does not contact the gate insulating film of the multilayer film, so a stable current is generated. It is possible to form a transistor with excellent thermal conductivity and to manufacture a highly reliable display device. Cut. [Brief description of the drawings]

[0026] [Figure 1] 1A and 1B are a diagram illustrating a display device which is one embodiment of the present invention and a circuit diagram illustrating a pixel. [Diagram 2] FIG. 2 is a top view illustrating a pixel of a display device which is one embodiment of the present invention. [Diagram 3] FIG. 1 is a cross-sectional view illustrating a display device according to one embodiment of the present invention. [Figure 4] 1A to 1C are cross-sectional views illustrating a method for manufacturing a display device according to one embodiment of the present invention. [Diagram 5] 1A to 1C are cross-sectional views illustrating a method for manufacturing a display device according to one embodiment of the present invention. [Figure 6] FIG. 2 is a top view illustrating a pixel of a display device which is one embodiment of the present invention. [Figure 7] FIG. 1 is a cross-sectional view illustrating a display device according to one embodiment of the present invention. [Figure 8] FIG. 2 is a top view illustrating a pixel of a display device which is one embodiment of the present invention. [Figure 9] FIG. 1 is a cross-sectional view illustrating a display device according to one embodiment of the present invention. [Figure 10] FIG. 2 is a top view illustrating a pixel of a display device which is one embodiment of the present invention. [Figure 11] FIG. 1 is a cross-sectional view illustrating a display device according to one embodiment of the present invention. [Figure 12] FIG. 1 is a top view illustrating a display device which is one embodiment of the present invention. [Figure 13] FIG. 1 is a cross-sectional view illustrating a display device according to one embodiment of the present invention. [Figure 14] 1A and 1B are a cross-sectional view and a top view illustrating a display device which is one embodiment of the present invention. [Figure 15] 1A to 1C are diagrams illustrating electronic devices using a display device which is one embodiment of the present invention. [Figure 16] 1A to 1C are diagrams illustrating electronic devices using a display device which is one embodiment of the present invention. [Figure 17] 13A and 13B are diagrams showing the relationship between current and voltage of a transistor and the relationship between voltage and capacitance of a capacitor included in a display device. [Figure 18] 1A to 1C are diagrams illustrating a method of operating a capacitor included in a display device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description, and it is understood by those skilled in the art that various changes can be made in form and detail. The present invention is not limited to the description of the following embodiments. It is not something that is done.

[0028] In the configuration of the present invention described below, the same parts or parts having similar functions are designated by the same reference numerals. The same reference numerals are used in common among different drawings, and the repeated explanations are omitted. When referring to a part having a function, the hatch pattern shall be the same and no symbol shall be attached. There is.

[0029] In each figure described in this specification, the size of each structure, the thickness of the film, or the area is not shown for clarity. The figures may be exaggerated for illustrative purposes and are not necessarily limited to that scale.

[0030] In this specification and elsewhere, ordinal numbers such as 1st, 2nd, etc. are used for convenience. The order of steps or stacking is not intended to indicate the order of steps or stacking. It does not indicate a specific name for the purpose of reference.

[0031] In addition, the function of the "source" and "drain" in the present invention is to provide a current in the circuit operation. For this reason, in this specification, The terms "source" and "drain" may be used interchangeably.

[0032] Voltage is the potential difference between two points, and potential is the electrostatic field at a certain point. This refers to the electrostatic energy (electrical potential energy) possessed by a unit charge in a particle. However, in general, the potential at a certain point and the reference potential (for example, ground potential, source potential) The potential difference between the potential and the voltage is simply called potential or voltage, and potential and voltage are used synonymously. Therefore, in this specification, unless otherwise specified, potential is interpreted as voltage. Alternatively, voltage may be read as potential.

[0033] In this specification, when etching is performed after photolithography, The mask formed by the photolithography process is removed.

[0034] (Embodiment 1) In this embodiment, a display device which is one embodiment of the present invention will be described with reference to drawings. In this embodiment mode, a display device using a liquid crystal element will be described as an example.

[0035] Configuration of the Display Device FIG. 1A shows an example of a display device. The display device shown in FIG. 1A has a pixel portion 100 and The scanning line driving circuit 104 and the signal line driving circuit 106 are arranged in parallel or approximately in parallel to each other. The m scanning lines 107 are connected to the scanning line driver circuit 104 and have potentials controlled by the scanning line driver circuit 104. The n lines are arranged in parallel or approximately in parallel, and the potentials of which are controlled by the signal line driver circuit 106. and a signal line 109. The pixel section 100 further includes a plurality of The pixels 101 are arranged parallel or approximately parallel to each other along the scanning line 107. The capacitance lines 115 are arranged parallel to the signal lines 109. Alternatively, they may be arranged substantially parallel to each other.

[0036] Each scanning line 107 corresponds to one of the pixels 101 arranged in m rows and n columns in the pixel section 100. The signal lines 109 are electrically connected to the n pixels 101 arranged in any one of the rows. is m pixels 101 arranged in m rows and n columns, which are arranged in any one of the columns. 1. Both m and n are integers of 1 or more. is n pixels 101 arranged in any row among the pixels 101 arranged in m rows and n columns. 1. Capacitor lines 115 are arranged parallel to each other along the signal line 109. In the case where the pixels 101 are arranged in m rows and n columns, the pixels 101 are arranged in a substantially parallel manner. The pixel array 102 is electrically connected to m pixels 101 arranged in a row.

[0037] FIG. 1B is an example of a circuit diagram of a pixel 101 included in the display device shown in FIG. The pixel 101 shown in FIG. 1B is electrically connected to a scanning line 107 and a signal line 109. A transistor 103, one electrode of which is the drain electrode of the transistor 103 and the pixel electrode 121, and the other electrode is electrically connected to a capacitance line 115 that supplies a constant potential. The connected capacitor element 105 and pixel electrode 121 are connected to the drain electrode and The capacitor element 105 is electrically connected to one of the electrodes of the pixel electrode 121. A liquid crystal element 108 is electrically connected to a wiring 155 that supplies a potential to an electrode (counter electrode) that is connected to the liquid crystal element 108. , has.

[0038] The capacitor element 105 has a part of the pixel electrode 121 as one electrode and is connected to the capacitor line 115. The electrode connected to the other electrode may be the other electrode. In this case, if the other electrode has a higher conductivity, In this case, it can be shown as the circuit diagram shown in FIG. When the conductivity is low, it can be shown as the circuit diagram shown in FIG. 1(C).

[0039] The pixel 101 shown in FIG. 1C is electrically connected to a scanning line 107 and a signal line 109. A transistor 103 is connected to the drain electrode of the transistor 103 and the pixel electrode. The other electrode is electrically connected to a capacitance line 115 which supplies a constant potential. The pixel electrode 121 is connected to the drain electrode of the transistor 103. The capacitor element 105 is electrically connected to one of the electrodes of the pixel electrode 121. The liquid crystal element 108 is electrically connected to a wiring 155 that supplies a potential to an electrode (counter electrode) that is connected to the liquid crystal element 108. And, it has.

[0040] In the capacitor 105 shown in FIG. 1C, the multilayer film 119 is used for the transistor 103. The multilayer film 119 has the same layer structure as the multilayer film 111 that is used in the present embodiment. The multilayer film 119 controls the applied potential to be in a conductive state. The multilayer film 119 functions as the other electrode of the capacitor 105. Therefore, the capacitance element 105 is a MOS (Metal Oxide Semiconductor) It can be said that this is a capacitor structure.

[0041] The multilayer film 119 of the capacitance element 105 is an enhancement type transistor. Since the multilayer film 111 included in the transistor 103 is formed in the same manner, the process is simple. The capacitance element 105 detects the potential difference (VP When the voltage Vcc-Vcc becomes equal to or higher than 0 V, charging begins (see Figures 17(B) and 17(C)). Therefore, the threshold voltage (Vth) of the capacitance element 105 is 0 V or more. The IV curve and threshold of transistor 103, an enhancement mode transistor. 17A shows the value voltage Vth. Note that the vertical axis in FIG. 17A is a logarithmic axis.

[0042] FIG. 17B shows the CV (Capacitance-Voltage) of the capacitance element 105. In FIG. 17B, the horizontal axis represents the relationship between the pixel electrode 121 of the capacitance element 105 and the capacitance line 1 The vertical axis represents the potential difference (VP-VC) between the capacitor 105 and the capacitor 105, and the vertical axis represents the capacitance C of the capacitor 105. When the voltage frequency during CV measurement is lower than the frame frequency of the display device, , the CV curve shown in FIG. 17(B) is obtained.

[0043] The multilayer film 119 of the capacitance element 105 is formed in the same manner as the multilayer film 111 of the transistor 103. Since the process can be used to intentionally increase the carrier density and thus the electrical conductivity. The multilayer film 1 is an oxide semiconductor film that has not been subjected to a treatment for adding impurities. The carrier density of 19 is equal to the carrier density of the multilayer film 111 .

[0044] The liquid crystal element 108 is formed on a substrate on which the transistor 103 and the pixel electrode 121 are formed. The optical modulation effect of the liquid crystal sandwiched between the substrate and the counter electrode causes the light transmission The optical modulation of liquid crystals is achieved by controlling the electric field applied to the liquid crystals. (including transverse, longitudinal or diagonal electric fields).

[0045] Next, a specific example of the pixel 101 of the liquid crystal display device will be described. This is shown in Figure 2. Note that the counter electrode and the liquid crystal element are omitted in Figure 2.

[0046] In FIG. 2, the scanning lines 107 extend in a direction substantially perpendicular to the signal lines 109 (the left-right direction in the figure). The signal lines 109 extend in a direction substantially perpendicular to the scanning lines 107 (the vertical direction in the figure). The capacitance line 115 is provided so as to extend in a direction parallel to the scanning line 107. The scanning line 107 and the capacitance line 115 are connected to a scanning line driving circuit 104 (FIG. 1( A). The signal line 109 is electrically connected to the signal line driver circuit 106 (see FIG. 1(A).)

[0047] The transistor 103 is provided in the area where the scanning line 107 and the signal line 109 intersect. The transistor 103 includes a gate electrode and a gate insulating film provided on the gate electrode. (not shown in FIG. 2 ), and a multilayer film 11 including an oxide semiconductor layer provided on the gate insulating film. In addition, the region of the scanning line 107 that overlaps with the multilayer film 111 is a transistor. The gate electrode of the gate electrode 103 overlaps the multilayer film 111 in the signal line 109. The region where the conductive film 113 is formed functions as a source electrode of the transistor 103. The region overlapping with the film 111 functions as the drain electrode of the transistor 103. , the gate electrode, the source electrode, and the drain electrode are respectively connected to the scanning line 107, the signal line 10 9 and the conductive film 113. In FIG. In terms of shape, the end is located outside the end of the multilayer film 111. This functions as a light-shielding film that blocks light from the backlight. The multilayer film 111 including the oxide semiconductor layer is not irradiated with light, and fluctuations in electrical characteristics are suppressed. It is possible.

[0048] In addition, the multilayer film 111 including the oxide semiconductor layer can be used as a transistor by processing the multilayer film 111 under appropriate conditions. This can reduce the off-current of the transistor 103 significantly. can be reduced.

[0049] In this embodiment, the multilayer film 111 including an oxide semiconductor layer includes a first oxide layer, a second oxide layer which is an oxide semiconductor and is in contact with the first oxide layer; and a third oxide layer in contact with the first oxide layer.

[0050] The conductive film 113 is electrically connected to a light-transmitting pixel electrode 121 through an opening 117. Therefore, the light-transmitting pixel electrode 121 and the transistor 103 are electrically connected. To be continued.

[0051] The capacitance element 105 is surrounded by a capacitance line 115 and a signal line 109 in the pixel 101. The capacitor 105 is provided in a light-transmitting region. Since the capacitance element 105 can be formed large (with a large area) within the pixel 101, the aperture ratio It is possible to obtain a display device having an increased charge capacity while improving the light-emitting performance.

[0052] For example, in high-definition display devices, such as liquid crystal display devices, the area of ​​pixels becomes smaller. Therefore, in a high-definition display device, the area of ​​the capacitor element 105 is small. However, the capacitance of the capacitor 105 shown in this embodiment is small. Since the capacitor 105 has a light-transmitting property, the capacitor 105 is provided in each pixel. In the conventional liquid crystal display, the aperture ratio can be increased while obtaining a sufficient charge capacity. 200ppi (pixels per inch) or more, even 300ppi or more The present invention can be suitably used for a high-definition display device. This allows for efficient use of light from light sources such as backlights. This makes it possible to reduce the power consumption of the display device.

[0053] Here, a method for driving a display device according to one embodiment of the present invention will be described. Since the display device has a capacitance element 105 having a MOS capacitor structure, In order to stably operate the element 105, the other electrode of the capacitor element 105 and The potential VC applied to the multilayer film 119 (in other words, the capacitance line 115) acting as a do.

