JPH01253971A - Semiconductor radiation detector and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a semiconductor radiation detector which has a very small leakage current and can also detect neutrons by providing a boron nitride film as an insulating protective film covering a single crystal semiconductor substrate. CONSTITUTION:A film 5 containing at least boron nitride is provided as an insulating protective film covering a single crystal semiconductor substrate 1. As the boron nitride film 5 is an excellent insulating film, it can be used for protecting an element without increasing a leakage current. The concentration of an isotop <10>B of boron is not much different from the concentration of <10>B of a boron film and neutrons can be also detected. With this constitution, a semiconductor radiation detector with a very small leakage current can be obtained.

Description

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

Conventional technology Conventionally, a protective film for a semiconductor radiation detector was disclosed in Japanese Patent Application Laid-Open No. 59-21.
A boron coating is used as shown in Japanese Patent No. 8732. Further, the boron coating is
As shown in Publication No. 2082, it is also used in semiconductor radiation detectors that detect neutron rays by generating α rays using the 1iIB (n, α) reaction of the boron isotope 1@B. There is. Its structure is shown in FIG. 3 and will be explained.

That is, the structure is such that a P-type layer 12 is formed on an N-type single crystal 81 substrate 11, and a boron coating 13 is formed only on the north side of the P-type layer 12.

Problems to be Solved by the Invention However, conventional boron coatings are electrically conductive. Therefore, even if the hardness is high, it can only protect a part of the device made using the crystalline semiconductor substrate, and cannot be used as an insulating protective film to cover the whole. surface and its edges 14 remained unprotected, which increased leakage current. However, silicon nitride, silicon dioxide, etc., which have traditionally been known as insulating protective films for devices using single-crystal semiconductor substrates, cannot be used for neutron detection, and if they are used, the manufacturing process will increase and become complicated. .

In particular, in the case of semiconductor radiation detectors, a high reverse bias voltage of several tens of square meters is applied because the depletion layer should be expanded as much as possible in the thickness direction of the single crystal semiconductor substrate, and the junction area of the element is usually several meters.
Since it is as wide as m2, leakage current tends to increase and a large signal current cannot be obtained, so an increase in leakage current has a serious effect on radiation detection sensitivity. Therefore, even if the conductive boron film is used as a protective film or for detecting neutron beams, a high voltage is applied to the film, resulting in an rR problem in which the leakage 'fL flow increases. In addition, the processability of the boron coating is poor,
There is also the problem that residual or creases remain in unnecessary parts during the manufacturing process, and because they are conductive, they increase leakage current and reduce the manufacturing yield.

As a result of the above, it has been impossible to obtain a semiconductor radiation detector that has an insulating protective film that can also be used for detecting neutron beams and has good characteristics such as low leakage current.

Furthermore, the manufacturing process is complicated! Mari was also bad.

The present invention aims to solve such problems.

Means for Solving the Problems In order to solve the above problems, the present invention provides a film containing at least boron nitride as an insulating protective film covering a single crystal semiconductor substrate.

Effects The effects of the present invention produced by using the above-mentioned means are as follows. By providing a boron nitride film, for example, as a protective film containing at least boron for a device fabricated using a single crystal semiconductor substrate, the boron nitride film is an excellent insulating film and can protect the device without increasing leakage current. Since the concentration of the boron isotope +11B is not much different than that of a boron film, a semiconductor radiation detector with low leakage current that can also detect neutron beams can be obtained. In addition, since the boron nitride film is an insulator, its residue or adhesion during the manufacturing process will not contribute to an increase in leakage current, and a single film functions as an insulating protective film and a neutron detection film.
The manufacturing process is also simplified and the yield is improved.

Furthermore, if a boron nitride film is formed by a CVD (vapor phase growth) method using discharge of a mixed gas, a high-quality amorphous film can be obtained at low temperature, and the coverage for the device can be improved. The hydrogen contained at this time compensates for electrically active defects on the surface and edges of the substrate and reduces leakage current. In addition, since it is a low-temperature process, it is possible to eliminate the occurrence of crystal defects and the diffusion of impurities, especially when a single crystal semiconductor substrate with high purity, low defect density, and high resistance is required, such as in semiconductor radiation detectors. Therefore, it is possible to create a device with low leakage current.

