JPS6139574A - Image sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the reduction of reliability due to the dispersion of a photo detective area or the contamination in the process of manufacture by limiting the photo detective area providing an insulation layer between a bottom electrode and a photo conductive layer. CONSTITUTION:A sensor S consists of a bottom electrode 12 consisting of an electrode 12a divided on a glass substrate 11 and a lead wire 12b, an insulation layer 13 of a silicon oxide film, a photoconductive layer 14 of a-Si:H, a translucent top electrode 15 and a surface protection film 16. A driving mechanism D is connected to the lead wire of each sensor and consists of wiring layers 17, 18 each arranged in longitudinal or transverse stripes. The lead wire 12b is covered with the insulation layer 13 and only the electrode 12a is kept in contact with the photoconductive layer 14 as the bottom electrode 12. A photo detective area is precisely limited by the bottom electrode 12 and the insulation layer 13 and the materials used are not damaged by such a process as photoetching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image sensor and a method for manufacturing the same, and more particularly to a high-resolution image sensor used as a contact type document reading device.

[Conventional technology]

A close-contact image sensor that uses a long reading (reading) element with a sensor part the same width as the original is made of amorphous silicon (
a-8i) or cadmium sulfide (CdS)-cadmium selenide (CdSe')
) etc. as a photoconductor layer, it is possible to use it as a large-area device that does not require a reduction optical system, and it is attracting attention for its wide use in small document reading devices, etc. has been done.

One of the basic structures of the sensor section of this image sensor is a Santoi type sensor. As shown in FIG. 8, this sandwich type sensor consists of a lower electrode 2 formed on a substrate 1, a photoconductor layer 4 sandwiched between a light-transmitting upper electrode 3 and K, and has an image of a close-contact type sensor. In sensors,
A plurality of these sandwich type sensors are installed on a long board (for example, in the case of 8 dots/Ii, 1728 sensors are installed for No. 4 in row A of the Japanese Industrial Standards, and 2048 sensors are installed for No. 4 in row B of the same standard).
) installed in parallel. In order to make accurate reading possible, these sensors must be completely independent of each other, and the areas of the light receiving sections must be the same.

For this reason, various attempts have been made to define the light-receiving area of each sensor on a long substrate.

For example, in the most basic contact type image sensor, as shown in FIG. 9, the lower electrode 2 and the photoconductor layer 4 are formed separately for each sensor, and the translucent upper electrode 3 is also formed separately in important parts. The area where the photoconductor layer is sandwiched between the lower electrode 2 and the light-transmitting upper electrode 3 is defined as a light-receiving area, and each sensor is formed separately.

In this structure, a photolithography process must be used for all of the formation of the lower electrode, the photoconductor layer, and the upper electrode, and the manufacturing process is complicated.
(Due to pattern misalignment, etc.), there were disadvantages such as variations in the light-receiving area of each sensor. In addition, during the etching and etching process for forming the upper electrode, the end of the photoconductor layer is contaminated and damaged at the boundary with the mask, resulting in decreased reliability and yield. there were.

In addition, in a contact image sensor using non-doped amorphous silicon as the t-ff1 conductor layer, the amorphous silicon itself has a high resistance (resistivity in the dark ~10Ωcr).
rL), the separation (isolation) between adjacent pits (between each adjacent senna) is omitted, and the first
As shown in Figure 0, for example, only the lower electrode is formed separately,
The photoconductor layer 4 and the upper electrode 3 are integrally formed. Even with such a configuration, there is no overlap between the upper and lower electrodes).
The light-receiving area is defined by Although the process is simplified, the underlying photoconductor layer is also damaged at the edges of the metal mask, leading to a reduction in manufacturing yield.

In order to solve these problems, as shown in FIG. 11 or FIG. 12, a method of defining the light-receiving area not by the constituent members of the senna itself but by a light-shielding film 5 has also been considered.

First, FIG. 11 shows how damage to the photoconductor layer that occurs near the end of the upper electrode 3 in the structural example shown in FIG. 10 affects the sensor characteristics. In order to prevent this, the unnecessary portion including that portion is shielded with a light-shielding film 5, and the light-receiving surface is the same as 1 by the light-shielding film and the lower electrode.

In this configuration, the light-shielding film only supplementally defines the light-receiving area defined by the base electrode.
As for the lead wire 6 of the base electrode, a hole is formed in the part exposed from the light-shielding film, and the influence of the area of the lead wire 6 is also a cause of variations in the characteristics of each sensor. It had become.

Further, as shown in FIG. 12, the lower electrode 2 is formed in a larger quarter turn, and the entire surface of the substrate on which the sensor is formed is first covered with a surface protection film 7, and then the light shielding film 5 is formed. In this case, the light-receiving area is defined only by the light-shielding film. In this case, since the patterning of the window portion W formed in the light shielding film requires precision, it is carried out by photolithography or the like.

This configuration improves reliability, but processes such as forming the protective film and turning the light shielding film are M14.

