Semiconductor device

Abstract

In a semiconductor device including a photosensor that uses silver as a cathode of a photoconductive film, an increase in resistance and a decrease in light reflection characteristics due to oxidation of silver are prevented. A semiconductor device has a thin film transistor formed over a substrate (100), characterized in that an electrode electrically connected to the thin film transistor is formed of a silver film (128), a first ITO film (129) is formed over the silver film, and an alumina (AlOx) film (130) is formed over the first ITO film (129).

Description

Technical Field

[0001] The present invention relates to a semiconductor device having a photosensor using a photoelectric conversion element made of an organic material. Background Art

[0002] Photoelectric conversion-based photosensors are not only used for image recognition but also in fields such as biometric authentication, and their applications are widespread. Photoelectric materials using organic materials can reduce dark current, improve photoelectric conversion efficiency, and add wavelength selectivity, etc., and thus development is being promoted.

[0003] As a document describing an organic material used as a photoelectric conversion element, for example, Patent Document 1 is cited. In addition, as a document describing the film structure of a photoelectric conversion element using an organic material, Patent Document 2 is cited.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: WO2014 / 054255A1

[0007] Patent Document 2: JP-A-2014-22525 Summary of the Invention

[0008] A sensor device using a photodiode using an organic photoconductive film (hereinafter, also referred to as an organic photoconductive film diode OPD: Organic Photo Diode) uses a reflective electrode in order to improve the utilization efficiency of light from the outside. Silver with a high reflectivity is used as the reflective electrode. Moreover, silver is used as one electrode of the organic photoconductive film diode. Silver is used as a film of about 100 nm, but this film has a high reduction effect and immediately combines with oxygen in the atmosphere to oxidize after the film is formed, resulting in a high resistance.

[0009] On the other hand, the organic photoconductive film material is sensitive to moisture, and therefore, it is necessary to block moisture from the atmosphere. An alumina film (hereinafter also referred to as alumina (AlOx)) has excellent characteristics with respect to blocking moisture. Therefore, alumina (AlOx) is used in a stacked manner with silver as the reflective electrode in order to block moisture.

[0010] However, alumina (AlOx) contains oxygen. In addition, alumina (AlOx) is mostly formed by reactive sputtering and therefore contains more oxygen. Therefore, the silver stacked with alumina (AlOx) becomes more easily oxidized due to the oxygen from alumina (AlOx). If the silver is oxidized, it becomes a high resistance, and not only cannot function as an electrode, but the oxidized silver becomes black or transparent and also cannot function as a reflective electrode.

[0011] An object of the present invention is to address problems caused by silver film oxidation in the case of using a stacked film of a silver film and an alumina (AlOx) film for one electrode of a photodiode. In addition, such problems are not limited to the case of photodiodes, and are the same, for example, in an organic EL display device (OLED) using an organic material.

[0012] The present invention solves the above problems, and the main specific means are as follows.

[0013] (1) A semiconductor device having a thin film transistor formed on a substrate, wherein an electrode electrically connected to the thin film transistor is formed of a silver film, a first ITO film is formed on the silver film, and an alumina (AlOx) film is formed on the first ITO film.

[0014] (2) The semiconductor device according to (1), wherein the semiconductor device has a photosensor on an upper layer of the thin film transistor, the photosensor includes a photodiode composed of an anode, a photoconductive film, and a cathode, and the electrode is the anode of the photodiode.

[0015] (3) The semiconductor device according to (2), wherein the photoconductive film is an organic photoconductive film.

[0016] (4) The semiconductor device according to (3), wherein the thickness of the first ITO film is 5 nm to 20 nm.

[0017] (5) The semiconductor device according to (4), wherein the thickness of the silver film is 90 nm to 200 nm.

[0018] (6) The semiconductor device according to (5), wherein the thickness of the alumina (AlOx) film is 10 nm to 50 nm.

[0019] (7) The semiconductor device according to (6), wherein the first ITO film is amorphous. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a plan view of a photosensor.

[0021] Figure 2 is a plan view of photosensor elements.

[0022] Figure 3 is a cross-sectional view of the photosensor of Example 1.

[0023] Figure 4A is a cross-sectional view of Sample A.

[0024] Figure 4B It is a cross-sectional view of Sample B.

[0025] Figure 4C It is a cross-sectional view of Sample C.

[0026] Figure 4D It is a cross-sectional view of Sample D.

[0027] Figure 5 It is an example of the film formation conditions of ITO.

[0028] Figure 6 It is a graph showing the effect of ITO between the silver film and the alumina (AlOx) film.

