JPH0287681A - Semiconductor radiation detector - Google Patents

Abstract

PURPOSE:To obtain a semiconductor radiation detector which improves the detection sensitivity of neutron with low operating voltage and lessens aged changes and is superior in characteristics of a resistance to environment by providing a coating containing boron on a single crystal semiconductor substrate and at a part of the region on an amorphous semiconductor layer which forms heterojunction. CONSTITUTION:A coating 3 containing at least boron is provided on a single crystal semiconductor substrate 1 and at least at a part of the region on an amorphous semiconductor layer 2 which forms heterojunction and then, metallic electrodes 4 and 5 which cover the coating are mounted on the coating. As it is possible to cause the amorphous semiconductor layer 2 to have the film thickness of 200 nm or less, it is sufficiently thin as an insensitive layer to alpha rays. As there is a structure where the boron coating 3 and a heterojunction interface are formed across the above layer 2, the alpha rays may arrive at a depletion layer efficiently. Further, in this structure, as there is the boron coating 3 that is the generation source of the alpha rays by neutrons in the vicinity of the depletion layer even under inverse biased voltage, this configuration does not worsen the sensitivity of its detector. The covering of boron coating 3 with the metallic electrodes 4 and 5 protects the coating from contact with the outside air.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor radiation detector for detecting radiation, particularly including neutron radiation.

Conventional technology Conventionally, a semiconductor radiation detector for neutron beams was disclosed in Japanese Patent Application Laid-open No. 61-3.
As shown in Japanese Patent No. 5384, it has a structure as shown in FIG.

That is, a hydrogenated amorphous semiconductor layer 12 is deposited on an N-type single-crystal St substrate 11 to form a heterojunction.
The structure is such that a boron coating 13 is provided on the other surface, and electrodes 14 and 15 are finally formed.

Its operation uses the "B (nl α)" reaction of boron isotope + eB, which has a large neutron absorption cross section, to generate α rays 21.Then, the α rays generate the reverse bias voltage applied to the heterojunction. The neutron beam 2 enters the depletion layer 16 formed by
2 is detected.

However, the signal strength is weak, and a high reverse bias voltage is applied to widen the depletion layer, so the reduction of leakage current is
This is important for improving the ratio.

Problems to be Solved by the Invention However, in the conventional structure, the range of α rays generated in the boron coating 13 (for example, at 4.4 MeV and about 20
The problem is that the efficiency with which α rays reach the depletion layer is low because the length (μm) is short. Moreover, since the depletion layer spreads into the St substrate 11 from the heterojunction interface by applying a reverse bias voltage, the depletion layer spreads to the vicinity of the boron coating 13 formed on the other surface of the St substrate 11 on the opposite side to the heterojunction interface. requires the application of a fairly high reverse bias voltage.

Therefore, leakage current increases and noise increases. Furthermore, in order to obtain a high reverse bias voltage, the control circuit becomes complex and expensive. Further, the boron coating 13 suffers from changes over time due to contact with the surrounding air, and may peel off, resulting in a lack of stability.

The present invention aims to solve such problems.

Means for Solving the Problems In order to solve the above problems, a film containing at least boron was provided in at least a partial region on an amorphous semiconductor layer that forms a heterojunction with a single crystal semiconductor substrate. Further, a metal electrode was provided on the boron-containing film to cover it.

Effects The effects of the present invention produced by using the above-mentioned means are as follows. The thickness of the amorphous semiconductor layer is 20
Since the thickness can be reduced to 0 nm or less, it is sufficiently thin as a layer insensitive to alpha rays. Since the structure is such that a boron film and a heterojunction interface are formed between them, α rays can efficiently reach the depletion layer. In addition, with this structure, even at a low reverse bias voltage, there is no reduction in sensitivity because there is a boron coating near the depletion layer that is a source of α rays generated by neutrons.

Furthermore, covering the boron coating with a metal electrode protects it from contact with the surrounding atmosphere.

EXAMPLE Hereinafter, a first example of the present invention will be described with reference to FIG. 1, which shows a cross-sectional configuration diagram thereof. In the experiment, the resistivity was 10Ω・
About Cm, plane orientation (111), thickness 500μm and 5mm
A square p-type single crystal Si substrate 1 was used. The manufacturing process is as follows. A cleaned single-crystal Si substrate 1 is heated to a substrate temperature of 200 using a capacitively coupled plasma CVD apparatus using SiH4 gas and CH4 gas at a gas mixing ratio of 7:3.
Amorphous SiC film 2 as hydrogenated amorphous semiconductor layer at °C
was deposited to a thickness of 200 nm. Gas pressure is 0.5TOOr
+ High frequency power is less than IW/cffIt (13,56
MHz). A boron coating 3 was deposited on the amorphous SiC film using the capacitively coupled plasma CVD apparatus described above by changing the introduced gas to B2H6 (5% based on H2) without changing the substrate temperature. A thickness of 3 to 1 μm was deposited.

The gas pressure at that time was 0.1 to 1 Tors, and the applied surface frequency power was equal to or higher than that for forming the amorphous SiC film. The boron coating 3 had a specific resistance of several tens of Ω·cm or less and was electrically conductive, so there was no problem in applying voltage to the amorphous SiC film and electrical signals could be extracted. and the boron coating 3
was patterned into several mrrlJ by ion beam etching using Ar using a resist as a mask. Next, metal electrodes 4.5 were formed on the boron coating 3 and on the back surface of the single crystal Si substrate 1 by vapor depositing AI with a thickness of 400 nm.

Finally, although not shown in the figure, the metal electrode 4.5 and the lead wire were connected with silver paste, and the entire detector was sealed with resin. As a result, the detection sensitivity of the neutron beam 22 is improved, and vice versa.
The bias voltage, which was required to be about 50V in the conventional example, can be reduced to 20 to 30V. As a result, leakage current was also reduced to a fraction of that.

Furthermore, a semiconductor radiation detector with improved environmental resistance and less deterioration over time was obtained.

Effect of the invention The effects of the present invention are as follows.

By providing a film containing at least boron in at least a partial region of the amorphous semiconductor layer that forms a heterojunction with the single crystal semiconductor substrate, α rays generated in the boron film by neutron beams can be absorbed into the depletion layer. This has become easy and efficient to produce semiconductor radiation detectors with low operating voltages and improved neutron detection sensitivity.

In addition, the boron coating is metal 7I! By protecting the boron coating by covering it with an electrode, a semiconductor radiation detector with good environmental resistance and less deterioration over time was created.

The structure of the present invention has the same structure regardless of whether the single crystal semiconductor substrate is p-type or n-type;
A similar effect can be obtained using Pl CdTe or the like.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram of a first embodiment of a semiconductor radiation detector of the present invention, and FIG. 2 is a cross-sectional configuration diagram of a conventional semiconductor radiation detector. 1... Single crystal Si substrate, 2... Amorphous SiC film, 3
...Boron coating, 4...Metal electrode, 5...Metal electrode.

Claims (2)

[Claims] (1) A film having a heterojunction between a single crystal semiconductor substrate and an amorphous semiconductor film formed on the single crystal semiconductor substrate, and containing at least boron in at least a partial region on the amorphous semiconductor film. A semiconductor radiation detector characterized by being provided with. (2) At least the film containing boron is conductive and is formed only in a part of the amorphous semiconductor film, and a metal electrode is provided on the film containing boron to cover this film. A semiconductor radiation detector according to claim 1, characterized in that: