JPS61232668A - Image sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To specify the area of light-reception, and to obtain a high-resolution image sensor having high reliability by forming a light-shielding film into a photoconductor layer. CONSTITUTION:A chromium thin-film is applied onto an insulating glass substrate 1, and a lower electrode 2 is shaped through photolithographic etching. Polyimide is applied and dried as an insulating film 3, and patterning for prescribing the area of a lower electrode and the formation of a through-hole for changing wirings into multilayers are conducted. A first amorphous hydride silicon layer 4a constituting one part of a photoconductor layer is deposited. A chromium thin-film is shaped, an internal light-shielding electrode 5 is formed through patterning by photolithographic etching, the surface of the substrate is etched for several sec by diluted hydrofluoric/nitric acid, and the photoconductor layer 4 is constituted. Lastly, an indium oxide tin film as a light-transmitting upper electrode 6 is shaped, and a polyimide resin film as a surface protective film 7 is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image sensor and its FJ usage method, and particularly relates to a contact type image sensor with high m-image resolution and high reliability.

[Prior art] A contact image sensor that uses a long reading element with a sensor length that is the same width as the original is made of amorphous silicon (
a-8i') or cadmium sulfide (CdS), cadmium selenide (Cd
By using a polycrystalline thin film such as Se) as a photoconductor layer, it is possible to use it as a large-area device that does not require a reduction optical system, and its wide use in small document reading devices is attracting attention. .

The basic structure of the sensor section of this image sensor is a Zandwich type sensor. As shown in FIG. 9, this four-node hedge sensor has a photoconductor layer 104 sandwiched between a lower electrode 102 formed on a substrate 101-J2 and a transparent upper electrode 103. In the case of a contact image sensor, a plurality of Zandwich-type sensors are mounted on a long substrate (for example, in the case of 8 dots h/mm, 1728 sensors are used for Japanese Industrial Standards A row No. 2048 pieces for row 4) are arranged in parallel. In order to enable accurate reading, these sensors must be independent from each other and the areas of their sensor sections must be the same.

For this reason, various attempts have been made to define the effective sensor area, or light-receiving area, of each sensor on a long substrate. A method of forming separate layers (FIG. 11),
(2) A method of forming a light-shielding film on the soil portion of the light-receiving element (FIGS. 12 and 13), (3) A method of defining the area of the lower electrode (FIG. 10), etc.

Among these methods, the method (3) is, as shown in FIG. 105 selectively intervening to define the effective light-receiving surface 1 (t area) (Patent Application No. 59-16)
0126), which is the most effective method from the viewpoint of simplicity of the manufacturing process, but as the demand for higher resolution of image sensors increases, the spacing between each element becomes finer, and the distance between adjacent elements increases. There is a problem in that mutual leakage current from each light-receiving element becomes large, and there is a limit to high resolution.

Methods (1) and (2) are better for solving this problem, but they do not avoid problems such as complication of the respective processes, especially defects caused by the photo-etching process. That's it.

That is, in the method (1), as shown in FIG. 11, for example, the lower electrode 202 and the photoconductor layer 204 are formed separately for each light receiving element, and the transparent upper electrode 203 is also electrically separated. The connected patterns are formed in sections, and the area where the photoconductor layer is sandwiched between the lower electrode and the transparent upper electrode is defined as the light receiving area (sensor area). The elements are separated.

In this method, a photolithographic etching process must be used for all of the formation of the lower electrode, photoconductor layer, and upper electrode, making the manufacturing process complicated, and causing pattern misalignment, etc. There were disadvantages such as variations in the light-receiving area. In addition, during the photolithography process for patterning the photoconductor layer, the edges of the photoconductor layer are contaminated and damaged at the boundary with the mask, resulting in decreased reliability and yield. There was also a crucial problem.

Furthermore, as shown in FIG. 12, method (2) is a method in which the light receiving area is not defined by the component part of the sensor itself, but by the light shielding film 205.
In order to prevent damage to the photoconductor layer 204 that occurs near the end of the upper electrode 203 in method (1) shown in the figure from affecting sensor characteristics, unnecessary parts including that part are covered with a light-shielding film. 205, and the light receiving area is defined by the light shielding film 205 and the lower electrode.

In this configuration, the underlying light-transmitting electrode is directly damaged during the photolithography process for forming the window of the light-shielding film, and the bonding characteristics at the interface between the photoconductor layer and the light-transmitting electrode deteriorate, which is an inconvenience. was there.

Furthermore, the light-shielding film only supplementally defines the light-receiving area defined by the lower electrode, and a sensor is formed in the part of the lower electrode lead line 206 that is exposed from the light-shielding film. Therefore, the influence of the area of the lead line 206 also causes variations in the characteristics of each sensor.

