JPS62186573A - Manufacture of light receiving element - Google Patents

Abstract

PURPOSE:To stabilize characteristics, in a manufacturing method of light receiving elements including a process for forming a photoconductive film and a process for activating heat treatment of the film, by controlling each process so that the relationship between a photocurrent and response speed becomes a specified exponential relationship. CONSTITUTION:CdS powder and CdSe powder, which have undergone primary activating heat treatment, are mixed. A common fusing agent such as CdSl2, low melting-point glass frit and an organic oil component are added in the mixture. The mixture is crushed and kneaded for a specified time, and a printing paste for photoconductive film is prepared. The paste is printed on a substrate 1, which is then arranged so as to face a reaction controlling printed film 5. Thereafter, activating heat treatment is performed. Each of the above described processes is controlled so that the correlation between the signal current of a light receiving element and an optical response speed becomes a specified exponential relationship. The light receiving element obtained in this way is stable for a long period, the characteristics are not fluctuated and sufficiently high reliability is obtained.

Description

[Detailed Description of the Invention] <Industry> 2 Field of Application The present invention is a photoconductive film made of Cd-containing -VI group compound as a total conductor material, which can be made into a long or large-area photoconductive film. This relates to a method for producing a light receiving element, which is particularly suitable for use as a light receiving element for a contact type image sensor, which has high photosensitivity, high-speed optical response, and is capable of adopting a real-time signal reading method. The present invention relates to a method for manufacturing an element.

[Prior art and its problems] Conventionally, as a method for producing a long photoconductive film or a photoconductive film with an ID large area of 7"L, vacuum evaporation method and sputtering method using a redundant electrically conductive material have been used. Alternatively, thin film fabrication techniques such as glow discharge electrophase formation techniques are used.In these thin film fabrication techniques, the quality of the film properties largely depends on the manufacturing technology of the manufacturing equipment, yield, and reliability. For example, when producing an amorphous hydrogenated silicon thin film by anti-BB sputtering method or glow discharge electric phase epitaxy method,
-I- Requires advanced technology to control discharge plasma12.
Furthermore, in order to use the photoconductive element as a photoconductive element that utilizes the resistance change of the photoconductive film, a highly accurate doping control technique is required, and it is difficult to obtain reproducibility and uniformity of film properties. Δ: Even in the method of manufacturing the II-VI group compound semiconductor thin film containing Cd used in the present invention by sputtering or dry vapor deposition, the deviation from the stoichiometric composition of 1 may occur depending on the manufacturing conditions. Cd, e to slightly change and give photoconductivity 4=j
Doping with halides such as u or idAg, as well as activation heat treatment, have the disadvantage that reproducibility is difficult to obtain depending on the manufacturing conditions.The present invention is a simple method suitable for mass production and is capable of achieving reproducibility.

A photoconductive film with good controllability, stable photoconductive properties, and high reliability is produced, and a method for manufacturing photodetectors such as photodetector arrays that require a long photoconductive film, such as contact image sensors, is provided. It is intended for this purpose.

Means and operation for solving the above problems> In order to achieve the above object, the method for manufacturing a light receiving element of the present invention uses a Cd-containing n-■ group compound semiconductor or two or more of these H
- A process of printing and coating a paste containing a semiconductor material mainly composed of a group VI compound semiconductor to form a photoconductive film, a process of heat-treating the photoconductive film for activation, and a process of heat-treating the photoconductive film for activation. The activated photoconductive film described in item 1 or the photocurrent (iph) (x: rise response speed (τr) (n=2.5 to 4.0)
) and photocurrent (i, h: + t-x: falling response speed (τd) 11·(m, -). With this configuration, long-life characteristic stability and excellent Accordingly, it is possible to realize a light-receiving element having photoconductive properties with high reliability.

In particular, in the present invention, if characteristics that deviate from the above-mentioned functional relationship are obtained due to poor control of the activation heat treatment conditions, a light receiving element exhibiting such characteristics will have poor heat resistance in the device fabrication process, and the reliability of the characteristics over time will deteriorate. While lacking in sex,
It has been found that even in light-receiving elements manufactured under poor control, only those elements which coincidentally satisfy the above-mentioned functional relationship can achieve long-life characteristic stability.

Therefore, by using structural conditions that satisfy the above-mentioned functional relationship, it is possible to establish a method for manufacturing a light receiving element with high yield and high reliability.

<Example> Next, embodiments of the present invention will be described in detail.

Example 1 In an example of the method for manufacturing a light-receiving element of the present invention, a case will be described below in which cds and CdSe-based conductive materials are used as Cd-containing H-VI group compound semiconductors used for producing a photoconductive film. will be described as an example, but the present invention is not limited thereto.

