JPH08179044A - Manufacture of cdte radioactive ray detector - Google Patents

Abstract

PURPOSE: To reduce a dark current, decrease dispersion, and improve the resolution of the pulse wave height spectrum analysis by sticking a CdTe radioactive ray detecting element fitted with electrodes to an insulating substrate formed with a conducting pattern with a conducting epoxy resin, then heat-treating it. CONSTITUTION: A CdTe crystal added with chlorine is machined to manufacture a CdTe monocrystal wafer polished on both faces. The wafer is etched with a Br-methanol solution to remove a processed alteration layer on the surface, then electrodes are formed on the surface and the back face by electroless platinum plating. The wafer is diced at the prescribed size, it is stuck to an alumina substrate formed with a conducting pattern with a silver epoxy resin, then it is heat-treated at the temperature of 55-85 deg.C, preferably 60-80 deg.C. The heat treating time differs according to the heat treating temperature, the heat treatment for less than 2hr at the heat treating temperature of 60 deg.C is ineffective, and the heat treatment for 30min or above at 80 deg.C is effective, for example.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method of manufacturing a CdTe radiation detector.

[0002]

2. Description of the Related Art A CdTe radiation detector is a device in which electrons and vacancies generated when radiation is transmitted through a semiconductor are subjected to a bias voltage on an electrode provided on the surface thereof and measured as a current. Since CdTe has a wide band gap, it can operate at room temperature, and since the atomic numbers of the constituent elements are large, the absorption coefficient of X-rays and γ-rays is large and high sensitivity can be obtained. Such a CdTe radiation detector is used for a monitor of a radiation use facility, a spectrum survey meter, or the like. In addition, the detectors can be miniaturized and arrayed, and they are beginning to be applied to medical diagnostic devices and industrial nondestructive inspection devices. However, the CdTe radiation detector thus produced has a problem that the dark current, which is a current flowing even if the detector is not hit by radiation, is as high as 20 nA on average, and its variation is large (σ = 6 nA). The dark current value is 4 mm square CdT with a thickness of 2 mm.
e A bias voltage of 100 V was applied to the radiation detecting element, and the measurement was performed after 30 minutes had elapsed. In addition,
The dark current becomes a noise component in the pulse height spectrum analysis, makes the spectrum shape broad and reduces the resolution.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above problems, and an object of the present invention is to reduce the dark current and reduce its variation.

[0004]

Means and Actions for Solving the Problems
As a result of various studies to solve the above problems, a CdTe radiation detecting element with an electrode is adhered with an electrically conductive epoxy resin on an insulating substrate having an electrically conductive pattern, and then heat treated. By doing so, they have found that the above objectives can be achieved.

That is, according to the present invention, in a method of manufacturing a CdTe radiation detector, a CdTe radiation detection element having electrodes on its front and back surfaces is electrically conductive on an insulating substrate on which a conductive pattern is formed. Cd characterized by being bonded with an epoxy resin and then heat-treated at a temperature of 55 ° C. or higher and 85 ° C. or lower, more preferably 60 ° C. or higher and 80 ° C. or lower.
A method for manufacturing a Te radiation detector is provided.

The temperature of the heat treatment is 55 ° C. or more and 85
The temperature is lower than or equal to 80 ° C., more preferably 60 ° C. or higher and lower than or equal to 80 ° C., because the temperature lower than the lower limit, for example, 50 ° C., has no effect of reducing the dark current, and the temperature higher than the upper limit, for example, 90 ° C. has no effect. is there.

Regarding the heat treatment time, if the heat treatment temperature is 60 ° C., it is not effective unless it is kept for 2 hours or more. On the other hand, if the heat treatment temperature is 80 ° C., it is effective if it is kept for 30 minutes or more. Therefore, the required heat treatment time varies.

[0008]

The present invention will be described below with reference to the manufacture of a CdTe radiation detector as an example. The CdTe crystal added with chlorine grown by the THM method was processed to prepare a CdTe single crystal wafer having a thickness of 2 mm and having both sides polished. This wafer is 1
% Br-methanol solution to remove the work-affected layer on the surface, and then electrodes were formed on the front and back surfaces by electroless platinum plating. This wafer is diced into a 2 mm square and adhered to an alumina substrate on which a conductive pattern is formed with a silver epoxy resin. After the silver epoxy resin is cured, 7
Hold at a temperature of 0 ° C. for 24 hours. As a result of measuring the dark current of the CdTe radiation detector manufactured in this way, the average is 13 nA and the variation σ = 0.6 nA, and the dark current value can be reduced and the variation can be reduced as compared with the case where the heat treatment is not performed. It was The dark current value was measured after 30 minutes had passed after applying a bias voltage of 100V.

[0009]

As described above, according to the present invention,
A CdTe radiation detecting element with an electrode is attached to a conductive pattern.
The dark current can be reduced and its variation can be reduced by heat-treating it after adhering it to the insulating substrate on which the conductive film is formed with a conductive epoxy resin. Therefore, the resolution in the pulse height spectrum analysis can be improved.

Claims (1)

[Claims] 1. A method of manufacturing a CdTe radiation detector, wherein a CdTe radiation detection element having electrodes on its front and back surfaces is bonded with an electrically conductive epoxy resin onto an insulating substrate on which a conductive pattern is formed. After making it 55 ℃ or more 8
A method for manufacturing a CdTe radiation detector, which comprises performing heat treatment at a temperature of 5 ° C. or lower, more preferably 60 ° C. or higher and 80 ° C. or lower.