WO1993026046A1

WO1993026046A1 - Semiconductor device

Info

Publication number: WO1993026046A1
Application number: PCT/JP1993/000794
Authority: WO
Inventors: Sin-Ichiro Kurata; Kenji Kobayashi; Tomoyoshi Zenki
Original assignee: Kanegafuchi Kagaku Kogyo Kabushiki Kaisha
Priority date: 1992-06-15
Filing date: 1993-06-14
Publication date: 1993-12-23

Abstract

A semiconductor device for an original reader having a switching element such as a diode, an optical sensor element comprising a photoelectric conversion element and a switching element, and a switching element used in an image reader for inputting image information in a facsimile apparatus, an image scanner, and the like. In a semiconductor device (90) provided with a semiconductor element (blocking diode) (94) having a switching function and comprising a lower electrode (94a), a semiconductor layer (94b), an upper electrode (94c), all of which are formed vertically in this order; at least either one of the lower electrode (94a) and the upper electrode (94c) consists of one or more layers, and out of the conductive layers at least the one which is in contact with the semiconductor layer (94b) is transparent. An optical sensor element and an original document reader according to the present invention employ such semiconductor devices having switching function. In such a semiconductor device thus structured, the reverse direction current involved in switching elements such as blocking diodes and in optical sensor elements can be reduced, making it possible to enhance the switching speed, and to obtain exact signal output from the optical sensor element. Further, in an original document reader having these switching elements or optical sensor elements, inverted residual images can be reduced, and at the same time, the reading can be executed at a higher speed.

Description

Specification

Semiconductor device technology

The present invention relates to a semiconductor device, and more particularly, to a switching element such as a diode formed on a substrate such as glass, an optical sensor element composed of a photoelectric conversion element and a switching element, and a facsimile and image sensor. The present invention relates to a semiconductor device such as a document reading device used in an image reading unit for inputting image information in a scanner or the like.

BACKGROUND ART-In recent years, image reading units, such as facsimile image scanners, have been widely replaced with document reading devices generally called contact image sensors, instead of CCD document reading devices requiring a reduction optical system. Has been adopted.

For example, as shown in FIG. 19, a conventional document reading apparatus 1 has a glass substrate 2 on which a photodiode 3 as a photoelectric conversion element, a blocking diode 4 as a switching element, and electricity from a photodiode 3 are arranged. channel interconnection C for reading an electrical signal,. C _2.... C "and is to be constituted by forming.

The photodiode 3 and the blocking diode 4 are composed of opaque lower electrodes 3a and 4a, both made of metal, semiconductor layers 3b and 4b of amorphous silicon made of amorphous silicon, and IT0 ( Indi um Tin Oxi de) transparent upper electrode 3 c made of, 4 c is also _P is configured by sequentially deposited, photodiode 3 and the blocking diode 4 is covered by a transparent interlayer insulating film 5 made of SiO This interlayer insulating film 5 Are connected in series by the connection wiring 7 via the contact hole 6 formed at the reverse polarity. On the other hand, the lower electrode 3a constituting the photodiode 3 is connected to the channel wirings CLC S .... C „through the contact holes 8 formed in the interlayer insulating film 5. The upper electrode 4c of the blocking diode 4 is transparent because it is deposited at the same time as the upper electrode 3c of the photodiode 3 to simplify the manufacturing process. there because it is. these photodiode 3 and the blocking diode 4, in a one-dimensional as shown in the second 0 Figure is mx n number sequence, m-number of blocks beta every n,. beta _2. ... Βπ, the anode electrode of the blocking diode 4 is connected in common within the block Β B ₂ .'... B _m , and the anode electrode of the photodiode 3 is connected to the channel wiring CC ₂ .... by C „ Blocks B and B ₂ .... Βπ, which are relatively connected at the same position. These blocking diode 4 follower Toda Iodo 3 blocks beta, which are necessary in order to sequentially select each. B ₂ .... B _m.

The document reading device 1 is intended to operate in a charge accumulation mode, as shown in Taimuchiya one bets second 1 view, the drive pulse Vp ,. Vp ₂ .... Vp _ra is plotted click 8 _1. 8 _2. ... applied in cycle T every B _m . When these drive pulses Vp ,. Vp ₂ .... _Vpr are applied, the blocking diode 4 in the block Β,. Β ₂ .... B _m becomes forward-biased and the photodiode 3 Is reverse biased. Therefore, the parallel capacitance of the photodiode 3 is charged quickly. This state is a reading state. Meanwhile, when the drive pulse Vp ,. Vp ₂ .... Vp _m is not applied, the block 'Β,. B ₂ .... blocking diode 4 in B _m is reverse biased. Therefore, if light enters the photodiode 3 during this time, the parallel capacitance of the photodiode 3 is discharged by the photocurrent generated in accordance with the amount of light. This state The state is the accumulation state.

That is, each block Β, .B ₂ ..., B _m repeats the reading state at time t and the accumulation state at time T-t. From the block 読出,. B ₂ .... B _{m in the} read state, the output current lout,. Iout ₂ .... Iout „corresponding to the amount of light incident during the accumulation state up to that point is the channel. Wiring C then flows out through C ₂ .... C _n , and these output currents lout, Iout ₂ .... Iout _n are amplified and integrated by an external signal processing circuit, and then output in time series For example, when the first block B, is in the read state, the output current lout flows out of the first block B, Iout ₂ .... lout _n , and then the first block B, is in the accumulation state. is second block B ₂ to the becomes a read state, the output current lout ,. Iout ₂ .... Iout "flows out it from the second block B _2.

However, in practice, immediately after the block Β ,. B ₂ .... B _m switches from the read state to the accumulation state, the output current lout !. Iout ₂ .... Iout 電流referred to as a "reverse current". it should be noted, also referred to as a "reverse current""reverse direction recovery _{current".) ΙΙ. ΙΓ 2 .... Ir} n flows. The magnitude of this reverse current Ir ,. Ir ₂ .... Ir _n reaches 10 to 20% of the normal output current lout ,. Iout ₂ .... Iout _n , and the convergence time Tr is 10 -In the order of ³ seconds. Thus, white is read, for example the first block beta, and the second block beta _2, if the black in the third block beta ₃ has been read, the second pro click beta ₂ becomes read state the output current lout ,. Iout ₂ .... Io ut _n reverse current than the normal Ir ,. Ir ₂ .... Ir "minute only decreases, and et to the third block B ₃ which flows when the output current lout ,. Iout ₂ .... Iout _n that should not flow flows to the amount corresponding reverse reverse current ΙΙ. Ir ₂ .... Ir _n when it is read state.

This phenomenon is caused by the fact that in a reproduced image, black read immediately after reading white is blacker than normal black, and white read immediately after reading black is It is called “reversed afterimage” because it appears whiter than white. In particular. The first block B, in white is read, if the ash (1 0 -? 0% brightness of white) is read in the second block B _2, the output current from the second block B ₂ l ou t,. I ou t 2.... I ou t " etc. would indicate black, were not accurate signal output obtained. Further, under low illumination order to like reduction in power consumption However, there is a problem that the relative ratio of the reversal afterimage increases because the size of the reversal afterimage does not decrease even under the low illuminance, and only the signal output decreases. to avoid as much as possible this state, the driving pulse VP L VP S.... Vp Ca ^ signal reading speed that must take a longer width t of _m is disadvantageously delayed.

The cause of this reverse current is that even if the voltage applied to the blocking diode 4 is changed from forward bias to reverse bias, the carrier injected during forward bias does not disappear instantaneously, It is thought that it flows to. That is, it is considered that the switching speed of the blocking diode 4 is limited by the reverse current.

Therefore, the present inventors generally improve the switching speed by reducing the reverse current associated with a switching element such as a blocking diode and an optical sensor element including the same, and improve the accuracy of the optical sensor element. In order to obtain a high signal output, and to provide a document reading device having these switching elements or optical sensor elements, intensive research has been conducted to reduce reversal afterimages and to enable higher-speed reading. As a result, the present invention has been achieved. Disclosure of the invention

The gist of the semiconductor device according to the present invention is to provide a semiconductor device including one or more semiconductor elements having a switching function and configured by sequentially stacking a lower electrode, a semiconductor layer, and an upper m-pole. The lower electrode and At least one of the upper electrode and the upper electrode may be formed of one or more conductive layers, and at least the conductive layer in contact with the semiconductor layer may be formed of a transparent conductive layer.

In this semiconductor device, one or a plurality of optical sensor elements configured by serially connecting the semiconductor element having the switching function and a photoelectric conversion element in which a lower electrode, a semiconductor layer, and an upper electrode are sequentially stacked are provided. It is here.

Further, in this semiconductor device, a semiconductor element having the switching function and an optical sensor element configured by serially connecting a photoelectric conversion element in which a lower electrode, a semiconductor layer, and an upper electrode are sequentially stacked are connected to a primary element. A plurality of optical sensor elements are originally arranged and divided into a plurality of blocks by a certain number, and one of these optical sensor elements is commonly connected in the block, and the other is relatively connected between the blocks by channel wiring. That is, they are commonly connected to each other at the same position.

Further, in such a semiconductor device, at least one of a lower electrode and an upper electrode of the semiconductor device is provided with at least one semiconductor element having the switching function, and the semiconductor element includes a transparent conductive layer. It is in.

Further, in such a semiconductor device, in a semiconductor device provided with at least one or more semiconductor elements having the switching function, the transparent conductive layer of the semiconductor element is made of ITO.