[Gap points to be solved by the invention]

The present invention has been made in view of the above-mentioned circumstances in order to solve the above-mentioned problems such as variations in light-receiving area, decreased reliability due to contamination in the manufacturing process, and complexity of the manufacturing process. The purpose of the present invention is to provide a highly reliable image sensor with a simple manufacturing process and no variation in the characteristics of each sensor.

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a photoconductor layer consisting of a lower electrode divided into desired shapes and arranged in parallel on a substrate and an amorphous semiconductor layer. In order to define the light-receiving area (sensor area), an insulating layer is additionally interposed in between, corresponding to the lower electrode, thereby forming a sandwich-structured sensor.

In addition, during manufacturing, after forming the lower electrode and prior to forming the photoconductor layer, a step of forming an insulating layer corresponding to /9 turns of the lower electrode was added to the normal Senna manufacturing process, and this insulating layer The light receiving area (sensor area) is defined.

[Effect]

In other words, the light-receiving area can be determined before the formation of the sensor, especially before the formation of the photoconductor layer, which is easily damaged. An image sensor with characteristics consistent with the design can be formed using a process that is consistent with the design.

Furthermore, since the light-receiving area is defined on the lower electrode side by making full use of the microfabrication technology of the IJ non-etching method, the characteristics of the sensor are uniform and highly accurate.

〔Example〕

Hereinafter, a matrix-driven image sensor with an IJ wiring section according to an embodiment of the present invention will be described, in which a sensor consisting of 1728 photoelectric conversion elements is arranged in parallel on a scale board, and the image sensor is shown in Figure g1. As shown in FIG. 2, which shows a plan view of the main part and a sectional view taken along the line A in FIG. A chromium electrode as the lower electrode 12, which even shows the lead line part 12a and the lead line part 12b, and an insulating layer 13 made of a silicon oxide film (SIO) formed to cover the lead line part 12b and expose the electrode part 12m.
A photoconductor layer 14 made of an amorphous hydrogenated silicon layer (a-8l:H) is integrally formed on the upper layer, and a photoconductor layer 14 is formed on the photoconductor layer 14 so as to overlap with the lower electrode 12. Indium tin oxide (I
It consists of a transparent upper electrode 15 made of a TO) film, and a surface protection film 16 made of a polyimide resin film formed to cover the entire surface of the sensor section of the substrate.

In addition, the drive section is connected to the lead wire of each sensor,
A first wiring layer 17 made of a chromium thin film arranged in stripes in the vertical direction, and a second wiring layer 18 made of a chromium thin film arranged in stripes in the horizontal direction with an insulating layer 13 in between. These wiring layers 17 and 18 are
They are electrically connected via a through hole 19 at only one point where they intersect, and the second wiring layer is connected to a power supply circuit (not shown).

With this configuration, the drawer a12b is covered with the insulating layer 13, and only the electrode part 12m comes into contact with the photoconductor layer 14 as the lower electrode 12, and the lower electrode 12 and the insulating layer 13 are separated ( Since the light-receiving area is defined only by the lower electrode side, it can be precisely defined, and the constituent members of each sensor will not be damaged by the etching process, etc., so the characteristics of each sensor can be improved. This makes it possible to almost eliminate variations in .

In addition, since the sensor area (light receiving area) is defined only on the lower electrode side by the lower electrode and the insulating layer laminated thereon, the photoconductor layer and the upper electrode are It does not contribute to the regulation of the light-receiving area. Therefore, the photoconductor layer and the upper electrode should be turned to a large extent to sufficiently cover the light-receiving area defined on the lower electrode side. Since it does not act as a sensor component, stable characteristics can be obtained, and a high-resolution contact image sensor that can perform accurate image reading can be obtained.

Next, a method for manufacturing this matrix-driven image sensor will be described.

First, a chromium thin film C is deposited on an insulating glass substrate 11 by vapor deposition as shown in Figure 3.

Next, as shown in FIG. 4, the unnecessary portions of the chromium thin film C are selectively etched away by a photorin etching method to form a lower electrode 12 of a desired shape and a wire connected to the lead wire 12b of this lower electrode 12. The first striped
No J? with the wiring layer 17? Form a turn.

Thereafter, a silicon oxide film having a thickness of approximately 2 μm is deposited using a CvD method. Then, the photolithography method is used.
As shown in the figure, in the sensor part, the lead wire 1 of the lower electrode
The silicon oxide film is patterned to cover the electrode portion 2b and expose the electrode portion 12a, and to form a through hole 19 in the driving portion while leaving other portions as they are. At this time, the reason why the thickness of the silicon oxide film is kept to about 2 μm is that mask alignment becomes easier if the i4 turn of the lower electrode can be seen through during patterning. It does not necessarily have to be transparent, and the thickness may be set considering only pattern accuracy and insulation degree.

Subsequently, a thin chromium film is deposited by vapor deposition, and then patterned into a striped second wiring layer 18 by photo-etching, as shown in FIG.

