JPH01248675A - Image sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an image sensor, the speed of optical response of which is increased and which has excellent photoelectric conversion characteristics, by forming a photoconductive film of InPS. CONSTITUTION:A transparent conductive film 6 with a light-guide window 10, a common electrode 4, a photoconductive film 2 and a discrete electrode 5 are formed successively on a substrate 3 in an image sensor 1, and a light source 7 and an erect magnification lens array 8 are mounted on the reverse side of the photoconductive film 2 in the substrate 3. The photoconductive film 2 is formed from InPxS1-x (0.15<=x<=0.70). Since the reproducibility of film quantity is improved and high mobility is acquired in the photoconductive film 2, the film 2 is shaped through an organometallic CVD method. Accordingly, the speed of response is increased, and photoelectric conversion characteristics are enhanced.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an image sensor using a photoconductive film.

<Prior Art> Image sensors using photoconductive films are used in facsimiles and the like.

Conventionally, materials for photoconductive films include amorphous silicon and Cd5, which can be made large in area to almost the same size as the original.
-CdSe etc. are used, and these photoconductive films are
It is used in close-contact image sensors such as full-contact image sensors or image sensors that use erect equal-magnification lenses.

However, these photoconductive film materials have the following problems.

Amorphous silicon light J'! The membrane is PIP.

It has a multilayer structure like NIN, NI, etc., so it has low biomagnetic properties. Further, since the film is formed by plasma CVD, the cost is high, and it is difficult to uniformly form a film on many large substrates (A4, B4 size, etc.). Furthermore, the plasma CVD method tends to produce flakes, making it difficult to obtain a defect-free film.

Furthermore, the film tends to become unstable due to surface adsorption of O, H, O, etc.

The Cd5-CdSe photoconductive film has a photoresponse speed of 8 to 10 m.
Because it is slow at 5ec, it is difficult to read high-speed facsimiles and color documents. Furthermore, it is difficult to obtain a film with constant conversion efficiency, resulting in poor yield.

In order to solve the above-mentioned problems that occur when amorphous silicon, Cd5-CdSe, etc. are used for a photoconductive film, the present inventors developed an image having a photoconductive film formed from (TiBr), (Tit)l-X, etc. A sensor has been proposed (Japanese Patent Application No. 1983-292839).

<Problems to be Solved by the Invention> The photoconductive film formed from (Tier) Conductive films are required to have even higher optical response speeds. Further, in order to obtain high reproducibility for multi-gradation originals, even better charge conversion characteristics are required.

An object of the present invention is to provide an image sensor that has a fast optical response speed and good photoelectric conversion characteristics.

Means to solve problems〉 Such objects are achieved by the invention described below.

That is, the present invention provides an image sensor having a photoconductive film whose conductivity changes depending on the incidence of light, wherein the photoconductive film has a conductivity of I n P +c S 1-X (where 0.
15≦x≦0.70).

Further, the present invention is a method for manufacturing an image sensor, in which a photoconductive film is formed by an organometallic CVD method when manufacturing such an image sensor.

Hereinafter, a specific configuration of the present invention will be explained in detail.

A preferred embodiment of the image sensor of the present invention is shown in FIGS. 1 and 2.

The image sensor 1 of the present invention shown in FIGS. 1 and 2 includes a transparent conductive film 6 having a light guiding window 10 on a substrate 3;
It has a common electrode 4, a photoconductive film 2 and an individual electrode 5 in this order,
A light source and an erect equal-magnification lens array 8 are provided on the opposite side of the photoconductive film 2 of the substrate 3.

The image sensor 1 guides light emitted from a light source 7 and reflected on the surface of a document 9 to a photoconductive film 2 in a light guide window 10 using a royal equal-magnification lens array 8 to measure the conductivity of the photoconductive film 2. The light guide windows 10 facing each other with the photoconductive film 2 in between
It reads changes in the current generated between the transparent conductive film 6 and the individual electrodes 5 inside, and converts the intensity of reflectance due to the density distribution on the surface of the document 9 into the intensity of the current.

In the present invention, the photoconductive film 2 is formed from InP, S, and □. However, 0.15≦x≦0.7.

When X is less than the above range, the degree of mobility decreases and the photoresponse speed decreases.

When X exceeds the above range, the photosensitivity shifts to the long wavelength side, resulting in a decrease in sensitivity to green light, particularly to 555 nm light.

Note that the photoconductive film 2 is preferably formed of only In%P and S, but it may also contain Ti2, Zn, S as impurities.
t% Sn, Cd, etc. may be contained in an amount of 5 wt% or less of the total.

Such a photoconductive film is usually a polycrystalline film of InP, S, -0.

Further, the thickness of the photoconductive film 2 is generally preferably about 0.1 to 5 μm, particularly about 0.5 to 1.0 μm.

The photoconductive film 2 of the image sensor 1 of the present invention has good reproducibility of film quality and high mobility;
Preferably, the film is formed by an organometallic CVD method.

The organometallic CVD method is a chemical vapor deposition (CVD) method that uses an organometallic compound or an organometallic complex as a reaction gas, and a thin film of a desired compound is formed by introducing a raw material gas onto a substrate heated to a predetermined temperature. It is a film.

