Semiconductor device

Abstract

The invention relates to a semiconductor device. The purpose of the present invention is to cope with poor electrode connection in a semiconductor device having an optical sensor based on a PIN-type photoconductive film. The configuration of the present invention is as follows. A semiconductor device having an optical sensor, characterized in that a thin film transistor is formed on a substrate of the optical sensor, a photodiode is formed on an upper layer of the thin film transistor, the photodiode is composed of an anode (131), a photoconductive film (130), and a cathode (126), the cathode (126) is composed of a titanium film, and the photoconductive film (130) is formed on the substrate of the optical sensor. A first transparent conductive film (201) is formed between the titanium film and the photoconductive film.

Description

[0001] This application is a divisional application of Chinese invention patent application No. 202080069889.2 (PCT application number is PCT / JP2020 / 041532), with an application date of November 6, 2020 and an invention name of “Semiconductor Device”. Technical Field

[0002] The present invention relates to a semiconductor device having a photosensor using a photoelectric conversion element. Background Art

[0003] Optical sensors that utilize photoelectric conversion are widely used in fields such as image recognition and biometric authentication. PIN photodiodes are photodiodes that have an intrinsic layer between a p+ layer and an n+ layer. They have excellent response speed and low dark current, so they can achieve a large S / N ratio.

[0004] Patent Document 1 describes a vertical PIN photosensor using a-Si. Patent Document 2 describes an example in which a planar PIN photodiode is used as an image sensor.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2-159772

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 6-314779 Summary of the invention

[0009] Problems to be solved by the invention

[0010] When a photodiode is used as a flat image sensor, a switching TFT and a driving TFT are formed together with the photodiode by TFT (Thin Film Transistor). In addition, in order to supply power to the photodiode or detect the output from the photodiode, a power line, a detection line, a scanning line, etc. are required.

[0011] A thin film is used in the electrode connected to the photodiode. On the other hand, since a switching TFT and a driving circuit are arranged adjacent to the photodiode or in the lower layer of the photodiode, unevenness is easily generated in the region where the photodiode is formed. Therefore, due to the unevenness, a fault is generated in the conductive film connected to the photodiode, which impairs the reliability as a sensor.

[0012] An object of the present invention is to prevent unevenness from being generated near a photodiode, to prevent disconnection of an electrode connected to the photodiode, and to realize a highly reliable optical sensor.

[0013] Means for solving problems

[0014] The present invention is an invention for solving the above-mentioned problems, and main specific means are as follows.

[0015] (1) A semiconductor device having a light sensor, characterized in that the light sensor has a thin film transistor formed on a substrate, a photodiode formed on an upper layer than the thin film transistor, the photodiode is composed of an anode, a photoconductive film, and a cathode, the cathode is composed of a titanium film, and a first transparent conductive film is formed between the titanium film and the photoconductive film.

[0016] (2) A semiconductor device having a light sensor, characterized in that the light sensor has a thin film transistor formed on a substrate, a photodiode formed on an upper layer than the thin film transistor, the photodiode is composed of an anode, a photoconductive film, and a cathode, the cathode is composed of a titanium film, the titanium film is in contact with a first transparent conductive film, and the titanium film is formed between the first transparent and photoconductive films.

[0017] (3) A semiconductor device having a light sensor, characterized in that the light sensor has a thin film transistor formed on a substrate, a photodiode formed on an upper layer than the thin film transistor, the photodiode is composed of an anode, a photoconductive film, and a cathode, a first organic insulating film is formed in a manner covering a portion of the anode, and the anode is connected to a connecting electrode extending above the first organic insulating film.

[0018] This application relates to the following items:

[0019] Item 1. A semiconductor device having a light sensor, characterized in that:

[0020] The optical sensor has a thin film transistor formed on a substrate.

[0021] A photodiode is formed in an upper layer than the thin film transistor,

[0022] The photodiode is composed of an anode, a photoconductive film, and a cathode.

[0023] The cathode is composed of a titanium film,

[0024] A first transparent conductive film is formed between the titanium film and the photoconductive film.

[0025] Item 2. The semiconductor device according to Item 1, wherein the photoconductive film is composed of an a-Si film having an n+ layer, an i layer (intrinsic layer), and a p+ layer from the cathode side.

[0026] Item 3. The semiconductor device according to Item 2, wherein the first transparent conductive film has an opening at a position overlapping with the photoconductive film, and the n+ layer and the cathode are in direct contact with each other at the opening.

[0027] Item 4. The semiconductor device according to Item 1, wherein the first transparent conductive film has a first portion overlapping with the photoconductive film and a second portion not overlapping with the photoconductive film between the photoconductive film and the cathode.

[0028] Item 5. The semiconductor device according to Item 1, wherein the anode is formed of a second transparent conductive film.

[0029] Item 6. A semiconductor device having a light sensor, characterized in that:

[0030] The optical sensor has a thin film transistor formed on a substrate.