[0029] Figure 7 It is a cross-sectional view near the photoconductive film of the photosensor of Example 2. Detailed implementation mode

[0030] Hereinafter, the content of the present invention will be described using examples. In Example 1, a photosensor device in the case of receiving light from the lower surface of the sensor array will be described. In Example 2, a photosensor device in the case of receiving light from the upper surface of the sensor array will be described. In addition, the present invention can also be applied to an organic EL display device (OLED) using an organic material as a light-emitting element.

[0031]

Example 1

[0032] Figure 1 It is a plan view of the photosensor device to which the present invention is applied. In Figure 1 In the sensor area, sensor elements are formed in a matrix. The size of the sensor area is, for example, a length xx of 3 cm in the horizontal direction and a length yy of 3 cm in the vertical direction. In the sensor area, scan lines 11 extend in the horizontal direction (x direction) and are arranged in the vertical direction (y direction). Detection lines 12 and power supply lines 13 extend in the vertical direction and are arranged in the horizontal direction. The area surrounded by the scan line 11 and the detection line 12, or the scan line 11 and the power supply line 13, becomes a sensor element. Inside each sensor element, a switching TFT 15 and an organic photoconductive film diode 10 are formed.

[0033] A scan line drive circuit 20 is arranged horizontally outside the sensor area, a power supply circuit 40 is arranged in the upper direction, and a detection circuit 30 is arranged in the lower direction. The scan line drive circuit 20 or the detection circuit 30 is formed by TFTs. The scan lines 11 are sequentially selected from above by the shift register in the scan line drive circuit 20.

[0034] The power supply line 13 is connected to the anodes of the respective photodiodes, extends longitudinally, and is connected to the same power supply in the power supply circuit 40 above the sensor region. Then, the anode potential is supplied to the power supply line 13. The detection line 12 is connected to the drain of the switching TFT, and the source of the switching TFT is connected to the cathode of the photodiode 10. The detection line 12 extends downward from each sensor element, and the photocurrent is detected by the detection circuit 30. In Figure 1 when light is applied to the sensor element selected by the scanning line 11, a photocurrent is generated from the photodiode 10, and this photocurrent is detected by the detection circuit 30 through the detection line 12.

[0035] Figure 2 is a plan view of each sensor element. To avoid complicating the drawing, in Figure 2 part of the electrodes and the like are omitted. The size of each sensor element is, for example, 50 μm in the horizontal direction x1 and 50 μm in the vertical direction y1. In Figure 2 the scanning line 11 extends in the horizontal direction and is arranged longitudinally. In addition, the power supply line 13 and the detection line 12 extend in the longitudinal direction and are arranged horizontally. The cathode 126 of the photodiode, the organic photoconductive film 127, the anode 128, etc. are formed in the region surrounded by the scanning line 11 and the power supply line 13, or the scanning line 11 and the detection line 12.

[0036] In addition, the anode electrode 128 is integrally formed over the entire sensor region. That is, there is one anode electrode 128 over the entire sensor region, and multiple cathode electrodes 126 overlap this one anode electrode 128.

[0037] The semiconductor film 107 extends in the x direction from the detection line 12 via the through hole 135, bends, and passes under the scanning line 11. At this time, a TFT is formed. In this case, the scanning line 11 becomes the gate electrode of the TFT. The semiconductor film 107 extends in the y direction and is connected to the cathode 126 of the photodiode formed of ITO in the through hole 123. The through hole 123 is formed in a very thick organic passivation film 122 as described in Figure 3 and thus has a large diameter. An organic photoconductive film 127 is formed over the cathode 126, and an anode 128 is formed thereon using a silver film. Thus, an organic photoconductive film diode is formed. In addition, the organic photoconductive film 127 is also integrally formed over the entire sensor region and is not formed in an island shape for each of the multiple sensor elements in the sensor region. That is, there is one organic photoconductive film 127 over the entire sensor region, and one anode electrode 128 and multiple cathode electrodes 126 overlap this one organic photoconductive film 127.

[0038] In Figure 2In the configuration described above, the organic photoconductive film 127 and the anode 128 are formed over the entire sensor area in common for each element. Therefore, in Figure 2 only the shape of the cathode 126 is drawn within the sensor element, but the organic photoconductive film 127 and the anode 128 are laminated on the cathode 126. More specifically, between the cathode electrodes 126 adjacent to each other in the first direction x and the second direction y, that is, in the region where the cathode electrode 126 is not formed, there are also the organic photoconductive film 127 and the anode electrode 128. The anode electrode 128 is formed of a silver film 128 of about 100 nm and has a very small film thickness. Therefore, by connecting to a plurality of power supply lines 13, the resistance of the entire cathode is reduced. The power supply line 13 can extend toward the power supply circuit 40 laminated on the silver film 128, or can extend on the same layer as the drain electrode or the source electrode of the TFT via a through hole formed in the organic passivation film 122 in the middle.