[0054] From the above, the CV curve of the capacitance element 105 is a threshold voltage as shown in FIG. The CV curve is obtained when the voltage is equal to or higher than 0 V. To operate the capacitor 105 stably means to keep the capacitor 105 in a sufficiently charged state. For example, during this period, the potential V The potential difference (VP-VC) between P and the potential VC of the multilayer film 119 is set to V1 or more as shown in FIG. The objective is to provide a potential VC such that:

[0055] In addition, during the period in which the capacitance element 105 is operated, the potential VP of the pixel electrode 121 is It fluctuates in the positive and negative directions according to the signal input to 109. The potential of the video signal fluctuates in the positive and negative directions based on the central potential of the video signal. During this period, the potential difference between the potential of the pixel electrode 121 and the potential of the multilayer film 119 is V1. In order to obtain V1 and V2, the potential of the multilayer film 119 is calculated by subtracting the capacitive element from the values ​​of V1 and V2. The potential should be lowered by at least the threshold voltage of the transistor 105 (see FIG. 18). In FIG. 8, the lowest potential among the potentials supplied to the scanning line 107 is GVss, and the highest The higher potential is GVdd.

[0056] In other words, in order to operate the capacitive element 105, During this period, the potential difference between the pixel electrode 121 and the multilayer film 119 becomes equal to or larger than the threshold voltage of the capacitance element 105. It is sufficient if the voltage is higher than the threshold voltage.

[0057] The multilayer film 119 of the capacitance element 105 and the multilayer film 111 of the transistor 103 have the same structure. Since the capacitor 105 has a threshold voltage equal to that of the transistor 103, Therefore, the potential VC of the multilayer film 119 is changed from the potential VP of the pixel electrode 121 to the potential VP of the transistor 122. The potential should be set to a value equal to or lower than the threshold voltage of the transistor 103. During the period in which the capacitance element 105 is operated, the multilayer film 119 is always kept in a conductive state. This allows the capacitor element 105 to operate stably.

[0058] As described above, by using the driving method of one embodiment of the present invention, Display device including a capacitor having a light-transmitting conductive film and a light-transmitting insulating film In this way, the capacitive element can be operated stably over time.

[0059] The transistor 103 is an enhancement type transistor, and the capacitor 10 5 is formed by using the formation process of the transistor 103, which is an enhancement type transistor. Therefore, the voltage range required to drive the display device according to one embodiment of the present invention is A depletion type transistor is used as the transistor 103, and the capacitor element 105 is a depletion type transistor. An oxide semiconductor device with increased carrier density formed by utilizing the formation process of a pressure-type transistor. This is narrower than the voltage range required to drive a display device formed using a nitride semiconductor film. Therefore, according to one embodiment of the present invention, the power consumption of a display device can be reduced.

[0060] Here, cross-sectional views of the dashed lines A1-A2 and B1-B2 in FIG. 3(A) shows the same.

[0061] In FIG. 3A, the cross-sectional structure of a pixel 101 of the liquid crystal display device is as follows. The display device is formed by a device portion formed on a first substrate 102 and a display device formed on a second substrate 150. The liquid crystal display device has an element portion between which the liquid crystal layer 160 is sandwiched.

[0062] First, the structure of the element portion provided on the first substrate 102 will be described. On the plate 102, a scan line 107 having a gate electrode of the transistor 103 and a scan line 107 The scanning line 107 and the capacitance line 115 are provided on the same surface. A gate insulating film 127 is provided on the scanning line 115. A multilayer film 111 is provided on the region overlapping with the capacitor element 105. A multilayer film 119 is provided on the gate insulating film 127. A signal line 109 including the source electrode of the transistor 103 and a drain electrode of the transistor 103 are connected to the signal line 109. A conductive film 113 including a gate electrode is provided.

[0063] In addition, the gate insulating film 127 in the region where the capacitance element 105 is formed has a gate insulating film 127 that reaches the capacitance line 115. The opening 123, the gate insulating film 127, and the multilayer film 119 A conductive film 125 is provided thereon.

[0064] In addition, the gate insulating film 127, the signal line 109, the multilayer film 111, the conductive film 113, the conductive film 12 5, and a protective insulating film for the transistor 103 and an insulating film for the capacitor element 105 are formed on the multilayer film 119. The insulating film 129, the insulating film 131, and the insulating film 132 functioning as a conductor are provided. In addition, the insulating film 129, the insulating film 131, and the insulating film 132 have openings reaching the conductive film 113. An opening 117 is provided, and a pixel electrode 121 is provided on the opening 117 and the insulating film 132. It is being done.

[0065] The capacitor 105 has a light-transmitting property and includes a pixel electrode 121, an insulating film 129, and It is composed of an insulating film 131 , an insulating film 132 , and a multilayer film 119 .

[0066] In addition, an insulating film 158 that functions as an alignment film is provided on the pixel electrodes 121 and the insulating film 132. The first substrate 102, the scanning lines 107, the capacitance lines 115, and the gate A base insulating film may be provided between the gate insulating film 127 and the gate insulating film 127 .

[0067] In addition, the α region (gate insulating film 127, multilayer film 111, FIG. 3B shows an enlarged view of the signal line 109 and the insulating film 129. FIG. 3C shows an enlarged view of the multilayer film 119, the conductive film 125, and the insulating film 129, respectively. Indicates.

[0068] In FIG. 3B, the multilayer film 111 includes a first oxide layer 1 in contact with a gate insulating film 127. A second oxide layer 111_1 is an oxide semiconductor layer that is in contact with the first oxide layer 111_1. 11_2 and a third oxide layer 111_3 on and in contact with the second oxide layer 111_2. The signal line 109 and the insulating film 129 are formed on the third oxide layer 111_3. The thickness of the first oxide layer 111_1 is 1 nm or more and 50 nm or less, preferably 5 nm or more. The thickness of the second oxide film is preferably 50 nm or less, more preferably 10 nm or more and 40 nm or less. The thickness of the material layer 111_2 is 1 nm or more and 50 nm or less, preferably 3 nm or more and 40 nm or less. The thickness of the third oxide layer 111_3 is preferably 5 nm or more and 30 nm or less. , 1 nm or more and 50 nm or less, preferably 3 nm or more and 40 nm or less, and more preferably 5 nm or more and 50 nm or less. The length should be between m and 30 nm.

[0069] The first oxide layer 111_1 is composed of only one element other than oxygen that constitutes the second oxide layer 111_2. The second oxide layer 111_2 is made up of at least one of these elements, and has an electron affinity smaller than that of the second oxide layer 111_2 by 0.2 eV or more. When an electric field is applied to the gate electrode, the oxide semiconductor layer is In the layer film 111, a channel is formed in the second oxide layer 111_2 having a large electron affinity. That is, the first oxide layer 111_2 is formed between the second oxide layer 111_2 and the gate insulating film 127. By including 1_1, the channel of the transistor 103 is in contact with the gate insulating film 127. It can be formed on a layer that does not have a dielectric constant (here, the second oxide layer 111_2).

[0070] The first oxide layer 111_1 may be made of, for example, aluminum, silicon, titanium, gallium, Germanium, yttrium, zirconium, tin, lanthanum, cerium or hafnium The oxide layer 111_2 may be an oxide film containing Zn at a higher concentration than the second oxide layer 111_2. The first oxide layer 111_1 contains the above-mentioned elements in a larger amount than the second oxide layer 111_2. An oxide film containing 5 times or more, preferably 2 times or more, and more preferably 3 times or more is used. Since this element strongly bonds with oxygen, it has the function of suppressing the occurrence of oxygen vacancies in the oxide film. That is, the first oxide layer 111_1 has more oxygen vacancies than the second oxide layer 111_2. It is an oxide film that is resistant to oxidation.

[0071] Alternatively, the second oxide layer 111_2 is an In-Ga-Zn oxide film, and the first oxide When the layer 111_1 is also an In-Ga-Zn oxide film, the first oxide layer 111_1 is made of In :Ga:Zn=x1:y1:z1 [atomic ratio], the second oxide layer 111_2 is In:Ga If Zn=x2:y2:z2 [atomic ratio], then y1 / x1 is greater than y2 / x2. The first oxide layer 111_1 and the second oxide layer 111_2 are preferably selected to have a thickness of 1000 nm or more. The first oxide layer 111_1 and the second oxide layer 111_2 in which y1 / x1 is 1.5 times or more larger than y2 / x2. and the second oxide layer 111_2. More preferably, y1 / x1 is greater than y2 / x2. The first oxide layer 111_1 and the second oxide layer 111_2 are selected so as to be at least twice as large as the first oxide layer 111_1 and the second oxide layer 111_2. More preferably, the first oxide film is selected such that y1 / x1 is at least three times larger than y2 / x2. A material layer 111_1 and a second oxide layer 111_2 are selected.

[0072] The third oxide layer 111_3 is composed of all elements other than oxygen constituting the second oxide layer 111_2. The second oxide layer 111_2 is made up of at least one of these elements, and has an electron affinity smaller than that of the second oxide layer 111_2 by 0.2 eV or more. In this case, even if an electric field is applied to the gate electrode, the third oxide layer 111 is not changed. No channel is formed in the second oxide layer 111_2. Since the third oxide layer 111_3 is composed of one or more elements, the second oxide layer 111_ The interface between the second oxide layer 111_2 and the third oxide layer 111_3 is unlikely to form an interface state. When the second transistor has the interface as a channel formation region, the second transistor has a different threshold voltage. This can cause the apparent threshold voltage of the transistor to vary. By providing the oxide layer 111_3, the electrical characteristics such as the threshold voltage of the transistor can be improved. It is possible to reduce the variation in the

[0073] For example, the third oxide layer 111_3 may be made of aluminum, silicon, titanium, gallium, Germanium, yttrium, zirconium, tin, lanthanum, cerium or hafnium The oxide layer 111_2 may be an oxide film containing Zn at a higher concentration than the second oxide layer 111_2. The third oxide layer 111_3 contains the above-mentioned elements in a larger amount than the second oxide layer 111_2. An oxide film containing 5 times or more, preferably 2 times or more, and more preferably 3 times or more is used. Since this element strongly bonds with oxygen, it has the function of suppressing the occurrence of oxygen vacancies in the oxide film. That is, the third oxide layer 111_3 has more oxygen vacancies than the second oxide layer 111_2. It is an oxide film that is resistant to oxidation.

[0074] Alternatively, the second oxide layer 111_2 is an In-Ga-Zn oxide film, and the third oxide When the layer 111_3 is also an In-Ga-Zn oxide film, the second oxide layer 111_2 is made of In :Ga:Zn=x2:y2:z2 [atomic ratio], the third oxide layer 111_3 is In:Ga :Zn=x 3: y 3: z3 [atomic ratio], y3 / x3 is greater than y2 / x2 The second oxide layer 111_2 and the third oxide layer 111_3 are preferably selected to be The second oxide layer 111_2 and the second oxide layer 111_3 in which y3 / x3 is 1.5 times or more larger than y2 / x2. and the third oxide layer 111_3. More preferably, y3 / x3 is greater than y2 / x2. The second oxide layer 111_2 and the third oxide layer 111_3 are selected so as to be at least twice as large as the first oxide layer 111_1. More preferably, the second oxide film is selected such that y3 / x3 is at least three times larger than y2 / x2. The material layer 111_2 and the third oxide layer 111_3 are selected.

[0075] In addition, the first oxide layer 111_1 to the third oxide layer 111_3 are formed by adding oxides having different crystallinity. In other words, a material in which the crystal parts of an amorphous oxide semiconductor or the like are clearly visible may be used. and a single-crystal oxide semiconductor, a polycrystalline oxide semiconductor, and a CAA Crystalline structures such as C-OS (for details of CAAC-OS, see embodiment 4). In addition, an oxide semiconductor having a structure (crystalline oxide semiconductor) may be appropriately combined. In addition, an amorphous oxide layer is formed on any one of the first oxide layer 111_1 to the third oxide layer 111_3. When an oxide semiconductor in which the crystal part is not clearly confirmed, such as a solid semiconductor, is used, the oxide semiconductor film This reduces the internal and external stresses of the transistor, reducing the variation in transistor characteristics. The amount of variation in threshold voltage due to aging and reliability testing of transistors can be reduced. .

[0076] For example, in the first oxide layer 111_1, a crystalline portion such as an amorphous oxide semiconductor is clearly observed. In addition, the second oxide semiconductor that can be a channel formation region is preferably an oxide semiconductor. The oxide layer 111_2 is preferably a crystalline oxide semiconductor. 111_3 is an oxide semiconductor in which crystal parts are not clearly identified, such as an amorphous oxide semiconductor, or It is preferable that the semiconductor layer is a crystalline oxide semiconductor. This can reduce the amount of variation in threshold voltage due to deterioration over time of the transistor or due to reliability testing.

