JP2594128B2 - Image sensor - Google Patents

Description

The present invention relates to an image sensor used in an image reading unit of a facsimile or an image reading unit of an image reader for inputting image data to a word processor, a personal computer, or the like. About.

(B) Conventional technology In recent years, as an image sensor used for reading an image of an image processing apparatus as described above, a contact type image sensor excellent in miniaturization, ease of economical design, and the like has been developed.

Such a contact type image sensor is, for example, amorphous silicon (hereinafter referred to as α-Si) which is relatively easy to form a large area, as reported in the Technical Report of the Television Society of Japan ED982 (October 23, 1986). (Abbreviation) has been proposed as a photoelectric conversion material, and has been put to practical use.

As described in the "Technical Report of the Television Society of Japan", there are a photovoltaic system and a photoconductive system as the operation system of the contact type image sensor. The former is composed of a photoelectric converter having a San-Germanic-type electrode structure for the α-Si layer, and can respond at high speed. However, the manufacturing process becomes complicated, and a switching element must be provided for each photoelectric converter. . On the other hand, the latter is composed of a photoelectric conversion unit having a coplanar electrode structure with respect to the α-Si layer.
Further, even in a circuit configuration, matrix wiring becomes easy, and the number of switching elements can be reduced.

FIG. 4 shows a conventional structure of a photoconductive image sensor. FIG. 1A is a plan view, and FIG. 1B is a sectional view taken along line BB.

In these figures, (1) is a glass substrate, (2) is a photoconductive layer made of a band-like α-Si extending in the longitudinal direction of the substrate (1), (3) is an individual electrode, (3) Reference numeral 4) denotes a common electrode, and all of the electrodes (3) and (4) are formed by simultaneously patterning a first metal layer such as aluminum. (6) is an insulating film made of polyimide or the like for protection on the α-Si layer (2) and interlayer insulation on the individual electrode (3), and (5) is a wiring in which the individual electrode (3) is a lower wiring. An upper layer wiring is disposed on the upper layer via an insulating film (6), and an opening (7) is provided in a required portion of the insulating film at an intersection of the upper and lower wirings, whereby the upper and lower wirings (3) ( 5) is connected in a matrix as shown in FIG. (8) is a reflector disposed on the photoconductive layer (2) via the electrodes (3) and (4) and the insulating film (6), and a second metal layer together with the upper wiring (5). Is obtained by patterning.

In the image sensor having such a structure, the matrix wiring of the plurality of individual electrodes (3) (3)... Is positioned on the opposite side of the common electrode (4) with respect to the strip-shaped photoconductive layer (2). Will be done. Therefore, since the output pads of the individual electrodes (3), (3)... And the output pads of the common electrode (4) are present on the substrate (1) on both sides of the photoconductive layer (2), they are separated. )
However, there is a drawback that the image sensor unit becomes large in size and the image sensor unit becomes large.

Furthermore, the above-mentioned reflector (8) for increasing the photoelectric conversion efficiency
Are not separated for each pixel of the individual electrodes (3), (3)... And extend in a strip shape on the pixel column, so that the light enters from below the substrate (1) as shown in FIG. The reflected light is reflected by the reflector (8) even at the boundary between pixels. Accordingly, the resistance value of the photoconductive layer (2) at the boundary portion also decreases similarly to that of the pixel portion, and photoelectric conversion is performed accordingly. Therefore, the crosstalk current between adjacent pixels lowers the resolution of the image signal. there were.

(C) Problems to be Solved by the Invention The present invention is to provide a small-sized image sensor capable of suppressing a crosstalk current flowing between pixels of a photoelectric conversion element.

(D) Means for Solving the Problems An image sensor according to the present invention comprises a semiconductor photoconductive layer extending in a strip shape on an insulating substrate, a common electrode disposed on one side of the photoconductive layer, A plurality of individual electrodes arrayed and formed on the other side of the photoconductive layer, and for each individual electrode extending from the other side of the photoconductive layer to the one side via a dielectric film on the common electrode via an insulating film. It is composed of a lead-out metal pattern, and the pattern covers the gap between the individual electrode and the common electrode from the back surface for each individual electrode.

(E) Function According to the image sensor of the present invention, the metal pattern for deriving the individual electrode covers the gap between the individual electrode and the common electrode from the back surface for each individual electrode. The terminal of the metal pattern and the terminal of the common electrode can be arranged on the same side with respect to the photoconductive layer, and the gap between the individual electrode units is not provided with the metal pattern having a light reflecting effect.

(C) Embodiment FIG. 1 shows an embodiment of the one-dimensional image sensor of the present invention, wherein FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional view.

The configuration of the image sensor shown in FIG. 1 will be described below according to the manufacturing process.

First, amorphous silicon, which is an amorphous semiconductor mainly composed of silicon with excellent photoconductivity, is provided on the surface opposite to the light incident side of a transparent and insulating substrate (11) such as glass, quartz, plastic, or organic resin. A photoconductive layer (12) made of (hereinafter abbreviated as a-Si) is formed by a plasma CVD method or the like, and is patterned into a belt shape. As a method of patterning, a method of patterning using a metal mask at the time of formation, a method of etching using lithography after formation, and the like can be adopted.

