JPS6259894B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an image reading element using a photoconductive film having cadmium selenide (CdSe) or CdSe as a base material as a sensor material.

An image reading device using a photoconductive film as a sensor is generally a device that converts an image into an electrical signal by changing the resistance of the photoconductive film in accordance with the image, that is, optical information. The sensor element section of this device has a plurality of opposing electrode pairs arranged in accordance with a desired resolution,
It is formed by connecting opposing electrodes with a photoconductive film. An example of the circuit configuration is shown in FIG. In the same figure, 1 is a DC power supply, 2 is a load resistance, and 31 to
3n is a photoconductive film sensor array, and 41 to 4n are switching element arrays. Light reflected from the original is introduced onto the photoconductive film sensor arrays 31 to 3n through a self-cleaning lens, optical fiber, etc., and the switches 41 to 4n are sequentially switched to read the resistance of the photoconductive film, thereby transmitting optical information. It can be read out in series. As can be seen from FIG. 1, this configuration example shows an example in which one side of a plurality of opposing electrode pairs is connected in common.

FIG. 2 is an example of a pattern configuration around the sensor element having the configuration shown in FIG. Reference numeral 5 designates a common electrode in which one side of a plurality of opposing electrode pairs is commonly connected, and reference numerals 61 to 6n designate individual electrodes that individually oppose the common electrode 5. That is, the common electrode 5 and the individual electrodes 61 to 6n form a plurality of opposing electrode pairs. All of these patterns are formed by ordinary thin film processes such as vapor deposition, sputtering, and photoetching.

CdSe or CdSe-based compounds, such as CdSe _1-x Tex and CdSe _1-x Sx, have high photoconductivity as a physical property and can be easily formed into thin films by vapor deposition or sputtering, so they are suitable for use in image reading devices. Suitable as a photoconductive film.

However, CdSe or CdSe-based compound thin films formed by vapor deposition or sputtering have poor crystallinity and must be activated by heat treatment at 500 to 600°C in order to obtain sufficient characteristics as image reading elements. is necessary. Furthermore, CdSe or a compound thin film based on CdSe has poor chemical resistance and has the disadvantage of being corroded by most etching solutions for etching metal electrodes.

When forming an image reading element using CdSe or a compound thin film containing CdSe as a base material as a photoconductive film, the photoconductive film must be subjected to high-temperature treatment as described above. However, regardless of whether the metal thin film normally used as an electrode material has a single-layer or multilayer structure, oxidation, solid phase diffusion, peeling, etc. occur at the photoconductive film processing temperature (500 to 600°C), making it difficult to use as an electrode material. Functions and properties cannot be maintained, and at the same time solid phase reactions such as diffusion occur at the interface with the photoconductive film, making it impossible to maintain the properties of the photoconductive film. Therefore, when a metal thin film is used as the counter electrode material, a photoconductive film made of CdSe or a compound thin film having CdSe as a base material must first be formed and heat-treated, and then a counter electrode made of the metal thin film must be formed. X- of the element section in such a configuration
An example of the X' cross section is shown in Figure 3. Here, 3 is a photoconductive film made of a thin film of CdSe or a compound having CdSe as a base material, 5 is a common electrode, and 6 is an individual electrode.

Normally, the gap between the common electrode 5 and the individual electrodes 6 is required to be about several tens to 100 μm in order to increase the resolution of image reading. This value is in a range that cannot be controlled by mask evaporation using a metal mask or the like, and photolithographic etching or lift-off must be used. However, as mentioned above, CdSe or CdSe-based compound thin films have extremely poor chemical resistance and cannot be etched against any of the metals normally used as electrode materials, such as Al, Au, Cu, Ni, Mo, W, and Cr. It is also corroded by liquids. For these reasons, there are many restrictions on the selection of electrode materials. As for the electrode material, it is necessary to have a degree of freedom in selecting a material that satisfies each requirement, such as connection with an external circuit or bonding of a switching element.

On the other hand, in the lift-off method, a metal layer is formed on the photoresist, and then the resist is stripped off. Due to constraints in the resist stripping process, the metal layer is formed at a temperature below the resist hardening temperature (~150℃). A film must be formed, and it is difficult to obtain sufficient adhesion to the substrate, resulting in a decrease in yield and reliability.