[0077] In FIG. 3C, the multilayer film 119 is formed of a first oxide film in contact with the gate insulating film 127. A second oxide layer 119_1 is an oxide semiconductor film that is in contact with the first oxide layer 119_1. a third oxide layer 119_3 on and in contact with the second oxide layer 119_2; Note that the conductive film 125 and the insulating film 129 are formed over the third oxide layer 119_3. It has been done.

[0078] The multilayer film 119 that functions as the other electrode of the capacitance element 105 has the same layer structure as the multilayer film 111. That is, the multilayer film 119 is made of an oxide film applicable to the multilayer film 111. In addition, the multilayer film 119 can be formed at the same time as the multilayer film 111 is formed. Therefore, the multilayer film 119 contains a metal element of the oxide semiconductor that constitutes the multilayer film 111 .

[0079] The components of the above structure are described in detail below.

[0080] There is no particular restriction on the material of the first substrate 102, but at least the manufacturing process of the display device For example, the glass substrate must have sufficient heat resistance to withstand the heat treatment carried out in the manufacturing process. There are various types of substrates, such as glass, barium boron, and ceramic substrates. Non-alkali glass such as silicate glass, aluminoborosilicate glass or aluminosilicate glass It is also recommended to use a non-transparent substrate such as a stainless steel alloy. In this case, it is preferable to provide an insulating film on the surface of the substrate. The substrate 102 may be a quartz substrate, a sapphire substrate, a single crystal semiconductor substrate, a polycrystalline semiconductor substrate, a chemical Using compound semiconductor substrates, SOI (Silicon On Insulator) substrates, etc. It is also possible.

[0081] Since the scanning line 107 and the capacitance line 115 carry a large current, they are preferably formed of a metal film. The most typical examples are molybdenum (Mo), titanium (Ti), tungsten (W), and tantalum ( Ta), aluminum (Al), copper (Cu), chromium (Cr), neodymium (Nd), A single-layer structure using metal materials such as indium (Sc) or alloy materials that contain these as the main components. The structure is a laminated structure.

[0082] An example of the scanning line 107 and the capacitance line 115 is made of aluminum containing silicon. A single-layer structure with titanium laminated on aluminum, a two-layer structure with titanium laminated on titanium nitride, Two-layer structure with tungsten on titanium nitride, two-layer structure with tungsten on tantalum nitride, A two-layer structure in which copper is laminated on a copper-magnesium-aluminum alloy. A three-layer structure is used, in which copper is layered on titanium nitride and tungsten is then formed on top of that. There are some.

[0083] In addition, the material of the scanning line 107 and the capacitance line 115 is applied to the pixel electrode 121 described later. Any conductive material having a light-transmitting property can be used.

[0084] Furthermore, the scanning line 107 and the capacitance line 115 may be made of a metal oxide containing nitrogen. Specifically, nitrogen-containing In-Ga-Zn oxide, nitrogen-containing In-Sn oxide, and nitrogen-containing In-Ga oxide containing nitrogen, In-Zn oxide containing nitrogen, Sn oxide containing nitrogen, In oxides containing In and metal nitrides (InN, SnN, etc.) can be used. These materials have a work function of 5 eV or more. By using a metal oxide containing nitrogen as the electrode, the threshold voltage of the transistor 103 can be changed in the positive direction, making it easier to realize enhancement-type transistors. For example, when using an In-Ga-Zn oxide containing nitrogen, at least the oxide semiconductor The multilayer film 111 containing the conductor layer has a higher nitrogen concentration, specifically, a nitrogen concentration of 7 atomic % or more. -Ga-Zn oxide can be used.

[0085] The scanning lines 107 and the capacitance lines 115 are made of low resistance materials such as aluminum and copper. It is preferable to use aluminum or copper. By using aluminum or copper, the signal delay can be reduced and the display In addition, aluminum has low heat resistance and is prone to hillocks and cracks. Disks or migration defects are likely to occur. In order to prevent defects caused by oxidation, etc., molybdenum, titanium, tungsten, etc. are added to aluminum. It is preferable to laminate a metal material having a melting point higher than that of aluminum, such as copper. Even when using molybdenum, it is recommended to use molybdenum to prevent defects due to migration and the diffusion of copper elements. It is preferable to laminate a metal material having a higher melting point than copper, such as titanium or tungsten. stomach.

[0086] The gate insulating film 127 is made of, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, Insulating materials such as silicon nitride, aluminum oxide, gallium oxide or Ga-Zn oxide The insulating film is provided in a single layer structure or a laminate structure using the above.

[0087] In addition, the gate insulating film 127 is formed of an insulating film having a barrier property against oxygen, hydrogen, water, etc. By providing the insulating layer, oxygen can be diffused from the multilayer film 111 including the oxide semiconductor layer to the outside and from the outside to the outside. Therefore, it is possible to prevent hydrogen, water, and the like from entering the multilayer film 111 including the oxide semiconductor layer. Examples of insulating films that have a barrier property against oxygen, hydrogen, water, etc. include aluminum oxide, oxide Aluminum oxide nitride, gallium oxide, gallium oxide nitride, yttrium oxide, yttrium oxide nitride tritium, silicon nitride, etc.

[0088] The gate insulating film 127 preferably has the following laminated structure: A silicon nitride film with few defects is provided as a contact film, and a second silicon nitride film is formed on the first silicon nitride film. A silicon nitride film with a small amount of hydrogen desorption and ammonia desorption was used. On the second silicon nitride film, any one of the oxide insulating films listed in the gate insulating film 127 is formed. It is preferable to provide one of these.

[0089] The second silicon nitride film is a film that has a hydrogen molecule desorption rate of 5.0 or more in thermal desorption gas spectrometry. ×10 21 molecules / cm 3 Less than 3 x 10 21 molecules / cm 3 The following is more preferable: 1×10 21 molecules / cm 3 The number of ammonia molecules released is less than 1×10 22 molecule / cm 3 Less than 5 x 10 21 molecules / cm 3 Less than 1×10, more preferably 2 1 molecules / cm 3 It is preferable to use a nitride insulating film having the following properties. The silicon nitride film and the second silicon nitride film are used as a part of the gate insulating film 127, The gate insulating film 127 is made of a gate insulating film having a small amount of defects and a small amount of desorption of hydrogen and ammonia. As a result, hydrogen and Therefore, the amount of oxygen and nitrogen moving to the multilayer film 111 including the oxide semiconductor layer can be reduced.

[0090] The thickness of the gate insulating film 127 is preferably 5 nm or more and 400 nm or less, more preferably 10 nm or less. The thickness is preferably at most 300 nm, and more preferably at least 50 nm and at most 250 nm.

[0091] The multilayer film 111 and the multilayer film 119 including the oxide semiconductor layer may have an amorphous structure, a single crystal structure, or a Alternatively, the multilayer film 111 including the oxide semiconductor layer and the The thickness of the multilayer film 119 is 1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less. , more preferably 3 nm or more and 40 nm or less, and even more preferably 5 nm or more and 30 nm or less. This is what we should do.

[0092] As oxide semiconductors applicable to the multilayer film 111 and the multilayer film 119 including an oxide semiconductor layer, The energy gap is 2.5 eV or more, preferably 2.7 eV or more, and more preferably In this way, by using oxide semiconductors with a wide energy gap, Therefore, the off-state current of the transistor 103 can be reduced.

[0093] The multilayer film 111 and the multilayer film 119 including an oxide semiconductor layer may be, for example, an indium oxide film. In-Zn oxide, which is an oxide containing two kinds of metals, Sn- Zn oxide, Al-Zn oxide, Zn-Mg oxide, Sn-Mg oxide, In-Mg oxide In-Ga-Zn oxide (IG) (also written as ZO), In-Al-Zn oxide, In-Sn-Zn oxide, Sn-Ga- Zn oxide, Al-Ga-Zn oxide, Sn-Al-Zn oxide, In-Zr-Zn oxide In-Ti-Zn oxide, In-Sc-Zn oxide, In-Y-Zn oxide, In- La-Zn oxide, In-Ce-Zn oxide, In-Pr-Zn oxide, In-Nd-Z n-oxide, In-Sm-Zn oxide, In-Eu-Zn oxide, In-Gd-Zn oxide , In-Tb-Zn oxide, In-Dy-Zn oxide, In-Ho-Zn oxide, In- Er-Zn oxide, In-Tm-Zn oxide, In-Yb-Zn oxide, In-Lu-Z n-oxide, In-Hf-Zn oxide, and four-metal oxide In-Sn-Ga -Zn oxide, In-Al-Ga-Zn oxide, In-Sn-Al-Zn oxide It is possible.

[0094] Here, In-Ga-Zn oxide refers to an oxide containing In, Ga, and Zn as the main components. The atomic ratio of In, Ga, and Zn is not important.

[0095] In addition, as an oxide semiconductor, InMO3(ZnO) m Using materials expressed as (m>0) M may be a metal element selected from Ga, Fe, Mn, and Co, or Shows multiple metal elements.

[0096] For example, In:Ga:Zn=1:1:1, In:Ga:Zn=2:2:1, or In For example, an In-Ga-Zn oxide having an atomic ratio of Ga:Zn=3:1:2 can be used. Or, In:Sn:Zn=1:1:1, In:Sn:Zn=2:1:3 or In:S It is recommended to use In-Sn-Zn oxide with an atomic ratio of n:Zn=2:1:5. The atomic ratio of the oxide includes a variation of ±20% from the above atomic ratio as an error.

[0097] Here, features of a transistor including an oxide semiconductor are described. The transistor using an oxide semiconductor is an n-channel transistor. In addition, oxygen vacancies in an oxide semiconductor can generate carriers, which can cause the transistor to degrade. For example, the threshold voltage of a transistor may be increased by 100%. When the gate voltage is 0V, the drain current may flow. .

[0098] Therefore, defects, typically oxygen vacancies, contained in the multilayer film 111 including the oxide semiconductor layer are For example, the direction of the magnetic field is parallel to the film surface. The g value measured by the electron spin resonance method is 1.89 to 1.96 (typically 1.93). The spin density (corresponding to the defect density in the oxide semiconductor film) is below the lower limit of detection by the measuring instrument. Defects contained in the oxide semiconductor film, typically, oxygen, are preferably reduced to below the surface of the oxide semiconductor film. By reducing the defects as much as possible, the transistor 103 becomes a depletion type. This can suppress the generation of noise, thereby improving the electrical characteristics and reliability of the display device.

[0099] The negative shift in the threshold voltage of a transistor is not only due to oxygen vacancies, but also due to oxide It can also be caused by hydrogen contained in semiconductors (including hydrogen compounds such as water). Hydrogen contained in oxide semiconductors reacts with oxygen that bonds with metal atoms to form water, and In the lattice where oxygen has been removed (or the part where oxygen has been removed), there is a defect (which can also be called an oxygen vacancy). In addition, some of the hydrogen reacts with oxygen to generate electrons, which act as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is in a depletion state. It is easy for this to become shaped like a mold.

[0100] Therefore, the multilayer film 111 including the oxide semiconductor layer is required to have as little hydrogen as possible. Specifically, in the multilayer film 111 including the oxide semiconductor layer, the secondary ion mass Analysis method (SIMS: Secondary Ion Mass Spectrometry) ) hydrogen concentration is 5×10 18 atoms / cm 3 Less than 1x1 0 18 atoms / cm 3 Less than or equal to 5×10 17 atoms / cm 3 below, More preferably, 1×10 16 atoms / cm 3 The following applies.

[0101] The multilayer film 111 including the oxide semiconductor layer is also obtained by secondary ion mass spectrometry. The concentration of alkaline metals or alkaline earth metals is 1×10 18 atoms / cm 3 Below, good Preferably 2 x 10 16 atoms / cm 3 The following are alkali metals and alkaline earth metals: When a metal is bonded to an oxide semiconductor, carriers may be generated. This can increase the off-state current of the transistor.

[0102] In addition, when nitrogen is contained in the multilayer film 111 including the oxide semiconductor layer, the electron This causes the electrons to be generated, increasing the carrier density and making it easier to become n-type. Transistors using oxide semiconductors tend to be depletion type. In the multilayer film 111 including the conductor layer, it is preferable that the nitrogen content is reduced as much as possible. For example, the nitrogen concentration is 5×10 18 atoms / cm 3 It is preferable to do the following:

[0103] In this way, impurities (hydrogen, nitrogen, alkali metals or alkaline earth metals, etc.) can be removed. By reducing the amount of the oxide semiconductor layer as much as possible and forming the multilayer film 111 including the highly purified oxide semiconductor layer, The transistor 103 can be prevented from becoming a depletion type, and the off-state current of the transistor 103 can be reduced. Therefore, a display device having good electrical characteristics can be manufactured. In addition, a display device with improved reliability can be manufactured.