Next, by depositing and patterning a metal film, a plurality of individual electrodes (13) are provided on one side on the photoconductive layer (12), and a specific number is provided on the other side on the photoconductive layer (12). Are provided with an appropriate number of common electrodes (14) which face each other in a comb-tooth shape complementary to the individual electrodes (13) (13). Further, by this patterning, a specific number of independent lower wirings (15) for matrix wiring are formed along the common electrode (14) simultaneously with the electrodes (13) and (14). As the metal film, a material that is in ohmic contact with the photoconductive phase (12) is preferable. For example, Al, Ti, Mo, M
g, Au-Si and Cr are opened. Further, in order to obtain a good ohmic contact, a structure in which a phosphorus-doped n ⁺ -type a-Si layer is interposed at the interface between a-Si and these metals may be employed.

Thereafter, the meandering gap between the individual electrode (13) and the common electrode (14) is insulated and protected, and the upper layer wiring (18) for the matrix wiring and the lower layer wiring (15) formed later are formed. An insulating film (16) for interlayer insulation is formed. Furthermore, a contact for making a desired matrix connection between the upper wiring (18) and the lower wiring (15) and a connection for connecting the metal pattern (19) connected to the upper wiring (18) and the individual electrode (13). A hole (17) is formed in the insulating film (16). As the insulating film (16), for example, an organic resin material such as polyimide, photosensitive polyimide, or acrylic, or an inorganic material such as SiO, SiN, or SiON is used.

Finally, a metal film is formed, and a conductive pattern (19) is formed by patterning the individual electrode (13) as a reflection film on the back surface of the element and also serving as a lead wire extending from the individual electrode (13) to the upper wiring (18). To form This allows the photoconductive layer (1
In contrast to 2), matrix wiring of individual electrodes (13) can be formed on the common electrode (14) side. In this case, as the metal film, the same material as that of the lower wiring (15) is used, and a single-layer or multilayer film using Ag, Au, Cu, or the like having high reflectivity is used.

In a photoconductive image sensor having a matrix wiring having such a structure, the matrix wiring of the plurality of individual electrodes (13) is on the same side of the photoconductive layer (12) as the common electrode (14). Since the output pad of the individual electrode (13) and the output pad of the common electrode can be output from the same side to the optical sensor array, the image sensor board and the sensor unit are not connected with the external circuit or the on-chip IC. There is no need to increase the area.

Further, as is apparent from FIG. 1 (a), since the conductive pattern (19) also serves as the wiring for the back surface reflection material and the individual electrode (13), there is no back surface reflection material in the gap between each pixel of the individual electrode unit. Structure. For this reason, in the pixel portion shown in FIG. 2, when light incident from the transparent substrate (11) side enters the a-Si photoconductive layer (12) and is absorbed to generate a carrier, part of the light is transmitted and the insulating film ( 16) After passing through the conductive pattern (19) again with a-Si
Since it is incident on the photoconductive layer (12), it has the effect of increasing the photocurrent by about 20% to 50%. On the other hand, between the pixels in FIG.
Light transmitted through the Si photoconductive layer (12) does not return to the a-Si photoconductive layer (12) again because there is no back reflector. For this reason, there is no effect of increasing the amount of electrical crosstalk between pixels, and the ratio between the photocurrent and the crosstalk current increases, thereby improving the resolution.

A sensor having such a structure is effective when the thickness of the a-Si photoconductive layer (12) is 3000 to 8000 mm, and is particularly effective when a long-wavelength visible light LED such as a red LED is used as a light source. It is particularly effective when the product αd of the light absorption coefficient α [cm ⁻¹ ] of the conductive layer (12) and the film thickness d [cm] is close to 1.

(G) According to the image sensor of the present invention, a very compact, for example, one-to-one contact type image sensor unit can be realized, and the photocurrent is increased to improve the ratio with respect to crosstalk. This makes it possible to perform excellent image reading.

[Brief description of the drawings]

1 (a) and 1 (b) are a plan view and a cross-sectional view of an image sensor of the present invention, FIG. 2 is a cross-sectional view in the main scanning direction showing an optical path of incident light of the image sensor of the present invention, and FIG. 3 is a matrix wiring. 4A and 4B are a plan view and a cross-sectional view of a conventional image sensor, and FIG. 5 is a cross-sectional view in the main scanning direction showing an incident light optical path of the conventional image sensor. (1) (11) ... transparent insulating substrate, (2) (12) ... photoconductive layer, (3) (13) ... individual electrode, (4) (14) ... common electrode, (6) ( 16) Insulating film, (19) Metal pattern.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Keiichi Sano 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Hiroshi Iwata 2-18 Keihanhondori, Moriguchi-shi, Osaka No. Sanyo Electric Co., Ltd. (56) References JP-A-63-17554 (JP, A)

Claims (1)

(57) [Claims] 1. An insulating substrate, a semiconductor photoconductive layer extending in a strip shape on the insulating substrate, a common electrode disposed on one side of the photoconductive layer, and the other side of the photoconductive layer A plurality of individual electrodes arranged in a matrix, and a conductive pattern for the individual electrodes extending from the other side of the photoconductive layer to one side of the photoconductive layer on the common electrode via an insulating film for each individual electrode. The conductive pattern covers a gap between the individual electrode and the common electrode for each individual electrode unit.