Therefore, as shown in FIG. 13, the lower N-pole 202' is formed in a larger pattern, and the entire surface of the substrate on which the sensor is formed is first covered with a protective film 207, and then the light-shielding film 202' is covered with a protective film 207.
A method has also been proposed in which the light-receiving area is defined only by the light-shielding film.

Although this method improves reliability, it has the disadvantage that processes such as forming the protective IQ and patterning the light-shielding film become complicated.

[Problems to be Solved by the Invention] In view of the above-mentioned circumstances, the present invention solves the problem of reducing reliability due to variations in light receiving area, contamination in the manufacturing process, etc.
In order to solve the above-mentioned problems such as the complexity of the culm, the purpose is to provide an image sensor that is easy to manufacture and has high reliability.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a sensor with a sandwich structure in which a photoconductor layer is sandwiched between a lower electrode and a translucent upper electrode to increase the light receiving area. In order to specify this, a light shielding film is formed inside the photoconductor layer.

Preferably, this light-shielding film is made of conductive material,
It may also be made to act as a third electrode.

In addition, during manufacturing, the photoconductor layer deposition process is performed in the first step.
During the second step, a step of forming a light shielding film is added.

[Function] That is, since the patterning of the light-shielding film that defines the light-receiving area can be performed prior to the formation of a bond at the interface between the photoconductor layer and the transparent upper electrode, the sensor An image sensor having the characteristics as designed can be formed by a simple process without causing a decrease in reliability.

In addition, the light-receiving area is determined by making full use of microfabrication techniques such as photolithography and etching. Since this is done by repeating the process, it is possible to obtain a long image sensor with high precision and no variation from element to element.

[Example] Hereinafter, embodiments of the present invention will be described with reference to the drawings. I will explain it in detail.

This image sensor has a resolution of 600spi (sp
ot per 1 nch), in which sensors consisting of 600 photoelectric conversion elements per inch are arranged side by side on the base soil of about 1000 yen per inch. As shown in cross-sectional views A and -A in the figure, the sensor part S is a chromium electrode as a lower electrode 2 consisting of an electrode part 2a and a lead wire part 2b which are divided into desired shapes on an insulating glass substrate 1. and covers the lead wire portion and the electrode portion 2.
an insulating layer 3 made of a polyimide film formed to expose a, a photoconductor layer 4 made of a hydrogenated amorphous silicon layer (a-3i:H) integrally formed on top of the insulating layer 3; An internal light-shielding electrode 5 made of a thin chromium film is formed in the conductor layer 4 to correspond to the lower electrode 2, and an inner light-shielding electrode 5 formed on the upper layer of the photoconductor layer 4 corresponds to the lower electrode 2 and the inner light-shielding electrode. a translucent upper electrode 6 made of an indium tin oxide (ITO) film integrally formed to
A surface protection film 7 made of a polyimide resin film is formed to cover the entire surface of the substrate.

Next, a method for manufacturing this image sensor will be explained.

First, a film with a thickness of 20 mm was deposited on an insulating glass substrate 1 by vapor deposition.
After depositing a 0OA thin chromium film (@film temperature: 250°
C) A lower electrode 2 is formed by photolithography as shown in FIG.

Next, as shown in FIG. 4, polyimide is applied and dried as an insulating film 3, and then patterned to define the area of the lower electrode and through holes (not shown) for multilayering the wiring are formed by photolithography. Let's do it.

Thereafter, a first hydrogenated amorphous silicon layer 4a constituting a part of the photoconductor layer is first deposited to a thickness of about 1 μm by plasma CVD. (Fig. 5) At this time, the film deposition temperature is 250°C.

Next, a thin chromium film with a thickness of about 50 OA was formed at 230° C. by vapor deposition, and then patterned by photolithography to form internal light-shielding electrodes 5 as shown in FIG.
form.

Then, it is diluted and 1=fluorous nitrate Am (1-lr: 1-I
After cleaning the surface of the first hydrogenated amorphous silicon Q'I'a by etching the substrate surface with NO3) for a few seconds, the second hydrogenated amorphous silicon 4b was etched again using the plasma CVD method. ) for 100
0A is formed, and the photoconductor layer 4 is constructed as shown in FIG.

Finally, after forming an indium tin oxide film as a transparent upper electrode 6 by sputtering, a surface protective film 7 is formed.
A polyimide resin film is applied as shown in Figures 1 and 2.
The image sensor shown in the figure is completed.

In such a configuration, J: So, light 1? [? While maintaining good bonding characteristics at the interface between the body layer and the upper electrode of the light-transmitting 1+ layer, it is possible to cover the light-receiving area in the photoconductor layer. The lead wire portion 2b is covered with the insulating layer, and only the electrode portion 2a is in contact with the photoconductor layer 4 through the lower electrode 2. Therefore, the light-receiving area can be defined with extremely high precision. It is possible to obtain a high-resolution image sensor that can exhibit stable characteristics without variations.