In the present invention, it is preferable to use trialkylindium such as triethyl indium as the source gas for In, phosphine or the like as the source gas for P, and hydrogen sulfide or the like as the source gas for S.

The flow rate of each of these raw material gases is preferably about 0.1 to 1103 CC for In, P, and S, respectively.

Further, it is preferable to use H2 or the like as the carrier gas, and the flow rate thereof is preferably about 100 to 2000 SCCM. And the temperature of the board is 400~7
It is preferable that the operating pressure is approximately 0.1 to ITorr. Note that the substrates on which the photoconductive film is formed in this case include a substrate 3, a common electrode 4, a transparent conductive film 6, etc., which will be described later.

Note that the photoconductive film of the image sensor of the present invention can be formed not only by the above-mentioned organometallic CVD method but also by sputtering method, vapor deposition method, screen printing method, etc.

The substrate 3 is not particularly limited as long as it has a high transmittance for light emitted from the light source 7, but it is usually formed of plate glass, quartz, various resins, or the like.

The thickness of the substrate 3 is usually about 0.5 to 3 mm.

The common electrode 4 has a light guide window 10 for guiding reflected light from the original 9 to the individual electrodes 5, and is made of an opaque material to prevent stray light and obtain high resolution, and has the function of a light shielding plate.

The dimensions of the light guide window 10 correspond to the dimensions of the individual electrodes 5, but
It is usually about 50x50 μm to 200x200 μm.

Note that a transparent conductive film, which will be described later, may be used as a common electrode, and a light shielding plate having the above function may be provided separately. In this case, the material of the light shielding plate may be a metal such as Cr%Mo or a non-conductive substance such as St.

Further, the material of the common electrode 4 includes Cu, Cr%Ni,
Pt or the like may be used.

The arrangement density of the individual electrodes 5 corresponds to the number of pixels, and is usually 6 to 6.
The number is about 16 pieces/mm.

As the material of the individual electrodes 5, Cu, Ni, Cr, Pt, etc. may be used.

A predetermined voltage is applied between the common electrode 4 and the individual electrodes 5, and a current flows between the two electrodes in accordance with the change in the conductivity of the photoconductive film 2.

The transparent conductive film 6 is provided in contact with the common electrode 4 and faces the individual electrodes 5 through the light-receiving portion of the photoconductive film 2. The current mainly flows between the transparent conductive film 6 and the individual electrodes 5.

The material of the transparent conductive film 6 is ITO.

NESA etc. may be used.

As the light source 7, it is preferable to use an LED because it saves space and consumes low current.

In the present invention, since InPXS+-- (however, 0.15≦x≦0.7) is used as the material of the photoconductive film 2, it is preferable to use a green-emitting LED from the viewpoint of photosensitivity, and in particular, it is preferable to use a green-emitting LED. It is preferable to use a green light-emitting LED with a wavelength of about 555 nm.

A known one may be used as the royal equal-magnification lens array 8,
Moreover, instead of this, a fiber lens array or the like may be used.

3 and 4 show other preferred embodiments of the image sensor of the present invention.

The image sensor 1 shown in these figures has a photoconductive film 2 on a substrate 3, and a common electrode 4 with this photoconductive film 2 in between.
and individual electrodes 5 are provided on the substrate 3.

The structure and operation of each member in this case are substantially the same as those described above in the explanation of FIGS. 1 and 2.

FIGS. 5 and 6 show still other preferred embodiments of the image sensor of the present invention.

The image sensor 1 shown in these figures is of a so-called complete contact type, and does not use an optical system such as an erecting equal-magnification lens array.

The image sensor 1 has a light source 7 on the upper side of the substrate 3, and has a common electrode 4, a photoconductive film 2, a transparent conductive film 6, and an individual electrode 5 in this order on the lower surface of the substrate 3, and further has a lower surface of the individual electrode 5. It has a transparent protective layer 11 on it.

The common electrode 4, the photoconductive film 2, and the transparent conductive film 6 are provided with a light guiding window 10 for guiding the light emitted from the light source to the original 9.

The light emitted from the light source 7 passes through the light guide window 10 and reaches the document 9.
The light is reflected from the surface and reaches the photoconductive film 2. After this, the density distribution on the surface of the document 9 is converted into the strength of the current in the same manner as in the embodiment described above.

In this embodiment, the transparent protective layer 11 is provided to protect each member from contact with the original 9, and its thickness is 3 to 3.
The thickness is preferably about 15 μm, and its materials include 5in2, Al2O3, Si3N4.5iCXO,
N,,SiB,O,Nzs 5iBxO,-,,S i
A I HOl-x, T a x Os, etc. may be used.

<Effects of the Invention> The image sensor of the present invention has a photoconductive film made of InP, lS, and -x.

Therefore, the image sensor of the present invention has a fast response speed,
It can be suitably used for high-speed facsimile and the like. Furthermore, since the photoelectric conversion characteristics are good, good reproducibility can be obtained for multi-tone originals.

The image sensor of the present invention having such an effect can be suitably used in combination with a green-emitting LED, especially because of its photosensitivity.