[0104] The reason why the off-state current of a transistor using a highly purified oxide semiconductor film is low is that This can be proved by various experiments. For example, when the channel width is 1×10 6 Channel length L in μm Even if the element has a thickness of 10 μm, the voltage between the source and drain electrodes (drain voltage) is 1 In the range from V to 10 V, the off-state current is below the measurement limit of the semiconductor parameter analyzer. , i.e. 1 × 10 -13 In this case, the transistor The off-state current, which is equivalent to the value divided by the channel width of the transistor, must be 100zA / μm or less. Also, by connecting a capacitance element and a transistor, the current flowing into or out of the capacitance element can be The off-state current was measured using a circuit in which the transistor controls charge flowing out. In the measurement, a highly purified oxide semiconductor film was formed in a channel formation region of the transistor. The off-state current of the transistor is measured based on the change in the amount of charge per unit time of the capacitor. As a result, when the voltage between the source and drain electrodes of the transistor is 3V, several It was found that an even lower off-current of 10 yA / μm could be obtained. A transistor including such an oxide semiconductor film has an extremely small off-state current.

[0105] A signal line 109 including the source electrode of the transistor 103, a drain electrode of the transistor 103 The conductive film 113 including the electrodes, and the multilayer film 119 of the capacitor element 105 are electrically connected to the capacitor line 115. The conductive film 125 for effectively connecting the scanning lines 107 and the capacitance lines 115 is made of a material that can be applied to the scanning lines 107 and the capacitance lines 115. In addition, it may have a single layer structure or a multilayer structure.

[0106] The insulating film functions as a protective insulating film of the transistor 103 and a dielectric film of the capacitor 105. The insulating film 129, the insulating film 131, and the insulating film 132 are made of a material that can be applied to the gate insulating film 127. In particular, the insulating films 129 and 131 are oxide insulating films. It is preferable that the insulating film 132 be a nitride insulating film. By this, impurities such as hydrogen and water are prevented from entering the transistor 103 (particularly the oxide semiconductor layer In addition, the insulating film 129 is not provided in the structure. It is also possible.

[0107] In addition, one or both of the insulating film 129 and the insulating film 131 may have a stoichiometric composition. It is preferable that the oxide insulating film contains more oxygen than oxygen. In addition, the oxygen in the oxide semiconductor layer is prevented from being released, and the oxygen in the oxygen-excess region is prevented from being released. The oxygen vacancies can be compensated for by transferring the oxygen to the oxide semiconductor layer. Gas analysis (hereafter referred to as TDS (Thermal Desorption Spectroscopy) opy) analysis. The amount of oxygen molecules released measured by 1 8 molecules / cm 3 By using the oxide insulating film having the above structure, oxygen contained in the oxide semiconductor film can be prevented from being easily The defect can be filled. In the case of The multilayer film 111 may be an oxide insulating film having at least an oxide semiconductor layer. The presence of an oxygen excess region in the overlapping region prevents oxygen from being released from the oxide semiconductor layer. At the same time, oxygen contained in the oxygen excess region is moved to the oxide semiconductor layer, and oxygen vacancies are eliminated. It will be possible to replenish.

[0108] The insulating film 131 is an oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition. In that case, the insulating film 129 is preferably an oxide insulating film that transmits oxygen. In the insulating film 129, all oxygen that enters the insulating film 129 from the outside passes through the insulating film 129. Some oxygen does not move and remains in the insulating film 129. Some oxygen is transferred from the insulating film 129 to the outside. An oxide insulating film having a large diffusion coefficient is preferable.

[0109] The thickness of the insulating film 129 is 5 nm or more and 150 nm or less, preferably 5 nm or more and 50 nm or less. The thickness of the insulating film 131 can be set to 10 nm or less and preferably 30 nm or less. The thickness can be set to 30 nm or more and 500 nm or less, preferably 150 nm or more and 400 nm or less. Cut.

[0110] When the insulating film 132 is a nitride insulating film, one or both of the insulating film 129 and the insulating film 131 is It is preferable that both of the insulating film and the insulating film have a barrier property against nitrogen. By using a nitride insulating film, it is possible to provide a barrier against nitrogen. When using 0.5% by weight hydrofluoric acid, the etching rate is 10 nm / min or less. It is preferable that the oxide insulating film be an oxide insulating film having the above formula:

[0111] One or both of the insulating film 129 and the insulating film 131 may be formed of silicon oxynitride or When using an oxide insulating film containing nitrogen, such as silicon nitride oxide, SIMS (Secondary The nitrogen concentration obtained by SIM S detection limit or higher 3×10 20 atoms / cm 3 Less than 1 x 10 18 atom s / cm 3 More than 1×10 20 atoms / cm 3 It is preferable to set it as follows. As a result, nitrogen is introduced into the multilayer film 111 including the oxide semiconductor layer included in the transistor 103. This also reduces the amount of migration of oxides containing nitrogen. The amount of defects in the velum itself can be reduced.

[0112] The insulating film 132 may be a nitride insulating film having a low hydrogen content. For example, the amount of hydrogen molecules released by the membrane as measured by TDS analysis is 5.0 × 10 21 molecules / cm 3 less than 3.0×10 21 molecules / cm 3 Less than More preferably, 1.0×10 21 molecules / cm 3 It is a nitride insulating film having a thickness of less than 100 nm.

[0113] The insulating film 132 can suppress the ingress of impurities such as hydrogen and water from the outside. For example, the thickness is 50 nm or more and 200 nm or less, preferably 50 nm or more and 150 nm or less. m or less, and more preferably from 50 nm to 100 nm.

[0114] The pixel electrode 121 is made of In-Sn oxide, In-W oxide, In-Zn-W oxide, In -Ti oxide, In-Ti-Sn oxide, In-Zn oxide, In-Si-Sn oxide, etc. The insulating film 11 is formed of a conductive material having light-transmitting properties.

[0115] Next, the structure of the element portion provided on the second substrate 150 will be described. 50, a light-shielding film 152 and an electrode provided on the light-shielding film 152 to face the pixel electrode 121. On the counter electrode 154, a layer functioning as an alignment film is provided. An insulating film 156 is provided.

[0116] The second substrate 150 may be made of the same material as the first substrate 102 .

[0117] The light-shielding film 152 is a film that blocks light from a backlight or an external source from being irradiated onto the transistor 103. The light-shielding film 152 is formed using a material such as metal or organic resin containing a pigment. In addition, the light-shielding film 152 is formed on the transistor 103 of the pixel 101 and also on the scanning The area other than the pixel section 100, such as the scan line driving circuit 104, the signal line driving circuit 106 (see FIG. 1), etc. It may also be provided in the area.

[0118] In addition, a colored film having a function of transmitting light of a predetermined wavelength is provided between adjacent light-shielding films 152. (also called a color filter) may be provided. Between the opposing electrode 154, impurities from the light-shielding film 152 and the colored film are absorbed on the liquid crystal layer 160 side. In order to suppress diffusion into the substrate, an overcoat film may be provided.

[0119] The counter electrode 154 is provided by appropriately using the same conductive material having light transmission as the pixel electrode 121. do.

[0120] The liquid crystal element 108 includes a pixel electrode 121, a counter electrode 154, and a liquid crystal layer 160. an insulating film 158 that functions as an alignment film and is provided in the element portion of the first substrate 102; The insulating film 156, which functions as an alignment film and is provided in the element portion of the second substrate 150, The pixel electrode 121 and the counter electrode 154 are sandwiched between the liquid crystal layer 160. Overlaps through 0.

[0121] As described above, according to one embodiment of the present invention, the transistor 103 and the capacitor 105 By using a multilayer film including an oxide semiconductor layer, it is possible to fabricate a large-area substrate, so the fabrication cost is In addition, the multilayer film 11 used in the capacitor element 105 can be formed by a method for manufacturing a display device having a low cost. Since the display device 9 has a light-transmitting property, the aperture ratio of the pixel is increased, and a display device with low power consumption is provided. In addition, in the multilayer film 111 used in the transistor 103, the gate insulating film Since the channel is formed in a layer that does not contact the 127, the transistor has stable electrical characteristics and is shaped Thus, a highly reliable display device can be manufactured.

[0122] In the display device according to one embodiment of the present invention, the polarization axis of the polarizing member (polarizing substrate) is parallel. The display mode of the display device is set to the liquid crystal element 10 when no voltage is applied. By making the display 8 normally black, which does not transmit light from light sources such as backlights, The area in which the light-shielding film 152 is provided in the pixel 101 can be reduced or eliminated. As a result, high-definition displays with pixel densities of 200 ppi or more, or even 300 ppi or more, are becoming possible. Even in the case of a device in which each pixel is small, the aperture ratio can be improved. By using the capacitor 105 having the above structure, the aperture ratio can be further improved.

[0123] (Embodiment 2) In this embodiment, a display device is provided on the first substrate 102 of the display device shown in FIG. 3 of the first embodiment. A method for manufacturing the element portion will be described with reference to FIGS.

[0124] <Method for manufacturing a display device> First, the scanning lines 107 and the capacitance lines 115 are formed on the first substrate 102. An insulating film 126, which will be processed into a gate insulating film 127 later, is formed so as to cover the capacitance line 115. Then, a multilayer film 111 is formed in the area of ​​the insulating film 126 that overlaps with the scanning line 107, and then a pixel electrode The multilayer film 119 is formed so as to overlap the region where 121 is to be formed (see FIG. 4(A)). .

[0125] The scanning line 107 and the capacitance line 115 are formed of a conductive film using the materials listed in the first embodiment. The conductive film can be formed by forming a mask on the conductive film and processing the conductive film using the mask. The conductive film can be formed by various methods such as deposition, PE-CVD, sputtering, and spin coating. The thickness of the conductive film is not particularly limited, and the time and the time required for forming the conductive film can be varied. The mask can be determined by taking into consideration the desired resistivity, etc. The conductive film can be processed by a resist mask formed by a deposition process. This can be done by dry etching and / or wet etching.

[0126] The insulating film 126 is formed by PE-CVD or the like using a material that can be used for the gate insulating film 127. The film can be formed by using various film formation methods such as a sputtering method.

[0127] The multilayer film 111 and the multilayer film 119 are formed using the materials listed in the first embodiment. Each oxide film constituting the multilayer film 111 and the multilayer film 119 can be formed in a vacuum. It is preferable to form each oxide film successively in a vacuum. It is possible to suppress impurities from being mixed into the interface of the material film.

[0128] The multilayer film 111 and the multilayer film 119 can be formed by a sputtering method, a coating method, a pulse laser, or the like. It can be formed by using a deposition method, a laser ablation method, or the like. By using this method, the multilayer film 111 and the multilayer film 119 that are isolated from each other are formed on the insulating film 126. It can be formed directly.

[0129] When the multilayer film 111 and the multilayer film 119 are formed by the sputtering method, plasma is generated. The power supply for the operation of the device may be an RF power supply, an AC power supply, or a DC power supply, as appropriate. The sputtering gas may be a rare gas (typically argon), oxygen gas, A mixture of rare gas and oxygen is appropriately used. In the case of a mixture of rare gas and oxygen, It is preferable to increase the ratio of oxygen to rare gas. It is only necessary to select an appropriate value according to the composition of the compound semiconductor film.

[0130] The multilayer film 111 and the multilayer film 119 are processed by dry etching and wet etching. This can be done by either etching or both. The etching conditions (etching gas, etching solution, etching time, etc.) are adjusted according to the material. Set the temperature etc. appropriately.

[0131] After the multilayer film 111 and the multilayer film 119 are formed, a heat treatment is performed to form the multilayer film 111. It is preferable to dehydrogenate or dehydrate the multilayer film 119. The temperature of the heat treatment is Typically, the temperature is 150° C. or higher and lower than the substrate distortion point, preferably 200° C. or higher and 450° C. or lower, and more preferably 150° C. or higher and lower than the substrate distortion point. The heat treatment is preferably performed at 300° C. or more and 450° C. or less. This may be performed on the multilayer film before it is processed into the multilayer film 119.

[0132] In the above heat treatment, the heat treatment device is not limited to an electric furnace, and may be a device using heated gas, etc. The heating medium may be a device that heats the workpiece by thermal conduction or thermal radiation from the medium. For example, GRTA (Gas Rapid Thermal Anneal) equipment, LRT RTA (Rapid Thermal Anneal) equipment such as A (Lamp Rapid Thermal Anneal) The LRTA device is a halo Gen lamps, metal halide lamps, xenon arc lamps, carbon arc lamps, high The light emitted by high pressure sodium lamps, high pressure mercury lamps, etc. (electromagnetic waves) The GRTA device heats the object to be treated by using high-temperature gas. It is a device.