An object of the present invention is to provide a method for manufacturing an image reading element that is free from such limitations on electrode material selection and from the risk of lowering yield and reliability.

In other words, transparent conductive films such as tin oxide (SnO ₂ ) and indium tin oxide (ITO) are sufficiently stable even at the heat treatment temperature of photoconductive films (500 to 600°C).
Moreover, the photoconductive properties of CdSe or a compound thin film having CdSe as a base material are not deteriorated. Therefore, such a structure may be adopted that these transparent conductive films are used as the counter electrode material, and that metal electrodes are wired in areas where connection with external electrodes or bonding with switching elements is required.

FIG. 4 shows a cross section of the element portion according to the present invention.
An example of the configuration of X′ is shown below. 3 is a photoconductive film made of CdSe or CdSe as a base material; 5 and 6 are common electrodes and individual electrodes formed of metal thin films; and 7 and 8 are common electrodes and individual electrodes formed of transparent conductive films.

The present invention will be explained below with reference to the embodiments shown in FIGS. 5a to 5d.

First, a 0.3% SnO ₂ film was deposited on a glass substrate by vapor deposition.
μm is formed, dry etching is performed using Freon 12 gas, and the common electrode 7 and individual electrodes 81 to 81 are formed.
A pattern of 8n is obtained (Fig. 5a). Next, a CdSe film 3 of approximately 1 μm thickness was formed on the electrode by vapor deposition, and heat treatment was performed at 600°C for 15 minutes in a small amount of oxygen atmosphere.
The photoconductive properties of the CdSe film are improved (Figure 5b).
At this time, the SnO ₂ film shows no deterioration even after heat treatment at 600° C., and also does not adversely affect the photoconductive properties of the CdSe film 3.

Next, the CdSe film 3 is etched to form sensor element parts 31 to 3n (FIG. 5c). A mixed solution of nitric acid and phosphoric acid may be used as the etching solution. Note that either of the heat treatment and etching steps for the CdSe film 3 may be performed first.

Thereafter, the common electrode 7 and the individual electrodes 81 to 8n, which are not deposited on the sensor element parts 31 to 3n formed by the CdSe film 3 and are formed by a transparent conductive film,
A metal electrode material, e.g. Cr0.1μm, Au1μm
are sequentially deposited and laminated, and etched in a desired pattern to form electrodes 5, 61 to 6n (FIG. 5d). Here, it is important that the metal electrode material not be deposited on the CdSe film 3. That is,
This is because since there is no metal on the CdSe film 3, the CdSe film 3 can be protected by the photoresist film when etching the metal layer to form an electrode.

By adopting the manufacturing method described above, in the present invention, restrictions on the selection of electrode materials are greatly relaxed,
It becomes possible to freely select a metal material having the necessary properties.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a sensor element section of a conventional image reading device, Fig. 2 is a pattern configuration diagram of Fig. 1, and Fig. 3 is a sectional view taken along the line X-X' in Fig. 2. , FIG. 4 is a sectional view of the sensor element portion of the present invention shown corresponding to FIG. 3, and FIGS. 5 a to 5 d are plan views of the manufacturing process shown for explaining the embodiment of the present invention. . 3... Photoconductive film, 5... Common electrode formed of a metal thin film, 6... Individual electrode formed of a metal thin film, 7... Common electrode formed of a transparent conductive film, 8
...Individual electrodes made of transparent conductive film.

Claims (1)

[Claims] 1. The first step is to form a plurality of opposing electrode pairs made of transparent conductive films on an insulating substrate, and cadmium selenide (CdSe) is formed to connect the opposing electrodes.
Alternatively, a second step of forming a photoconductive film using CdSe as a base material, a third step of heat-treating the photoconductive film, and no metal layer is attached on the photoconductive film;
and a fourth step of depositing a metal layer using a mask shaped so that the metal layer adheres to a portion of the common electrode and individual electrodes formed of the transparent conductive film, and forming the metal layer into a desired pattern. A method for manufacturing an image reading element, comprising a fifth step of etching to form a metal electrode.