JPH0430580A - Manufacture of photosensor - Google Patents

Abstract

PURPOSE:To enable large-scale cost-down by forming a thin film on an insulating substrate by coating then drying a paste obtained by additionally mixing a small amount of active agent to a mixture of CdS, CdSe or CdS and CdSe and adhering and diffusing a small amount of Cu or Ag to a semiconductor thin film after formation of a semiconductor thin film. CONSTITUTION:A film is formed on an insulating substrate by coating and drying a paste obtained by adding a small amount of active agent, for example, CdC2 to a mixture of CdS, CdSe or CdS and CdSe and then mixing such a mixture with polyethylene glycol into the predetermined shape by the screen printing method, etc. This film is baked at the temperature as high as about 500 to 800 deg.C in order to remove polyethylene glycol and to form a photoelectrically activated semiconductor film. Thickness after the baking is generally set to 5 to 20mum. Thereafter, a small amount of Cu or Ag is adhered to the semiconductor film, it is then subjected to the heat processing at 250 to 550 deg.C for 15 min or longer under the neutral atmosphere or the atmosphere including a small amount of oxygen for the purpose of diffusion into the film. Thereafter, counter electrode is formed by evaporated film of NiCr/Au and finally photosensor is formed by forming a protection film of polyimide.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing an optical sensor used in an image input section of office automation equipment such as a facsimile machine.

Conventional Technology Recently, close-contact line sensors have come to be widely used in the image input section of various office automation equipment such as facsimile machines.9 Optical sensors using CdS-based semiconductor thin films have been widely used for these close-contact line sensors. 4 This optical sensor is mainly made of CdS, CdSe or solid solution Cd5-CdSe on an insulating substrate such as glass, with a small amount of Cu.
A semiconductor thin film doped with carbon dioxide is formed by vapor deposition, and then exposed to Cdc12 vapor at high temperatures, heat-treated, photoelectrically activated, and then a counter electrode is formed (furthermore, a protective film is formed). Also, CdS, C
An optical sensor mainly composed of dSe or CdS-CdSe is characterized by a large photocurrent, and for this reason, it is easy to design peripheral circuits in a contact type line sensor using this sensor. - Person This optical sensor has a drawback that the response speed of the photocurrent Jp to light irradiation is slow. Sunawa L
The rise time τr and fall time τd of Jp are 2 to 3 m5eC and long t,% at the sensor surface intensity of 1001ux during normal use. The reading scanning speed of the line sensor is limited to 4 to 5 ms/line.

In the inventions described in JP-A No. 63-300558 and JP-A No. 1-110778, etc. (after activation heat treatment of a CdS-based semiconductor thin film formed on a companion substrate, either before or after electrode formation) C as a sensitizing impurity in
Problems to be Solved by the Invention The present invention does not realize a high-speed optical sensor by adhering and diffusing U or Ag onto the surface.The high-speed optical sensor obtained in this manner requires many processes to manufacture. (1) CdS thin film vapor deposition resistor For sensor pattern formation (2) Resist coating (3
) Exposure of sensor pattern (4) Development processing (5) Dry etching - (6) Resist removal Furthermore, for example, Cu
or (7) adhesion process for Ag adhesion and diffusion.
(8) Diffusion heat treatment and (9) Resist coating for electrode formation! (10) Exposure of electrode pattern (11) Development treatment (12) Electrode metal vapor deposition, (13) Resist removal, and finally (14) Resist coating &
(15) Although the optical sensor is completed by heat treatment, the fact that many processes are required for manufacturing is complicated and inconvenient in terms of production.4 The present invention takes into consideration the problems of the conventional technology. It is an object of the present invention to provide a method for manufacturing an optical sensor that can significantly reduce the manufacturing process compared to the prior invention without impairing the features of large Jp and fast optical response speed. Means: A paste made of CdS, CdSe, or a mixture of C, dS and CdSe mixed with a small amount of activator is applied and dried to form a thin film on an insulating substrate, and the thin film is heated at a high temperature to photoelectrically activate the paste. After forming the activated semiconductor thin film, a small amount of Cu or Ag is attached and diffused into the semiconductor thin film, a counter electrode is provided, and a protective film is further formed.

Alternatively, a paste of CdS, CdSe, or a mixture of CdS and CdSe mixed with a small amount of activator is applied onto an insulating substrate and then dried to form a thin film.
After heating the thin film at a high temperature to form a photoelectrically activated semiconductor thin film, a counter electrode is provided.After that, a small amount of Cu or Ag is attached and diffused to the semiconductor thin film, and a protective film is further formed. According to the method of the invention, it is possible to significantly reduce the manufacturing process without impairing the features of the CCd5-based photoconductive sensor, such as a large photocurrent value and fast photoresponse speed. To form a pattern, (1-) Form a sensor pattern by applying a CdS-based semiconductor material paste (screen printing). (2”) Equivalent to the processes in (1) to (6) above with only two processes including baking treatment. Moreover, there is no need for an expensive no-turn exposure device, etc. Therefore, it is possible to significantly reduce costs.

Example The present invention will be explained in detail below.