[0133] The heat treatment is carried out in an atmosphere of nitrogen, oxygen, or ultra-dry air (with a water content of 20 ppm or less, preferably Air at less than 1 ppm, preferably less than 10 ppb), or rare gases (argon, helium The above-mentioned nitrogen, oxygen, ultra-dry air, or rare gas may be added to hydrogen. It is preferable that the mixture does not contain water or the like. After heating in an inert gas atmosphere, it is heated in an oxygen atmosphere. The treatment time is from 3 minutes to 24 hours.

[0134] The first substrate 102, the scanning line 107, the capacitance line 115, and the gate insulating film 1 When a base insulating film is provided between the insulating film 27, the base insulating film is made of silicon oxide, silicon oxynitride, etc. Con, silicon nitride, silicon oxide nitride, gallium oxide, yttrium oxide, aluminum oxide The base insulating film can be formed of a material such as aluminum oxynitride or aluminum nitride. Formed with silicon nitride, gallium oxide, yttrium oxide, aluminum oxide, etc. Impurities, typically alkali metals, water, hydrogen, etc., are introduced from the first substrate 102 into the multilayer film 11. The base insulating film is formed by sputtering or PE-CVD. The electrode can be formed using:

[0135] Next, an opening 123 is formed in the insulating film 126 to reach the capacitance line 115, and a gate insulating film 127 is formed. Then, a signal line 109 including a source electrode of the transistor 103, The conductive film 113 including the drain electrode of the capacitor 103, the multilayer film 119 and the capacitance line 115 are electrically connected to each other. A conductive film 125 for connecting to the first and second electrodes is formed (see FIG. 4B).

[0136] The opening 123 is formed so that a part of the region of the insulating film 126 overlapping the capacitance line 115 is exposed. The formation of the mask can be achieved by forming a mask and processing the mask. The processing can be performed in the same manner as the scanning line 107 and the capacitance line 115.

[0137] The signal line 109, the conductive film 113 and the conductive film 125 are A conductive film is formed using a material applicable to the conductive film 125, and a mask is formed on the conductive film. The mask can be formed by processing the mask. This can be done in the same manner as the scan line 107 and the capacitance line 115.

[0138] Next, the multilayer film 111, the multilayer film 119, the signal line 109, the conductive film 113, the conductive film 125, and An insulating film 128 is formed on the gate insulating film 127, and an insulating film 130 is formed on the insulating film 128. Then, an insulating film 133 is formed on the insulating film 130 (see FIG. 5(A)).

[0139] The insulating film 128, the insulating film 130, and the insulating film 133 are successively formed in a vacuum. In this way, the insulating film 128, the insulating film 130, and the insulating film 1 It is possible to suppress the intrusion of impurities into the interfaces of the electrodes 33. ), the interface between the insulating film 128 and the insulating film 130 is indicated by a dashed line. When the insulating film 130 is made of the same material, the interface between the insulating film 128 and the insulating film 130 is Sometimes it's not clear.

[0140] The insulating film 128 is formed by PE-CVD or spa using a material applicable to the insulating film 129. The insulating film 130 can be formed by using various film forming methods such as a dipping method. The insulating film 133 can be formed using a material applicable to the insulating film 132. The material can be used to form the substrate.

[0141] The insulating film 128 (insulating film 129) can be formed under the following conditions. Regarding the case where a silicon oxide film or a silicon oxynitride film is formed as the oxide insulating film The formation conditions are as follows: the substrate is placed in a vacuum-evacuated processing chamber of a PE-CVD apparatus. The temperature is maintained at 180°C or higher and 400°C or lower, and more preferably 200°C or higher and 370°C or lower. A deposition gas containing silicon as a source gas and an oxidizing gas are introduced into the processing chamber. The pressure is set to 20 Pa or more and 250 Pa or less, and more preferably 40 Pa or more and 200 Pa or less. This is a condition for supplying high frequency power to an electrode provided in the processing chamber.

[0142] Representative examples of silicon-containing deposition gases include silane, disilane, trisilane, and fluoride. Silane, etc. Oxidizing gases include oxygen, ozone, nitrous oxide, nitrogen dioxide, etc. There is.

[0143] In addition, by increasing the amount of oxidizing gas to 100 times or more the amount of deposition gas containing silicon, It is possible to reduce the hydrogen content in the insulating film 128 (insulating film 129). Furthermore, the number of dangling bonds contained in the insulating film 128 (insulating film 129) can be reduced. The oxygen that moves from the insulating film 130 (insulating film 131) moves to the insulating film 128 (insulating film 129). Since the insulating film 128 (insulating When the dangling bonds contained in the insulating film 130 (insulating film 129) are reduced, 31) to the multilayer film 111 and the multilayer film 119, and It is possible to compensate for the oxygen vacancies in the multilayer film 11 and the multilayer film 119. The amount of hydrogen mixed into the oxide semiconductor film can be reduced, and oxygen vacancies in the oxide semiconductor film can be reduced. It is possible to reduce

[0144] The insulating film 130 (insulating film 131) is an oxide insulating film or a stoichiometric insulating film including the oxygen excess region. In the case where the oxide insulating film contains more oxygen than the theoretical composition, the insulating film 130( The insulating film 131) can be formed under the following conditions. The case of forming a silicon oxide film or a silicon oxynitride film will be described below. The conditions were as follows: the substrate was placed in the evacuated processing chamber of the PE-CVD device and heated to 180°C or higher for 2 The temperature is kept at 60° C. or less, more preferably at 180° C. or more and 230° C. or less, and the raw material gas is introduced into the processing chamber. The pressure in the processing chamber is then adjusted to 100 Pa or more and 250 Pa or less, more preferably 10 0 Pa to 200 Pa, and 0.17 W / cm to the electrode installed in the treatment chamber 2 More than 0 .5W / cm 2 Less than or equal to 0.25 W / cm 2 More than 0.35W / cm 2 below The object of the present invention is to supply high frequency power.

[0145] The source gas for the insulating film 130 (insulating film 131) can be applied to the insulating film 128 (insulating film 129). This can be used as a raw material gas.

[0146] The conditions for forming the insulating film 130 are: high frequency power of the above power density in a processing chamber at the above pressure; By supplying the gas, the decomposition efficiency of the source gas in the plasma increases, the number of oxygen radicals increases, As the oxidation of the source gas progresses, the oxygen content in the insulating film 130 becomes higher than the stoichiometric composition. However, when the substrate temperature is set to the above temperature, the bond between silicon and oxygen becomes weak. As a result, the amount of oxygen in the stoichiometric composition is less than that of the oxygen in the stoichiometric composition. It is possible to form an oxide insulating film that contains a large amount of oxygen and from which part of the oxygen is released by heating. In addition, an insulating film 128 is provided on the multilayer film 111. Therefore, the insulating film 130 In the formation process, the insulating film 128 serves as a protective film for the multilayer film 111. Even if the insulating film 130 is formed using high-frequency power, damage to the multilayer film 111 is suppressed. can.

[0147] In addition, by increasing the thickness of the insulating film 130, the amount of oxygen desorbed by heating is increased. Therefore, it is preferable that the insulating film 130 is thicker than the insulating film 128. By providing the insulating film 128, it is possible to improve the coverage even when the insulating film 130 is provided thick. can.

[0148] In the case where the insulating film 133 is a nitride insulating film with a low hydrogen content, the insulating film 133 has the following properties. In this embodiment, a silicon nitride film is used as the nitride insulating film. The formation conditions are as follows: The substrate placed in the chamber is heated to 80°C or higher and 400°C or lower, and more preferably 200°C or higher and 370°C or lower. The raw material gas is introduced into the processing chamber to maintain the pressure in the processing chamber at 100 Pa or more. The pressure in the processing chamber is set to 50 Pa or less, and preferably to 100 Pa or more and 200 Pa or less. The object of the present invention is to supply high frequency power to the electrodes.

[0149] The source gas for the insulating film 133 is a deposition gas containing silicon, nitrogen, and ammonia. Representative examples of deposition gases containing silicon include silane, disilane, and the like. The nitrogen flow rate is the same as the ammonia flow rate. It is preferable to set the ratio to 5 to 50 times, and more preferably to 10 to 50 times. By using ammonia as the source gas, the deposition gas containing silicon and the nitrogen This is because ammonia is decomposed by plasma energy or thermal energy. The energy released by the dissociation breaks down the bonds of the deposition gas molecules, including silicon. This is because it contributes to breaking down the bonds of nitrogen molecules. Silicon nitride has low resistance to impurities such as hydrogen and water from the outside. A silicon film can be formed.

[0150] After forming at least the insulating film 130, a heat treatment is performed to form the insulating film 128 or the insulating film 1 The excess oxygen contained in 30 is transferred to the multilayer film 111, and the oxygen vacancies in the multilayer film 111 are compensated for. It is preferable that the heat treatment is performed to dehydrogenate the multilayer film 111 and the multilayer film 119 or to remove the hydrogen from the multilayer film 111 and the multilayer film 119. This can be appropriately performed by referring to the details of the heat treatment for dehydration.

[0151] Next, the regions of the insulating film 128, the insulating film 130, and the insulating film 133 overlapping with the conductive film 113 are An opening 117 is formed in the insulating film 113 so as to reach the conductive film 113. 28, the insulating film 130, and the insulating film 133 are divided, and the insulating film 129, the insulating film 131, Then, the conductive film 113, the insulating film 129, and the insulating film 132 are formed. A light-transmitting conductive film is formed on the insulating film 132 and the insulating film 132, and unnecessary regions are removed. Thus, the pixel electrode 121 is formed (see FIG. 5(B)).

[0152] The opening 117 can be formed in the same manner as the opening 123. The light-transmitting film 114 is made of any of the materials listed above and is in contact with the conductive film 113 through the opening 117. A conductive film is formed, a mask is formed on the conductive film, and the conductive film is processed using the mask. The formation and processing of the mask is performed for the scanning line 107 and the capacitance line 115. It can be done in the same way.

[0153] Through the above steps, a display device which is one embodiment of the present invention can be formed.

[0154] As described above, according to one embodiment of the present invention, the transistor 103 and the capacitor 105 By using a multilayer film including an oxide semiconductor layer, it is possible to fabricate a large-area substrate, so the fabrication cost is In addition, the multilayer film 11 used in the capacitor element 105 can be formed by a method for manufacturing a display device having a low cost. Since the display device 9 has a light-transmitting property, the aperture ratio of the pixel is increased, and a display device with low power consumption is provided. In addition, in the multilayer film 111 used in the transistor 103, the gate insulating film Since the channel is formed in a layer that does not contact the 127, the transistor has stable electrical characteristics and is shaped Thus, a highly reliable display device can be manufactured.

[0155] This embodiment mode may be appropriately combined with any of the other embodiment modes.

[0156] (Embodiment 3) In this embodiment, a display device according to one embodiment of the present invention will be described with reference to the embodiment 1. The configuration different from the configuration shown in FIG. 6 to FIG. 11 will be described. In the display device shown in FIG. 1, the liquid crystal layer and the elements formed on the second substrate on the opposite side are Since the configuration is the same as that shown in FIG. 3, it is omitted in the illustration.

[0157] <Modification 1 of the display device configuration> First, a first modified example of the configuration of the display device will be described with reference to FIGS. 2 and 3. Only the capacitance element 165, which is different from the capacitance element 105 described in FIG. 6 is a top view of the pixel 161, and FIG. 7 is a top view of the pixel 161 between the dashed dotted lines C1 and C2 in FIG. 1 is a cross-sectional view taken along dashed dotted line D1-D2.

[0158] In the pixel 161, the conductive film 167 is in contact with the multilayer film 119 along its outer periphery. The conductive film 167 is in contact with the capacitor line 115 through the transistor 123. A signal line 109 including a source electrode of transistor 103 and a conductor including a drain electrode of transistor 103 Since the conductive film 113 is formed in the same formation process, it may have a light-shielding property. However, the conductive film 167 is preferably formed to have a small area. As long as the shape has all the functions, the practitioner can select the most suitable shape. Other configurations of this pixel 161 are similar to those in FIG.

[0159] As shown in FIG. 7A, in the pixel 161, the conductive film 167 is a multilayer film of the capacitor element 165. It is provided so as to cover the end portion of the layer film 119 .

[0160] In addition, the α region (gate insulating film 127, multilayer film 111, FIG. 7B shows an enlarged view of the signal line 109 and the insulating film 129. FIG. 7C shows an enlarged view of the multilayer film 119, the conductive film 167, and the insulating film 129, respectively. Indicates.

[0161] In this embodiment, the multilayer film 111 and the multilayer film 119 are configured as shown in FIG. The structure may be the same as that shown in FIG.

[0162] In addition, in the configurations shown in FIGS. 6 and 7, the conductive film 167 is formed in a loop shape. The entire portion of the conductive film 167 that is in contact with the multilayer film 119 is electrically connected to the capacitance line 115. In other words, a conductive film formed in the same formation process as the conductive film 167 may be used. It may be provided in contact with the multilayer film 119 while being separated from 167 .