Further, in such a semiconductor device, at least one or more semiconductor elements having the switching function, wherein at least a semiconductor layer in contact with the transparent conductive layer among semiconductor layers of the semiconductor element is a p-type. It is a semiconductor layer.

Further, in such a semiconductor device, at least one or more semiconductor elements having the switching function are provided. The semiconductor layer of the device consists of amorphous silicon hydride deposited continuously by plasma CVD and has a pin structure. Next, in such a semiconductor device, the semiconductor element having the switching function and the photoelectric conversion element each have a diode characteristic, and are connected in series with each other by force source electrodes.

Further, in such a semiconductor device, the semiconductor device having the switching function and the respective lower electrode, semiconductor layer, and upper electrode constituting the photoelectric conversion element are simultaneously deposited. Further, in such a semiconductor device, in a semiconductor device provided with one or a plurality of optical sensor elements configured by connecting the semiconductor element having the switching function and the photoelectric conversion element in series, At least one of the lower electrode and the upper electrode to be disposed is constituted by a transparent conductive layer at least in contact with the semiconductor layer. Although the operation of such a semiconductor device has not been theoretically elucidated, the lower electrode or the upper electrode or both of them consist of one or more conductive layers, and at least the conductive layer in contact with the semiconductor layer is made of ITO or the like. And an interface between the semiconductor layer and the transparent conductive layer is formed. It is considered that a barrier such as a potential level and a trap level generated by diffusing the material constituting the transparent conductive layer into the semiconductor layer are formed at this interface. Therefore, even when the voltage applied to the semiconductor device is changed from the forward bias to the reverse bias, most of the carriers injected during the forward bias are considered to be blocked by the barrier. As a result, it is presumed that the reverse current is rapidly converged, and its peak value is also reduced, thereby improving the switching speed.

According to another theoretical estimation of the operation of such a semiconductor device, the lower electrode or the upper electrode or both of them are composed of one or more conductive layers. In addition, since at least the conductive layer in contact with the semiconductor layer is made of a transparent conductive layer such as ITO, and is transparent, light leaking from the periphery passes through the lower electrode and upper electrode and enters the semiconductor layer. I do. Thereby, the recombination level in the semiconductor layer is increased, and the recombination speed is increased. Therefore, even when the voltage applied to the semiconductor device is changed from the forward bias to the reverse bias, it is considered that the carriers injected at the time of the forward bias quickly disappear by recombination. As a result, it is presumed that the reverse current is rapidly converged, and the peak value is also reduced, so that the switching speed is improved.

Next, according to a semiconductor device such as an optical sensor element composed of a semiconductor element having such a switching function and a photoelectric conversion element, a lower electrode or an upper electrode or both of the semiconductor elements having a switching function are formed. Comprises one or more conductive layers, and at least the conductive layer in contact with the semiconductor layer comprises a transparent conductive layer such as ITO. Therefore, the semiconductor device having the switching function performs the above-described presumed operation. As a result, the reverse current is rapidly converged, and its peak value is also reduced. Therefore, an accurate signal output can be obtained from the optical sensor element, and the switching speed can be improved.

Further, according to a semiconductor device such as a document reading device provided with a semiconductor element having the switching function and a photoelectric conversion element, the lower electrode or the upper electrode, or both of them, which constitute the semiconductor element having the switching function, is formed of one layer or two layers. At least the conductive layer in contact with the semiconductor layer is composed of a transparent conductive layer such as ITO. Therefore, the semiconductor element having the switching function performs the above-described estimated operation. As a result, the reverse current is rapidly converged, and the peak value is reduced, so that the switching speed of the switching element is improved. As a result, a semiconductor device such as a document reading device has a reverse image lag. The signal readout speed is greatly increased. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic cross-sectional view showing one embodiment of a switching element which is a semiconductor device according to the present invention. FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 is a schematic cross-sectional view showing another embodiment of a switching element which is a semiconductor device according to the present invention.

FIG. 8 is a schematic cross-sectional view showing one embodiment of an optical sensor element which is a semiconductor device according to the present invention. FIGS. 9 (a) and 9 (b) show the operation of the optical sensor element shown in FIG. FIG. 6 is a circuit diagram for explaining the operation of the embodiment. FIGS. 10, 11, and 12 are schematic cross-sectional views showing other embodiments of the optical sensor element which is the semiconductor device according to the present invention.

FIG. 13 is a schematic cross-sectional view showing one embodiment of a document reading apparatus which is a semiconductor device according to the present invention, and FIG. 14 is a partial plan view of the document reading apparatus shown in FIG. . FIG. 15 shows the results of a comparative experiment conducted to confirm the effect of the present invention, and is a graph showing the output voltage of an original manuscript reading apparatus actually manufactured. FIG. 16, FIG. 17, and FIG. 18 are all schematic cross-sectional views showing another embodiment of the document reading apparatus which is a semiconductor device according to the present invention.

FIG. 19 is a schematic sectional view showing an example of a document reading apparatus which is a conventional semiconductor device. FIG. 20 is a circuit diagram of the document reading apparatus shown in FIG. FIG. 21 is a time chart for explaining the operation of the original reading apparatus shown in FIGS. 19 and 20. BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the semiconductor device according to the present invention will be described in detail with reference to the drawings. First, the semiconductor device according to the present invention has a switching function. A description will be given using a switching element as a semiconductor element as an example.

As shown in FIG. 1, a switching element 10 according to the present invention includes a transparent lower electrode 14 made of ITO (Indium Tin Oxide) and an amorphous silicon on a substrate 12 made of glass or the like. A semiconductor layer 16 made of such as above and an upper electrode 18 are formed. Here, the semiconductor layer 16 includes, in order from the substrate 12 side, a p-type amorphous silicon layer 16 a in which holes serve as majority carriers, an i-type amorphous silicon layer 16 b in which an intrinsic semiconductor is provided, and a large number of carriers. An n-type amorphous silicon layer 16 c is laminated to form a pin structure.

To manufacture the switching element 10, first, a transparent conductive film (14) such as ITO is formed on the substrate 12 by a vacuum evaporation method using electron beam resistance heating or a sputtering method using DC or RF. ) Is deposited. Further, a p-type amorphous silicon film (16a), an i-type amorphous silicon film (16b), and an n-type amorphous silicon film (16c) are formed thereon by a plasma CVD method or the like. Deposits continuously. Then, a transparent conductive film (18) such as ITO is deposited thereon again by a vacuum evaporation method or a sputtering method. The thickness of each of these transparent conductive films (14, 18) is preferably about several hundreds to several thousand A, but is appropriately determined in consideration of the performance of the deposited amorphous silicon film and the characteristics of the transparent conductive films. It is what is done.

Next, the lower electrode 14, the semiconductor layer 16, and the upper electrode 18 are formed by sequentially patterning these films. For example, in the case of patterning by photolithography, a resist solution is first applied on the uppermost transparent conductive film (18), pre-baked, and then a mask with a predetermined pattern is used. Exposure is performed, followed by development and post baking. If ITO is used as the transparent conductive film, the transparent conductive film is etched with a mixed solution of salt and nitric acid to form the upper electrode 18. Form. Next, the amorphous silicon films (16a, 16b, 16c) are etched using a parallel plate type etching apparatus. That is, the switch Yanba 1 0 - was evacuated to ³ Torr or less, introducing a CF ₄ gas and 0 ₂ gas, 1 3. 5 6 MH z height while maintaining further pressure 5. 0 P a A power of 0.1 to 0.7 W / cm ² is supplied to the electrodes using a frequency power supply. Thus, the amorphous silicon film is etched to form the semiconductor layer 16. After the resist used for patterning is once removed, the lowermost transparent conductive film (14) is patterned by photolithography or the like in the same manner as the above-mentioned uppermost transparent conductive film (18). When the lower electrode 14 is formed, the switching element 10 including the lower electrode 14, the semiconductor layer 16 and the upper electrode 18 is manufactured. Here, the method of forming the lower electrode 14, the semiconductor layer 16, and the upper electrode 18 by photolithography has been exemplified. However, a film is formed in an unnecessary portion from the beginning by a mask method or the like. The manufacturing method is not limited at all, for example, it may be formed so as not to be deposited.

In the switching element 10, the lower electrode 14 and the upper electrode 18 are formed of a transparent conductive layer, and the semiconductor layer 16 and the lower electrode 14 and the upper electrode 18 which are transparent conductive layers, particularly the lower electrode 14 are formed. An interface is formed at the junction. It is considered that a potential barrier and a barrier such as a trap level formed by diffusing the material constituting the transparent conductive layer into the semiconductor layer 16 are formed at this interface. Therefore, even when the voltage applied to the switching element is changed from a forward bias to a reverse bias, most of the carriers injected during the forward bias are considered to be blocked by this barrier. Thus, reverse current 1 0 - ⁵ to be made to converge on the order of 1 0 _ ⁶ seconds, and the peak value becomes small, it is estimated that the switching speed is improved. Therefore, if this switching element 10 is used in a document reading device, a more accurate signal output can be obtained, and the signal reading speed can be further improved. It is also possible to increase the speed.

If the operation of the switching element 10 is explained by another presumed theory, the lower electrode 14 and the upper electrode 18 are transparent, and light leakage from the surroundings penetrates these to the semiconductor layer 16. Incident. As a result, a large number of trap levels exist in the semiconductor layer 16 made of amorphous silicon, and when light enters the semiconductor layer 16, these trap levels change and the recombination level changes. It is expected to increase. Therefore, the recombination speed is increased, and even when the voltage applied to the switching element 10 is changed from the forward bias to the reverse bias, the carriers injected at the time of the forward bias are considered to be quickly lost by the recombination. . Thus, reverse current 1 0-1 0 - allowed to converge on the order of ⁶ seconds, and the peak value becomes small, it is estimated that Suitsuchingu speed is improved.