[0039] Figure 3 is Figure 1 a cross-sectional view of the photosensor device. Figure 3 The photosensor shown is of a type in which light is input from the substrate 100 side. As Figure 1 shown, a drive circuit formed of TFTs is formed outside the sensor area. Since the mobility of the polysilicon semiconductor is high, it is advantageous that the TFTs constituting the drive circuit are formed of the polysilicon semiconductor.

[0040] On the other hand, it is advantageous that the switching TFTs formed in the sensor area are formed of an oxide semiconductor (sometimes also referred to as OS: Oxide Semiconductor) having a very small leakage current. Thus, in the present embodiment, an array substrate of a hybrid type using both polysilicon semiconductor TFTs and oxide semiconductor TFTs is used. In Figure 3 the left side is polysilicon TFTs for the peripheral circuit, and the central part is an organic film photodiode and its switching TFT.

[0041] For the polysilicon, so-called low-temperature polysilicon obtained by polycrystallizing a-Si using an excimer laser is used. Even so, the annealing temperature of the polysilicon semiconductor exceeds the process temperature for forming the oxide semiconductor. Therefore, the polysilicon semiconductor TFTs are formed first, and then the oxide semiconductor TFTs are formed. Therefore, the manufacturing starts from the peripheral circuit first.

[0042] In Figure 3 a base film 101 formed of a laminated film of silicon nitride (SiN) and silicon oxide (SiO) is formed over the glass substrate 100. This is to prevent impurities from the glass substrate 100 from contaminating the polysilicon semiconductor 102 or the oxide semiconductor 107. The thickness of the SiO film is, for example, 200 nm, and the thickness of the SiN film is, for example, 20 nm.

[0043] A polysilicon film 102 for a TFT is formed thereon. The polysilicon film 102 is first formed as an a-Si film. Thereafter, the a-Si is converted into polysilicon by an excimer laser and patterning is achieved. The thickness of the polysilicon film 102 is, for example, 50 nm. In addition, the SiO film, SiN film, and a-Si film serving as the base film 101 can be continuously formed by CVD.

[0044] Thereafter, a first gate insulating film 103 is formed of SiO to cover the polysilicon semiconductor film 102. The thickness of the first gate insulating film 103 is, for example, 100 nm. A first gate electrode 104 is formed of a metal or an alloy thereon. The first gate electrode 104 is formed of MoW, for example. In addition, the peripheral circuit region and the sensor region are formed simultaneously. Simultaneously with the formation of the first gate electrode 104, a light-shielding film 105 is formed of the same material as the first gate electrode 104 at a portion corresponding to the switching TFT in the sensor region. The light-shielding film 105 can also be used as the bottom gate electrode of the oxide semiconductor TFT formed later.

[0045] The first gate electrode 104 and the light-shielding film 105 are covered, and a first interlayer insulating film 106 is formed of a stacked film of an SiO film and an SiN film. The thickness of the SiN film is, for example, 300 nm, and the thickness of the SiO film is 200 nm. An oxide semiconductor film 107 is formed on the first interlayer insulating film 106. As the oxide semiconductor, there are IGZO (Indium Gallium Zinc Oxide), ITZO (Indium Tin Zinc Oxide), ZnON (Zinc Oxide Nitride), IGO (Indium Gallium Oxide), etc. In this embodiment, IGZO is used as the oxide semiconductor.

[0046] In addition, in order to maintain the characteristics of the oxide semiconductor, it is important to maintain the oxygen amount. Therefore, the upper layer of the first interlayer insulating film 106 needs to be an SiO film. This is because SiN supplies hydrogen and reduces the oxide semiconductor. If the SiO film is in contact with the oxide semiconductor film 107, oxygen can be supplied from the SiO film to the oxide semiconductor.

[0047] A drain protection electrode 108 is stacked in the drain region of the oxide semiconductor film 107, and a source protection electrode 109 is formed in the source region. The drain protection electrode 108 and the source protection electrode 109 are formed of a metal, and prevent the oxide semiconductor film 107 from disappearing due to hydrofluoric acid (HF) in the through holes on the oxide semiconductor TFT side when cleaning the through holes in the polysilicon TFT with hydrofluoric acid (HF).