[0163] By using the configuration shown in FIG. 6 and FIG. 7, the other electrode constituting the capacitance element The contact resistance between the multilayer film and the conductive film electrically connected to the capacitance line can be reduced. In addition, when the conductivity of the other electrode constituting the capacitance element is low, It has functions.

[0164] <Modification 2 of the display device configuration> Next, a second modified example of the configuration of the display device will be described with reference to FIGS. 8 and 9. Next, a capacitive element 175 different from the capacitive element 105 described with reference to FIGS. 2 and 3 will be described. 8 is a top view of the pixel 171, and FIG. 9 is a top view of the pixel 171 between the dashed and dotted lines E1-E2 and E3 in FIG. FIG. 2 is a cross-sectional view taken along line F1-F2.

[0165] In the pixel 171, the insulating film 129, the insulating film 131, and the insulating film 132 are covered with the multilayer film 11. 9, the gate insulating film 127, the insulating film 129, the insulating film 131, An opening 138 is provided in the insulating film 132, reaching the conductive film 135. A conductive film 137 is formed so as to cover the opening 138 and the insulating film 132 .

[0166] The pixel electrode 124 functions as one electrode of the capacitor element 175, and the multilayer film 119 functions as the other electrode. The multilayer film 119 functions as an electrode. The scanning line 107 is connected to a conductive film 135 formed in the same process as the scanning line 107 via a conductive film 137. By using such a connection method, the openings 117, 139, and 138 can be connected at the same time. Since it can be formed in one process, the number of masks can be reduced.

[0167] In addition, the α region (gate insulating film 127, multilayer film 111, FIG. 9B shows an enlarged view of the signal line 109 and the insulating film 129. FIG. 9C shows enlarged views of the insulating film 129, the multilayer film 119, and the insulating film 129, respectively.

[0168] In this embodiment, the multilayer film 111 and the multilayer film 119 are configured as shown in FIG. The structure may be the same as that shown in FIG.

[0169] <Modification 3 of the display device configuration> Next, a third modified example of the display device will be described with reference to FIGS. 10 and 11. Here, a capacitive element 185 different from the capacitive element 175 described in FIG. 8 and FIG. 9 will be described. FIG. 10 is a top view of the pixel 181, and FIG. 11 is a diagram showing the area between the dashed dotted lines G1 and G2 in FIG. and a cross-sectional view taken along dashed line H1-H2.

[0170] In the pixel 181, the conductive film 11 is formed on the insulating film 129, the insulating film 131, and the insulating film 132. An opening 149 is provided that reaches a conductive film 148 formed in the same process as the gate insulating film 13. 27, an opening 138 reaching the conductive film 135 is formed in the insulating film 129, the insulating film 131, and the insulating film 132. In addition, a conductive film is provided so as to cover the opening 138, the opening 149, and the insulating film 132. A membrane 137 is formed.

[0171] The pixel electrode 124 functions as one electrode of the capacitor element 185, and the multilayer film 119 functions as the other electrode. The multilayer film 119 functions as an electrode. A conductive film 137 formed in the same process as the scanning line 107 is interposed between the conductive film 137 and the scanning line 107. 35. By using such a connection method, the opening 117, the opening 149, and Since the opening 138 and the insulating layer 136 can be formed in the same process, the number of masks required can be reduced. By providing the conductive film 148 between the multilayer film 119 and the conductive film 137, the connection resistance can be reduced. It can be reduced.

[0172] In addition, in the α region (the gate insulating film 127 and the multilayer film 111) of the display device shown in FIG. 11B is an enlarged view of the β region (gate insulating film 1 11C shows enlarged views of the insulating film 129, the multilayer film 119, and the insulating film 127, respectively.

[0173] In this embodiment, the multilayer film 111 and the multilayer film 119 are configured as shown in FIG. The structure may be the same as that shown in FIG.

[0174] Note that the structure described in this embodiment mode may be appropriately combined with structures described in other embodiments. It can be used.

[0175] (Embodiment 4) In this embodiment, the transistors and An embodiment of a multilayer film including an oxide semiconductor layer in a capacitor will be described. do.

[0176] At least one layer of the multilayer film including the oxide semiconductor layer is made of a crystalline material such as an amorphous oxide semiconductor. An oxide semiconductor, a single crystal oxide semiconductor, and a polycrystalline oxide semiconductor in which a portion is not clearly identified In addition to the above, oxide semiconductors that contain crystalline parts (C Axis Aligned Crystal The 1000-kV AC power supply is made up of 1000-kV AC power supplies (CAAC-OS). It is preferable that

[0177] CAAC-OS is a type of oxide semiconductor film that has multiple crystal parts. The crystal part is so large that it fits inside a cube with one side less than 100 nm. The crystal parts contained in S are in cubes with sides less than 10 nm, less than 5 nm, or less than 3 nm. The CAAC-OS has a smaller defect density than a microcrystalline oxide semiconductor film. The CAAC-OS has the characteristic of being low in level density.

[0178] CAAC-OS was observed under a transmission electron microscope (TEM). When observed under a quartz microscope, clear boundaries between the crystals were observed. It is not possible to confirm the grain boundary. It can be said that AC-OS is less susceptible to the decrease in electron mobility caused by grain boundaries.

[0179] The CAAC-OS was observed by TEM from a direction roughly parallel to the sample surface (cross-sectional TEM observation ) It can be confirmed that the metal atoms are arranged in layers in the crystal part. Each layer is formed by reflecting the unevenness of the surface on which the CAAC-OS is formed (also called the surface on which the CAAC-OS is formed) or the upper surface. The CAAC-OS has a shape similar to that of the pores, and is arranged parallel to the surface on which the CAAC-OS is formed or the upper surface.

[0180] On the other hand, the CAAC-OS was observed by TEM from a direction roughly perpendicular to the sample surface (planar TEM). When the metal atoms were observed, they were found to be arranged in triangular or hexagonal shapes in the crystals. However, no regularity was observed in the arrangement of metal atoms between different crystal parts. stomach.

[0181] Cross-sectional and planar TEM observations revealed that the crystals of CAAC-OS have an orientation. It is clear that there are

[0182] X-ray diffraction (XRD) was used for CAAC-OS. For example, the structure of CAAC-OS with InGaZnO4 crystals was analyzed using the In the out-of-plane analysis, a peak appears at a diffraction angle (2θ) of approximately 31°. This peak is often attributed to the (009) plane of the InGaZnO4 crystal. From this, it is considered that the CAAC-OS crystal has a c-axis orientation, and the c-axis is approximately perpendicular to the surface on which the CAAC-OS is formed or the upper surface. You can see that it is pointing in the right direction.

[0183] On the other hand, in-plane X-ray irradiation is performed on CAAC-OS in which X-rays are incident from a direction approximately perpendicular to the c-axis. In the analysis by the ane method, a peak may appear at 2θ around 56°. This peak is This is attributed to the (110) plane of the InGaZnO4 crystal. In the case of a semiconductor film, 2θ is fixed at around 56°, and the normal vector of the sample surface is set as the axis (φ axis). When the sample is rotated and analyzed (φ scan), the crystal plane equivalent to the (110) plane is In contrast, in the case of CAAC-OS, 2θ is set at 56 Even when φ is fixed at around 100° and scanned, no clear peak appears.

[0184] From the above, it is considered that the a-axis and b-axis orientations are inconsistent between different crystal regions in CAAC-OS. The crystal is regular, but has a c-axis orientation, and the c-axis is parallel to the normal vector of the surface on which the crystal is formed or the upper surface. Therefore, the layered arrangement confirmed by the cross-sectional TEM observation mentioned above is consistent with the above. Each layer of aligned metal atoms is a plane parallel to the ab plane of the crystal.

[0185] The crystals are formed when the CAAC-OS film is formed or when a crystallization process such as heat treatment is performed. As mentioned above, the c-axis of the crystal is aligned along the CAAC-OS surface or the The orientation is parallel to the normal vector of the upper surface. Therefore, for example, the shape of the CAAC-OS is When the crystal is changed by etching, the c-axis of the crystal is aligned with the CAAC-OS surface or It may not be parallel to the normal vector of the top surface.

[0186] In addition, the crystallinity in the CAAC-OS may not be uniform. When the crystal part is formed by crystal growth from the vicinity of the top surface of the CAAC-OS, The area may have a higher crystallinity than the area near the surface to be formed. When impurities are added to the OS, the crystallinity of the region to which the impurities are added changes, resulting in partial crystallization. Regions of different crystallinity may also form.

[0187] In addition, the out-of-plane method of CAAC-OS with InGaZnO4 crystals In the analysis by , in addition to the peak at 2θ near 31°, a peak also appeared at 2θ near 36°. The peak at 2θ around 36° may be due to the c-axis orientation in some CAAC-OS. The CAAC-OS has a peak at 2θ of around 31°. It is preferable that the compound has a peak at 2θ of about 36°.

[0188] There are three methods for forming CAAC-OS.

[0189] In the first method, an oxide semiconductor film is formed at a film formation temperature of 100° C. or more and 450° C. or less. In this way, the c-axis of the crystal part included in the oxide semiconductor film is aligned with the normal vector of the formation surface or the surface This is a method for forming crystal parts that are aligned in a direction parallel to the normal vector of the crystal.

[0190] The second method is to form an oxide semiconductor film to a small thickness, and then heat the film at a temperature of 200° C. to 700° C. By performing heat treatment, the c-axis of a crystal part included in the oxide semiconductor film is aligned with the normal vector of the formation surface. This is a method for forming crystals aligned in a direction parallel to the normal vector of the crystal or surface.

[0191] The third method is to form a thin oxide semiconductor film as a first layer, and then heat the film at 200° C. or higher for 700 The second oxide semiconductor film is then formed by performing a heat treatment at 0.45°C or less. The c-axis of the crystal part included in the compound semiconductor film is the normal vector of the surface on which the film is formed or the normal vector of the surface. This is a method for forming crystals aligned in a direction parallel to the torsion.

[0192] A transistor that uses CAAC-OS for an oxide semiconductor film can be irradiated with visible light or ultraviolet light. Therefore, the change in electrical characteristics due to the application of CAAC-OS to the oxide semiconductor film is small. The transistor has good reliability.

[0193] In addition, the CAAC-OS uses a polycrystalline oxide semiconductor target and is It is preferable to form the film by a deposition method. When the ions collide with the target, the target The crystal regions contained in the crystal are cleaved from the ab plane and are flat or Sputtered particles may peel off as pellet-shaped particles. In this case, the plate-shaped or pellet-shaped particles may peel off. The CAAC process is achieved by the deposition of the crystalline sputtered particles, which reach the deposition surface while maintaining their crystalline state. -OS can be deposited.

[0194] In addition, in order to form a CAAC-OS film, the following conditions are preferably applied.

[0195] By reducing the amount of impurities mixed in during film formation, it is possible to prevent the crystal state from being destroyed by impurities. For example, the concentration of impurities (hydrogen, water, carbon dioxide, nitrogen, etc.) present in the deposition chamber can be In addition, the impurity concentration in the deposition gas may be reduced. A deposition gas having a temperature of −80° C. or lower, preferably −100° C. or lower is used.

[0196] In addition, by increasing the heating temperature (for example, the substrate heating temperature) of the surface to be film-formed during film formation, Specifically, when the temperature of the deposition surface is increased by 1 The film is formed at a temperature of 00°C or higher and 740°C or lower, preferably 150°C or higher and 500°C or lower. By increasing the temperature of the surface on which the film is to be formed, the plate-shaped or pellet-shaped sputtered particles are When the sputtered particles reach the target surface, migration occurs on the target surface, and the flat surface of the sputtered particles becomes It adheres to the surface on which the film is formed.

[0197] In addition, by increasing the oxygen ratio in the deposition gas and optimizing the power, plasma damage during deposition is reduced. The oxygen ratio in the deposition gas is preferably 30% by volume or more, and more preferably 100% by volume or more. Expressed as volume percent.

[0198] As an example of the target, an In-Ga-Zn oxide target will be described below.

[0199] InO X powder, GaO Y Powder and ZnO Z The powders are mixed in a specified number of moles and pressurized. Then, it is heated at a temperature between 1000℃ and 1500℃ to produce polycrystalline In-G The target is a-Zn oxide. The pressure treatment is performed while cooling (or cooling naturally). The reaction may be performed while heating, or while heating. X, Y, and Z are any positive numbers. Here, the predetermined molar ratio is, for example, InO X powder, GaO Y Powder and ZnO Z powder The ending is 2:2:1, 8:4:3, 3:1:1, 1:1:1, 4:2:3 or 3:1:2 The type of powder and the molar ratio of the powder to be mixed depend on the target to be produced. The above can be changed as necessary.

[0200] Note that the structure described in this embodiment mode may be appropriately combined with structures described in other embodiments. It can be used.

[0201] (Embodiment 5) In this embodiment mode, a display device, an example of which is shown in the above embodiment mode, and a part of a driver circuit or An example of forming a system-on-panel by forming the entire display unit on the same substrate as the pixel unit is shown in Fig. 12 to 14. Note that FIG. 13(A) and FIG. 13(B) are the same as FIG. 12(B). 13 is a cross-sectional view showing the cross-sectional configuration of a portion indicated by a dashed line MN in FIG. Therefore, only a part of the structure of the pixel portion is shown.

[0202] In FIG. 12A, a pixel portion 902 provided on a first substrate 901 is surrounded by a A sealant 905 is provided and the substrate is sealed with a second substrate 906. ) is different from the region surrounded by the sealant 905 on the first substrate 901. A signal line formed of a single crystal semiconductor or a polycrystalline semiconductor on a separately prepared substrate is placed in the region where the A driver circuit 903 and a scanning line driver circuit 904 are mounted. 903, a scanning line driver circuit 904, or various signals and potentials applied to the pixel portion 902 are , FPC(Flexible printed circuit)918a, FPC91 Powered by 8b.

[0203] In FIG. 12B and FIG. 12C, a pixel portion 901 is provided on a first substrate 901. A sealant 905 is provided so as to surround the gate electrode 902 and the scanning line driver circuit 904 . In addition, a second substrate 906 is provided over the pixel portion 902 and the scanning line driver circuit 904 . Therefore, the pixel portion 902 and the scanning line driver circuit 904 are formed by the first substrate 901 and the sealing material 905. The display element is sealed by the second substrate 906. In FIG. 12C, the area surrounded by the sealant 905 on the first substrate 901 A single crystal semiconductor or polycrystalline semiconductor is formed on a separately prepared substrate in a region different from the region. A signal line driver circuit 903 is mounted on the substrate 901. In FIG. 12(B) and FIG. 12(C), are applied to the signal line driver circuit 903, the scanning line driver circuit 904, or the pixel portion 902. The seed signals and potentials are supplied from FPC918.

[0204] In addition, in FIG. 12B and FIG. 12C, a signal line driver circuit 903 is separately formed. Although an example in which the scanning lens is mounted on the first substrate 901 is shown, the present invention is not limited to this configuration. A signal line driver circuit may be formed separately and mounted, or a part of a signal line driver circuit or a scanning line driver circuit may be mounted. Alternatively, only a part of the path may be formed separately and implemented.

[0205] The method of connecting the separately formed drive circuit is not particularly limited, and may be any method such as COG ( hip on glass method, wire bonding method, or TAB (Tape The Automated Bonding method can be used. This is an example in which a signal line driver circuit 903 and a scanning line driver circuit 904 are mounted by the COG method. FIG. 12B shows an example in which a signal line driver circuit 903 is mounted by the COG method. C) is an example in which a signal line driver circuit 903 is mounted by the TAB method.

[0206] The display device includes a panel in which a display element is sealed, and a controller for the panel. This includes modules in which ICs, etc., including lasers, are mounted.

[0207] In this specification, the term "display device" refers to an image display device, a display device, or a light source. (including lighting devices). Also refers to a connector, such as FPC or TCP, attached to the A module with a printed wiring board at the end of the TCP, or a display element Also includes modules with ICs (integrated circuits) directly mounted using the COG method as display devices. It shall be so.

[0208] In addition, the pixel portion and the scanning line driver circuit provided on the first substrate include a plurality of transistors. The transistor described in the above embodiment can be applied to the semiconductor device.

[0209] Examples of display elements provided in the display device include liquid crystal elements (also called liquid crystal display elements), light-emitting elements, and the like. A light-emitting element (also called a light-emitting display element) can be used. A light-emitting element is an element that emits light by applying a current or a voltage. This category includes elements whose brightness is controlled by a specific factor, such as inorganic EL (Electroluminescent) devices. These include organic EL elements, electronic inks, etc. It is also possible to use a display medium whose contrast changes due to electrical effects, such as a liquid crystal display. An example of a liquid crystal display device using a liquid crystal element as a display element is shown in FIG.

[0210] The liquid crystal display device shown in FIG. 13(A) is a vertical electric field type liquid crystal display device. has a connection terminal electrode 915 and a terminal electrode 916. The terminal electrode 916 is electrically connected to the terminal of the FPC 918 via the anisotropic conductive material 919. This is being continued.

[0211] The connection terminal electrode 915 is formed from the same conductive film as the first electrode 930, and the terminal electrode 916 The source and drain electrodes of the transistors 910 and 911 are formed of the same conductive film. It is being done.

[0212] A pixel portion 902 and a scanning line driver circuit 904 provided on a first substrate 901 are A transistor 910 included in a pixel portion 902 has a plurality of transistors. The transistors 910 and 911 included in the circuit 904 are illustrated. The insulating film 129, the insulating film 131, and the insulating film 132 shown in Embodiment 1 are formed over the transistor 911. An insulating film 924 corresponding to the film 132 is provided. It is a functional insulating film.

[0213] In this embodiment, the transistors 910 and 911 are the same as those in the above embodiment. In addition, the oxide semiconductor film 927 and the insulating film 9 The capacitor 926 is formed using the oxide semiconductor 24 and the first electrode 930. The body membrane 927 is connected to a capacitance wiring 929 via an electrode 928. The electrode 928 is The transistor 910 is formed from the same conductive film as the source electrode and the drain electrode of the transistor 911. The capacitance wiring 929 is connected to the gate electrodes of the transistors 910 and 911. Note that the capacitor 926 is formed from the same conductive film as that shown in Embodiment 1. Although the capacitance element shown in FIG. 1 is illustrated, the capacitance element shown in the other embodiments can be used as appropriate.

[0214] In addition, the transistor 911 included in the scan line driver circuit is oxidized over the insulating film 924. 9 shows an example in which a conductive film 917 is provided at a position overlapping a channel forming region of a semiconductor film. In this embodiment, the conductive film 917 is made of the same conductive material as the first electrode 930 and the first electrode 940. The conductive film 917 is provided so as to overlap with a channel formation region of the oxide semiconductor film. By doing so, reliability tests (e.g., BT (Bias Temperature) strike) can be performed. The amount of change in the threshold voltage of the transistor 911 before and after the non-resistance test is further reduced. The potential of the conductive film 917 can be the same as that of the gate electrode of the transistor 911. The conductive film may function as a second gate electrode. The potential of the conductive film 917 may be, for example, a ground potential, a source potential, a constant potential, or a gate potential. The potential of the electrode is taken as

[0215] The conductive film 917 also has a function of blocking an external electric field. (The circuit part including the transistor) The shielding function of the conductive film 917 prevents the device from being affected by external electric fields such as static electricity. This can prevent the electrical characteristics of the transistor from fluctuating. In FIG. 13, the scanning line driving circuit However, the transistors included in the signal line driver circuit are also shown. In the same manner as the transistor 911, the channel formation region of the oxide semiconductor film and the A conductive film may be provided at the overlapping position.

[0216] The transistor 910 provided in the pixel portion 902 is electrically connected to a display element. The display element is not particularly limited as long as it can display an image. It can be used.

[0217] The liquid crystal element 913, which is a display element, includes a first electrode 930, a second electrode 931, and a liquid crystal The liquid crystal layer 908 is sandwiched between insulating films 93 functioning as alignment films. 2, an insulating film 933 is provided. Also, the second electrode 931 is provided on the second substrate 906 side. The first electrode 930 and the second electrode 931 are overlapped with the liquid crystal layer 908 interposed therebetween. It is.

[0218] A first electrode and a second electrode (a pixel electrode, a common electrode, a counter electrode) for applying a voltage to a display element In the case of a photodiode, the direction of the light to be extracted, the location of the electrode, and the The light transmission or reflectivity can be selected according to the pattern structure.

[0219] The first electrode 930 and the second electrode 931 are the same as the pixel electrode 121 and the The same materials as those for the counter electrode 154 can be used appropriately.

[0220] The spacer 935 is a columnar spacer obtained by selectively etching an insulating film. In order to control the distance (cell gap) between the first electrode 930 and the second electrode 931, It should be noted that a spherical spacer may also be used.

[0221] When liquid crystal elements are used as display elements, thermotropic liquid crystal, low molecular weight liquid crystal, high molecular weight liquid crystal, etc. Liquid crystal, polymer dispersed liquid crystal, ferroelectric liquid crystal, antiferroelectric liquid crystal, etc. can be used. These liquid crystal materials can exhibit cholesteric, smectic, cubic, and chromatic phases depending on the conditions. It shows an isotropic phase, an isotropic phase, etc.

[0222] Alternatively, a liquid crystal that exhibits a blue phase without using an alignment film may be used. When the temperature of the cholesteric liquid crystal is increased, the cholesteric phase transitions to the isotropic phase. The blue phase appears only in a narrow temperature range, so it is necessary to improve the temperature range. In order to improve the alignment, a liquid crystal composition containing a chiral agent is used for the liquid crystal layer. The organic resin is made of an organic resin, and the organic resin contains hydrogen or water. In view of this, the electrical characteristics of the transistor in the display device may be deteriorated. By using a blue phase as the layer 160, it is possible to realize a surface treatment according to one embodiment of the present invention without using an organic resin. Therefore, a highly reliable display device can be obtained.

[0223] The first substrate 901 and the second substrate 906 are fixed together by a sealant 925 . The sealant 925 may be made of an organic resin such as a thermosetting resin or a photocurable resin. The sealant 925 is in contact with the insulating film 924. It corresponds to the sealing material 905 .

[0224] In addition, in liquid crystal display devices, black matrices (light-shielding films), polarizing members, and phase difference members Optical members (optical substrates) such as anti-reflection members are provided as appropriate. For example, a polarizing substrate and Circularly polarized light produced by a retardation substrate may be used. etc. may also be used.

[0225] In addition, since transistors are easily damaged by static electricity, etc., a protection circuit for protecting the drive circuit is It is preferable to provide a protection circuit using a non-linear element.

[0226] Next, a liquid crystal display device of the lateral electric field type will be described with reference to FIG. B) is an example of the FFS (Fringe Field Switching) method. ng mode liquid crystal display device. Unlike the vertical electric field type liquid crystal display device shown in FIG. The structure will be described below.

[0227] In the liquid crystal display device shown in FIG. 13B, the connection terminal electrode 915 is The terminal electrode 916 is formed from the same conductive film as the source electrodes of the transistors 910 and 911. The gate electrode is formed from the same conductive film as the gate and drain electrodes.

[0228] The liquid crystal element 943 includes a first electrode 940 and a second electrode 941 formed on the insulating film 924. The liquid crystal element 943 includes a capacitor 941 and a liquid crystal layer 908. The first electrode 940 may have a structure similar to that of the element 105. The materials shown in the first electrode 930 can be used appropriately. The surface shape is a comb shape, a step shape, a ladder shape, etc. The second electrode 941 functions as a common electrode. The first electrode 940 and the multilayer film 119 can be formed in a similar manner to the multilayer film 119 shown in the embodiment mode 1. An insulating film 924 is provided between the first electrode 922 and the second electrode 941 .

[0229] The second electrode 941 is connected to a common wiring 946 via an electrode 945. 45 is the same as the source electrode and drain electrode of the transistor 910 and the transistor 911. The common wiring 946 is formed of the same conductive film as the transistor 910 and the transistor 911. The gate electrode is formed from the same conductive film as the gate electrode of the liquid crystal element 943. Although the description has been given using the capacitance element shown in the first embodiment, the capacitance elements shown in the other embodiments may be used as appropriate. It can be used.

[0230] In FIG. 14, in the liquid crystal display device shown in FIG. 13(A), A common connection portion (pad portion) for electrically connecting to the second electrode 931 is provided on the first substrate 90. An example of forming it on 1 is shown below.

[0231] The common connection portion overlaps with a sealant for bonding the first substrate 901 and the second substrate 906. and electrically connected to the second electrode 931 via conductive particles contained in the sealing material. Or, a common connection part is provided in a place that does not overlap with the sealing material (excluding the pixel part). and a paste containing conductive particles is provided separately from the seal material so as to overlap the common connection portion. It may be electrically connected to the second electrode 931 .

[0232] FIG. 14(A) is a cross-sectional view of the common connection portion, which corresponds to IJ in the top view shown in FIG. 14(B). Correct.

[0233] The common potential line 975 is provided on the gate insulating film 922 and is connected to the transistor 9 shown in FIG. 10. The source electrode 971 or the drain electrode 973 is made of the same material and in the same process. do.

[0234] The common potential line 975 is covered with an insulating film 924. 5. The openings are for connecting the source and drain electrodes of the transistors 910. A contact that connects one of the electrode 971 or the drain electrode 973 to the first electrode 930 It is made using the same process as the hole.

