JPS6273679A - Manufacture of photoelectric exchange film - Google Patents

Abstract

PURPOSE:To adopt a real time type picture reading system by continuously baking a photoconductor material, low melting-point glass and a chloride under the conditions of the heat treatment of two kinds or more when low melting- point glass and the chloride are added to the photoconductor material and thermally treated. CONSTITUTION:CdSe powder, glass frit and a halide are added onto an insulating substrate 1 consisting of ceramics, glass, etc., and photoconductive paste 2 to which an organic solvent is added is applied in predetermined width. First activation heat treatment is conducted to the applied film 2, and a mixed gas in which the mixing ratio of oxygen to nitrogen is kept within a range of O2:N2=1:20-1:4 is made to flow at the rate of 1-10l/min. In the first heat treatment process, the growth of particles is inhibited and photocurrents are lowered when the partial pressure of oxygen is dropped. Second heat treatment is performed in an inert gas, and an electrode 3 is formed onto the photoconductive film 2. Accordingly, particles are grown and crystallizability is improved under separate conditions, thus remarkably enhancing the characteristics of a photoelectric conversion film prepared by using powder, then promoting its stabilization.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing a photoelectric conversion film suitable for use in a photoelectric conversion element that converts light into an electrical signal, and in particular to a method for producing a photoelectric conversion film suitable for use in a reading section of a facsimile, a scanner, etc. The present invention relates to a method for producing a photoelectric conversion film suitable for use in the present invention.

<Conventional technology> Conventionally, for example, CCDM was used in the reading section of facsimile machines, etc.
Optical sensors manufactured using IC technology, such as O5 type sensors, are used.

However, since such a sensor is manufactured using IC technology, it can only be manufactured with a length of several IQ mm, and in actual use, it is necessary to reduce and image the document. When performing reduced imaging, a lens optical path length is required, and generally a distance of 20 crn to 30 crn is essential. Such an optical path length poses a major problem in reducing the size and weight of the reading section.

In recent years, in contrast to the above-mentioned reduced-size sensors, a close-contact image sensor has been proposed in which a sensor with the same width as the original is fabricated and a fiber optic lens array is used to image the original at the same size on the sensor.

CdS is used as the photoelectric conversion element of this image sensor.

casxsr, vapor deposited film + aSl film, etc. have been proposed, but are they all vacuum gross? Since it is used, there are problems in terms of productivity and yield, resulting in high costs.

In addition, when used as an injection type device, carrier mobility,
The light response speed depends on the lifespan, etc., and the limit is about 5 m5 ec.

On the other hand, as a method for producing a photoelectric conversion film at a relatively low cost,
Cadmium sulfide, cadmium selenide, or sulfur/cadmium selenide powder is mixed with a small amount of activated impurities, a flux, and an organic binder and applied as a slurry onto a substrate.
This coated substrate is then heated using nitrogen gas or a fine 1t (0,8
%) of oxygen gas is known.
2-25305).

(Problems to be solved by the invention) However, according to the thick film forming method as described above, a photoelectric conversion film can be produced relatively inexpensively and with good reproducibility. It was not possible to produce a charge conversion film with excellent image signal output characteristics and photoresponse characteristics that made it possible to adopt this method, and it was difficult to apply this method to high-density, high-pixel reading units such as facsimiles.

The present invention was devised in view of the above-mentioned problems, and aims to provide a highly sensitive, low-cost method for producing a photoelectric conversion film that makes it possible to employ a real-time image readout method. .

Means for Solving the Problems> In order to achieve the above object, the present invention provides at least CdS
, CdSe, CdTe, Cd5) (mutx, Cd
5XTe+-xICd S exTe I-X In the method for producing a photoelectric conversion film, the photoconductor material is heat-treated by adding low melting point glass and chloride to the photoconductor material. The heat treatment is configured so that the firing is performed continuously under at least two types of heat treatment conditions.

<Function> Generally, in order to activate photoconductor material (for example, Cd5e) powder by heat treatment, it is necessary to grow the powder grains and fully promote binding between the grains.

However, powder occupies a very large proportion of the surface and is easily affected by compositional shifts and disordered crystal lattices on the surface. Therefore, along with grain growth, such surface lattice disturbances are included on the crystal surfaces and grain interfaces.

Such surface conditions such as compositional deviation create a trap level in the forbidden band of the semiconductor and have a negative effect on response speed, change over time, etc. However, in the present invention, while allowing grain growth, the surface condition In order to improve the condition, the heat treatment process is divided into two steps, and the first step is to bond the particles at a relatively low temperature, for example. Next, as a second step, the temperature is slightly raised to suppress grain growth while relaxing the lattice disorder on the surface, and to evaporate excess photoconductor material (Cd, Se, etc.).

A photoconductive film with good characteristics is produced by the above two heat treatment steps.

<Example> Next, as an example of the present invention, a two-step firing process using CdSe will be described using an actual manufacturing method as an example.

FIGS. 1(a) to 1(d) are process diagrams showing the manufacturing steps of an embodiment of the method for manufacturing an element including a photoelectric conversion element tabulated according to the present invention.

First, as shown in FIG. 1(a), a photoconductive paste 2 containing K Cd Se powder, 7 liters of glass, and a halide is added to an insulating substrate 1 made of ceramic, glass, etc., and is further coated with an organic solvent. Apply with a width of .