As described above, one embodiment of the switching element according to the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, and can be implemented in other aspects.

For example, as shown in FIG. 2, a transparent lower electrode 14 made of ITO or the like, a semiconductor layer 20 made only of an i-type amorphous silicon layer, and a metal A switching element 24 formed by forming an opaque upper electrode 22 may be used. In this switching element 24, a short-circuit barrier is formed at the interface between the i-type amorphous silicon layer (20) and the lower electrode 14, and the switching element 24 is operated in the same manner as described above.

As shown in FIG. 3, a transparent lower electrode 14 made of ITO or the like, a type amorphous silicon layer 26a and an i-type amorphous silicon layer 26b are formed on a substrate 12 made of glass or the like. The switching element 28 may be configured by forming a stacked semiconductor layer 26 and an opaque upper electrode 22 made of metal or the like. As is clear from this example, the semiconductor layer is pi It may be structured.

Further, as shown in FIG. 4, a transparent lower electrode 14 made of ITO or the like, an insulating layer 30, an i-type amorphous silicon layer 32 a and a p-type amorphous silicon A switching element 34 formed by forming a semiconductor layer 32 formed by laminating the layers 32b and an opaque upper electrode 22 made of metal or the like may be used. The switching element 34 is of a metal-insulator-semiconductor (MIS) type, and the semiconductor layer 32 is deposited on the lower electrode 14 via a thin insulating layer 30. As is clear from this example, the semiconductor layer may be deposited indirectly instead of directly on the lower electrode, and the same applies to other layers.

Although the embodiment in which the lower electrode 14 is made transparent has been described above, in the present invention, the electrode to be made transparent may be the lower electrode or the upper electrode, or both may be made transparent. That is, it is only necessary that at least one of the lower electrode and the upper electrode is transparent.

Next, the lower electrode or the upper electrode or both electrodes of the switching element, which is the semiconductor device according to the present invention, comprises one or more metal layers and a transparent conductive layer deposited on the metal layers. May be used.

For example, as shown in FIG. 5, the switching element 36 has a lower electrode 38 having a two-layer structure, a semiconductor layer 16 made of amorphous silicon or the like, and an upper electrode 18 formed on a substrate 12. It is configured. The lower electrode 38 of this two-layer structure is composed of a metal layer 38a made of chromium Cr or the like and a transparent conductive layer 38b made of ITO or the like deposited on the metal layer 38a. . The semiconductor layer 16 may have either a pin structure or a nip structure. From the substrate 12 side, a p-type amorphous silicon layer 16a in which holes serve as majority carriers and an i-type amorphous layer serving as an intrinsic semiconductor are provided. A pin structure in which a base silicon layer 16b and an n-type amorphous silicon layer 16c in which a large number of electrons are carried is preferably stacked. In order to manufacture the switching element 10, first, a metal film such as chromium Cr (38 a) is formed on the substrate 12 by a vacuum evaporation method using an electron beam or resistance heating, or a sputtering method using DC or RF. Is deposited. Next, a transparent conductive film (38b) such as ITO is deposited thereon by a vacuum evaporation method or a sputtering method. Thereafter, in the same manner as in the above-described embodiment, a p-type amorphous silicon film, an i-type amorphous silicon film, and an n-type amorphous silicon film are successively deposited, and a conductive film is deposited thereon. Next, the upper conductive film, the amorphous silicon film composed of three layers, and the lower transparent conductive film are patterned into a predetermined shape in order, and the upper electrode 18, the semiconductor layer 16, and the lower electrode 38 are patterned. And a transparent conductive layer 38b as a part. Next, after once removing the resist used for patterning, the metal film is again patterned into another predetermined shape by photolithography or the like, thereby forming a metal layer 38a that is a part of the lower electrode 38. As a result, a switching element 36 composed of the lower electrode 38, the semiconductor layer 16 and the upper electrode 18 is manufactured.

Here, the amorphous silicon film is deposited after the metal film (38a) and the transparent conductive film (38b) are deposited in a blanket state, but before the amorphous silicon film is deposited, the transparent silicon film is deposited. The transparent conductive layer 38b may be formed by patterning only the conductive film first. In this case, after forming the upper electrode 18 and the semiconductor layer 16 and then patterning the metal film in a blanket state to form the metal layer 38a, the same configuration as the switching element 36 described above can be obtained. Becomes Further, the deposition of the metal layer and the transparent conductive layer may be performed continuously without breaking the vacuum, or may be performed once by breaking the vacuum. Furthermore, here, the method of patterning mainly by photolithography has been exemplified, but a film may be formed by using a mask method or the like so that a film is not deposited on unnecessary portions from the beginning. It is not limited at all. In this switching element 36, the lower electrode 38 is composed of a metal layer 38a and a transparent conductive layer 38b, and an interface is formed at the junction between the semiconductor layer 16 and the transparent conductive layer 38b. ing. Therefore, this switching element 36 is operated in the same manner as the above-mentioned switching element. As a result, the reverse current is caused to converge on the order of 1 0-1 0 ⁶ seconds, and the peak value becomes small, the switching speed is improved. Therefore, if this switching element 36 is used in a document reading device, a more accurate signal output can be obtained, and the signal reading speed can be further increased.

Next, as shown in FIG. 6, a switching element 40 according to the present invention comprises a lower electrode 3 composed of a metal layer 38 a and a transparent conductive layer 38 b on a substrate 12 such as a glass. 8, a semiconductor layer 26 formed by laminating a p-type amorphous silicon layer 26a and an i-type amorphous silicon layer 26b, and an opaque upper electrode 22 formed of metal or the like. The semiconductor layer may have a pi structure, that is, as is clear from this example. In short, according to the present invention, a reverse current generated in the switching element may be prevented by forming an interface with the transparent conductive layer in the semiconductor layer constituting the switching element.

As shown in FIG. 7, a lower electrode 3.8 composed of a metal layer 38a and a transparent conductive layer 38b and a p-type amorphous silicon layer 42 are formed on a substrate 12 made of glass or the like. a switching element 46 composed of a semiconductor layer 42 formed by laminating a and an i-type amorphous silicon layer 42 b, an insulating layer 44, and an opaque upper electrode 22 made of metal or the like. May be. The switching element 46 is of the MIS type, and the upper electrode 22 made of metal is deposited on the semiconductor layer 42 via the insulating layer 44. As is clear from this example, the upper electrode may be deposited on the semiconductor layer indirectly instead of directly. Further, in the above embodiment, the metal layer 38a and the transparent conductive layer 38b constituting the lower electrode 38 have different shapes, but may have the same shape. In addition, when applying the present invention to a switching element, it goes without saying that various configurations can be appropriately adopted without any explanation.

The embodiment in which the semiconductor device according to the present invention is applied to a switching element has been described in detail above. Next, an embodiment in which the semiconductor device according to the present invention is applied to an optical sensor element will be described in detail with reference to the drawings.

As shown in FIG. 8, an optical sensor element 48 according to the present invention comprises a substrate 12 made of glass or the like, a photo diode 50 as a photoelectric conversion element, and a blocking diode 52 as a switching element. Are formed. Both the photodiode 50 and the blocking diode 52 have a transparent lower electrode 50a, 52a made of ITO (Indium Tin Oxide) or the like and a pin structure made of amorphous silicon or the like. Semiconductor layers 5Ob and 52b and transparent upper electrodes 50c and 52c made of ITO or the like are sequentially deposited. Here, the greatest feature of the present embodiment is that the lower electrode 52a constituting the blocking diode 52 is transparent.

These photodiodes 5 0 and blocking die O over de 5 2 is covered with Si O _x or SiN transparent interlayer insulating film made of such _x 5 4, contactor formed in the interlayer insulating film 4 of this Tohoru 5 6 Are connected in series by the connection wiring 58 with opposite polarities. That is, the photodiode 50 and the blocking diode 5 are connected by the cuff electrodes.

In order to manufacture the optical sensor element 48, first, a transparent conductive film (50a) such as ITO is formed on the substrate 12 by an electron beam, a vacuum deposition method using resistance heating, or a sputtering method using DC or RF. , 52 a) I do. For example when depositing I TO film by DC sputtering method, first set the substrate 1 2 Chiyanba in one, evacuating the chamber in one to 1 0 one ⁵ Torr or less. Then, while holding the substrate 1 2 1 0 0 to 25 0 ° C, and pressure 0. 1~1. 0 P a, argon gas and oxygen gas under DC power 0.. 1 to 1. 0 cm ² Is introduced at a fixed rate. Thereby, an ITO film can be deposited on the substrate 12. The thickness of the transparent conductive film is appropriately determined in consideration of the performance of the amorphous silicon film deposited thereon and the characteristics of the transparent conductive film. The degree is preferred.

On top of this, a p-type amorphous silicon film with many holes as carriers, an i-type amorphous silicon film as an intrinsic semiconductor, and an n-type amorphous silicon film with many electrons as carriers by plasma CVD. Are continuously deposited.