[0031] A photodiode is formed in an upper layer than the thin film transistor,

[0032] The photodiode is composed of an anode, a photoconductive film, and a cathode.

[0033] The cathode is composed of a titanium film,

[0034] The titanium film is in contact with the first transparent conductive film.

[0035] The titanium film is formed between the first transparent conductive film and the photoconductive film.

[0036] Item 7. The semiconductor device according to Item 6, wherein the photoconductive film is composed of an a-Si film having an n+ layer, an i layer (intrinsic layer), and a p+ layer from the cathode side.

[0037] Item 8. The semiconductor device according to Item 6, wherein:

[0038] An organic passivation film is provided below the first transparent conductive film.

[0039] The first transparent conductive film is sandwiched between the organic passivation film and the cathode, and overlaps with the photoconductive film.

[0040] Item 9. The semiconductor device according to Item 8, wherein:

[0041] The semiconductor device further includes an oxide semiconductor and a source electrode connected to the oxide semiconductor.

[0042] The source electrode is directly in contact with the first transparent conductive film via a contact hole formed in the organic passivation film.

[0043] Item 10. The semiconductor device according to Item 6, wherein the anode is formed of a second ITO.

[0044] Item 11. The semiconductor device according to Item 6, wherein:

[0045] A portion of the anode is covered with an inorganic insulating film,

[0046] The anode is connected to a connection electrode extending on the inorganic insulating film.

[0047] Item 12. A semiconductor device having a light sensor, characterized in that:

[0048] The optical sensor has a thin film transistor formed on a substrate.

[0049] A photodiode is formed in an upper layer than the thin film transistor,

[0050] The photodiode is composed of an anode, a photoconductive film, and a cathode.

[0051] A first organic insulating film is formed so as to cover a portion of the anode,

[0052] The anode is connected to a connection electrode extending on the first organic insulating film.

[0053] Item 13. The semiconductor device according to Item 12, wherein the photoconductive film is composed of an a-Si film having an n+ layer, an i layer (intrinsic layer), and a p+ layer from the cathode side.

[0054] Item 14. The semiconductor device according to Item 12, wherein the cathode is formed of a titanium film, and a second organic insulating film is formed under the cathode.

[0055] Item 15. The semiconductor device according to Item 12, wherein an inorganic insulating film is formed so as to cover a portion of the photoconductive film and a portion of the anode and under the first organic insulating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] [ Figure 1 ] is a top view of the light sensor.

[0057] [ Figure 2 ] is a top view of the optical sensor element.

[0058] [ Figure 3 ] is a cross-sectional view of the optical sensor.

[0059] [ Figure 4 ] is an enlarged top view showing the problematic area of ​​the optical sensor element.

[0060] [ Figure 5 ]for Figure 4 AA cross-section diagram.

[0061] [ Figure 6 ]for Figure 4 BB cross-section diagram.

[0062] [ Figure 7 ] is a cross-sectional view showing the structure of Example 1.

[0063] [ Fig. 8A ] is a cross-sectional view showing the initial process flow of the process for realizing the structure of Example 1.

[0064] [ Figure 8B ]for Fig. 8A A cross-sectional view of the subsequent process.

[0065] [ Figure 8C ]for Figure 8B A cross-sectional view of the subsequent process.

[0066] [ Fig.8D ]for Figure 8C A cross-sectional view of the subsequent process.

[0067] [ Fig. 8E ]for Fig.8D A cross-sectional view of the subsequent process.

[0068] [ Fig.8F ]for Fig. 8E A cross-sectional view of the subsequent process.

[0069] [ Fig. 9 ] is a cross-sectional view showing the structure of Example 2.

[0070] [ Fig. 10A ] is a cross-sectional view showing the initial step of the process flow for implementing the structure of Example 2.

[0071] [ Fig. 10B ]for Fig. 10A A cross-sectional view of the subsequent process.

[0072] [ Fig.11A ] is the first process flow, Fig. 10B A cross-sectional view of the subsequent process.

[0073] [ Fig. 11B ] is the first process flow, Fig.11A A cross-sectional view of the subsequent process.

[0074] [ Fig. 11C ] is the first process flow, Fig. 11B A cross-sectional view of the subsequent process.

[0075] [ Fig. 12A ] is the second process flow, Fig. 10B A cross-sectional view of the subsequent process.

[0076] [ Fig. 12B ] is the second process flow, Fig. 12A A cross-sectional view of the subsequent process.

[0077] [ Fig. 12C ] is the second process flow, Fig. 12B A cross-sectional view of the subsequent process.

[0078] [ Fig.12D ] is the second process flow, Fig. 12C A cross-sectional view of the subsequent process.

[0079] [ Fig.13 ] is a cross-sectional view showing the structure of Example 3.