[0235] In addition, the common potential line 975 and the common electrode 977 are connected at the opening. 7 is provided on the insulating film 924, and is connected to the connection terminal electrode 915 and the first electrode 930 of the pixel portion. They are made from the same materials and through the same process.

[0236] In this manner, the common connection portion is formed in the same manufacturing process as the switching element of the pixel portion 902. It can be manufactured.

[0237] The common electrode 977 is an electrode that comes into contact with the conductive particles contained in the sealing material, and is Electrical connection is made to the second electrode 931 of 906 .

[0238] 14C, a common potential line 985 is connected to the gate of a transistor 910. They may be made of the same material and in the same process as the electrodes.

[0239] In the common connection portion shown in FIG. 14C, a common potential line 985 is connected to the gate insulating film 922 and The gate insulating film 922 and the insulating film 924 are disposed below the common electrode 921 and the insulating film 924. The openings are located at positions overlapping with the position line 985. A contact that connects one of the electrode 971 or the drain electrode 973 to the first electrode 930 After etching the insulating film 924 in the same process as the hole, the gate insulating film 922 is further selected. The etched portion is formed by selectively etching the etched portion.

[0240] In addition, the common potential line 985 and the common electrode 987 are connected at the opening. 7 is provided on the insulating film 924, and is connected to the connection terminal electrode 915 and the first electrode 930 of the pixel portion. They are made from the same materials and through the same process.

[0241] As described above, according to one embodiment of the present invention, a transistor and a capacitor each include an oxide semiconductor. By using a multilayer film including a SiO2 layer, it is possible to fabricate a large-area substrate, so the fabrication cost is low. In addition, since the multilayer film used in the capacitor element has a light-transmitting property, The aperture ratio of the pixel is increased, and a display device with low power consumption can be provided. In the multilayer film used in a transistor, the channel is formed in the layer that does not contact the gate insulating film. Therefore, it is possible to form transistors with stable electrical characteristics, and to fabricate highly reliable display devices. It can be manufactured.

[0242] Note that the structure described in this embodiment mode may be appropriately combined with structures described in other embodiments. It can be used.

[0243] (Embodiment 6) The display device according to one embodiment of the present invention is applicable to various electronic devices (including game machines). The electronic equipment includes a television set (television or television receiver) (also called a monitor), computer monitors, digital cameras, digital video cameras , digital photo frames, mobile phones, portable game machines, personal digital assistants, audio playback devices , gaming machines (pachinko machines, slot machines, etc.), and game cabinets. An example of the device is shown in Figure 15.

[0244] FIG. 15A shows a table 9000 having a display section. A display unit 9003 is built into the housing 9001, and an image is displayed on the display unit 9003. It is possible to support the housing 9001 with four legs 9002. The housing 9001 also includes a power cord 9005 for supplying power.

[0245] The display device described in any of the above embodiments can be used for the display portion 9003. Therefore, the display quality of the display portion 9003 can be improved.

[0246] The display unit 9003 has a touch input function. By touching the display button 9004 displayed on the screen with a finger or the like, the screen can be operated or information can be input. It also allows communication with and control of other home appliances, It may also be used as a control device to control other home appliances by operating the screen. If a display device having a touch sensor function is used, the display unit 9003 can have a touch input function. It is possible.

[0247] In addition, the screen of the display unit 9003 can be fixed to the floor by a hinge provided in the housing 9001. It can also be placed vertically and used as a television set. A large-screen television set will take up a lot of free space, but it can be placed on a table. If the display unit is built into the device, the space in the room can be used more effectively.

[0248] FIG. 15B shows a television device 9100. A display unit 9103 is incorporated in a housing 9101, and an image is displayed on the display unit 9103. In this example, the housing 9101 is supported by a stand 9105. The figure shows a configuration in which

[0249] The television device 9100 can be operated using an operation switch provided on the housing 9101 or a separate remote control. This can be done by using a remote control operation device 9110. The channel and volume can be controlled by the 9109, and the display 9103 shows The remote control device 9110 can control the video. A display unit 9107 for displaying information output from the device 9110 may be provided.

[0250] A television device 9100 shown in FIG. 15(B) includes a receiver, a modem, and the like. The television device 9100 can receive general television broadcasts using a receiver. Furthermore, by connecting to a wired or wireless communication network via a modem, Either directional (from sender to receiver) or bidirectional (between sender and receiver or between receivers) It is also possible to carry out information communication.

[0251] The display device shown in any of the above embodiments can be used for the display portions 9103 and 9107. This makes it possible to improve the display quality of the television device.

[0252] FIG. 15C shows a computer 9200, which includes a main body 9201, a housing 9202, a display unit 9 203, keyboard 9204, external connection port 9205, pointing device 920 6, etc.

[0253] The display device described in any of the above embodiments can be used for the display portion 9203. This makes it possible to improve the display quality of the computer.

[0254] The display unit 9203 has a touch input function. By touching the keyboard 9204 displayed on the screen 03 with your finger, you can operate the screen and input information. It can also communicate with or control other home appliances. The device may be used as a control device that controls other home appliances by operating the screen.

[0255] FIG. 16(A) and FIG. 16(B) show a tablet-type terminal that can be folded in two. A) is an open state of the tablet terminal. The tablet terminal includes a housing 9630, a display unit 9631a, and a display unit 9631b. display unit 9631b, a display mode changeover switch 9034, a power switch 9035, a power saving It has a mode changeover switch 9036, a fastener 9033, and an operation switch 9038.

[0256] The display device described in any of the above embodiments has a display portion 9631a and a display portion 9631b. Therefore, it is possible to improve the display quality of tablet devices. do.

[0257] A part of the display unit 9631a can be used as a touch panel area 9632a. By touching the operation keys 9638 displayed on the display unit 96, data can be input. In 31a, as an example, half of the area has a display function only, and the other half The display unit 96 has a touch panel function, but is not limited to this. The entire area of ​​the display unit 931a may have a touch panel function. The entire surface of 631a is made to display keyboard buttons to serve as a touch panel, and the display section 9631b is made to display It can be used as a display screen.

[0258] In addition, in the display unit 9631b, as in the display unit 9631a, The part of the touch panel can be the area 9632b of the touch panel. Touch the area where the mode display switch button 9639 is displayed with your finger or a stylus. A keyboard button can be displayed on the display portion 9631b.

[0259] In addition, the touch panel area 9632a and the touch panel area 9632b are simultaneously You can also use touch input.

[0260] A display mode changeover switch 9034 is used to change the display orientation, such as portrait or landscape. You can switch between black and white and color display. The switch 9036 is a switch that turns on and off when the tablet terminal is in use and is detected by a light sensor built into the tablet terminal. The brightness of the display can be optimized according to the amount of light. In addition to sensors, other detection devices such as gyros, acceleration sensors, etc. that detect tilt may be incorporated.

[0261] FIG. 16A shows an example in which the display area of ​​the display portion 9631b is the same as that of the display portion 9631a. However, there is no particular limitation, and one size may be different from the other size. The quality of the display may also be different. For example, one display panel may provide a higher resolution display than the other. It may also be used as a rule.

[0262] FIG. 16B shows the tablet terminal in a closed state. The tablet terminal includes a housing 9630 and a solar cell 9 16B, the charge / discharge control circuit 96 As an example of the 34, a configuration having a battery 9635 and a DC-DC converter 9636 is described below. This is shown.

[0263] In addition, since the tablet device can be folded in half, the case 9630 can be folded when not in use. Therefore, the display portions 9631a and 9631b can be protected. This makes it possible to provide a tablet device that is highly durable and reliable even when used for a long period of time.

[0264] In addition, the tablet terminals shown in Fig. 16(A) and Fig. 16(B) are used in various Functions that display important information (still images, videos, text images, etc.), calendars, dates or times A function to display time and other information on the display, and to operate or edit the information displayed on the display by touch input. Touch input function, function to control processing by various software (programs), etc. It is possible to have.

[0265] The solar cell 9633 attached to the surface of the tablet device supplies power to the touch panel. The solar cell 9633 can supply the light to a display unit, a video signal processor, or the like. , which can be provided on one or both sides of the housing 9630, and can efficiently charge the battery 9635. This is preferable because it can be configured to perform the operation efficiently. The use of lithium ion batteries has the advantage of enabling miniaturization.

[0266] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. A block diagram is shown in (C) and explained. Figure 16(C) shows a solar cell 9633, a battery 9635, DC-DC converter 9636, converter 9637, switches SW1 to SW 3. The display unit 9631, the battery 9635, the DCDC converter 96 36, a converter 9637, and switches SW1 to SW3 are connected to the charge / discharge control circuit shown in FIG. This corresponds to the control circuit 9634.

[0267] First, an example of operation when power is generated by the solar cell 9633 due to external light will be described. The power generated by the solar cell is converted to a voltage to charge the Battery 9635. The CDC converter 9636 steps up or steps down the voltage. When power is supplied from the solar cell 9633, switch SW1 is turned on and the converter The voltage is increased or decreased by a voltage converter 9637 to a voltage required for the display unit 9631. When you do not want to display anything on the display unit 9631, turn SW1 off and SW2 on to turn on the battery. It is sufficient to configure it to charge the Lee 9635.

[0268] The solar cell 9633 is shown as an example of a power generating means, but is not limited thereto. , and other power generation methods such as piezoelectric elements and thermoelectric conversion elements (Peltier elements) For example, the battery 9635 may be charged. A non-contact power transmission module that transmits and receives power and charges, or a combination of other charging methods This may also be configured.

[0269] Note that the structure described in this embodiment mode may be appropriately combined with structures described in other embodiments. It can be used. [Explanation of symbols]

[0270] 100 pixels 101 pixels 102 First substrate 103 Transistor 104 Scanning line driving circuit 105 Capacitive element 106 Signal line driver circuit 107 Scan Lines 108 Liquid crystal element 109 Signal Line 111 Multilayer film 111_1 First oxide layer 111_2 Second oxide layer 111_3 Third oxide layer 113 Conductive Film 115 Capacitive Line 117 Aperture 119 Multilayer film 119_1 First oxide layer 119_2 Second oxide layer 119_3 Third oxide layer 121 Pixel electrode 123 Aperture 124 pixel electrode 125 Conductive Film 126 Insulating Film 127 Gate insulating film 128 Insulating film 129 Insulating Film 130 Insulating film 131 Insulating film 132 Insulating film 133 Insulating Film 135 Conductive Film 137 Conductive Film 138 Aperture 139 Aperture 148 Conductive Film 149 Aperture 150 Second Board 152 Light-shielding film 154 Counter Electrode 155 Wiring 156 Insulating Film 158 Insulating film 160 Liquid crystal layer 161 pixels 165 Capacitive element 167 Conductive Film 171 pixels 175 Capacitive element 181 pixels 185 Capacitive element 901 First substrate 902 Pixel section 903 Signal line driver circuit 904 Scanning line driver circuit 905 Sealing material 906 Second Board 908 Liquid crystal layer 910 Transistor 911 Transistor 913 Liquid crystal element 915 Connection terminal electrode 916 Terminal electrode 917 Conductive Film 918 FPC 918b FPC 919 Anisotropic conductive agent 922 Gate insulating film 923 Insulating Film 924 Insulating film 925 Sealing material 926 Capacitor 927 Oxide Semiconductor Film 928 Electrode 929 Capacitance wiring 930 electrode 931 Electrode 932 Insulating film 933 Insulating film 935 Spacer 940 electrode 941 Electrode 943 Liquid crystal element 945 Electrode 946 Common Wiring 971 Source Electrode 973 Drain electrode 975 Common potential line 977 Common electrode 985 Common potential line 987 Common electrode 9000 Table 9001 Case 9002 Legs 9003 Display section 9004 Display button 9005 Power Cord 9033 Fastener 9034 Switch 9035 Power Switch 9036 Switch 9038 Operation switch 9100 Television equipment 9101 Case 9103 Display section 9105 Stand 9107 Display section 9109 Operation key 9110 Remote control device 9201 Main unit 9202 Case 9203 Display section 9204 Keyboard 9205 External connection port 9206 Pointing Device 9630 Case 9631 Display section 9631a Display section 9631b Display section 9632a area 9632b area 9633 Solar Cells 9634 Charge / discharge control circuit 9635 Battery 9636 DC-DC Converter 9637 Converter 9638 Operation key 9639 Button

Claims

[Claim 1] a transistor electrically connected to a light-transmitting pixel electrode and a capacitor; The transistor is a gate electrode; and a gate insulating film provided on the gate electrode; a first multilayer film provided on the gate insulating film and including an oxide semiconductor layer; The capacitive element is a pixel electrode; and a second multilayer film having the same layer structure as the first multilayer film, the second multilayer film being overlapped with the pixel electrode and arranged at a predetermined interval; a channel formation region of the transistor is at least one layer of the first multilayer film that is not in contact with the gate insulating film.

Images