[0048] The second gate insulating film 110 is formed of a SiO film so as to cover the oxide semiconductor film 107. The thickness of the SiO film is about 100 nm. A gate alumina film 111 is formed on the SiO film, and the second gate electrode 112 is formed thereon using, for example, a MoW alloy. By supplying oxygen from the second gate insulating film 110 formed of SiO and the gate alumina film 112 to the oxide semiconductor film 107, the characteristics of the oxide semiconductor film 107 are stabilized.

[0049] The second interlayer insulating film 113 is formed of a stacked film of a SiO film and a SiN film so as to cover the second gate electrode 112. The SiO film is, for example, 300 nm, and the SiN film is 100 nm. The SiO film is mostly disposed on the lower side closer to the oxide semiconductor film 107. After the second interlayer insulating film 113 is formed, vias 118 and 119 are formed on the polysilicon TFT side of the peripheral circuit, and vias 120 and 121 are simultaneously formed on the oxide semiconductor TFT side of the sensor region side.

[0050] In order to remove the oxide film, the vias 118 and 119 on the polysilicon TFT side are cleaned with hydrofluoric acid (HF). However, at this time, the hydrofluoric acid (HF) also enters the vias 120 and 121 on the oxide semiconductor TFT side. In order to prevent the oxide semiconductor film 107 from disappearing, the drain protection electrode 108 and the source protection metal film 109 are used.

[0051] The first drain electrode 114 and the first source electrode 115 are formed corresponding to the vias 118 and 119 on the polysilicon TFT side, and the second drain electrode 116 and the second source electrode 117 are formed corresponding to the vias 120 and 121 on the oxide semiconductor TFT side. The second drain electrode 116 is connected to the detection line 12.

[0052] An organic passivation film 122 is formed of a resin such as acrylic acid so as to cover the second interlayer insulating film 113. The organic passivation film 122 also serves as a planarization film, and thus is formed thick to be about 2 μm. In the organic passivation film 122, a via 123 for connecting the source electrode 117 and the cathode 126 of the photodiode is formed corresponding to the source electrode 117 of the TFT. Since the thickness of the organic passivation film 122 is very thick, the diameter of the via 123 becomes large.

[0053] An inorganic passivation film 124 is formed of SiN with a thickness of about 20 to 100 nm so as to cover the organic passivation film 122. Moisture and other impurities are discharged from the organic passivation film 122 in order to prevent contamination of the organic photoconductive film 127 formed thereon.

[0054] On top of the inorganic passivation film 124, a cathode electrode 126 is formed of an ITO (Indium Tin Oxide) film with a thickness of about 50 nm, for example. The ITO film is crystallized by annealing to reduce the resistance. A via hole 125 is formed in a part of the via hole 123 of the organic passivation film 122 in the inorganic passivation film 124 to connect the cathode electrode 126 and the source electrode 117. In the present invention, ITO is also used for the upper electrode side as the anode electrode 128 side. Therefore, for the purpose of distinction, the ITO serving as the cathode electrode 126 is sometimes referred to as cathode ITO 126.

[0055] An organic photoconductive film 127 is formed on the cathode 126 with a thickness of 300 nm to 500 nm. The organic photoconductive film 127 is formed by sputtering or vacuum evaporation. Since the organic photoconductive film 127 can have excellent photoconductive characteristics and wavelength selectivity, it can be used as a so-called biometric recognition sensor such as a vein image.

[0056] An anode electrode 128 is formed on the upper side of the organic photoconductive film 127 using a silver film. Silver has excellent reflectivity when it is 90 nm or more. In addition, its work function is also preferable as the anode electrode 128, and its conductivity is also preferable.

[0057] On the other hand, since the organic photoconductive film 127 is sensitive to impurities such as moisture, it needs to be blocked from the outside. Therefore, an aluminum oxide (AlOx) film 130 is formed with a thickness of about 30 nm so as to cover the silver film 128 serving as the anode electrode 128. The aluminum oxide (AlOx) film 130 is formed by sputtering, but the film formation rate is very slow. Therefore, reactive sputtering is used to form it. The aluminum oxide (AlOx) 130 formed by reactive sputtering contains a large amount of oxygen. In addition, for this purpose, the aluminum oxide (AlOx) film is preferably in the range of 10 to 50 nm.

[0058] In addition, silver has strong reducibility. Therefore, it takes away oxygen from the aluminum oxide (AlOx) film 130 to achieve oxidation. If the silver film 128 is oxidized, the resistance increases and it turns black. Then, if it is further oxidized, it becomes transparent. If so, the silver film 128 does not function as a reflective electrode.