[0080] [ Fig.14A ] is a cross-sectional view showing the initial process flow of the process flow for realizing the structure of Example 3.

[0081] [ Fig. 14B ]for Fig.14A A cross-sectional view of the subsequent process.

[0082] [ Fig. 14C ]for Fig. 14B A cross-sectional view of the subsequent process.

[0083] [ Fig.14D ]for Fig. 14C A cross-sectional view of the subsequent process.

[0084] [ Fig.14E ]for Fig.14D A cross-sectional view of the subsequent process.

[0085] [ Fig.15 ] is a cross-sectional view showing other structures of Example 3. DETAILED DESCRIPTION

[0086] Figure 1 It is a top view of a light sensor device to which the present invention is applied. Figure 1In the sensor area, the sensor elements are formed in a matrix shape. The size of the sensor area is, for example, a horizontal diameter xx of 3 cm and a vertical diameter yy of 3 cm. In the sensor area, the scanning line 11 extends in the horizontal direction (x direction) and is arranged in the vertical direction (y direction). The detection line 12 and the power line 13 extend in the vertical direction and are arranged in the horizontal direction. The area surrounded by the scanning line 11 and the detection line 12, or the scanning line 11 and the power line 13 becomes a sensor element. In each sensor element, a switching TFT 15, a PIN photoconductive film diode 10, and a storage capacitor 16 are formed. One electrode of the storage capacitor 16 is connected to the source of the TFT 15, and the other electrode is connected to a reference potential, for example.

[0087] A scanning line driving circuit 20 is arranged in the lateral direction outside the sensor area, a power supply circuit 40 is arranged above, and a detection circuit 30 is arranged below. The scanning line driving circuit 20 and the detection circuit 30 are formed of TFTs. The scanning lines 11 are selected sequentially from the top by the shift register in the scanning line driving circuit 20.

[0088] The power line 13 is connected to the anode of each photodiode, extends in the longitudinal direction, and is connected to the same power supply in the power circuit 40 on the upper side of the sensor area. In addition, the anode potential is supplied to the power 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 detection circuit 30 detects the photocurrent. Figure 1 In the embodiment, when light is irradiated to a sensor element selected by the scanning line 11 , a photocurrent is generated from the photodiode 10 , and the photocurrent is detected by the detection circuit 20 through the detection line 12 .

[0089] Figure 2 A top view of each sensor element. Figure 2 In order to avoid complicating the figure, some electrodes 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. Figure 2 In the embodiment, the scanning line 11 extends in the horizontal direction (x direction) and is arranged in the vertical direction (y direction). In addition, the power line 13 and the detection line 12 extend in the vertical direction and are arranged in the horizontal direction. In the area surrounded by the scanning line 11 and the power line 13, or the scanning line 11 and the detection line 12, a cathode 126, a photoconductive film 130, an anode 131, etc. of the photodiode are formed.

[0090] The semiconductor film 107 extends from the detection line 12 through the through hole 140 in the x direction, 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 titanium (Ti) in the through hole 125. Figure 3As described above, since the through hole 125 is formed in the thick organic passivation film, the diameter is large. The photoconductive film 130 is formed on the cathode 126, and the anode 131 is formed thereon with ITO (Indium Tin Oxide). Thus, a photodiode is formed.

[0091] exist Figure 2 In the embodiment, power is supplied to the photodiode via the connection electrode 133 between the anode 131 and the power line 13. The power line 13 may extend directly to the power circuit 40 on the surface insulating film, or may extend to the same layer as the drain electrode or the source electrode of the TFT via a through hole.

[0092] Figure 3 yes Figure 1 A cross-sectional view of a light sensor device. Figure 3 The optical sensor shown is a system in which light is input from the opposite side of the substrate 100, that is, the anode 131 side. Figure 1 As shown in FIG. 1 , a driving circuit formed of TFTs is formed outside the sensor region. Since polycrystalline silicon semiconductors have high mobility, it is advantageous that the TFTs constituting the driving circuits are formed of polycrystalline silicon semiconductors.

[0093] On the other hand, it is advantageous for the switching TFT formed in the sensor region to be formed of an oxide semiconductor (sometimes referred to as OS) with low leakage current. Therefore, in this embodiment, a hybrid array substrate using both polysilicon semiconductor TFT and oxide semiconductor TFT is used. Figure 3 In the figure, the left side is a polysilicon TFT for peripheral circuits, and the center part is a PIN photodiode and a switching TFT used therefor.

[0094] As for polysilicon, so-called low-temperature polysilicon obtained by polysiliconizing a-Si using an excimer laser is used. However, since the annealing temperature of the polysilicon semiconductor exceeds the process temperature for forming the oxide semiconductor, the polysilicon semiconductor TFT is formed first, and then the oxide semiconductor TFT is formed. Therefore, the manufacturing starts with the peripheral circuit first.

[0095] Figure 3 In the embodiment, a base film 101 composed of a stacked film of silicon nitride (SiN) and silicon oxide (SiO) is formed on a glass substrate 100. This is to prevent impurities from the glass substrate 100 from contaminating the polysilicon semiconductor 102 and 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.

[0096] A polysilicon film 102 for TFT is formed thereon. The polysilicon film 102 is formed by first forming an a-Si film, then converting the a-Si into polysilicon using an excimer laser and patterning it. The thickness of the polysilicon film 102 is, for example, 50 nm. It should be noted that the SiO film, SiN film, and a-Si film as the base film 101 can be formed continuously by CVD.

[0097] Then, a first gate insulating film 103 is formed of SiO in a manner covering the polycrystalline silicon semiconductor film 102. The thickness of the first gate insulating film 103 is, for example, 100 nm. A first gate electrode 104 is formed thereon from a metal or an alloy. The first gate electrode 104 is formed, for example, from MoW. Here, the peripheral circuit region and the sensor region are formed simultaneously. While forming the first gate electrode 104, a light shielding film 105 is formed in a portion of the sensor region corresponding to the switching TFT using the same material as the first gate electrode 104. The light shielding film 105 can also be used as a bottom gate electrode of an oxide semiconductor TFT formed later.

[0098] The first interlayer insulating film 106 is formed by a stacked film of SiO film and SiN film in a manner covering the first gate electrode 104 and the light shielding film 105. 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 oxide semiconductors, 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.

[0099] In order to maintain the characteristics of the oxide semiconductor, it is important to maintain the amount of oxygen. Therefore, the upper layer of the first interlayer insulating film 106 must be a SiO film. This is because SiN will supply hydrogen to reduce 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.

[0100] 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 metal, and when the through hole in the polysilicon TFT is cleaned with hydrofluoric acid (HF), the oxide semiconductor film 107 is prevented from disappearing in the through hole on the oxide semiconductor TFT side due to the hydrofluoric acid (HF).

[0101] The second gate insulating film 110 is formed of a SiO film in a manner covering the oxide semiconductor film 107. The thickness of the SiO film is about 100 nm. A gate aluminum oxide film 111 is formed on the SiO film 110, and a second gate electrode 112 is formed thereon, for example, from a MoW alloy. By supplying oxygen from the second gate insulating film 110 formed of SiO and the gate aluminum oxide film 111 to the oxide semiconductor film 107, the characteristics of the oxide semiconductor film 107 are stabilized.

[0102] In this embodiment, by extending the source protection electrode 109, a capacitor electrode 114 having the same structure as the gate electrode 112 is formed at the opposite portion, thereby forming a storage capacitor via the second gate insulating film 110 and the capacitor aluminum oxide (AlOx) film 113. The capacitor aluminum oxide (AlOx) film 113 and the capacitor electrode 114 are formed simultaneously with the gate aluminum oxide film 111 and the gate electrode 112. The thickness of the capacitor aluminum oxide (AlOx) film is less than 10 nm, so it has almost no effect on the value of the capacitor.

[0103] The second interlayer insulating film 115 is formed by a stacked film of a SiO film and a SiN film in a manner covering the second gate electrode 112 and the capacitor electrode 114. The thickness of the SiO film is, for example, 300 nm, and the thickness of the SiN film is, for example, 100 nm. The SiO film is mostly arranged on the lower side closer to the oxide semiconductor film 107. After the second interlayer insulating film 115 is formed, through holes 120 and 121 are simultaneously formed on the polysilicon TFT side of the peripheral circuit, and through holes 122 and 123 are simultaneously formed on the oxide semiconductor TFT side of the sensor region side.

[0104] The through holes 120 and 121 on the polysilicon TFT side are cleaned with hydrofluoric acid (HF) to remove the oxide film. At this time, in order to prevent the hydrofluoric acid (HF) from entering the through holes 122 and 123 on the oxide semiconductor TFT side and causing the oxide semiconductor film 107 to disappear, a drain protection electrode 108 and a source protection metal film 109 are used.

[0105] The first drain electrode 116 and the first source electrode 117 are formed corresponding to the through holes 120 and 121 on the polysilicon TFT side, and the second drain electrode 118 and the second source electrode 119 are formed corresponding to the through holes 122 and 123 on the oxide semiconductor TFT side. The second drain electrode 118 is connected to the detection line 12. The first drain electrode 116, the first source electrode 117, the second drain electrode 118, the second source electrode 119, etc. are formed of a stacked film of Ti, Al, and Ti, and the thickness of each layer is, for example, 50 nm, 450 nm, and 50 nm, respectively, from the bottom layer.

[0106] The organic passivation film 124 is formed of a resin such as acrylic acid so as to cover the second interlayer insulating film 115. Since the organic passivation film 124 also serves as a planarization film, it is formed thickly to be about 2 μm. In the organic passivation film 124, a through hole 125 for connecting the source electrode 119 to the cathode 126 of the photodiode is formed corresponding to the source electrode 119 of the TFT. Since the thickness of the organic passivation film 124 is thick, the diameter of the through hole 125 becomes larger.

[0107] A cathode 126 is formed of Ti on the organic passivation film 124. The cathode 126 has a thickness of about 100 nm and extends into the through hole 125 of the organic passivation film 124. A PIN film 130 is formed on the cathode 126. The PIN film 130 is constructed as follows: an n+ layer 127 is formed on the cathode 126 with a thickness of about 40 nm, an i layer (a-Si layer) 128 is formed on the n+ layer 127 with a thickness of 600 nm, and a p+ layer 129 is formed on the i layer with a thickness of 30 nm. It should be noted that these values ​​of the PIN film 130 are examples. The n+ layer 127, the i layer 128, and the p+ layer 129 are all formed of a-Si. They can all be formed continuously by CVD. Hereinafter, the PIN film 130 (photoconductive film 130) is sometimes referred to as the a-Si film 130.

[0108] An ITO film 131 is formed on the p+ layer 129 to a thickness of, for example, 50 nm, as an anode. Then, in order to prevent leakage, a third interlayer insulating film 132 is formed of, for example, SiN. In the third interlayer insulating film 132, a hole is formed on the surface of the anode 131, and an anode potential can be supplied from this portion via the power line 13 and the connection electrode 133.

[0109] Figure 3 In the embodiment, the connection electrode 133 formed simultaneously with the power supply line 13 extends on the third interlayer insulating film 132, is connected to the anode 131 in the hole of the third interlayer insulating film 132, and supplies the anode potential to the photodiode. The connection electrode 133 is formed of a stacked structure of a Ti film with a thickness of 100 nm, an aluminum film with a thickness of 300 nm, and a Ti film with a thickness of 100 nm.

[0110] The inorganic passivation film 134 is formed of, for example, SiN so as to cover the connection electrode 133 , the anode 131 , the third interlayer insulating film 132 , and the like. Figure 3In the embodiment, the organic passivation film 124 is covered by the third interlayer insulating film 132 and the inorganic passivation film 134 in the portion other than the cathode 126. The organic passivation film 124 absorbs moisture from the atmosphere or the like during the process. If the moisture is discharged from the organic passivation film 124 during operation, it may cause film peeling or the like. Therefore, a drainage hole 135 is formed in the third interlayer insulating film 132 and the inorganic passivation film 134 covering the organic passivation film 124 so that the moisture contained in the organic passivation film 124 can be discharged.

[0111] The optical sensor device is completed in the above manner, but in this state, the surface is SiN film 134 with a thickness of about 200 nm, so the mechanical strength is insufficient. Therefore, in order to mechanically protect the optical sensor, an organic protective film 136 is sometimes formed on the inorganic passivation film 134. The organic protective film 136 is formed of, for example, acrylic resin and has a thickness of, for example, 2 μm.

[0112] Figure 4 A top view of the sensor element. Figure 4 TFT is omitted. Figure 4 In the embodiment, a sensor element is formed in a region surrounded by the detection line 12, the power supply line 13, and the scanning line 11. Figure 4 In the embodiment, a cathode 126 is formed of Ti in such a manner as to cover a through hole 125 formed in an organic passivation film 124. A photoconductive film 130 formed of a-Si and having a PIN structure is formed on the cathode 126, and an anode 131 is formed of ITO thereon. Furthermore, on the anode 131, a connection electrode 133 extends from the power supply line 13 to supply a potential to the anode 131. Figure 4 The AA portion and the BB portion in are the parts that the present invention aims to solve.

[0113] Figure 5 for Figure 4 The AA cross-sectional view is the first problem to be solved by the present invention. Figure 5 In , the parts other than the layer that is the part in question are omitted. Figure 5 In the embodiment, a source electrode 119 is formed on the second interlayer insulating film 115, and the source electrode 119 is connected to a cathode 126 formed of Ti via a through hole 125 formed in the organic passivation film 124. An a-Si film 130 as a photoconductive film (PIN film) is formed on the cathode 126, and an anode 131 formed of ITO is formed on the a-Si film 130.

[0114] exist Figure 5In the embodiment, the a-Si film 130 as the photoconductive film is formed by dry etching, but at this time, since the etching selectivity ratio between the a-Si film 130 and the Ti film 126 (cathode 126) is small, the Ti film as the cathode 126 is also etched at the same time, and the cathode 126 becomes thinner. Thus, the cathode 126 is disconnected, especially in the through hole 125.

[0115] Figure 6 yes Figure 4 The BB cross-sectional view is a cross-sectional view showing the second problem and the third problem to be solved by the present invention. Figure 6 In , the parts other than the layer that is the part in question are omitted. Figure 6 In the embodiment, a source electrode 119 is formed on the second interlayer insulating film 115, and the source electrode 119 is connected to a cathode 126 formed of Ti via a through hole 125 formed in the organic passivation film 124. An a-Si film 130 as a photoconductive film 130 is formed on the cathode 126, and an anode 131 formed of ITO is formed on the a-Si film 130. A third interlayer insulating film 132 is formed to cover the periphery of the anode 131 and the photoconductive film 130, and a connecting electrode 133 is formed on the third interlayer insulating film 132.

[0116] exist Figure 6 In the embodiment, the photoconductive film 130 formed of a-Si is patterned by dry etching, but the etching selectivity ratio of the a-Si film 130 to the organic passivation film 124 is smaller than the etching selectivity ratio of the a-Si film 130 to the Ti film 126. Therefore, when the a-Si film 130 is dry-etched, the organic passivation film 124 is etched using the Ti film 126 as a cathode as a mask (refer to FIG. Figure 6 ). If the third interlayer insulating film 132 and the connecting electrode 133 are formed in such a way as to cover the step difference portion of the organic passivation film 124 formed at this time, the third interlayer insulating film 132 cannot cover the step difference. In addition, there is a risk that the connecting electrode 133 will be disconnected due to the step difference. This is the second problem.

[0117] exist Figure 6 In the embodiment, the photoconductive film 130 is formed of a p+ layer 129, an a-Si layer (i layer) 128, and an n+ layer 127, and patterned by dry etching. The etching rate of the p+ layer 129 is lower than that of the a-Si layer 128 and the n+ layer 127. Therefore, after patterning, an eave of the p+ layer 129 is formed on the photoconductive film 130. Furthermore, if the third interlayer insulating film 132 and the connecting electrode 133 are formed in a manner covering the photoconductive film 130, the connecting electrode 133 will be disconnected due to the influence of the eave of the p+ layer 129. This is the third problem.

[0118] Hereinafter, a configuration for solving the first problem will be described with reference to Example 1, a configuration for solving the second problem will be described with reference to Example 2, and a configuration for solving the third problem will be described with reference to Example 3.

[0119] Example 1

[0120] Figure 7 This is a cross-sectional view showing the structure of Example 1 for solving the first problem. Figure 7 and Figure 5 The difference is that an ITO film 201 is formed in a manner covering the cathode 126. The thickness of the ITO film 201 is 30nm to 50nm. Since the dry etching selectivity of ITO and a-Si is high, the ITO film 201 is hardly etched when the a-Si film 130 is dry-etched. Therefore, the Ti film 126, which is the cathode located in the lower layer, is protected, avoiding the disconnection of the cathode 126.

[0121] However, in order to maintain the characteristics as a photodiode, it is preferred that the n+ layer 127 is in contact with the Ti film 126. Therefore, the ITO film 201 is removed to form an opening 2011 except for the portion in contact with the peripheral portion of the n+ layer 127, and the n+ layer 127 is formed in the opening 2011 of the ITO film 201 to be in contact with the Ti film 126. The ITO film 201 may also be a structure without the opening 2011, and the n+ layer 127 is in direct contact with the ITO film 201 stacked on the cathode 126.

[0122] FIG. 8A to FIG. 8F It shows the realization Figure 7 A cross-sectional view of the process of forming the same. Fig. 8A It is a cross-sectional view showing a state where an ITO film 201 is formed on a Ti film 126 serving as a cathode. Figure 8B This is a cross-sectional view showing a state where the ITO film 201 and the Ti film 126 except for the vicinity of the photodiode are removed using the resist 500 . Figure 8C It is a cross-sectional view showing a state where the ITO film 201 is removed from a portion where the photoconductive film (a-Si film) 130 is formed.

[0123] Fig.8D This is a cross-sectional view showing a state in which an a-Si film 130 is formed so as to cover the cathode 126 and the ITO film 201 , and an ITO film 131 serving as the anode 131 is formed thereon. Fig. 8E It is a cross-sectional view showing a state where the ITO film 131 on the a-Si film 130 is patterned to form the anode 131 .

[0124] Fig.8F1 is a cross-sectional view showing a state where the photoconductive film 130 is formed by patterning the a-Si film 130. When the a-Si film 130 is dry-etched, the ITO film 201 is hardly corroded because the etching selectivity between a-Si and ITO is large. Therefore, a stable cathode 126 can be formed.

[0125] Example 2

[0126] Fig. 9 This is a cross-sectional view showing the structure of Example 2 for solving the second problem. Fig. 9 and Figure 6 The difference is that an ITO film 202 is formed in the lower layer of the cathode 126. The thickness of the ITO film 202 is 30nm to 50nm. The selectivity of ITO and a-Si in dry etching is high. That is, after the Ti film 126 as the cathode 126 is patterned, the ITO film 202 of the lower layer also remains, and in this state, the a-Si film 130 as the photoconductive film 130 is patterned. At this time, since the organic passivation film 124 is protected by the ITO film 202, it will not be dry-etched. Therefore, the step difference of the organic passivation film 124 generated when the a-Si film 130 is dry-etched is avoided. Then, after the a-Si film 130 is dry-etched, the ITO film 202 is patterned.

