JPH0572111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light receiving element, and particularly to a long thin film light receiving element used in facsimiles, digital copying machines, and other image processing apparatuses.

Conventional light-receiving elements that convert optical signals into electrical signals include photodiodes, phototransistors, and CCD sensors. These light receiving elements are small compared to the image to be read, and have the inconvenience of requiring the use of a reduction optical system.

In view of these points, an elongated thin-film light-receiving element that can read an image in its original size without any reduction has been proposed.

An example of such a thin film photodetector is shown in Figures 1A and 1B.
Shown below. In this figure, A is a perspective view showing the whole, and B is an exploded view. As shown in the figure, the thin film light receiving element 90 has four divided electrodes 92 formed on an insulating substrate 91, and a photoelectric conversion film 93 overlaid on a part of the electrodes.
is formed, and furthermore, another electrode 94 is provided thereon.

As the insulating substrate 91, glass, ceramic, a metal plate with an insulated surface, a silicon wafer, or the like is used. Next, the divided electrodes 92 are made of aluminum, chromium, platinum tin oxide (SnO ₂ ).
A composite film of indium oxide (In ₂ O ₃ ) and indium oxide (In 2 O 3 ) (hereinafter referred to as "ITO film") is used. Further, as the photoelectric conversion film 93, hydrogenated amorphous silicon (including n-type containing only hydrogen and p-type doped with an acceptor), Se-Te-As, CdS, CdSe, CdTe
etc. are used. Furthermore, as the upper electrode 94,
ITO film, SnO ₂ , In ₂ O ₃ , Al, Cr, Au, etc. are used.

Note that, by combining these materials, a joint portion having various characteristics is formed at the interface between the photoelectric conversion film 93 and the electrodes 92 and 94. This characteristic
Whether it is an ohmic type, a blocking type, or a diode type is determined depending on the relationship with the signal readout circuit.

Next, the view from the arrow in Figure 1A is the second one.
FIG. In FIGS. 2 and 3, a light receiving section 95 having a function as a light receiving element is shown.
is a region where the lower divided electrode 92 and the upper electrode 94 intersect, and not all of the photoelectric conversion film 93 effectively functions as a device. Note that at least one of the electrodes 92 and 94 needs to be formed of a transparent material so that light can enter from the outside, and in the case that light is input from the split electrode 92 side, the insulating substrate 91 must also be formed. The material must be translucent.

FIG. 4 shows an example of a readout circuit, in which the divided electrodes 92 are connected to semiconductor switches 82 and 82, respectively.
The electrode 94 is input to the amplifier 83 via the power supply 81 . One of the light receiving sections 95 is the semiconductor switch 82.
The selected signal is amplified by an amplifier 83 and output.

The thin film light receiving element having the above configuration is arranged as shown in FIG. 5 in, for example, a facsimile transmitter. In this figure, a document (not shown) is fed from above the figure by a roller 88 rotating in the direction of arrow F1, and is irradiated with light from a light source 89. This light is reflected by the original as indicated by arrow F2 and enters the thin film light receiving element 87. Of the scanning of the document surface, the sub-scanning in the feed direction is performed mechanically by a motor (not shown), and the main scanning perpendicular to this is performed electrically by using the semiconductor switch shown in Figure 4. This is becoming more and more common.

Therefore, as shown in FIGS. 1 to 3, if the ends of the electrodes 94 are misaligned for some reason, the light receiving section 95, which is a functional part, will be affected.
This results in variations in characteristics. Therefore, there is a problem that the resolution changes between the light receiving sections 95, that is, the resolution becomes non-uniform in the main scanning direction.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thin film light-receiving element which can be sufficiently put to practical use by reducing the resolution of each element non-uniformly.

That is, the present invention achieves the above object by narrowing the width of the lead-out portion of the electrode for each element comprising one light-receiving section, thereby making the area intersecting with other common electrodes uniform. , which attempts to reduce fluctuations in resolution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thin film light receiving element according to the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

6 to 9 are diagrams showing a thin film light receiving element according to the present invention, of which FIG. 6A is an overall perspective view, FIG. 6B is an exploded view, and FIG. 7 is a view of FIG. 6A. FIG. 8 is a plan view as seen from the arrow, and FIG. 8 is a front view as seen from the arrow in FIG. 6A. Furthermore, FIG. 9 is an explanatory diagram showing the overlapping of electrodes.

6 to 9, first, on the substrate 11 made of an insulating material, there is a rectangular electrode portion 22 having a width LA for configuring the light receiving portion 15 which is a functional portion, and other An electrode section 21 for extraction, whose width in the direction perpendicular to the direction in which the end of the electrode (hereinafter referred to as "common electrode") 14 changes is LB.
A plurality of divided electrodes 20 and a substantially U-shaped electrode 12 for leading out other electrodes are formed as shown in the figure. Among these, on the divided electrode 20,
A photoelectric conversion film 13 is formed to sufficiently cover at least the electrode section 20 , and a common electrode 14 is further provided to cover this photoelectric conversion film 13 and have an end thereof overlapped with the electrode 12 . The degree of overlap between this common electrode 14 and the divided electrodes 20 is the ninth
As shown in the figure, at least the electrode portion 22 is sufficiently covered by the common electrode 14.

Note that the materials used for the above-mentioned components are the same as conventional ones.