[0059] The present invention is characterized in that by forming an ITO film 129 between a silver film (or an anode electrode) serving as a reflective electrode 128 and an alumina (AlOx) film 130 for blocking moisture, oxidation of the silver film 128 caused by the alumina (AlOx) film 130 is prevented. The thickness of the alumina (AlOx) film 130 may be a thin film of about 7 nm. If the thickness of the ITO film becomes large, crystallization develops and the surface unevenness of the ITO becomes obvious. Therefore, even when formed thickly, it is preferably about 70 nm. The film thickness of the ITO film 129 formed for this purpose is, for example, 5 nm to 70 nm, more preferably 7 nm to 20 nm.

[0060] The ITO film 129 can be continuously sputtered in the chamber where the silver film 128 has been sputtered without breaking the vacuum. Therefore, oxidation of the silver film 128 due to oxygen in the atmosphere can be prevented. On the other hand, the alumina (AlOx) film 130 is sputtered in a chamber different from the silver film 128. Therefore, if the ITO film 129 does not exist, the silver film 128 will also be oxidized by oxygen in the atmosphere before the alumina (AlOx) 130 is formed. However, in this embodiment, the silver film 128 has been covered with the ITO film 130, thereby preventing oxidation due to oxygen in the atmosphere.

[0061] The ITO film 129 itself also contains oxygen. However, the amount of oxygen supplied from the ITO film 129 is much less than the amount of oxygen supplied from the alumina (AlOx) film 130. In addition, the ITO film 129 on the anode side is formed after the organic photoconductive film 127 is formed. The organic photoconductive film 127 is sensitive to heat. Therefore, the ITO film 129 on the anode side is formed at a low temperature, for example, with the substrate temperature maintained at about 30 degrees. Moreover, since the film thickness is about 7 nm and is also very thin, the ITO 129 on the anode side is formed in an amorphous state. It can be speculated that such an amorphous ITO thin film 129 does not supply oxygen to the extent that the silver film 128 serving as a reflective electrode is oxidized.

[0062] In addition, since the film thickness of the ITO film 129 on the anode side is about 7 nm and is very thin, it can also be formed by normal sputtering without using reactive sputtering using oxygen. From this point, the amount of oxygen contained in the ITO film 129 can also be suppressed compared to normal.

[0063] In Figure 3 above the alumina (AlOx) film 130, an organic protective film 131 is formed of a resin such as acrylic for mechanical protection. This organic protective film 131 may also be omitted depending on the product.

[0064] Figures 4A - 6This is a diagram showing the effects of this embodiment. In this embodiment, on the anode side, an ITO film 129 for preventing oxidation of the silver film 128 is formed between the silver film 128 serving as a reflective electrode and the alumina (AlOx) film 130 for blocking moisture. For this configuration, Figures 4A - 6 To verify what kind of effects can be obtained when the ITO film 129 is formed into a thin film with a thickness of about 7 nm.

[0065] In Figures 4A - 4D are samples composed of various films for confirming the effects. In Figures 4A - 4D the thickness of the ITO film 202 is 7 nm, and the thickness of the alumina (AlOx) film is 30 nm. For the thickness of the silver film 201, samples with varying thicknesses such as 100 nm, 200 nm, 300 nm, 400 nm, and 500 nm were created. All the films were formed by sputtering.

[0066] Figure 4A This is a cross-sectional view when only the silver film 201 is formed on the glass substrate 200. Figure 4B This is the case where alumina (AlOx) 203 is formed on the silver film 201. Figure 4C This is the case where the ITO film 202 is formed on the silver film 201. Figure 4D This is the case where the ITO film 202 is formed on the silver film 201 and the alumina (AlOx) film 203 is formed thereon, which is composed of the films in this embodiment.

[0067] Figure 5 These are the formation conditions for the ITO film 202 of the sample. The ITO film 202 is formed to a thickness of 7 nm by sputtering, but it is characterized in that the sample substrate is maintained at 30 degrees. That is, the heat-resistant temperature of the organic photoconductive film in Figure 3 is considered. In addition, the oxygen flow rate is 0.05 sccm (standard cubic centimeter per minute), which is very small compared to the argon (Ar) flow rate of 140 sccm. Considering that the ITO film formed under these conditions is amorphous and the oxygen content is small.