Furthermore, after a non-doped amorphous hydrogenated silicon layer is deposited as a photoconductor layer 14 by a glow discharge method so as to sufficiently cover the electrode part 12a of the lower electrode 12 of the sensor part, a light-transmitting upper layer is further deposited on this upper layer. Form an indium tin oxide film (by sputtering method) as the electrode 13,
As shown in FIG. 7, a sandwich type sensor, that is, a photoelectric conversion device is formed. ζThe light-receiving area is defined by the lower electrode and the insulating layer laminated on the lower electrode, so when patterning the amorphous silicon hydride layer and the indium tin oxide film, the above-mentioned defined light-receiving range is required. It is sufficient to cover a sufficiently wide area in terms of image and width, and pattern accuracy is not required. Therefore, here, the film may be selectively deposited using a metal mask having a selection window in the band-shaped region to which the film is to be deposited.

And finally, the senna part formed in this way /
Covered with a surface protection film 16 made of an IJ imide resin film,
As shown in FIG. 1, an IJ drive type image sensor is completed.

With this method, the light-receiving area can be defined with high accuracy without performing a photophosphor etching process after the formation of the photoconductor layer, so there is no possibility of deterioration due to contamination of the edges of the photoconductor layer. This makes it possible to obtain a highly reliable image sensor with good sensor characteristics.

Further, the patterning of the insulating layer may be performed in the same process as that of the interlayer insulating film of the drive section, and it is important to simplify the manufacturing process.

By the way, in matrix wiring, especially as image sensors become longer, the wiring length becomes longer and the capacitance of the wiring layer itself cannot be ignored. Measure and a. Therefore, it is necessary to consider the substrate, air atmosphere, etc. as the insulating material between the wirings, but changes in the humidity of the air atmosphere will not only change the insulation degree over a considerable range but also affect the surface resistance of the substrate. Although this may change the characteristics of the sensor, since the insulating layer covers the entire substrate surface except for the through holes, the reliability of the sensor is improved.

In addition, although a silicon oxide film was used as the insulating layer in the examples, other insulating films such as other inorganic insulating films such as silicon nitride film (stNx) or organic insulating films such as polyimide resin films may also be used. Similar effects can be obtained by using

Furthermore, in the embodiments, a matrix-driven IJ drive type image sensor has been described; however, the invention is not necessarily limited to this; This is particularly effective when forming the section using multilayer wiring technology. In this case, it is sufficient to form an insulating layer for defining one light-receiving area at the same time as forming the interlayer insulating film.
There is no need to add any process.

Furthermore, it goes without saying that the insulating layer for defining the light-receiving area does not necessarily need to be formed integrally with the interlayer insulating film of the driving section, and may be formed in a separate process.

〔Effect of the invention〕

As explained above, according to the present invention, since the light receiving area (Senna area) is defined by the lower electrode and the insulating layer laminated thereon, the characteristics of each Senna are uniform and the accuracy is low. It will be good.

In addition, since the light-receiving area is determined by forming an insulating layer prior to forming the photoconductor layer, manufacturing is easy and the photoconductor layer is less susceptible to damage due to photolithography and etching processes. It is possible to improve the reliability of Senna without having to change it.

Furthermore, in the case of a device that involves a multilayer wiring process, it is sufficient to form an insulating layer for defining a light receiving area at the same time as forming an interlayer insulating film, so that it can be conveniently manufactured without adding any additional processes.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main parts of a matrix-driven image sensor according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIGS. 3 to 7 are shown in FIG. FIG. 8 is a diagram showing the basic structure of a sandwich type sensor, and FIGS. 9 to 12 are diagrams showing structural examples of conventional sensors. 1... Substrate, 2... Lower electrode, 3... Lower electrode,
4... Photoconductor layer, 5... Light shielding film, 6... Leading line, 7... 13... Insulating layer, 14... Photoconductor layer, 15... Upper electrode, 16...Surface protective film, 17
...first wiring layer, 18...second wiring layer, 19.
...Through hole, C...Chromium thin film, S...Sensor part, D...Drive part. Applicant Agent Takahisa Kimura Figure 1 Figure 3 Figure 4 Figure 5 One Figure 6 Figure 10 Figure 11 Figure 12

Claims (3)

[Claims] (1) In a sandwich-type image sensor in which an amorphous semiconductor layer as a photoconductor layer is sandwiched between a lower electrode formed on a substrate and an upper electrode, the amorphous semiconductor layer is sandwiched between the lower electrode and the amorphous semiconductor layer. An image sensor characterized in that an insulating layer is provided to partially prevent contact between a lower electrode and an amorphous semiconductor layer, and an effective light-receiving area is defined by the insulating layer. (2) The image sensor according to claim (1), wherein the insulating layer is formed to cover at least a lead-out line portion of the lower electrode. (3) In a method for manufacturing a sandwich-type image sensor in which an amorphous semiconductor layer as a photoconductor layer is sandwiched between a lower electrode and an upper electrode formed on a substrate, after forming a lower electrode pattern, Prior to forming the conductor layer, an insulating layer forming step of forming an insulating layer on the lower electrode pattern to define an effective light-receiving area by partially blocking contact between the lower electrode pattern and the photoconductor layer. A method for manufacturing an image sensor, characterized by comprising: