JPH01120864A - Image sensor - Google Patents

Abstract

PURPOSE:To lessen influence of flaws and foreign substance liable to appear on a sensor surface coming into contact with manuscript notes and obtain a structure in which element characteristic is not degraded by further providing a different part in level including a flat area in the outside part of a recess which is made on the surface of a transparent protective film of a light receiving part. CONSTITUTION:For example, individual electrodes 5 composed of an Al layer are provided to make a sensor on an one-sided face, for example, on a common electrode composed of a Cr layer and an a-Si layer 4 performing phtoelectric transfer action, for example, in an optoelectric transducer in which a transparent electric conductive film 3 composed of an ITO film has a sandwich structure. A light introducing window 7 reaching a glass substrate is provided in a sandwich part of the sensor, and a transparent protective film 6 is formed on the whole sensor part including this. Different parts 7-1, 7-2 in level having two surface areas are provided on the protective film 6. Flaws are limited even if they are produced in the transparent protective film of the sensor brought into contact with manuscript notes 8 scanned by making such a structure without receiving light as noise, the different part 7-2 in level exists between a contact surface area A and a light receiving surface area B to separated and cut production can be prevented in order that the surface area B does not come in contact with manuscript notes 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to image sensors, and in particular to the structure of a fully contact type image sensor having high resolution. Image sensors are being actively developed as light-receiving parts of image reading elements used in image reading devices such as the present invention.

The image sensor is a reduction type image sensor that uses a combination of a reduction lens system and COD that reduces and reads the original, and a contact type image sensor that uses a Selfoc system that focuses the read image on a line-shaped sensor part of the same size as the original. It is broadly classified into sensors. In order to improve image reading speed, image quality, and reduce the size and cost of the device, we used Selfoc lenses, etc., and used amorphous semiconductors, which can be formed over large areas, as photoelectric conversion films. Contact image sensors are particularly useful.

FIG. 5 shows an example of a contact image sensor using an erect, equal-magnification SELFOC lens array.

FIG. 5 is a sectional view of the image sensor.

An amorphous silicon layer (hereinafter a-8i
A layer 54 is provided and used as a photoelectric conversion element (senna section). Light that enters the LED array 59 as a light source is reflected by the surface of the original 58, is converged by the SELFOC lens array 56, and is received by the light receiving window 52-1 provided in the common electrode 52. Common electrode 5 except for light receiving window 52-1
Since the light is completely blocked by the lens 2, a high resolution paper of the read image can be obtained.

However, even in the contact type image sensor shown in FIG. 5 above, there is a lens system between the document to be read and the sensor unit, which makes it difficult to miniaturize the device, lower the price, and improve the resolution. It was an obstacle.

Therefore, a completely contact image sensor that does not have a lens system between the original and the sensor unit has been proposed (for example, Pro
ceedings of Symposium on
Recent Progress in Amorpho
us 5ilicon Devices p 53~5
6. May 24th 1985 in 0sak
a, see). An example is shown in FIG. Figure 6 (a
) is a plan view of this fully contact type image sensor, and Figure 6 (
b) is a sectional view taken along line aa' in FIG.

In FIG. 6, a photoelectric conversion element array (sensor section) is formed on one side of a glass substrate 61, and the sensor section is in close contact with the surface of a document 68 with a transparent protective layer 66 interposed therebetween.

The basic structure of each sensor section is a sandwich structure similar to the contact type image sensor shown in FIG. 5, but a common electrode 62. Transparent conductive film 63 and a-8i layer 6
A feature is that a light guide window 67 is provided that penetrates through the light guide window 4.

LE arranged on the opposite surface of the glass substrate 61 to the senna part
The light emitted from the D array 69 passes through the light guide window 67 and reaches the surface of the original 68 and is reflected, and the reflected light passes through the transparent protective film 66 and the transparent conductive film 63 and enters the a-8i layer 64. do.

By adopting this structure, adjacent elements are protected.

Only a small amount of stray light reaches the light receiving section, and the one-to-one correspondence between the light receiving section and the light guide window 69 contributes to improved resolution and further miniaturization and cost reduction of the device.

[Problem that the invention seeks to solve]

However, in the fully contact type image sensor mentioned above,
A transparent protective film 66 on the surface of the sensor unit is used to protect the document to be read.
Due to direct contact with the surface of the light guide window 67, the transparent protective film 66 on the surface of the cell part may be scratched, and the concave part 66-1 of the transparent protective film formed corresponding to the light guiding window 67 may be scratched. Foreign matter such as dust is easily resistant to adhesion. The presence of these scratches and foreign objects not only scatters the light from the light source, but also scatters the light reflected from the original, resulting in a decrease in the light intensity of the reflected light input to the sensor section and detection of scattered light. There was a problem in that the /N ratio and MTF (resolving power) were lowered, and the characteristics of the senna portion were significantly deteriorated with use.

Therefore, an object of the present invention is to provide a completely contact type image sensor that has a structure that reduces the effects of scratches and foreign substances that are likely to be formed on the sensor surface that comes into contact with a document, and that does not deteriorate the element characteristics. Means for Solving the Problem] In order to achieve the above object, in the present invention, in a fully contact type image sensor, a step portion including a flat area is further provided on the outer side of the recess formed on the surface of the transparent protective film of the light receiving portion. It is characterized by this.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a structural diagram of a complete contact type image sensor of the present invention, FIG. 1(a) is a plan view, and FIG. 1(b) is a
) is a sectional view taken along the aa' line. FIG. 2 is an explanatory diagram of the optimum area of the image sensor of the present invention.

FIG. 3 is a characteristic comparison diagram of each sensor, and FIG. 4 is a manufacturing process diagram of the sensor of the present invention.

In FIGS. 1 and 4, 1 is a glass substrate.

2 is a common electrode, 3 is a transparent conductive film, and 4 is an a-8i layer.

5 is an individual electrode layer, 6 is a transparent protective film of the present invention, 7 is a light guide window, 8 is a document, 9 is an LED array, and 10 is a structural layer.

In this embodiment, a common electrode 2. made of a Cr layer, for example, similar to the conventional one, is formed on one side of a glass substrate 1. A-3i layer 41 having a photoelectric conversion function, for example, a transparent conductive film 3 made of an ITO film
Individual electrodes 5 made of, for example, an M layer are provided on a photoelectric conversion element having a sandwich structure to form a sensor section. A light guide window 7 reaching the glass substrate is provided at a predetermined position in the sandwich type portion of the sensor section, and a transparent protective film 6 made of silicon oxynitride, for example, is formed over the entire sensor section including the light guide window 7.

A feature of the present invention is that the transparent protective film 6 is provided with at least two stepped portions each having a surface area. That is, 3
A stepped portion 7-1 having a surface area B naturally formed from the shape of the individual electrode 5, and a stepped portion 7-2 having a surface area C in a region located outside the end of the first surface area B. It is.

The outer surface area A of the transparent protective film 6 is in direct contact with the original 8. Incident light from an LED array 9 located on the back side of the glass substrate 1 passes through a light guide window 7 having a surface area and is reflected on the surface of the document. The reflected light enters the sensor section using the surface area B of the transparent protective film 6 as a light receiving surface.

In addition, the two-step portion 7-2 has a surface area B as shown in FIG. 1(b).
It has a surface area C having at least an end thereof at a position corresponding to the end of the individual electrode 5 located outside of the electrode.

With the structure of this embodiment, even if the transparent protective film 6 of the sensor is scratched due to contact with the document being scanned, the damage is limited to the surface area.

The various scattered lights caused by this are reflected by the individual electrodes 5, which are attenuated because the area is far from the light receiving area (surface area B), and are not received as noise.

Further, there is a step 7-2 between the surface area A of the transparent protective film 6 that contacts the document and the surface area B that acts as a light-receiving surface.
Furthermore, they are far apart in terms of distance.

Since the surface area B does not come into contact with the document 8, it is possible to completely prevent the occurrence of scratches due to contact of the surface area B with the document.

Furthermore, due to the existence of the surface area C with a step between the surface area A and the surface area C, dirt such as dust generated during document scanning etc. accumulates on the surface area C, and the surface area corresponding to the surface area B and the light guide window. This prevents dirt from forming on the surface of the substrate, and it is possible to prevent a decrease in light transmittance due to dirt on these surface areas.

Here, in Figure 1, the height difference between surface area A and surface area B is h
[μm] 9 Surface area The distance between the surface area and the end of the individual electrode 5 (i.e. the width of the surface area C)! [μm].

When the distance between the ends of the light receiving part is L [μm], the relationship between the two is as follows (1), (21 must be satisfied0(h/)Xlo''>17...・・・・・・
・・・・・・・・・・・・(1)((h/I,) X
10") X l 〉12・・・・・・・・・・・・
...(2) This area is shown in FIG. Area I is (1)
This is the area that satisfies the formula and does not cause scratches on the light-receiving surface, and the area ■
represents a region where equation (2) is satisfied and the S/N ratio is not reduced by scattered light.

FIG. 3 shows a comparison of characteristics of image sensors that satisfy each condition. That is, A is an image sensor formed under conditions such that region I and region ■ in FIG. 2 overlap, and B is
is an image sensor formed under the same conditions of only area ■,
C is an image sensor similarly formed under the conditions of only region I, and the respective characteristic curves are shown in the figure. Note that the x mark indicates an image sensor with a conventional structure.

As is clear from the figure, when sensor A satisfies equations (1) and (2), that is, satisfies the conditions of the overlapping area of area ■ and area ■ in Figure 2, the cumulative reading length reaches 10 km or more. However, it is possible to manufacture a highly reliable device with sufficient resolution.

Next, FIG. 4 shows an example of the manufacturing process of an image sensor having the structure of the present invention.

(1) First, a Cr layer is deposited on a glass substrate 1 by a method similar to that of a conventional contact type image sensor, and then patterned by photolithography to form a common electrode 2. next,
After forming an a-8i layer on the Cr layer by plasma CVD, the photoelectric conversion layer 4 is formed by patterning. Further, an ITO film is deposited and patterned on the layer 4 to form a transparent conductive film 3 (see FIG. 4(a))0 (2) Next, an M layer is deposited and patterned to form individual electrodes 5. , the transparent conductive film L''-8i layer 4. The common electrode 2 is etched by mask etching the portion corresponding to the light guiding window 7, thereby forming the light guiding window 7 that reaches the glass substrate 1 (FIG. 4). (see (b)).

(3) For example, M
A structural layer 10 consisting of layers is selectively formed (see FIG. 4(e)).

(4) Finally, after heat treatment to reduce the dark current and stabilize the characteristics of the senna portion, as shown in FIG. 1(b), a layer of silicon oxynitride, for example, with a thickness of 3 to 10 μm is formed as the transparent protective film 6. As a result, a predetermined portion of the sensor section 6 has a surface area B at a position corresponding to the light guide window 7, a surface area B9 at a position corresponding to the light receiving surface on the transparent conductive film 3, and a surface area C on the individual electrode 5. In both cases, a transparent protective film 6 having two steps 9 is formed. In addition.

Since the surface area A of the transparent protective film 60 is in direct contact with the document 8,
Of course, it is formed to be smooth (first
(See figure (a)).

In the manufacturing method of the above embodiment, as a method for forming a step having one surface area C, 1. In this embodiment, a method for providing a structural layer 10 has been described; 9. The present invention is not limited thereto; 2. For example, formation of a transparent protective film 6 rear.

The step 7-2 having the surface area C can also be formed by performing mesa etching while masking the surface areas A, B, and D.

〔Effect of the invention〕

By using the structure of the present invention for the transparent protective film of the light-receiving part of the fully contact image sensor, the influence of dirt such as scratches and dust that easily occurs on the surface of the transparent protective film that comes into contact with the original can be reduced to 1.
It is possible to completely prevent reflected light from being directly applied to the senna section, such as the light receiving surface or the light guiding window surface.

Therefore, the functional characteristics of the sensor section can be dramatically improved as shown in FIG. 3, contributing to the miniaturization and cost reduction of image reading devices.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an image sensor of the present invention. FIG. 2 is an explanatory diagram of the optimum area of the image sensor of the present invention. FIG. 3 is a comparison diagram of the resolution characteristics of each image sensor. FIG. 4 is a manufacturing process diagram of the image sensor of the present invention. FIG. 5 is a structural explanatory diagram of a conventional contact type image sensor. FIG. 6 is an explanatory diagram of the structure of a conventional fully contact type image sensor. 1...Glass substrate. 2...Common electrode. 3...Transparent conductive film. 4...a-3i layer. 5...Individual electrode. 6...Transparent protective film. 7...Light guiding window. 8...Manuscript. 9...LED array. 10... Structural constituent layer. Patent Applicant: TDC Co., Ltd. Representative Patent Attorney Akira Yamatani Figure 2 Reading and Accumulation Director (Ni'm) Figure 5 Figure 6

Claims (2)

[Claims] (1) In a fully contact image sensor having a photoelectric conversion element formed on one side of a substrate, a light guide window penetrating through the element area, and a transparent protective film covering these, an area outside the light receiving part of the transparent protective film An image sensor characterized in that the image sensor is provided with a step having a flat area. (2) The step difference between the surface of the transparent protective film having the flat area and the light receiving surface is h [μm], the distance between the edge of the surface of the transparent protective film and the end on the light receiving part side is l [μm], and the light receiving surface is When the distance between the end parts is L [μm], each area of the element is as follows (1),
The image sensor according to claim 1, which satisfies the condition (2) and further includes a new plane area provided between the light-receiving surface and the transparent protective film. (h/L)×10^2≧l/6・・・・・・・・・・・・
・・・・・・・・・・・・(1) {(h/L)×10^2}×l≧12・・・・・・・・・
・・・・・・・・・(2)