The above photoconductive material is prepared by adding CuCl2 in advance to dope 250 to 2,000 ppm of CO to a compound obtained by a known chemical precipitation method, and depositing the compound at a temperature of 600 to 900°C (preferably in a N2 gas atmosphere). t/
Activation heat treatment was performed at 1800° C. for 15 minutes to impart photoconductivity in advance (hereinafter referred to as primary activation heat treatment and primary activation heat treated powder). At this time, the average particle size of the fired powder obtained is 2 to 3 μm. The primary activated heat-treated powders of CdS and CdSe prepared in this way are mixed at a CdS/CdSe molar ratio of 2/8, and a common flux is made of, for example, CdC12 and CdS.
/CdSe 5.2-6.0 molar ratio to the e component,
Low melting point glass frit with a glass transition temperature of 300°C to 400°C is contained in an amount of 1 to 5% by weight based on the CdS/CdSe component.
, α- containing ethyl cellulose as an organic oil component
A suitable amount of terpineol was added, and the mixture was ground and kneaded using a sand grinder for about 20 hours to prepare a photoconductive film printing paste. In this step, the primary activated heat-treated powder is pulverized to a particle size of 1 μm or less (average particle size 0.5 μm). Next, using this photoconductive film printing paste,
A photoconductive film 2 having a coating thickness of about 10 μm was formed on a 59 glass substrate 1 (see FIG. 1) by screen printing. A reaction control printed film (
CdS film) 5 uses CdCl2 as a fluxing agent for CdS.
A paste containing 5.0 mol of the same organic oil component as described above was added to the substrate 4 to create a paste. These 2
The sheets of printed films 2 and 5 are arranged facing each other as shown in FIG.
Activation heat treatment (hereinafter referred to as secondary activation heat treatment) was performed at 470'C/1 hour in an atmosphere with an oxygen partial pressure of N2 gas of 0.18. The thickness of the photoconductive film after the activation heat treatment was approximately 6 μm. When the secondary electron image of the photoconductive film thus prepared was observed using a scanning electron microscope, it was found that the primary activation heat-treated powder, which had been pulverized to 1 μm or less during printing, was removed from the secondary activation heat-treated powder. The particles grow by
It was confirmed that the particles had a particle size of 1 to 2 μm and were bound together. In addition, Cd5-CdSe was formed by secondary activation heat treatment.
The mixed powder has completed the mixed crystallization reaction, and Cd5o, zSeo,
It was confirmed from analysis of the X-ray diffraction pattern that a mixed polycrystalline film named s was formed.

Next, as shown in FIG.
A planar electrode (Ti) row 3 having an electrode opening length of 65 μm and a pitch of 125 μm per electrode was formed by a lift-off method, and the manufacturing process of the light receiving element was completed.

Regarding the large number of light receiving elements prototyped in this way, 69
Light emitting diode (]60μw with center wavelength at 5nm
/crn2) under pulse source irradiation (+p11
) and photoresponse speed were measured. The photoresponse speed is determined by the riser response speed (τr (50%
) and τr(90%)), falling light response speed (rd(50%) and (rd
(90%)).

The signal current (iph
) Light response speed (rd (50%), \τd (90%),
The correlation between τr (50%) and τ, (90%)) is shown in Figure 3, and the photodetector fabricated under favorable conditions has the following relationship: i, h∝ (r(1)''+ (50%) (m= 1
．． 85), 1ph∝ (rd); l (90%) (
m=2.06), 1ph∝-9(τr)-i(50%) Cn=2.64) and I
phOC-ratio (τr)-,! (90%) (1=3.Q2).

All of the light-receiving elements that we prototyped by controlling each process to exhibit these characteristics were exposed to 60°C under 5001x white fluorescent lamp irradiation.
℃, 95% RH in high temperature and high humidity for 10,000 hours. Characteristic variation after driving test was less than 5%. Seventy-sufficiently high reliability was obtained, making it suitable for practical use as a light-receiving element for contact-type dimensional image sensors. gender has been confirmed.

Incidentally, when the surface composition of the photoconductive film of these light-receiving elements was analyzed by Auger electron spectroscopy, it was found to be Cd.

In addition to the main components of S and Se, Q + P b + Sl and C with atomic concentration ranging from Iat, % to l0at,
The photoconductive film is not particularly limited to the manufacturing method of this example, as long as a CI of 2a t,% or less is detected, the photoconductive film has such a composition, and exhibits the above device characteristics. , the above-mentioned good high reliability characteristics were obtained.

Example 2 Cd5o as in Example 1. When fabricating a light receiving element using a 2SeO,8 mixed polycrystalline film as a photoconductive film (7. In order to change the reaction conditions, the fluxing agent (CdCI2) in the printed film for reaction control, which is placed opposite to the photoconductive film, was replaced with CdS. A large number of light-receiving elements were trial-produced using the same manufacturing process using a printed film with an increased amount of 10 mol.The signal current (iph), light response speed (τd (90%), and rr (
90%)) is shown in Figure 4. In the devices prototyped under such conditions, there were almost no devices exhibiting the characteristic relationship observed in the light receiving device of Example 1, and several samples were 1 pdcx: (τ, 1) (90%) (m= t, 9
5) and l pl) C'C-9(rr) (90%) (n=2.96).

The former sample group was irradiated with a 5001x white fluorescent lamp.
After a 1,000-hour reliability drive test at 60°C and 95°RH high temperature and high humidity, the optical signal current value decreased by about one digit, and the variation in characteristics between adjacent clusters in the photodetector array increased significantly. On the other hand, the variation in the latter light-receiving element was within 5%.

Light-receiving elements manufactured under such inappropriate reaction conditions have large variations in their characteristic reliability, resulting in a significant reduction in manufacturing yield.

As is clear from the above examples, it is clear that control of the reaction atmosphere is extremely important in order to fabricate a photodetector with excellent photoconductive properties and high reliability with good controllability. The device characteristics are preferably jphr (τ
d) (m: 1.5.-2.5, more preferably 2
) and iph■(rr) (n: 2.5 to 40°, preferably tri3)')V
It has become clear that a highly reliable device can be obtained by optimizing C manufacturing conditions.

In addition, in the above example, Cd5-CdSe system, especially Cd5-CdSe-based
Although only an example of manufacturing a d5o,2 Se0.8 mixed polycrystalline film has been described, Cd5X5e1. , -X system has special [
Although it is limited to X=0.2, it can be applied to other material systems as well.

<Effects of the Invention> As described below, according to the present invention, II-
In the manufacturing method of a light receiving element using a photoconductive film mainly composed of a Group VI compound semiconductor, it is difficult to control the production of a highly reliable element. By controlling and optimizing manufacturing conditions, a highly reliable light receiving element can be manufactured at a high yield.

[Brief explanation of drawings]

FIG. 1 is a substrate layout diagram for explaining one embodiment of the method for manufacturing a light receiving element of the present invention, and FIG. 2 is a diagram showing an example of the structure of a light receiving element manufactured according to the present invention. ) is a cross-sectional view, FIG. 3(b) is a perspective view, and FIGS. 3 and 4-4 are diagrams showing the correlation between the signal current and the light response speed of the light-receiving element manufactured according to the embodiment of the present invention. l...Substrate, 2...Photoconductive film, 3...Planar electrode, 4...Substrate, 5...Reaction atmosphere control film (Cd
S).

Claims (1)

[Claims] 1. A photoconductive film is formed by printing and coating a paste containing a semiconductor material mainly composed of a II-VI group compound semiconductor containing Cd or two or more of these II-VI group compound semiconductors. a step of heat-treating the photoconductive film for activation; and a step of providing an electrode on the photoconductive film subjected to the heat-activation treatment, and the photoconductive film has a photocurrent (i_p_h) ^∝ rising photoresponse rate ( τ＿
r)^-^n:n=2.5~4.0 Photocurrent (i_p_h)^∝Falling light response speed (τ_
d) A method for manufacturing a light receiving element, characterized in that each of the above steps is controlled so as to have a characteristic expressed by the functional relationship: ^m: m = 1.5 to 2.5. 2. The Cd-containing Group II-VI compound semiconductor material is produced by adding at least one type of halogen such as Cu, Ag or Al as an impurity to a compound powder synthesized by a chemical precipitation method, and then adding an inert gas to the compound powder. 600℃~90℃ in atmosphere
It is a crystalline powder imparted with photoconductivity obtained by firing at a heat treatment temperature of 0°C, and is characterized by using a fine powder material obtained by pulverizing the powder to a particle size of 1 μm or less. A method for manufacturing a light receiving element according to claim 1. 3. The photoconductive film is made of a II-VI group compound semiconductor containing Cd or a semiconductor material mainly composed of two or more of these II-VI group compound semiconductors, a halide containing Cd as a flux, and a low melting point glass. and an organic oil; and activating the printed film by arranging it to face a reaction control printed film consisting of a semiconductor material mainly composed of CdS, a halide containing Cd, and an organic oil. 2. The method of manufacturing a light-receiving element according to claim 1, wherein a planar electrode is formed on the photoconductive film which has been prepared through the activation heat treatment process. 4. The photoconductive film is treated at an activation heat treatment temperature of 450°C to 550°C, and the surface composition of the photoconductive film after the activation heat treatment includes oxygen having an atomic concentration of 1.0 at% or more in addition to the main component. (O), lead (Pb), silicon (Si), carbon (C
) and 2.0 at% or less of chlorine (Cl).