The present inventors conducted the following experiment in order to confirm the effects of the present invention.

[Experimental Example 1] A photoconductive film with a thickness of 0.7 μm was formed on a 50×250 mm quartz substrate by organometallic CVD. The composition is I
It was n Po, s So, s.

The raw material gas and its flow rate are as follows.

In (C2)(5)3 13CCMP)I,
0.5SCCMH2S
Note that the carrier gas was H2, and its flow rate was 500 SCCM. Further, the operating pressure was 0.4 Torr, and the substrate temperature was 550°C.

This photoconductive film was sandwiched between opposing Cu electrodes as shown in FIG. 4 to form a photoelectric conversion element, and the relative sensitivity to light wavelength was measured.

Note that the Cu electrode was formed to a thickness of 1.5 μm by vapor deposition, and was formed into a predetermined pattern by wet etching.
Etchant contains 20%) 12SO4, 10%Cry
3 aqueous solution was used.

Further, the etching rate was 2 μm/min.

The results are shown in FIG.

From the results shown in FIG. 7, the photoconductive film made of InPo, sSO, and S has maximum sensitivity in the green region, and the green light emitting LE
It can be seen that the present invention can be suitably applied to an image sensor using D.

[Experimental Example 2] Using the photoelectric conversion element produced in Experimental Example 1, a pure green LED with a wavelength of 555 nm was used as a light source, and photocurrent with respect to light intensity was measured.

Note that the applied voltage was 10V.

The results are shown in FIG.

As shown in FIG. 8, I n Pa, s So, s
It is clear that the photoconductive film made of the above has a photocurrent that increases almost linearly with respect to the light intensity, and can be suitably used for image sensors.

[Experimental Example 3] Using a GaP-LED with a coloring wavelength of 555 nm, I n
Relative sensitivity and mobility were measured by varying X in PXS1-X.

The results are shown in Figure 9. From the results shown in FIG. 9, the photoconductive film used in the image sensor of the present invention (0,15≦x
≦0.7), it is found that the sensitivity is high and the mobility is high, that is, the photoresponse speed is fast.

[Experimental Example 4] Using the above photoelectric conversion element, response speed (rise and fall) to light irradiation was measured.

A GaP-LED with an emission wavelength of 555 nm was used as a light source.

The rise time was 10 tlsec or less, and the fall time was 20 μsec or less.

As a result, it can be seen that the photoconductive film used in the image sensor of the present invention has a fast optical response speed and can be suitably applied to high-speed facsimiles and the like.

[Experimental Example 5] According to Experimental Example 1 above, an image sensor having the configuration shown in FIG. 4 was manufactured and its characteristics were measured.

The details and characteristics of this image sensor are shown in Table 1 below.

Table 1 Number of elements 1728 pixels Element density 8 pixels/mm Photosensitivity O, FμA/1x Spectral sensitivity
555nm SN ratio 10:1 or more Inter-element variation ±10% or less Photoresponse speed 0.8m5ec or less In Table 1 above, the photosensitivity is 10:1 or more and green light emitting L is used as a light source at an applied voltage of 10V.
This is when ED (wavelength: 555 nm) is used, and the spectral sensitivity indicates the peak wavelength. In addition, the S/N ratio is a binary value of black and white, and the light response speed is at a peak illuminance of 100.
This is from the time of Lux.

From the results shown in Table 1, the image sensor of the present invention has
It can be seen that the characteristics are good.

[Brief explanation of the drawing]

1 and 3 are plan views of preferred embodiments of the image sensor of the present invention, and FIGS. 2 and 4 are plan views of the image sensor shown in FIGS. 1 and 3, respectively.
11 and IV-IV. FIG. 5 is a longitudinal sectional view of another embodiment of the image sensor of the present invention, and FIG. 6 is a bottom view of the image sensor shown in FIG. 5. FIG. 7 is a graph showing the relationship between light wavelength and relative sensitivity, FIG. 8 is a graph showing the relationship between light intensity and current amount,
FIG. 9 is a graph showing the relationship between the composition of the photoconductive film and the relative sensitivity and mobility. Explanation of symbols 1... Image sensor, 2... Photoconductive film, 3... Substrate, 4 Common electrode, 5... Individual electrode, 6... Transparent conductive film, 7... Light source, 8 ...Optical system, 9. Original document, 10. Light guiding window, 11. Transparent protective layer patent applicant TDC Co., Ltd. FIG.
1 FIG, 2 FIG, 3 FIG, 4 FIG, 6 FIG, 7 /- Liquid surface (nm) FIG, 8 Light elasticity (l×) Eye Nu dimension Shoulder height K<yo-) Moving layer (cm ″/V'sec)

Claims (3)

[Claims] (1) An image sensor having a photoconductive film whose conductivity changes with the incidence of light, the photoconductive film being formed from InP_xS_1_-_x (0.15≦x≦0.70) sensor. (2) The image sensor according to claim 1, wherein the light is emitted from a green LED. (3) A method for manufacturing an image sensor, in which a photoconductive film is formed by an organometallic CVD method when manufacturing the image sensor according to claim 1 or 2.