In addition, with this method, the light-receiving area can be accurately determined without performing photolithography after the formation of the surface of the photoconductor layer or the bonding surface where the bond is formed between the light-transmitting electrodes. Since it can be well defined, an image sensor with good sensor characteristics and high reliability can be manufactured without deterioration of bonding characteristics.

Further, the surface of the first hydrogenated amorphous silicon layer is cleaned through surface treatment after forming the internal light-shielding electrode, and then
Since the second hydrogenated amorphous silicon layer is laminated, the performance of the device does not deteriorate.

Further, as another embodiment of the present invention, as shown in FIG.
It is also possible to apply a bias to the internal light-shielding electrode 5. Here, the second hydrogenated amorphous silicon layer 4b' had a thickness of about 1 μm to prevent dielectric breakdown. The structure is exactly the same as that shown in FIGS. 1 and 2.

During actual driving, when a bias of Ov is applied to the lower electrode, -10V to the light-transmitting upper electrode, and -5V to the internal light-shielding electrode, the potential distribution inside the photo-S electric layer 4' is vertically distributed. It will be almost like 1.

Here, A1~carriers (photoelectrons) generated at the portion between the inner light-shielding electrode and the upper electrode are captured by the inner light-shielding electrode and do not leak out of the inner light-shielding electrode. Therefore, the first carriers generated outside the required light-receiving area (outside the specified light-receiving area) are captured by the internal light-shielding electrode, making it possible to drastically reduce leakage to the external adjacent pit. Become.

Note that the depth of the internal light-shielding electrode extending into the photoconductor layer, that is, the ratio of the film thicknesses of the first and second hydrogenated amorphous silicon layers can be changed as necessary.

Further, in the embodiment, the light-receiving area was also defined by forming an insulating film on the lower electrode, but this insulating film may be removed and the light-receiving area may be kept constant at 12 by using only the internal light-shielding film.

Furthermore, although this internal light-shielding film is made of a conductive material in the embodiment, it does not necessarily have to be conductive.

[Effects] As explained above, according to the present invention, in a sensor having a Zandwich structure in which a photoconductor layer made of an amorphous semiconductor layer is sandwiched between a lower electrode and a transparent upper electrode,
Since the light-receiving area is defined by forming a light-shielding film inside the photoconductor layer, it is possible to obtain a highly reliable, high-resolution image sensor.

Furthermore, according to the method of the present invention, since the light-shielding film is formed at an intermediate stage of forming the photoconductor layer, deterioration of the bonding characteristics between the photoconductor layer and the upper electrode is significantly suppressed. is,
A high-yield, high-resolution image sensor can be obtained extremely easily.

[Brief explanation of drawings]

FIGS. 1 and 2 are partial schematic diagrams showing an image sensor according to an embodiment of the present invention, and FIGS. 3 to 7 are images of the same.
FIG. 8 shows a modification of the image sensor of the present invention, and FIGS. 9 to 13 show conventional image sensors. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Lower electrode, 2a... Electrode part, 2b... Leading wire part, 3... Insulating film, 4.
/l'...Photoconductor layer, 7'la, 4a'...
・First hydrogenated amorphous silicon layer, 4b, 4b'
...Second hydrogenated amorphous silicon layer, 5...
- Internal light shielding I11.6... Upper electrode, 7... Surface protective film, 101.201... Substrate, 102.202...
・Lower electrode, 103. 203...-
Toden SE V, 104.204...Amorphous semiconductor layer, 205.205'...Light shielding film, 206...
Lower electrode lead line, 207... surface protection film. Figure 9 Figure 10 Figure 11 Figure 12 Figure 1 (

Claims (5)

[Claims] (1) In an image sensor with a sandwich structure in which a photoconductor layer is sandwiched between a lower electrode and a transparent upper electrode, a light-shielding film is provided inside the photoconductor layer to define the light-receiving area. An image sensor featuring: (2) The image sensor according to claim (1), wherein the light shielding film is an internal light shielding electrode made of a conductive material. (3) The image sensor according to claim (1) or (2), wherein the photoconductor layer is made of an amorphous silicon layer. (4) A method of forming a sandwich-structured image sensor by sequentially laminating a lower electrode, a photoconductor layer, and a light-transmitting upper electrode on a substrate, in which the formation of the photoconductor layer includes forming the first and second photoconductor layers. A method for manufacturing an image sensor, comprising a second step, and including a step of forming a light-shielding film pattern after the first step and before the second step. (5) The method for manufacturing an image sensor according to claim (4), further comprising an etching step for cleaning the substrate surface after forming the light-shielding film pattern.