Then, a transparent conductive film such as ITO is deposited thereon again by a vacuum deposition method or a sputtering method in the same manner as the lowermost transparent conductive film described above. The thickness of the transparent conductive film is appropriately determined in consideration of the performance of the amorphous silicon film, the characteristics of the transparent conductive film, and the like, and is preferably about several hundred to several thousand A. If so, about 600 A is preferable. Next, these films are sequentially patterned to form lower electrodes 50a and 52a, semiconductor layers 50b and 52b, and upper electrodes 50c and 52c. For example, when patterning is performed by photolithography, a resist solution is first applied to the uppermost transparent conductive film, prebaked, and then exposed using a mask engraved with a predetermined pattern. Further, development and postbaking are performed. If ITO is used for the transparent conductive film, the transparent conductive film is etched with a mixed solution of hydrochloric acid and nitric acid to form upper electrodes 50c and 5.2c. Next, the amorphous silicon film is etched using a parallel plate type etching apparatus. Sand Chi, after evacuating the chamber one to 1 0- ³ Torr or less, introducing a CF ₄ gas and 0 ₂ gas, 1 3. 5 6 MH z while maintaining further pressure to 5. 0 P a An electric power of 0.1 to 0.7 W./cm ² is supplied to the electrodes using a high frequency power supply. This allows the amorphous silicon film to be etched to form the semiconductor layers 50b and 52b. Further, after the resist used for patterning is once removed, the lowermost transparent conductive film is patterned by photolithography or the like in the same manner as the uppermost transparent conductive film described above, and the lower electrodes 50a and 52a are formed. , A photodiode 50 and a blocking diode 52 can be formed.

Next, SiO _x and SiN _x are deposited on the photo diode 50 and the blocking diode 52 by a thermal CVD method, a normal pressure CVD method, a plasma CVD method, a sputtering method, or the like. An interlayer insulating film 54 is formed by patterning into a predetermined shape by photolithography or the like. For example, when depositing a silicon oxide film by a plasma CVD method, the inside of the chamber is evacuated to 10 to ² Torr or less, the substrate 12 is heated and maintained at a predetermined temperature, and then silane gas of 20 to 60 sccm is added. Nitrogen oxide gas is introduced at 150 to 3 Osccm and maintained at a pressure of 0.3 to 1.2 Torr. Here, hydrogen gas or nitrogen gas may be introduced as needed. Then, after the pressure is stabilized, a power of 0.01 to 0.5 W / cm ² is supplied to the electrode facing the substrate 12 using a high-frequency power supply of 13.6 MHz. Here, the power to be supplied depends on the structure of the device and the quality of the film to be deposited. In the case of a silicon oxide film, a parallel plate type etching device can be used. As a result, the silicon oxide film can be patterned, and the interlayer insulating film 54 can be formed. The contact hole 56 on the photodiode 50 and the blocking diode 52 may be formed at this time.

Further, a metal such as Cr, Ni, Pd, Ti, Mo, Ta, Al or the like is formed on these in a single layer or a multilayer by a vacuum deposition method or a sputtering method. Deposits 500 A thick Cr and 1.5 am Al in two layers. Next, this is patterned into a predetermined shape by a photolithography method or the like, and a connection wiring 58 is formed. As a result, the upper electrodes 50 c 52 c are electrically connected to each other through the connection wiring 58, and the optical sensor element 48 composed of the photodiode 50 and the blocking diode 52 is manufactured. Become. Here, when the connection wiring 58 is a two-layer film of A1 and Cr, the etching of A1 may be performed with a mixed solution of phosphoric acid, nitric acid, and acetic acid, while the etching of Cr is performed using ceric ammonium nitrate. Just do it. These materials are not limited to metal as long as they can be electrically connected, and are not particularly limited.

Here, a method of patterning mainly by photolithography has been described as an example, but a manufacturing method such as forming a film such that a film is not deposited on unnecessary portions from the beginning by a mask method or the like may be used. Is not limited at all.

Next, the operation of the optical sensor element 48 will be described.

As shown in FIG. 9 (a), the anode electrode (lower electrode 52a) of the blocking diode 52 has a positive potential Vp with respect to the anode electrode (lower electrode 50a) of the photodiode 50. In this case, the blocking diode 52 becomes forward-biased, and the photodiode 50 becomes reverse-biased. As a result, the parallel capacitance 60 of the photodiode 50 is charged, and the potential at the connection between the photodiode 50 and the blocking diode 52 increases. Then, as shown in FIG. When the anode electrode of the blocking diode 52 is grounded, the blocking diode 52 becomes reverse-biased. When light enters the photodiode 50 in this state, the parallel capacitance 60 of the photodiode 50 is discharged by the photocurrent Ip generated there. Thereafter, when the anode electrode of the blocking diode 52 is again set to the positive potential Vp, the blocking diode 52 becomes forward-biased and The parallel capacitance 60 of the diode 50 is charged again. The charging current flowing at this time corresponds to the photocurrent IP and flows as an output current. Therefore, if this output current is detected, the amount of light incident on the photodiode 50 will be detected.

In this example, since the lower electrode 52 a and the upper electrode 52 c of the blocking diode 52 are formed of a transparent conductive layer, the semiconductor layer 52 b and the lower electrode 52 a that is a transparent conductive layer are formed. An interface is formed at the junction with the upper electrode 52c. Therefore, it is considered that the blocking diode 52 as a switching element is operated in the same manner as described above. Thus, reverse current 1 0 - ⁵ are made to converge at ~ 1 0 seconds order one, and also decreases the peak value. Therefore, an accurate signal output can be obtained from the optical sensor element 48, and the switching speed can be improved. Furthermore, if this optical sensor element 48 is used in a document reading device, a more accurate signal output can be obtained, and the signal reading speed can be further increased.

As described above, one embodiment of the optical sensor element according to the present invention has been described in detail. However, the optical sensor element to which the present invention is applied is not limited to the above-described embodiment, but may be implemented in other aspects. is there.

For example, in the above-described embodiment, the upper electrode 50 c constituting the photodiode 50 and the upper electrode 52 c constituting the blocking diode 52 are connected by the connection wiring 58. As shown in FIG. 10, the lower electrode 62 constituting the photodiode 50 and the lower electrode 62 constituting the blocking diode 52 are common. The optical sensor element 64 may be configured such that the photodiode 50 and the blocking diode 52 are connected in series by 2. In this case, the lower electrode 62 may be formed of a transparent conductive layer such as ITO. The upper electrode 50 c of the photodiode 50 and the blocking diode 52 The upper electrode 52 c may be extracted to the outside by the lead wirings 66 and 68, respectively. In this example, the photodiode 50 and the blocking diode 52 are connected by anode electrodes and are connected in series with opposite polarities.

Here, in the above-described embodiment, the lower electrodes 50a and 52a and the semiconductor layers 5Ob and 5b constituting the photodiode 50 and the blocking diode 52 are formed for reasons such as simplification of the manufacturing process. 2b and the upper electrodes 50c and 52c are deposited simultaneously and are made of the same material, respectively, but the upper electrode 50C constituting the photodiode 50 'must be transparent. However, the upper electrode 52 c constituting the blocking diode 52 need not be transparent. In addition, the lower electrode 50a constituting the photodiode 50 may not be transparent, and at least the lower electrode 52a constituting the blocking diode (switching element) 52 may be transparent. ,

As described above, the embodiment in which at least the lower electrode of the switching element is configured to be transparent in the optical sensor element as the semiconductor device according to the present invention has been described. The electrode may be composed of one or more metal layers and a transparent conductive layer deposited on the metal layer. Next, this embodiment will be described in detail with reference to the drawings.

As shown in FIG. 11, an optical sensor element 70 according to the present embodiment has a photo diode 72 as a photoelectric conversion element on a substrate 12 made of glass or the like, similarly to the above-described embodiment. And a blocking diode 74 serving as a switching element.

Both the photodiode 72 and the blocking diode 74 are composed of a lower electrode 72 a, .74 a having a two-layer structure and a semiconductor layer 72 b, 74 having a Pin structure made of amorphous silicon or the like. b and IT 0 (Ind i um T in Oxide) and a transparent upper electrode 7 2. C, 74 c are sequentially deposited. Lower electrode 74 a blocking die O over de 74, the metal layer 74 a made of chrome Cr, and the metal layer 74 a, is composed of such a composed a transparent conductive layer 74 a ₂ Metropolitan I TO deposited on I have. Is the largest feature of this point the present embodiment, and the other similar to the previous embodiments, is covered by the photodiode 72 and flop locking die O over de 74 SiO _x or SiN X, such as a transparent interlayer insulating film 54 made of The connection is made in series by the connection wiring 58 through the contact hole 56 formed in the interlayer insulating film 54 with the opposite polarities.

In order to manufacture the optical sensor element 70, first, a metal film such as chromium Cr is deposited on the substrate 12 by a vacuum evaporation method using electron beam resistance heating or a sputtering method using DC or RF. Next, a transparent conductive film such as ITO is deposited thereon by a vacuum evaporation method or a sputtering method. For example, when depositing a metal film and a transparent conductive film by the DC sputtering method, first, the substrate 12 is set in the first chamber, and the inside of the first chamber is evacuated to less than 10 ⁵ Τοι. after, while maintaining the substrate 1 2 1 0 0- 25 0 ° C, pressure 0. 1~1. 0 P a, under DC power 0. 1~ OWZcm ^2, argon gas and oxygen gas It is performed by introducing at a fixed rate and sequentially depositing a metal film and a transparent conductive film.

Thereafter, in the same manner as in the above-described embodiment, an amorphous silicon film is deposited in the order of P-type, i-type, and n-type, and then a transparent conductive film such as ITO is deposited. The thickness of each of the metal film and the transparent conductive film is preferably about several hundred to several thousand A, but is appropriately determined in consideration of the characteristics of these films and the performance of the amorphous silicon film. is there. For example, when chromium Cr is used as the metal film and ITO is used as the transparent conductive film, the thickness of the metal film is preferably about 150 to 200 A, and the thickness of the transparent conductive film is lower (72 a _2, It is preferable that 74 a ₂ ) be about 1200 A and the upper layer (72 c, 74 c) be about 600 A.

Next, similarly to the above-described embodiment, the upper transparent conductive film, the three-layer amorphous silicon film, and the lower transparent conductive film are patterned into a predetermined shape in order, and the upper electrodes 72 c and 7 are formed. 4 and c, to form the semiconductor layer 7 2 b, 7 4 b, and a lower portion electrode 7 2 a, 7 4 transparent conductive layer is part of _{a 7 2 a 2, 7 4} a 2. Next, after the resist used for patterning is once removed, the metal film is again patterned into another predetermined shape by photolithography or the like, and the metal layer which is a part of the lower electrodes 72 a and 74 a is formed. 7 2 a,, 7 4 a, are formed. As a result, a photodiode 72 and a blocking diode 74 are formed. Here, in the case where chromium Cr is used as the gold film, etching may be performed using, for example, a second cellium nitrate ammonium nitrate.

Next, an interlayer insulating film 54 and a contact hole 56 are formed on the photo diode 72 and the blocking diode 74 in the same manner as in the above-described embodiment, and a metal is simply formed thereon. After being deposited in layers or multilayers, it is patterned and the connection wiring 58 is formed. As a result, the upper electrodes 72 c and 74 c are electrically connected to each other by the connection wiring 58, and the optical sensor element 70 composed of the photodiode 72 and the blocking diode 74 is manufactured. Become.

Here, the amorphous silicon film is deposited after the metal film and the transparent conductive film are deposited in a blanket state, but before depositing the amorphous silicon film, only the transparent conductive film is first patterned to form a transparent film. conductive layer _{7 2 a 2, 7 4 a} 2 may be formed of. In this case, after forming the upper electrodes 72c, 74c and the semiconductor layers 72b, 74b, the blanket state metal film is patterned to form the metal layers 72a, 74a. , Are the same as those of the optical sensor element 70 described above. In addition, metal layer and transparent conductive The deposition with the layer may be performed continuously without breaking the vacuum or may be performed discontinuously once the vacuum is broken. Furthermore, here, the method of patterning mainly by photolithography has been exemplified, but a film may be formed by preventing the film from being deposited on unnecessary portions from the beginning by a mask method or the like. It is not limited at all.

The operation of the optical sensor element 70 is the same as the operation of the optical sensor element 48 described above, and a description thereof will be omitted.

Next, for example, in the above-described embodiment, the upper electrode 72 c constituting the photodiode 72 and the upper electrode constituting the blocking diode 74

7 4 c are connected by connection wiring 58, as shown in FIG. 12, as shown in FIG. 12, a lower electrode 76 forming a photodiode 72 and a lower electrode 76 forming a blocking diode 74. The lower electrode 76 may be used as an optical sensor element 78 in which the photodiode 72 and the blocking diode 74 are connected. In this case, the metal layer

80 and the transparent conductive layers 8 2 and 8 4 are sequentially deposited to form the lower electrode 76, so that an interface is formed at the junction between the semiconductor layer 74 b and the transparent conductive layer 84. Good. Also, the upper electrode 72 c of the photo diode 72 and the upper electrode 74 c of the blocking diode 74 can be taken out to the outside by the lead wirings 86, 88 via the contact holes 56, respectively. You should. In this example, the photo diode 72 and the blocking diode 74 are connected between the anode electrodes and are connected in series with opposite polarities.

In yet mentioned above embodiments, the metal layer 7 2 a,, 7 4 a ,, 8 0 and the transparent conductive layer _{7 2 a 2, 7 4 a} 2, 8 2, but with a 8 4 different shapes, Same — may be shaped.

Further, in the above-described embodiment, the photodiodes 72 and the blocking diodes 74 are formed for reasons such as simplification of the manufacturing process. The lower electrodes 72a and 74a, the semiconductor layers 72b and 74b, and the upper electrodes 72c and 74c are simultaneously deposited, and are made of the same material. However, the upper electrode 72c constituting the photodiode 72 must be transparent, but the upper electrode 74c constituting the blocking diode 74 need not be transparent. Further, the lower electrode 72 a constituting the photo diode 72 does not need to be composed of the metal layer and the transparent conductive layer, and at least the lower electrode 72 a constituting the blocking diode (switching element) 74. 4 a may be composed of a metal layer 7 4 a, the transparent conductive layer 7 4 a ₂ Prefecture. In short, according to the present invention, the reverse current generated in the switching element may be prevented by forming an interface with the transparent conductive layer in the semiconductor layer constituting the switching element.

Although the embodiment in which the semiconductor device according to the present invention is applied to the switching element and the optical sensor element has been described above, the present invention may be further applied to a document reading apparatus. Next, an embodiment in which the present invention is applied to a document reading apparatus will be described in detail with reference to the drawings.

As shown in FIGS. 13 and 14, an original reading device 90 according to the present invention includes a photodiode 92 as a photoelectric conversion element and a switching element on a substrate 12 made of glass or the like. there flops locking diode 9 4, photodiode 9 Chiyan'ne Le wiring C for reading an electrical signal from the 2,. C _2.... C "and is to be constituted by forming. in this case the, full The photodiode 92 and the blocking diode 94 constitute an optical sensor element.

These photodiodes 9 2 and flop locking die O one de 9 4, and the monitor ITO (Indi um Tin Oxi de) and Sn0 ₂ transparent lower electrode consisting of a 9 2 a, 9 4 a, amorphous silicon a the semiconductor layer 9 2 b of the pin structure consisting of a -Si, 9 4 b and, ITO or transparent upper made of a Sn0 ₂ Electrodes 92c and 94c are sequentially deposited.

These photodiodes 9 2 and flop locking da I O over de 9 4 is covered with SiO _x or transparent interlayer made of a SiN _x insulating film 9 6, contactors Tohoru 9 formed in the interlayer insulating film 9 6 This They are connected in series with opposite polarities by a connection wiring 100 via 8. That is, the photodiode 92 and the blocking diode 94 are connected by the cathode electrodes. On the other hand, the lower electrode 92 a of the photodiode 92 is connected to the channel wirings C. C ₂ ... C via contact holes 102 formed in the interlayer insulating film 96. Further, the entirety is covered with a protective film 104.

As in the conventional case, these photodiodes 92 and blocking diodes 94 are arranged in mxn units in one dimension, and are divided into m blocks Β, .B ₂ ... B _m every n units. have been, § Roh one cathode electrode of blocking diode 9 4 proc B,. B ₂ .... are connected in common in a B _m, follower Toda Iodo 9 2 § Roh once electrode channel interconnection C, . C ₂ .... C _n Niyotsu Te block B,. B ₂ .... are in between those in the same relative position between B _m are connected to the Common.

Here, the method for manufacturing a document reading apparatus 9 0, like the production method of the aforementioned light sensor element, after first depositing a transparent conductive film such as I TO and Sn0 ₂ on the substrate 1 2, this above, the amorphous silicon film a p-type, i-type, continuously deposited in the order of n-type, further on this is deposited a transparent conductive film such as an I T0 and Sn0 _2. The thickness of the uppermost transparent conductive film is preferably about several hundred to several thousand A, but is appropriately determined in consideration of the performance of the amorphous silicon film, the characteristics of the transparent conductive film, and the like.

Next, after patterning the uppermost transparent conductive film and the three-layer amorphous silicon film by photolithography or the like, the lowermost transparent conductive film is also patterned by photolithography or the like. Thus, a photodiode 92 and a blocking diode 94 are formed.

Next, formed on these follower Todaio de 9 2 and the blocking diode 9 4, and the like is deposited SiO _x or SiN _x, an interlayer insulating film 9 6 is patterned into a predetermined shape, such as by which the follower tri lithography method I do. That is, a contact hole 98 is formed on the photo diode 92 and the blocking diode 94, and a contact hole 102 is formed on the lower electrode 92a. In the region where the extraction electrode 106 is formed on the electrode 94a, the interlayer insulating film 96 is removed.

Further, a single layer or multiple layers of metals such as Cr, Ni, Pd, Ti, Mo, Ta, and Al are deposited thereon by a vacuum evaporation method, a sputtering method, or the like. The connection wiring 100 and the channel wiring C and C ₂ ... C „and the extraction electrode 106 are formed by patterning into a predetermined shape by, for example, the upper electrode 9 2 c, 9 4 with c and line 1 0 0 and are electrically connected via a contactor Tohoru 9 8, the lower portion electrode 9 2 a and the channel line CC ₂ .... C "and are contactor Tohoru 1 0 2 electrically. Note that these materials are not particularly limited, for example, they may not be metals as long as they can be electrically connected.

Finally, silicon oxide, silicon nitride, tantalum oxide, etc. are deposited on the entire surface by plasma CVD, sputtering, or the like, and are patterned into a predetermined shape by photolithography to obtain the extraction electrode 1. A protective film 104 is formed so as to cover all regions except for the extraction electrodes (not shown) of the channel wirings C 6 and C ₂ .. C ₂ .. C „. diode 9 2, blocking diode 9 4, channel wiring C]. C ₂ .... C "Oh intended to protect from moisture Ya scratches, etc. o According to this original reading device 90, since the lower electrode 94a of the blocking diode 94, which is a switching element, is made of a transparent conductive layer, the semiconductor layer 94b and the lower electrode 94a are joined. An interface is formed in the part. It is considered that a potential barrier and a barrier such as a trap level formed by the substance of the lower electrode 94a constituting the transparent conductive layer being diffused into the semiconductor layer 94b are formed at this interface. Therefore, the block _{Β,. B 2...} . B ra is reverse current flows immediately after switched from the read state to the storage state Ir

Ir ₂ ... Ir _n is considered to be blocked by this barrier, and the reverse current I, lr ₂ ... Ir „converges to 1 (on the order of T ⁵ to 10 seconds). As a result, the switching speed of the blocking diode 120 is improved, and the reversal afterimage is greatly reduced, so that an accurate signal output can be obtained. Of course, it is also possible to increase the signal reading speed, and since the reversal afterimage is sufficiently reduced, an accurate signal output can be secured even when the original is read under low illuminance. As described above, the lower electrode 94a of the blocking diode 94, which is a switching element, is made of a transparent conductive layer, so that it is possible to reduce power consumption. Light leakage Ngudaiodo 9 4 of the semiconductor layer 9 4 also causes the recombination rate recombination level is increased is increased by entering the b and considered Erareru.

Next, in order to confirm such effects, an embodiment of the document reading apparatus according to the present invention and a comparative example of a conventional document reading apparatus were prepared and a comparative experiment was performed. .

Example 1

First, the original reading apparatus according to the present invention was manufactured by the following method.

Substrate 1 and 2 are made of Corning Co., Ltd. Al-free glass (# 7005) First, an ITO film having a thickness of 1200 A was deposited on the substrate 12 by a DC sputtering method. That is, set the substrate 1 2 Chiyanba in one, was evacuated and the chamber in one to 1 0- ⁵ Torr or less, and holds the substrate 1 2 1 0 0-2 5 0 hands, pressure 0. 1 to 1.0 Pa, DC power 0.1 to 1.0 W / cm ² , by introducing argon gas and oxygen gas at a constant rate, the ITO film on the substrate 12 Was deposited. Furthermore, a p-type amorphous silicon film having a thickness of 500 to 300 A, an i-type amorphous silicon film having a thickness of 700 to 1200 A, and a An n-type amorphous silicon film having a thickness of about 300 A was sequentially deposited. Then, a .1TO film having a thickness of 600 A was deposited thereon again in the same manner as the ITO film.

Next, the uppermost ITO film and the three-layer amorphous silicon film are patterned by photolithography to form upper electrodes 92c, 94c and semiconductor layers 92b, 94b. did. In other words, a resist solution is applied on the uppermost ITO film, pre-baked, exposed using a mask engraved with a predetermined pattern, and further developed and boost-baked. Was. Then, after etching the ITO film with a mixed solution of hydrochloric acid and nitric acid, the amorphous silicon film was etched using a parallel plate type etching apparatus. Here, the chamber one 1 0 - was evacuated to ³ Torr or less, introducing a CF ₄ gas and 0 ₂ gas, a high frequency power source 1 3. 5 6 MHz while maintaining the pressure to 5. 0 P a A power of 0.1 to 0.7 W / cm ² was supplied to the electrodes to etch the amorphous silicon film. Then, after removing the resist used for patterning, the lowermost ITO film is patterned by photolithography in the same manner as the uppermost ITO film described above to form lower electrodes 92a and 94a. did.

The numbers of the photodiodes 92 and the blocking diodes 94 are assumed to be 1728, respectively, and these are divided into 56 blocks every 32. Minutes. Further, as shown in FIG. 14, the size of the photodiode 92 was set to 105 zm × 125 μm, and the size of the booking diode 94 was set to 33 mx 33 zm.

Next, a silicon oxide film having a thickness of 1.5 μm was deposited on the photodiode 92 and the blocking diode 94 by a plasma CVD method. That is, after evacuating the inside of the chamber one to 1 0- ² Torr or less, and heating and holding the substrate 1 2 to a predetermined temperature, silane gas 2 Less than six 0 seem and, nitrous oxide gas 1 5 0 to 3 0 O sccm , And maintained at a pressure of 0.3 to 1.2 Torr (here, nitrogen gas may be introduced if necessary). After that, wait for the pressure to stabilize, and then supply electric power of 0.01 to 0.5 W / cm ² to the electrode facing the substrate 12 using a high-frequency power supply of 13.56 MHz. A silicon oxide film was deposited. Next, the resultant was patterned into a predetermined shape by photolithography to form an interlayer insulating film 96. Here, a parallel plate type etching apparatus was used for the etching.

Furthermore, two layers of Cr and A1 are deposited on these by the sputtering method, patterned into a predetermined shape by the photolithography method, and the connection wiring 100 and the channel wirings C, C ₂ .. .. to form a C _n and the lead electrode 1 0 6. Here, the thickness of Cr was 500 A, and the thickness of A1 was 1.5. The etching of A1 was performed with a mixture of phosphoric acid, hydrochloric acid, nitric acid and acetic acid, and the etching of Cr was performed with a second cell ammonium nitrate.

Finally, a 5,000 A thick silicon nitride film was deposited on all of them by plasma CVD. That is, after evacuating the inside of the chamber one to 1 0 _ ² Torr or less, and heating and holding the substrate 1 2 to a predetermined temperature, introducing the silane gas 2 0 to 6 0 sccm, ammonia gas 1 5 0~ 3 0 0 sccm , 0.3-1.

The pressure was maintained at Torr (here, hydrogen gas or nitrogen gas may be introduced as necessary). After that, wait for the pressure to stabilize, and then use a high frequency power supply of 13.56 MHz to apply a voltage of 0.01 to 0 to the electrode facing the substrate 12. A power of 5 WZcm ² was supplied to deposit a silicon nitride film. Next, the resultant was patterned into a predetermined shape by photolithography to form a protective film 104. A parallel plate type etching apparatus was used for the etching here.

Comparative Example 1

On the other hand, as a comparative example of the conventional manuscript reading apparatus, a manuscript reading apparatus different from the above-described embodiment 1 only in the material of the lower electrodes 92a and 94a was manufactured. That is, instead of the above-mentioned ITO film, a chromium film having a thickness of 1500 to 2000 persons is deposited by the sputtering method, and this is patterned by the photolithography method. Opaque lower electrodes 92a and 94a were formed.

Next, a driving circuit and a signal processing circuit were connected to the first embodiment and the first comparative example, and the frequency of the clock pulse was set to 500 kHz, the reading speed was set to 5 msec Zline, and the color was changed from white to black. The document to be read was illuminated with an illumination of 20 lux and read. As a result, an output voltage Vout as shown in FIG. 15 was obtained from the signal processing circuit. In this figure, the solid line indicates the output voltage Vout of the example, and the dotted line indicates the output voltage Vout of the comparative example.

As described above, the inverted image Vr appears in the output voltage Vout immediately after reading white, which causes black read immediately after reading white to be blacker than normal black. However, the reversal afterimage Vr of Example 1 was smaller than the reversal afterimage Vr of Comparative Example 1, and the convergence time was shorter. Table 1 summarizes the results. Here, the output voltage V out corresponding to white was 160 to 180 mV. Table 1

As described above, the embodiment of the document reading apparatus according to the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, and can be implemented in other aspects.

For example, in the above-described embodiment, the upper electrode 92c constituting the photodiode 92 and the upper electrode 94c constituting the blocking diode 94 are connected by the connection wiring 100. As shown in FIG. 16, the lower electrode 108 forming the photodiode 92 and the lower electrode 108 forming the blocking diode 94 are common, and the lower electrode 108 The document reading device 110 may be a device in which the photodiode 92 and the blocking diode 94 are connected to each other. In this case, the lower electrode 108 is formed of ITO or the like. Further, the upper electrode 92 c of the photodiode 92 is taken out by a lead wire 112 through a contact hole 98 formed in the interlayer insulating film 96, and the channel wire CC is connected through a contact hole 102. ₂ ... C „, and the upper electrode 94 c of the blocking diode 94 is drawn out to the outside by a lead wire 114 through a contact hole 98. In this example, The photodiode 92 and the blocking diode 94 are connected by the same anode electrode, and are connected in series with opposite polarities.

In the embodiment described above, the anode electrodes or Chikarasoichido electrode flop locking die O over de 9 4 proc _{B,. B 2...} . Are connected in common in a B _m, Follower Todaio de 9 2 § Roh once electrode or Chikarasoichi de electrode channel wiring d. C s.... Block BB ₂ by C _n.... Relatively same position between B _m Although they are connected to each other, the arrangement of the photodiode and the blocking diode is reversed, and the anode electrode or force electrode of the photodiode is connected in common in the block, and the blocking diode is connected. Anode electrodes or force source electrodes may be connected to each other at a relatively same position between blocks by channel wiring. That is, a plurality of optical sensor elements, each composed of a photodiode (photoelectric conversion element) and a blocking diode (switching element), are arranged one-dimensionally, and are divided into a plurality of blocks every fixed number. It is only necessary that one of these optical sensor elements is commonly connected in the block, and that the other is commonly connected by the channel wiring to those at relatively the same position between the blocks.

In the above-described embodiment, the lower electrodes 92 a and 94 a and the semiconductor layer 92 b constituting the photodiode 92 and the blocking diode 94 are formed for reasons such as simplification of the manufacturing process. , 94 b and the upper electrodes 92 c, 94 c are deposited simultaneously, so they are each composed of the same material, but the upper electrode 92 c constituting the photodiode 92 is formed. Must be transparent, but the upper electrode 94 c constituting the blocking diode 94 may not be transparent. Also, the lower electrode 92 a constituting the photodiode 92 may not be transparent, and at least the lower electrode 94 a constituting the blocking diode (switching element) 94 may be transparent.

As described above, the embodiment in which the original reading apparatus which is the semiconductor device according to the present invention has the lower electrode of the blocking diode 94 which is the switching element constituting the original reading apparatus constituted by at least the transparent conductive layer has been described. In the document reading apparatus according to the present invention, at least a switching element is configured. The lower electrode may be composed of at least one metal layer and a transparent conductive layer deposited on the metal layer. Next, an embodiment of the document reading apparatus having such a configuration will be described in detail with reference to the drawings.

As shown in FIG. 17 and FIG. 14 described above, the original reading apparatus 1 16 according to the present invention includes a photodiode 1 18 as a photoelectric conversion element on a substrate 12 made of glass or the like. , a flop locking diode 1 2 0 is Suitsuchingu element, photodiode 1 1 8 and the channel line C ,. C ₂ .... C of order to read out the electric signals from has to be constituted by forming . Here, an optical sensor element is constituted by the photodiode 118 and the blocking diode 120.

Each of the photodiode 118 and the blocking diode 120 has a lower electrode 118 a, 120 a having a two-layer structure, and a semiconductor layer 118 b having a pin structure made of amorphous silicon or the like. , 120b and transparent upper electrodes 118c, 120c made of ITO (Indium Tin Oxide) or the like are sequentially deposited. These lower electrode 1 1 8 a, 1 2 0 a is, Cr, Ni, Pd, Ti , Mo, Ta, and the like Al metal layer 1 1 8 a,, 1 2 0 a, a, I TO, Sn0 ₂ , and a Ti0 ₂ transparent conductive layer made of a 1 1 8 a 2, 1 2 0 a 2 Prefecture.

The photodiode 118 and the blocking diode 120 are covered with a transparent interlayer insulating film 96 as in the above-described embodiment, and the contact holes formed in the interlayer insulating film 96 are formed. They are connected in series with opposite polarities by connecting wires 100 through 98. On the other hand, the lower electrode 1 18 a of the photodiode 1 18 is connected to the channel wiring CC ₂ ... C „via a contact hole 102 formed in the interlayer insulating film 96, These components are entirely covered with a protective film 104. Other configurations are the same as those of the above-described embodiment.

Here, an example of a method of manufacturing the original reading device 116 is different from the above. The point will be mainly described briefly.

First, a metal film such as Cr, Ni, Pd, Ti, Mo, Ta, or Al is deposited on the substrate 12 by a vacuum deposition method using an electron beam or resistance heating, or a sputtering method using DC or RF. Then on this, it deposits a transparent conductive film such as ITO or Sn0 ₂ by vacuum deposition Yasu sputtering method. Further, an amorphous silicon film is successively deposited thereon in the order of p-type, i-type, and n-type, and a transparent conductive film is further deposited thereon. The thickness of the metal film and the transparent conductive film is preferably about several hundreds to several thousand A, but is appropriately determined in consideration of the characteristics of these films and the performance of the amorphous silicon film. Next, the upper transparent conductive film, the three-layer amorphous silicon film, and the lower transparent conductive film are patterned into a predetermined shape by photolithography or the like, and then the metal film is patterned into another predetermined shape. Thus, a photodiode 118 and a blocking diode 120 are formed.

Then, on these photodiodes 1 1 8 and the blocking diode 1 2 0, after depositing and Si O _x and SiN _x by a conventional method, an interlayer insulating film 9 6 by patterning into a predetermined shape Form. At this time, contact holes 98 and 102 are formed at predetermined positions on the photodiode 118, the blocking diode 120 and the metal layer 118a, and the metal layer 120a is formed. On the other hand, in the region where the upper extraction electrode 106 is to be formed, the interlayer insulating film 96 is removed.

Further, on these, after depositing a metal single layer or multilayer by a conventional method by patterning into a predetermined shape, line 1 0 0 and Chiya tunnel line _{C,. C 2...} . C „And the extraction electrode 106 are formed, whereby the upper electrodes 118c and 120c are electrically connected to each other by the connection wiring 100, and the metal layers 11.8a, And the channel wiring CC ₂ ... C „. These charges can be connected electrically. If it is, it does not need to be a metal and is not particularly limited. Throughout these last, silicon oxide, silicon nitride, after depositing and tantalum oxide, by patterning into a predetermined shape, the extraction electrodes 1 0 0 and channel line C]. C ₂ ... A protective film 104 is formed so as to cover the entire region except for the c 電極 extraction electrode (not shown).

Here, after depositing the metal film and the transparent conductive film in a blanket state, the force for depositing the amorphous silicon film, and before depositing the amorphous silicon film, the transparent conductive film alone is first patterned. The transparent conductive layers 1 18 a 2 and 120 a 2 may be formed in advance. In this case, after the upper electrodes 118c, 120c and the semiconductor layers 118b, 120b are formed, the metal film in the blanket state is patterned to form the metal layer 118a. ,, 120 a., The configuration is the same as that of the original reading device 1 16 described above. Further, the deposition of the metal layer and the transparent conductive layer may be performed continuously without breaking the vacuum, or may be performed discontinuously once the vacuum is broken. Furthermore, here, a method of patterning mainly by photolithography has been described as an example, but a film may be formed by using a mask method or the like so that a film is not deposited on unnecessary portions from the beginning. Is not limited at all.

In this original reading device 1 16, since the lower electrode 120 a is composed of the metal layer 120 a and the transparent conductive layer 120 a ₂ , the semiconductor layer 120 b and the transparent conductive layer interface is formed at the junction of the 1 ₂ 0 a 2. This is interfacial potential barrier and is considered to Baria such as a transparent conductive layer 1 2 0 a ₂ trap level substance constituting occurs diffused into the semiconductor layer 1 2 0 b a is formed. Therefore, it is considered that the same operation as that of the above-described original reading apparatus 90 is performed, and as a result, the same effect is obtained.

In order to confirm such effects, a document reading apparatus according to the present example was manufactured, and a comparative experiment was performed with Comparative Example 1 described above. Example 2

First, the document reading apparatus according to the present example was manufactured by the following method.

The substrate 12 is made of Al-free glass (# 7509) manufactured by Koingen Co., Ltd. First, the substrate 12 is placed on the substrate 12 by the DC sputtering method. An A thick chromium film was deposited, followed by a 600 A thick ITO film. Specifically, it sets the substrate 1 2 Chiyanba in one, after evacuating the inside of the Chiyanba until 1 0 _ ⁵ Torr or less, and holds the substrate 1 2 1 0 0~ 2 5 0 ° C , Chromium film and ITO film by introducing argon gas and oxygen gas at a constant rate under pressure 0.1 to 0 Pa, DC power 0.1 to 1. OW / cm ² And were sequentially deposited. Further, as in Example 1, an amorphous silicon film was deposited thereon in the order of p-type, i-type, and n-type, and an ITO film was further deposited thereon.

Next, in the same manner as in Example 1, the upper ITO film, the three-layer amorphous silicon film, and the lower ITO film were patterned into a predetermined shape, and the upper electrodes 118 c and 120 c were formed. and the semiconductor layer 1 1 8 b, 1 2 0 b, to form the lower electrode 1 1 8 a, 1 2 0 a is part transparent conductive layer 1 1 8 a ₂ of, 1 ₂ 0 a 2. The lower electrode 1 1 8 a, 1 2 0 a is part transparent conductive layer 1 1 8 a ₂ of, 1 2 0 a _2, the upper electrode 1 1 8 c, 1 2 0 c and the semiconductor layer 1 1 Using the resist used for patterning 8b and 120b, the underlying ITO film was etched using a mixture of hydrochloric acid and nitric acid. Then, after removing the resist used for patterning, the chromium film is patterned into a predetermined shape by photolithography, and the metal layer 118 a, which is a part of the lower electrodes 118 a and 120 a, is formed. ,, 120 a, are formed. The second chromium ammonium nitrate was used for etching the chromium film. In this way, the photodiodes 118 and the blocking diodes 120 were formed in the same number, configuration, and size as in Example 1. So Thereafter, in the same manner as in Example 1, the interlayer insulating film 96, the connection wiring 100, and the protective film 104 were formed, and a document reading apparatus was manufactured.