A paste made by adding a small amount of activator such as CdCl2 to CdS, CdSe or a mixture of CdS and CdSe and mixing it with polyethylene glycol is applied onto an insulating substrate such as glass into a predetermined shape using a screen printing method and then dried. Forms a film. 500~800
A firing heat treatment is carried out at a high temperature of about 10°C to remove polyethylene glycol and other substances and form a photoelectrically activated semiconductor film.The film thickness after firing is usually 5 to 20 μm.After that, a small amount of Cu or Ag is 250 to 5 in a neutral or a small amount of oxygen-containing atmosphere to be attached to the semiconductor thin film.
Heat treatment is performed at 50° C. for 1511 inches or more to diffuse into the film. After that, a counter electrode is formed with a vapor deposited film of NiCr/Au, etc., and finally a protective film such as polyimide is formed to complete the optical sensor. After that, a small amount of Cu or Ag is deposited on the semiconductor thin film and heat-treated for 15 ml or more at 250 to 400° C. in a neutral atmosphere or an atmosphere containing a small amount of oxygen to diffuse into the film. You may also use a method in which a protective film such as polyimide is formed at the end.
It is preferable in terms of characteristics to use a film that does not contain g.Cu or Ag should be deposited by vacuum evaporation or chemical adhesion.The amount is 0.005% of the base semiconductor.
If the amount of sensitizing impurities is less than 0.005 mol%, the high speed will be insufficient.If the amount of sensitizing impurities is less than 0.005 mol%, the current will be small. Next, a specific example will be explained below.
x 1.2 mm3) with a thickness of 8 μm Cd Ss, eS
es, 4 films are formed, ie 'L Cd80.6
Mono I/, Cd5eO14 mo, CdCl20.0
Dissolve 2 moles in polyethylene glycol, mix it, and print it on the substrate in the form of a strip in the main scanning direction by screen printing.
Apply this strip-like film to 600°C (approximately IH).
After being heat-treated and photoelectrically activated to form a photoconductor film,
0.0 for the parent Cd Ss, eS ei, a film.
01 to 0.1 mol% of Cu is vapor deposited and diffused. The substrate temperature during Cu vapor deposition is 150°C, and the diffusion process is performed in N2 gas.
After that, a counter electrode (NiCr/Au vapor deposited film) was formed on the band-shaped film, that is, a common electrode and individual electrodes were arranged in a 1728-bit arrangement at a rate of 8 bits/ram.

The width of the opposing electrode is 90 μm, and the gap is 60 μm.

Finally, a polyimide protective film is formed to complete the line sensor.Table 1 summarizes the results of investigating the characteristics of one bit of these line sensors.

The characteristics are that the applied voltage is 10 V DC, and the light irradiation is green LED light (570 nm, 1001 ux) at I Hz (0,5
The response time measured by flashing at
The time it takes for p to rise from 0 to 50% of the saturation value is defined as the rise time τr, and the time it takes for Jp to fall from the saturation value to 50% of the saturation value as the fall time τd. 63-300558) The characteristics of the optical sensor are also described.

(Left below) Table 1 Like this Photocurrent is a few μA as in conventional high-speed optical sensors
The rise time τr of the photocurrent is apparently large, and the photoresponse speed is also fast. Becomes bias light,
Although the effective rise time τr of this light is constantly irradiated to the sensor is extremely small, its effect is shown in the rightmost column of Table 1. Other characteristics due to this level of bias light irradiation (
There is almost no change in Cd55. Excellent properties can be obtained by depositing and diffusing Cu after forming the eSe-14 film. A similar effect can be obtained even if the adhesion and diffusion of Cu is performed after electrode formation. CdS@.

The same effect can be obtained by using CdS, CdSe, or a solid solution Cd5-CdSe with a different composition ratio instead of 6SeL4.Also, the same effect can be obtained by using Ag instead of Cu.

Effects of the Invention According to the present invention, it is possible to realize an optical sensor with a significantly high photoresponse speed while maintaining a large photocurrent value with fewer manufacturing processes than in the past. This also makes it possible to significantly reduce costs.

Claims (4)

[Claims] (1) CdS, CdSe or Cd on an insulating substrate
A paste made by adding and mixing a small amount of activator to a mixture of S and CdSe is coated and dried to form a thin film, and the thin film is heated at high temperature to form a photoelectrically activated semiconductor thin film. A method for manufacturing an optical sensor, comprising the steps of adhering and diffusing Cu or Ag to the semiconductor thin film, providing a counter electrode, and further forming a protective film. (2) CdS whose base is the amount of deposited Cu or Ag;
0.005 of CdSe or solid solution CdS-CdSe
~0.1 mol%, and the heat treatment temperature during diffusion is 250 ~
The method for manufacturing an optical sensor according to claim 1, wherein the temperature is 550°C. (3) CdS, CdSe or CdS on an insulating substrate
A paste prepared by adding and mixing a small amount of an activator to a mixture of . Thereafter, a small amount of Cu or Ag is attached and diffused into the semiconductor thin film, and a protective film is further formed. (4) CdS whose base is the amount of deposited Cu or Ag;
CdSe or solid solution CdS-CdSe (7) 0.0
05 to 0.1 mol%, and the heat treatment temperature during diffusion is 25%.
4. The method of manufacturing an optical sensor according to claim 3, wherein the temperature is 0 to 400C.