[0068] In Figures 4B - 4D the silver film 201 and the ITO film 202 are continuously formed in the same chamber, and the alumina (AlOx) film 203 exposes the substrate 200 formed up to the ITO film to the atmosphere once, and then sputtering is performed using another chamber. Since the oxidation state of the silver film 201 is significantly reflected by the resistance, the oxidation state of the silver film 201 was measured by measuring the sheet resistance of the silver film 201.

[0069] After forming Figures 4A - 4DAfter the film, the sheet resistance of the silver film 201 was measured using Lowlesta (product name). Lowlesta is a product for measuring sheet resistance using four needles. Since it penetrates through the alumina (AlOx) film 203 that serves as the surface insulator, etc., the sheet resistance of the silver film 201 can be measured. As long as the silver film 201 is oxidized, its sheet resistance becomes very large.

[0070] Figure 6 is a graph showing the evaluation results. In Figure 6 the horizontal axis represents the film thickness of the silver film 201, and the vertical axis represents the sheet resistance of the silver film 201. Since the resistance of the silver film 201 changes significantly due to oxidation, the vertical axis is on a logarithmic scale. For the cases where the film thickness of the silver film 201 is 100 nm, 200 nm, and 300 nm, samples 4A to 4D were all created and evaluated. For the cases where the film thickness of the silver film 201 is 400 nm and 500 nm, only samples 4A and 4B were created and evaluated. The resistance value was measured immediately after the film was made.

[0071] In Figure 6 A corresponds to sample 4A, B corresponds to sample 4B, C corresponds to sample 4C, and D corresponds to sample 4D. When the film thickness of the silver film 201 is 100 nm, the resistance of sample B with the alumina (AlOx) film 203 laminated on the silver film 201 is 9×10 6 , which is very large compared to other samples. That is, it can be seen that the silver film 201 is oxidized by alumina (AlOx) throughout the entire layer thickness direction.

[0072] In contrast, there is almost no difference in the resistance values among sample A which is only the silver film 201, sample B with the ITO film 202 laminated on the silver film 201, and sample D with the ITO film 202 and the alumina (AlOx) film 203 laminated on the silver film 201. In particular, when focusing on sample B and sample D, it can be seen that the ITO film 202 with a film thickness of 7 nm exists only between the silver film 201 and the alumina (AlOx) film 203, and can almost eliminate the oxidation effect on the silver film 201 caused by the alumina (AlOx) film 203 with a film thickness of 30 nm.

[0073] This tendency is the same when the film thickness of the silver film 201 is 200 nm. As shown in sample B, even when the film thickness of the silver film 201 is 200 nm, the sheet resistance is roughly the same as that when the film thickness is 100 nm. That is, it can be seen that the influence of the alumina (AlOx) film 203 reaches up to about 200 nm of the film thickness of the silver film 201, oxidizing the silver.

[0074] On the other hand, when focusing on Samples A, C, and D, when the thickness of the silver film 201 is 200 nm, the resistance of the silver film 201 becomes approximately half the size compared to the case where the thickness of the silver film 201 is 100 nm ( Figure 6 The vertical axis is on a logarithmic scale). Therefore, it can be seen that Samples A, C, and D are hardly oxidized.

[0075] If the film thickness of silver becomes 300 nm, in Sample B, the sheet resistance value of the silver film 201 decreases to the extent that it is basically in the same order of magnitude as that of the other Samples A, C, and D. That is to say, it can be seen that the influence of the 30-nm-thick aluminum oxide (AlOx) film 203 does not reach around 300 nm of the silver film 201. Therefore, it can be seen that the influence of the 30-nm-thick aluminum oxide (AlOx) film 203 spreads from the interface between the silver film 201 and the aluminum oxide (AlOx) film 203 to around 200 nm to 300 nm.

[0076] On the other hand, when comparing Sample C and Sample D, there is almost no difference in the sheet resistance of the silver film 201. That is to say, by having an ITO film 202 with a thickness of around 7 nm between the silver film 201 and the aluminum oxide (AlOx) film 203, the influence of the aluminum oxide (AlOx) film 203 on the silver film 201 can be basically eliminated.

[0077] In the case where the film thickness of the silver film 203 is 400 nm and in the case where the film thickness of the silver film 203 is 500 nm, measurements were only carried out for Samples A and B. As the film thickness of the silver film 201 increases, the influence of the aluminum oxide (AlOx) film 203 laminated on the surface of the silver film 201 becomes smaller. However, in actual products, from the perspective of cost, forming a silver film 201 with a thickness of more than 300 nm is disadvantageous. In actual products, the film thickness of the silver film 103 is used to be 200 nm or less, and more preferably 90 nm or more and 120 nm or less.