Next, a drive circuit and a signal processing circuit were connected to the original reading apparatus obtained in Example 2 and the original reading apparatus obtained in Comparative Example 1 described above, and the frequency of the quick pulse was set to 500 KH. At a scanning speed of 5 msec / line, the original that changed from white to black was illuminated at 20 lux and read. As a result, an output voltage Vout as shown in FIG. 15 was obtained from the signal processing circuit. As described above, the inverted image Vr appears in the output voltage Vout immediately after reading white, and this causes black read immediately after reading white to be blacker than normal black. However, the inversion image Vr of the example was smaller than the inversion image Vr of the comparative example, and the convergence time was shorter. Table 1 summarizes the results. Here, the output voltage Vout corresponding to white was 160 to 18 OmV. Next, for example, in the above-described embodiment, the original reading device according to the present invention includes an upper electrode 118 c constituting the photodiode 118 and an upper electrode 1 constituting the blocking diode 120. 20 c is connected by connection wiring 100, and as shown in FIG. 18, the lower electrode 122 constituting the photodiode 118 and the blocking diode 120 are connected to each other. The lower electrode 1 2 2 is common, and the lower electrode 1 2 2 connects the photodiode 118 and the blocking diode 120 to the original reading device 1. 2 4 is acceptable. In this case, the metal layer 1 26 and the transparent conductive layer 1 28 are sequentially deposited to form the lower electrode 122, and the semiconductor layers 1 18 b and 120 b and the transparent conductive layer 1 2 8 It is configured so that an interface with is formed. In addition, the upper electrode 1 18 c of the photodiode 1 18 is taken out by the lead-out wiring 130 via the contact hole 98 and the channel wiring C,. C ₂ ... via the contact hole 102. Connect to C „ On the other hand, the upper electrode 120c of the blocking diode 120 is configured to be taken out to the outside through the contact hole 98 by the lead wiring 132. In this example, the photodiode 118 and the blocking diode 120 are connected by the anode electrodes, and are connected in series with opposite polarities.

In the embodiment shown in FIG. 17 or FIG. 18 described above, the metal layer 1 18 a 1, 120 a, and the transparent conductive layer 1 18 a ₂ , 120 a ₂ , or Although the metal layer 126 and the transparent conductive layer 128 have different shapes, they may have the same shape.

In the embodiment described above, the anode electrode or Chikarasoichido electrode flop locking die O over de 1 2 0 are connected to a common within to proc B B ₂ .... B _m, Anodo the photodiode 1 1 8 Although the electrode or force cathode electrode are connected with each other being in the same relative position between the blocks Β ,. B ₂ .... B _m by channel wiring d. Cs .... C _n, the Photo Invert the arrangement of the diode and the blocking diode, connect the anode electrode or the force electrode of the photodiode in the block, and connect the anode electrode or the force electrode of the blocking diode. The electrodes may be connected to each other at relatively the same position between blocks by channel wiring. That is, a plurality of photosensor elements, each composed of a photodiode (photoelectric conversion element) and a blocking diode (switching element), are arranged one-dimensionally, and are divided into a plurality of blocks every fixed number. Therefore, it is only necessary that one of these optical sensor elements is commonly connected in the block and that the other is commonly connected by the channel wiring at the relatively same position between the blocks. .

Further, in the above-described embodiment, the lower electrodes 1 18a and 120 a of the photodiodes 118 and the blocking diodes 120 are formed for reasons such as simplification of the manufacturing process. , The semiconductor layers 1 18 b, 12 O b and The upper electrodes 1 18 c and 120 c are respectively deposited simultaneously and are made of the same material, respectively, but the upper electrodes 1 18 c constituting the photodiode 118 are formed. Must be transparent, but the upper electrode 120c constituting the blocking diode 120 may not be transparent. Further, the lower electrode 118a constituting the photodiode 118 does not need to be composed of a metal layer and a transparent conductive layer, and at least a blocking diode (switching element) 120 is required. lower electrode 1 2 0 a power constituting, metallic layer 1 2 0 a, and may be composed of a transparent conductive layer 1 2 0 a ₂ Prefecture. That is, in the present invention, a reverse current generated in the switching element may be prevented by forming an interface between the semiconductor layer constituting the switching element and the transparent conductive layer. The number of metal layers may be one, but may be two or more. ―

As described above, all of the semiconductor devices according to the present invention are stacked mainly in the order of pins from the substrate 12 side. On the contrary, the semiconductor devices may be stacked in the order of nip and have a niP structure. It is preferable that the lower electrode or the upper electrode formed of the transparent conductive layer and the P layer of the semiconductor layer are in contact with each other. In addition to the pin type described above, ni-type, pi-type, pn-type, MIS-type, hetero-junction-type, homo-junction-type, Schottky barrier-type, or a combination of these are deposited in a single layer or multilayer. May be done. In addition, amorphous silicon constituting the semiconductor layer includes other materials such as amorphous silicon hydride a-Si: H, amorphous silicon carbide a-SiC: H, and amorphous silicon nitride. However, simple amorphous silicon a-Si is preferred, but amorphous silicon-based semiconductors composed of alloys of silicon and other elements such as carbon, germanium, and tin, or amorphous or microcrystals may be deposited. These structures are not limited at all. Further, the semiconductor layer to which the present invention is applied is not limited to amorphous or microcrystal, but may be a single crystal. In addition, the photoelectric conversion element is not limited to a photovoltaic element such as a photodiode, but may be, for example, a photoconductive element. In addition, the present invention can be implemented in various modified, modified, and modified embodiments based on the knowledge of those skilled in the art without departing from the gist of the present invention, such as a case where the switching element may be a TFT. Industrial applicability

In the semiconductor device including the semiconductor element having the switching function according to the present invention, at least one of the lower electrode and the upper electrode is formed of the transparent conductive layer, so that the interface between the semiconductor layer and the transparent conductive layer is formed. Therefore, the reverse current is rapidly converged by the barrier formed at this interface, and its peak value is also reduced. Therefore, the switching speed can be greatly improved. It is also considered that light leaked from the periphery penetrates through the lower electrode and the upper electrode and is incident on the semiconductor layer, whereby the reverse current is rapidly converged, and the peak value is also reduced. Next, at least one of the lower electrode and the upper electrode constituting the switching element is a photosensor element comprising the photoelectric conversion element and the semiconductor element having a switching function, which is the semiconductor device according to the present invention. Since the interface is formed of the transparent conductive layer, an interface between the semiconductor layer and the transparent conductive layer is formed, so that the reverse current is rapidly converged by the barrier formed at this interface, and However, its peak value also becomes smaller. Therefore, a more accurate signal output can be obtained, and the switching speed can be improved. It is considered that the light leaked from the periphery enters the semiconductor layer constituting the switching element, the reverse current is rapidly converged, and the peak value is also reduced.

Further, the original reading apparatus, which is a semiconductor device according to the present invention, has at least one of a lower electrode and an upper electrode constituting a switching element. Since one of the transparent conductive layers forms an interface between the semiconductor layer and the transparent conductive layer, the reverse current is rapidly converged by the barrier formed at this interface, and The peak value is also reduced, and the switching speed of the switching element is improved. For this reason, inversion inversion is reduced, and an accurate signal output can be obtained. This is particularly advantageous when reading a document under low illuminance, and can reduce power consumption. Further, the signal reading speed can be greatly increased. In addition, light leaked from the periphery enters the semiconductor layer constituting the switching element, and the reverse current is rapidly converged, and the peak value is also reduced. As a result, the switching speed of the switching element is improved. It is thought that it can be done. As described above, the present invention has various excellent effects.

Claims

The scope of the claims

1. In a semiconductor device having one or more semiconductor elements having a switching function and configured by sequentially stacking a lower electrode, a semiconductor layer, and an upper electrode,

A semiconductor device, wherein at least one of the lower electrode and the upper electrode comprises one or more conductive layers, and at least the conductive layer in contact with the semiconductor layer comprises a transparent conductive layer.

2. An optical sensor element configured by serially connecting a semiconductor element having a switching function according to claim 1 and a photoelectric conversion element formed by sequentially stacking a lower electrode, a semiconductor layer, and an upper electrode is referred to as an optical sensor element. Or a semiconductor device including a plurality of the semiconductor devices.

3. An optical sensor element configured by serially connecting a semiconductor element having a switching function according to claim 1 and a photoelectric conversion element formed by sequentially stacking a lower electrode, a semiconductor layer, and an upper electrode is a primary element. Originally, it is arranged in plurals, divided into multiple blocks by a certain number,

A semiconductor device, wherein one of these optical sensor elements is commonly connected in a block, and the other is commonly connected by the channel wiring to those at relatively the same position between the blocks. .

4. A semiconductor device provided with at least one or more semiconductor elements having the switching function, wherein at least one of the lower electrode and the upper electrode of the semiconductor element is made of a transparent conductive layer. The semiconductor device according to claim 1.

5. A semiconductor device comprising at least one semiconductor element having the switching function, wherein the transparent conductive layer of the semiconductor element is made of ITO. Semiconductor equipment

6. In a semiconductor device provided with at least one or more semiconductor elements having the switching function, it is preferable that at least a semiconductor layer in contact with the transparent conductive layer among the semiconductor layers of the semiconductor element is a P-type semiconductor layer. 6. The semiconductor device according to claim 1, wherein the semiconductor device is a semiconductor device.

7. In a semiconductor device provided with at least one or more semiconductor elements having the switching function, a semiconductor layer of the semiconductor element is made of hydrogenated amorphous silicon continuously deposited by a plasma CVD method, and has a pin structure. 7. The semiconductor device according to claim 1, wherein:

8. The semiconductor device according to any one of claims 2 to 7, wherein the semiconductor element having the switching function and the photoelectric conversion element each have a diode characteristic and are connected in series by their respective cathode electrodes. Semiconductor

9. The semiconductor device having the switching function and the lower electrode, the semiconductor layer, and the upper electrode constituting the photoelectric conversion device are respectively deposited simultaneously. The semiconductor device according to any one of the above.

10. In a semiconductor device provided with one or a plurality of optical sensor elements configured by serially connecting the semiconductor element having the switching function and the photoelectric conversion element, a lower electrode positioned on the side opposite to the light incident side; 10. The semiconductor device according to claim 2, wherein one of the upper electrodes is formed of a transparent conductive layer at least in contact with the semiconductor layer.