Specifically, CdSe was created using a chemical precipitation method, using a previously activated fine powder rod, and adding low melting point glass and 3 mo1% CdCl2k to this CdSe microcrystalline powder.
Photoconductive paste 2 further made into a paste with an organic solvent
is applied onto the substrate l to a predetermined width.

In this example, screen printing was used to obtain a film with a film thickness of IOμ~20μ.
It was applied to μ.

Next, the film 2 coated in the step shown in FIG. 1(a) is shown in FIG.
In step b), a first activation heat treatment is performed.

The first heat treatment mainly promotes the growth of grains, and in this example, in which all oxygen is mixed, it was carried out in a mixed gas of oxygen and nitrogen. The mixing ratio was set in the range of 02+N2=l:20 to 1:4, and the mixed gas was flowed at a rate of 1 to 10 per minute. Moreover, the temperature of the heat treatment was 430°C to 500°C.

In this first heat treatment step, when the oxygen partial pressure is lowered, particle growth is suppressed and the photocurrent is reduced. Furthermore, when the oxygen partial pressure is increased, grain growth progresses, but the surface roughness deteriorates and the yield in electrode formation etc. decreases.

FIG. 2 shows the dependence of grain growth and surface roughness on the firing atmosphere due to the activation treatment in the first heat treatment step. As is clear from Fig. 2, when the oxygen partial pressure is increased, the grain growth becomes remarkable and grows to about 5 μm, but on the other hand, the surface roughness deteriorates, causing defects etc. when forming the upper electrode part. . In addition, if the oxygen partial pressure is lowered, the growth of particles is suppressed, and as shown in Figure 3, the required minimum output (1.0 μA) is achieved.
will not be obtained. Therefore, in this example, the oxygen partial pressure is 172
Elements were fabricated with a ratio of 0 to 1/4.

Next, following the first heat treatment step shown in FIG. 1(b) K, a second heat treatment shown in FIG. 1(c) is performed.

The second heat treatment was performed in an inert gas, and in this example, the electrode 3 was formed using a flow process in nitrogen at a temperature of 480°C to 550°C. Figure 4 shows the changes in grain growth in each process in Figure 1, together with the photocurrent in each process, and Figure 5 shows the changes in grain growth in each process in Figure 1. This shows the response speed. In the first heat treatment step shown in FIG.
In the second heat treatment step shown in Figure (C),
An example of heat treatment at 00°C for 1 hour is shown.

As is clear from FIG. 4 above, in the step of FIG. 1(a), the grain size of several +oooX grows to several μm''! in the first heat treatment step shown in FIG. 1(b).Furthermore, in the step of FIG. In the second heat treatment step (c), there is almost no growth.The output also changes in the same way as the grain growth.On the other hand, the response speed is 10 m5ec in the first heat treatment step (b), as shown in Figure 5. However, in the second heat treatment step, it was further improved to several m5ec.
become.

FIG. 6 is a diagram showing changes over time, and in the same figure, ■
is the first. It is a graph showing the change over time of the sample that has gone through the second heat treatment process, and ■ is a graph showing the change over time of the sample that has gone through the first heat treatment process.

As is clear from Fig. 6, the sample @ subjected to only the first heat treatment has a large change over time, but the sample that has undergone two heat treatment steps, the first and second, has a change within 10% even after 100OH. is suppressed by changes in

<Effects of the Invention> As described above, the present invention uses multi-step heat treatment conditions and improves grain growth and crystallinity under separate conditions. The characteristics can be significantly improved, and a high-performance device can be realized.

[Brief explanation of drawings]

Figures 1 (a) to (respectively are process diagrams showing an example of the manufacturing process of an element equipped with a photoelectric conversion film manufactured according to the present invention, and Figure 2 is a diagram showing particle size with respect to partial pressure of oxygen and nitrogen during heat treatment. Figure 3 is a diagram showing the output with respect to oxygen and nitrogen partial pressures, Figure 4 is a diagram showing the relationship between the element fabrication process, particle size, and photocurrent, and Figure 5 is a diagram showing the relationship between the element manufacturing process, particle size, and photocurrent. FIG. 6 is a diagram showing the relationship with the response speed, and a diagram showing the change over time in the optical output of the element. 1... Insulating substrate, 2... Photoconductive film, 3... Electrode. Agent. Patent attorney Aihiko Fukushi (and 2 others) RANO wo 弗人稌;

Claims (1)

[Claims] 1. At least CdS, CdSe, CdTe, CdS_
xSe_1_-_x, CdS_xTe_1_-_x, C
dSe_xTe_1_-_x A method for producing a photoelectric conversion film comprising at least one type of photoconductor material as a main component and heat-treated by adding low melting point glass and chloride to the photoconductor material, wherein at least two types of the above-mentioned heat treatment are performed. A method for producing a photoelectric conversion film characterized by successive firing under the above heat treatment conditions. 2. The heat treatment step includes two steps: a step of heat-treating at least the photoconductive film in an atmosphere containing at least oxygen and a step of heat-treating it in an inert gas. A method for producing a photoelectric conversion film as described in Section 1. 3. The method for producing a photoelectric conversion film according to claim 1 or 2, wherein the heat treatment step of the photoconductive film is performed by successively firing the photoconductive film at at least two different temperatures.