[0127] Fig. 10A , Fig. 10B and FIG. 11A to FIG. 11C It shows the realization Fig. 9 A cross-sectional view of a first example of a process flow of the structure of. Fig. 10A In the embodiment, an organic passivation film 124 is formed to cover the second interlayer insulating film 115 and the source electrode 119, and a through hole 125 is formed in the organic passivation film 124. An ITO film 202 and a cathode 126 made of a Ti film are formed to cover the organic passivation film 124 and the through hole 125. Fig. 10B It is a cross-sectional view showing a state where only the cathode 126 on the ITO film 202 is patterned.

[0128] Fig.11A It is a cross-sectional view showing a state where an a-Si film 130 as a photoconductive film is formed so as to cover the ITO film 202 and the cathode 126 . Fig. 11B 1 is a cross-sectional view showing a state where the a-Si film 130 as a photoconductive film is patterned. When the a-Si film 130 is patterned, since the organic passivation film 124 is covered by the ITO film 202, it is not dry-etched, and therefore, no step difference is formed. Then, the ITO film 202 is patterned. The ITO film 202 is patterned into a shape that is almost the same as the cathode 126.

[0129] Fig. 11C 1 is a cross-sectional view showing a state where the anode 131 is patterned using a resist after the ITO film 131 serving as the anode is formed so as to cover the photoconductive film 130. At this time, the ITO film 202 can also be patterned using the Ti film 126 serving as the cathode as a mask. In this way, according to the first process flow, it is possible to prevent the generation of a step difference on the organic passivation film 124 and prevent the generation of a disconnection in the connecting electrode 133.

[0130] Fig. 10A , Fig. 10B and FIG. 12A to FIG. 12D It shows the realization Fig. 9 A cross-sectional view of a second example of a process flow of the structure. Fig. 10A and Fig. 10B As described in the first process flow. Fig. 12A This is a cross-sectional view showing a state in which an a-Si film 130 serving as a photoconductive film is formed so as to cover an ITO film 202 and a cathode 126 formed of Ti, and an ITO film 131 serving as an anode is formed on the a-Si film 130 .

[0131] Fig. 12B It is a cross-sectional view showing a state where the ITO film 131 is patterned to form the anode 131 . Fig. 12C 1 is a cross-sectional view showing a state where a resist 500 is formed and a-Si film 130 is patterned. Then, Ti film 126, which is a cathode, is used as a resist to pattern ITO film 202. Since the selectivity between ITO film 202 and organic passivation film 124 is large, organic passivation film 124 is not etched during patterning of ITO film 202.

[0132] Fig.12D 1 is a cross-sectional view showing a state where the resist 500 located on the anode 131 is subsequently removed. Fig.12D As shown, in the second process flow, it is also possible to achieve Fig. 9 Such a structure can prevent disconnection of the connection electrodes and improve the reliability of the optical sensor.

[0133] Example 3

[0134] Fig.13 This is a cross-sectional view showing the structure of Example 3 for solving the third problem. Fig.13 and Figure 6 The difference is that the organic insulating film 300 is formed to cover the anode 131 and the third interlayer insulating film 132 , and the connection electrode 133 and the anode 131 are connected via a through hole 145 formed in the organic insulating film 300 .

[0135] The thickness of the organic insulating film 300 is about 2 μm, so the surface is leveled, and the eaves of the p+ layer 129 formed in the photoconductive film 130 do not affect the connection electrode 133. Therefore, disconnection of the connection electrode 133 can be prevented. Fig.13 The structure of can also eliminate the second problem, that is, eliminate the influence of the step difference caused by the etching of the organic passivation film 124 at the end of the Ti film 126 serving as the cathode. This is because the step difference formed on the organic passivation film 124 is also covered by the organic insulating film 300. That is, Fig.13 The structure can address the second and third problems at the same time.

[0136] FIG. 14A to FIG. 14E is realized Fig.13 The process flow of the composition. Fig.14A It is a cross-sectional view showing a state in which an a-Si film 130 as a photoconductive film is formed on the cathode 126 on the organic passivation film 124 , and an anode 131 is formed on the a-Si film 130 . Fig. 14B 1 is a cross-sectional view showing a state in which the third interlayer insulating film 132 is formed so as to cover the organic passivation film 124 , the cathode 126 , the a-Si film 130 , and a part of the anode 131 .

[0137] Fig. 14C 1 is a cross-sectional view showing a state in which an organic insulating film 300 is formed so as to cover the third interlayer insulating film 132 and the anode 131, and a through hole 145 is formed in the organic insulating film 300 at a portion corresponding to the anode 131. Fig. 14C As shown, since the ends of the a-Si film 130 and the cathode 126 are covered by the organic insulating film 300 , even if irregular shapes occur in these portions, they will not affect the surface of the organic insulating film 300 where the connection electrode 133 is formed.

[0138] Fig.14D 1 is a cross-sectional view showing a state where a connection electrode 133 is formed in a through hole 145 formed in an organic insulating film 300. Since the surface of the organic insulating film 300 is leveled and flat, no fault or the like is generated on the connection electrode 133. Then, the entire optical sensor is protected by the inorganic passivation film 134. Thus, Fig.13 The optical sensor shown has high reliability.

[0139] Fig.15 This is a modified example of FIG. 14 . Fig.1514 is that there is no third interlayer insulating film formed of an inorganic film such as SiN covering the a-Si film 130, the anode 131, the organic passivation film 124, etc. The third interlayer insulating film can be omitted as long as impurities such as moisture generated from the organic passivation film 124, etc. do not contaminate the a-Si film, etc., which is the photoconductive film 130.

[0140] In addition to not needing Fig. 14B In addition to the process, Fig.15 The composition can be obtained by Fig.14A , 14C to Fig.14E This is formed by the process flow. Fig.15 The structure of FIG. 14 can suppress the manufacturing cost in comparison with the structure of FIG. 14 in that the process of forming the third interlayer insulating film is not required.

[0141] Description of Reference Numerals

[0142] 10…photodiode, 11…scanning line, 12…detection line, 13…power supply line, 15…TFT, 16…storage capacitor, 20…scanning line driving circuit, 30…detection circuit, 40…power supply circuit, 100…substrate, 101…base film, 102…polycrystalline silicon 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 aluminum oxide film, 112…second gate electrode, 113…capacitor aluminum oxide film, 114…capacitor electrode, 115…second interlayer insulating film, 116…first drain electrode, 117…first source electrode 117 ... second drain electrode, 119 ... second source electrode, 120 ... first through hole, 121 ... second through hole, 122 ... third through hole, 123 ... fourth through hole, 124 ... organic passivation film, 125 ... fifth through hole, 124 ... inorganic passivation film, 125 ... sixth through hole, 126 ... cathode, 127 ... n+ layer, 128 ... i layer (a-Si layer), 129 ... p+ layer, 130 ... photoconductive film (a-Si film), 131 ... anode, 132 ... third interlayer insulating film, 133 ... connecting electrode, 134 ... inorganic passivation film, 135 ... drainage hole, 136 ... protective film, 140 ... through hole, 145 ... through hole, 201 ... ITO film, 202 ... ITO film, 300 ... organic insulating film, 2011 ... opening of ITO film

Claims

1. A semiconductor device having a light sensor, characterized in that: The optical sensor has a thin film transistor formed on a substrate. A photodiode is formed in an upper layer than the thin film transistor, The photodiode is composed of an anode, a photoconductive film, and a cathode. The cathode is composed of a titanium film, The titanium film is in contact with the first transparent conductive film. The titanium film is formed between the first transparent conductive film and the photoconductive film. An organic passivation film is provided below the first transparent conductive film. The first transparent conductive film is sandwiched between the organic passivation film and the cathode, and overlaps with the photoconductive film.

2. The semiconductor device according to claim 1, wherein The photoconductive film is composed of an a-Si film having an n+ layer, an i layer (ie, an intrinsic layer), and a p+ layer from the cathode side.

3. The semiconductor device according to claim 1, wherein The semiconductor device further includes an oxide semiconductor and a source electrode connected to the oxide semiconductor. The source electrode is directly in contact with the first transparent conductive film via a contact hole formed in the organic passivation film.

4. The semiconductor device according to claim 1, wherein: The anode is formed of a second ITO.

5. The semiconductor device according to claim 1, wherein: A portion of the anode is covered with an inorganic insulating film, The anode is connected to a connection electrode extending on the inorganic insulating film.

6. A semiconductor device having a light sensor, characterized in that The optical sensor has a thin film transistor formed on a substrate. A photodiode is formed in an upper layer than the thin film transistor, The photodiode is composed of an anode, a photoconductive film, and a cathode. A first organic insulating film is formed so as to be in contact with and cover a portion of the anode. The anode is connected to a connection electrode extending on the first organic insulating film.

7. The semiconductor device according to claim 6, wherein: The photoconductive film is composed of an a-Si film having an n+ layer, an i layer (ie, an intrinsic layer), and a p+ layer from the cathode side.

8. The semiconductor device according to claim 6, wherein: The cathode is composed of a titanium film, and a second organic insulating film is formed under the cathode.

9. The semiconductor device according to claim 6, wherein: An inorganic insulating film is formed so as to cover a portion of the photoconductive film and a portion of the anode and under the first organic insulating film.

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