[0078] Within this film thickness range of the silver film 202, forming the ITO film 202 between the silver film 201 and the aluminum oxide (AlOx) film 203 is very effective. According to this configuration, an optical sensor using an organic photoconductive film with excellent reflection characteristics and high reliability can be achieved.

[0079] In the above description, the organic photoconductive film and the cathode, that is, the silver film, are formed together in the entire sensor area, but the same applies to the case where the organic photoconductive film or the cathode is formed for each sensor element. In addition, in the above description, the case where the ITO thin film is arranged between the silver film and the aluminum oxide (AlOx) film is described, but in addition to ITO, the usual effect can be obtained for transparent oxide conductive films such as AZO (Antimony Zinc Oxide: Antimony Zinc Oxide) and IZO (Indium Zinc Oxide: Indium Zinc Oxide).

[0080] [Example 2]

[0081] The optical sensor of the first embodiment is a light L from Figure 3 On the other hand, there is also a type of photosensor in which light is incident from the opposite side of the substrate 100, that is, the upper electrode 128 side of the photoconductive film 127. In the case where light is incident from the upper electrode 128 side, a reflective film is formed on the lower electrode 126 side, and the upper electrode 128 becomes a transparent electrode. The configuration in which light is incident from the upper electrode 128 side enables a switching TFT or a driving TFT to be formed between the lower electrode 126 and the substrate 100, and is therefore advantageous from a spatial perspective.

[0082] In addition, if silver is formed into a thin film with a thickness of 50 nm or less, especially 30 nm or less, it can transmit visible light. By utilizing this property, it is possible to realize a light sensor in which light is incident from the upper electrode 128 side (hereinafter also referred to as an upper light incident type) without changing the basic structure of the light sensor described in Example 1.

[0083] Figure 7 is a cross-sectional view of the organic photodiode portion in Example 2. The configuration of the switching TFT or the driving TFT is similar to that in Figure 3 The structure described in is the same, therefore, Figure 7 In, only the organic photodiode part is described. Figure 7 In the embodiment, an inorganic passivation film 124 is formed on an organic passivation film 122, for example, with a SiN film having a thickness of 100 nm. On the inorganic passivation film 124, a reflective film 150 is formed with silver, aluminum, or an aluminum alloy with a thickness of about 100 nm. On the inorganic passivation film 124, a cathode 126 is formed with an ITO film having a thickness of about 50 nm. The reflective film 150 is formed with a metal under the cathode 126, which is similar to the embodiment 1. Figure 3 different.

[0084] An organic photoconductive film 127 is formed on the cathode 126 with a thickness of 300 nm to 500 nm. Figure 3 The anode 128 is formed of a silver film on the organic photoconductive film 127.Figure 7 In this case, the silver film serving as the anode 128 does not function as a reflective electrode and needs to transmit light. Therefore, the film thickness of the silver film 128 is 50 nm or less, preferably 20 nm to 30 nm. If the silver film has such a film thickness, it has a transmittance equal to or higher than that of ITO.

[0085] An ITO film 129 for preventing silver oxidation with a thickness of about 7 nm is formed on the anode 128 formed of the silver film. The ITO film 129 is formed continuously with the silver film 128 by low-temperature sputtering. Similar to the film described in Example 1, the ITO film 129 becomes an amorphous film. However, in Figure 7 this configuration, in order to prevent light attenuation, it is preferable to suppress the film thickness of the ITO film 129. Therefore, a more preferable film thickness is 5 nm to 20 nm.

[0086] On the ITO film 129, an alumina (AlOx) film 130 with a thickness of about 10 nm to 50 nm is formed, which is the same as in Example 1. This is to prevent the influence of external moisture, etc. on the organic photoconductive film. In Figure 7 this configuration, the more preferable range of the alumina film 130 is also 10 nm to 30 nm in order not to attenuate light. Oxygen from the alumina film 130 is blocked by the ITO film 129, so it does not reach the cathode 128, and the silver film 128 will not be oxidized, and its conductivity can be maintained.

[0087] The silver film 128 is very thin, but as Figure 1 、 Figure 2 shown, the power line 13 extends longitudinally in the sensor region, so the potential drop of the cathode 128 can be prevented. That is to say, as long as the thin silver film 128 only functions as a conductive film in each sensor element, there is no substantial problem as long as the increase in the resistance value caused by thinning the silver film 128 does not oxidize the silver film 128.

[0088] In this way, by forming the ITO thin film 129 between the silver film 128 serving as the anode and the alumina (AlOx) 130 for blocking moisture, the oxidation of the silver thin film 128 can be prevented. Therefore, a photosensor with an upper-surface incident light type organic photoconductive film can be realized.

[0089] In the above description, a sensor using an organic photoconductive film has been described as a photosensor, but the present invention is not limited thereto, and other photosensors using silver as the cathode or anode can also be applied. In addition, above, the present invention has been described for a photosensor using an organic photoconductive film, but the present invention is not limited thereto, and it can also be used for an organic EL display device using an organic EL film, etc.

[0090] Description of reference numerals

[0091] 10… Organic optoelectronic diode, 11… Scan line, 12… Detection line, 13… Power supply line, 15… TFT, 20… Scan line driving circuit, 30… Detection circuit, 40… Power supply circuit, 100… Substrate, 101… Base film, 102… Polysilicon semiconductor film, 103… First gate insulating film, 104… First gate electrode, 105… Light shielding film, 106… First interlayer insulating film, 107… Oxide semiconductor film, 108… Drain protection electrode, 109… Source protection electrode, 110… Second gate insulating film, 111… Gate alumina film, 112… Second gate electrode, 113… Second interlayer insulating film, 114… First drain electrode, 115… First source electrode, 116… Second drain electrode, 117… Second source electrode, 118… First through hole, 119… Second through hole, 120… Third through hole, 121… Fourth through hole, 122… Organic passivation film, 123… Fifth through hole, 124… Inorganic passivation film, 125… Sixth through hole, 126… Cathode, 127… Organic photoconductive film, 128… Anode (silver film), 129… ITO film, 130… Alumina (AlOx) film, 131… Organic protective film, 135… Through hole, 200… Sample substrate, 201… Sample silver (Ag) film, 202… Sample ITO film, 203… Sample alumina (AlOx) film, L… Light.

Claims

1. A semiconductor device having a thin film transistor formed thereon a substrate, characterized in that, The electrode electrically connected to the thin film transistor is formed of a silver film, a first ITO film is formed on the silver film, and an AlOx film is formed on the first ITO film, wherein the AlOx film is an aluminum oxide film. The semiconductor device has a photosensor. The photosensor includes a photodiode in the upper layer of the thin film transistor. The photodiode is composed of a cathode, a photoconductive film formed on the cathode, and an anode formed on the photoconductive film. The electrode is the anode of the photodiode. The thickness of the silver film is 90 nm to 200 nm.

2. The semiconductor device according to claim 1, characterized in that, The photoconductive film is an organic photoconductive film.

3. The semiconductor device according to claim 2, characterized in that, The thickness of the first ITO film is 5 nm to 20 nm.

4. The semiconductor device according to claim 1, characterized in that, The thickness of the aluminum oxide film is 10 nm to 50 nm.

5. The semiconductor device according to claim 4, characterized in that, The first ITO film is amorphous.

6. The semiconductor device according to claim 5, characterized in that, The cathode is formed of a second ITO film and is connected to the thin film transistor.

7. The semiconductor device according to claim 6, characterized in that, The second ITO film is crystallized ITO.

8. A semiconductor device having a photosensor, characterized in that, In the photosensor, A thin film transistor is formed on a substrate. A photodiode is formed in the upper layer of the thin film transistor. The photodiode is composed of a cathode, a photoconductive film formed on the cathode, and an anode formed on the photoconductive film. The photosensor detects light from the side opposite to the substrate. The anode is formed of a silver film, a first ITO film is formed on the silver film, and an AlOx film is formed on the first ITO film, wherein the AlOx film is an aluminum oxide film. The thickness of the silver film is 20 nm to 50 nm.

9. The semiconductor device according to claim 8, characterized in that, The photoconductive film is an organic photoconductive film.

10. The semiconductor device according to claim 8, characterized in that, The thickness of the first ITO film is 5 nm to 20 nm.

11. The semiconductor device according to claim 8, characterized in that, The thickness of the aluminum oxide film is 10 nm to 30 nm.

12. The semiconductor device according to claim 11, characterized in that, The first ITO film is amorphous.

13. The semiconductor device according to claim 12, wherein, The cathode is formed of a second ITO film, and a reflective electrode formed of a metal or an alloy exists on the lower surface of the second ITO film.

14. The semiconductor device according to claim 13, wherein, The second ITO film is crystallized ITO.

15. The semiconductor device according to claim 2, wherein, A plurality of the thin film transistors are formed in the sensor region of the substrate. The organic photoconductive film, the anode, the first ITO film, and the aluminum oxide film are integrally formed on the entire surface of the sensor region and overlap with the plurality of thin film transistors.

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