Next, the shape of the divided electrode 20 will be explained.
As shown in FIG. 9, the common electrode 14 and the divided electrode 2
0, as described above, completely intersect and overlap in the electrode portion 22, and this entire portion functions as the light receiving portion 15. On the other hand, the electrode section 21 and the common electrode 14 only partially intersect and overlap near the electrode section 22.
This overlapping portion (hereinafter referred to as "intersection area") has a function as a light receiving section. The size of the overlap between the common electrode 14 and the electrode part 21 is determined by the ninth
As shown in the figure, if LC is assumed (LC≠0), the intersection area SB is SB=LC・LB...(1). If SA is the area of the electrode section 22, that is, the area of the light receiving section 15, then the amount of extra signal GS due to only this section is expressed as GS=SB/SA (2). The practically acceptable value of GS is 0.1 or more from the viewpoint of ease of signal multi-level conversion, design of the signal processing circuit, and cost, so that the signal from SB is 10% or less of the signal from SA. It turns out that something is desirable. In other words, GS≦0.1...(3) Generally, when trying to fabricate a thin film photodetector with a length (main scanning direction) of 100 mm or more,
Approximately ±10μ as long as normal patterning methods are used.
It is said that an error of about m is generated. Therefore, the size of the overlap LC is approximately 20 μm at maximum. Therefore, in a thin film photodetector having a resolution of about 100 μm LA and 10000 μm ² , that is, about 8 bits/mm, in order to make GS less than 0.1,
From the above formulas (1) to (3), LB≦50 μm. That is, with respect to the width LA of the electrode part 22, half the width LB
If the electrode part 21 is formed as follows, even if GS≦0.1 and unevenness occurs in the end position of the common electrode 14,
Changes or variations in the resolution of the light receiving section can be reduced to a practically negligible extent.

For reference, a numerical example of a device prototyped in connection with this invention is shown. First of all, the first prototype example is 200℃
After chromium is deposited to a thickness of 2000 Å on a glass substrate by electron beam evaporation, a pattern of divided electrodes 20 as shown in FIG. 6 is formed by ordinary photolithography. Width LA is 100μm, LB is
It is 25 μm. Further, the electrode portion 22 has a square shape. Next, a hydrogenated amorphous silicon film with a thickness of 1 μm is formed as a photoelectric conversion film 13 on this electrode by plasma CVD. Furthermore, a transparent electrode, ie, a light incident electrode, is formed on this layer through a suitable mask to a thickness of 100 Å. At this time, LC is
30 to 40μm within the same element, and 10μm between elements
The thickness was between 40 μm and 40 μm.

In the thin film photodetector fabricated as described above,
When the output signal of each element was measured, it was found that it was ±2% within an element and ±5% between elements, which sufficiently satisfied the above equation (3).

Next, the second prototype example is a 10 μm thick film on ceramic.
Chromium was deposited on a glass substrate heated to 250°C using electron beam evaporation.
Deposit to a thickness of 3000 Å. Similarly, a pattern such as the divided electrode 20 shown in FIG. 6 etc. is processed. width
LA is 80 μm and width LB is 20 μm. Note that the photoelectric conversion film 13 and the common electrode 14 are the same as in the first prototype example.

In this example, LC varies from 20 to 20 within the same device.
The distance between the elements was 30 μm, and the distance between the elements was 10 to 40 μm. Similarly, when the output signal of each element was measured, it was ±3% within an element and ±6% between elements.

In addition, in the above embodiment or prototype example,
Although the electrode interposed between the substrate 11 and the photoelectric conversion film 13 is a divided electrode, this electrode may be used as a common electrode for each element, and the common electrode 14 may be used as a divided electrode for each element.

As explained above, according to the thin film light receiving element according to the present invention, by narrowing the width of the lead-out portion of the divided electrode of each element or each light receiving part, variations in the cross area between the electrodes can be reduced. As a result, the uniformity of the characteristics of each element can be improved, and the non-uniformity of resolution can be reduced to a practically negligible level, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1A is a perspective view showing a conventional thin film light receiving element;
Figure B is an exploded view, Figure 2 is a plan view, and Figure 3 is a front view. FIG. 4 is a circuit diagram showing an example of the drive circuit, and FIG. 5 is a perspective view showing the state of use. 6th
In the drawings, A is a perspective view showing a thin film light receiving element according to the present invention, B is an exploded view, FIG. 7 is a plan view, FIG. 8 is a front view, and FIG. 9 is an explanatory view showing overlapping of electrodes. . 11... common electrode, 15... light receiving section, 20...
Divided electrode, 21... Extraction portion, 22... Light receiving portion forming portion, TA, TB... Width of electrode.

Claims (1)

[Claims] 1. A thin film light-receiving element in which a plurality of divided electrodes, a photoconductive layer, and a transparent common electrode are sequentially deposited on an insulating substrate, wherein the divided electrodes are made of a conductive material. a light-receiving portion forming portion; and a draw-out portion made of the same material and extending from the light-receiving portion-forming portion, the width of the draw-out portion being narrower than the width of the light-receiving portion forming portion. A thin film light receiving element, wherein the photoconductive layer and the common electrode are deposited so that both the light receiving part forming part and a part of the extraction part are covered by the photoconductive layer and the common electrode.