EXAMPLE Hereinafter, a first example of the present invention will be described with reference to a cross-sectional configuration diagram shown in FIG. 1. For the experiment, a resistivity of 10 kΩ”
cm, plane orientation (111), thickness 500μm and 5mm
A square p-type single crystal Si substrate 1 was used. 200 nrn of amorphous SiC of the amorphous semiconductor film 2 was deposited on a small crystal Si substrate l) using a capacitively coupled plasma CVD apparatus using 5iHa gas and CHa gas at a gas mixture ratio of 7:3. . Next, the top of the amorphous semiconductor film 2 and the small crystal 81 substrate 1
A metal electrode 3.4 was formed by depositing 400 nm of AI on the back surface of the substrate and patterning it into a 3 mm square. Then, using a capacitively coupled plasma CVD device, the gas pressure was 0.7 Torr.
r, substrate temperature below 400°C, hydrogen diluted B2H6 gas,
Using N H3 gas, N2 gas, etc., a high JMI wave of 13.56 MHz is applied to discharge the amorphous 13 N film 5.
0 to 11000n was deposited. This amorphous BN film 5 is an insulator, and its hydrogen content was measured from an infrared absorption spectrum to be several percent or more of O6. This hydrogen compensates for defects on the surface and side edges of the single crystal Si substrate 1, further reducing leakage current. The amorphous BN film 5 is formed by photoprocessing and ion beam etching.
Patterning was performed to open a contact window with the metal electrode 3. (Not shown) Finally, although not shown, the metal electrode layer 3.4 and the lead wire were connected with silver paste, and the entire detector was sealed with resin. As a result, a semiconductor radiation detector capable of detecting neutron beams with a leakage current of 20 percent less than conventional ones at a reverse bias voltage of 50 V was created.

As in this example, when a heterojunction between an amorphous SiC film and a single-crystal Sl substrate is used as one of the electrical connections on the surface of a single-crystal semiconductor substrate, the amorphous SiC film can be Since the film and the BI'J film can be deposited, the process and equipment can be simplified, making it easy to manufacture large-area products.

Next, a second embodiment in which the electrical junction is a Schottky junction will be described with reference to FIG. 2. The same parts as in the first embodiment have been explained using the same symbols. In this case, in place of the amorphous semiconductor film of the first embodiment, 1100 nm of platinum 6 was deposited to form a Schottky barrier. The manufacturing method is the same as that of the first embodiment except that platinum 6 is deposited by vapor deposition and the platinum 6 also serves as the metal type Fii3. Since the Schottky junction uses platinum 6, the metal electrode 3 is not required, and a semiconductor radiation detector similar to the first embodiment with a thinner insensitive layer than other electrical junctions is obtained. Further, even if the electrical junction is a PN junction, the present invention provides a semiconductor radiation detector that solves the same problem.

Furthermore, when the amorphous BN film 5 was deposited by sputtering using a BN film as a target so as not to contain hydrogen, the leakage current was smaller in the case where hydrogen was contained. When the amorphous BN film 5 was deposited using the capacitively coupled plasma CVD method, the device coverage was better than when using the sputtering method, and the film could be deposited up to the side edges of the substrate. Furthermore, when an experiment was carried out by replacing the amorphous BN film 5 with a polycrystalline BN film, it was found that the density was poor and the protective properties against moisture in the surrounding air were poor due to accelerated diffusion from the polycrystalline grain boundaries, resulting in poor deterioration over time. It was big. Since the manufacturing process was also at a high temperature of 500 to 800° C., crystal defects were also generated in the single crystal S substrate 1 due to thermal stress, and the leakage current was smaller in the amorphous film.

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

By providing a boron nitride film as an insulating protective film covering a single crystal semiconductor substrate, it fulfills the dual functions of insulation protection and neutron beam detection, and is a semiconductor radiation detector that can also detect neutron beams with less leakage current than conventional ones. The detector has been created.

Further, the manufacturing process is simplified, and since the amorphous BN film 5 is an insulator, even if it remains around the single crystal semiconductor substrate 1 during patterning, leakage current does not increase and the yield improves.

When the amorphous BN film 5 contains hydrogen, the hydrogen compensates for defects on the surface and side edges of the single crystal semiconductor substrate, reducing leakage current. Furthermore, the hydrogen (n, p
) reaction also improved the detection sensitivity of fast neutrons. As a manufacturing method, using discharge of a mixed gas containing boron, nitrogen, and hydrogen elements, it can be used as a protective film containing hydrogen in a single-crystal semiconductor substrate without causing crystal defects in a low-temperature process of 400°C or less. An amorphous BN film with good properties was formed, and a semiconductor radiation detector with good protection characteristics and reduced leakage current was obtained.

Although not described in the embodiments of the present invention, the same effect can be obtained even if the single crystal semiconductor substrate is made of GaAs, InP, CdTe, etc. and the electrical junction thereof is a PN junction or a Schottky junction.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional diagram of a first embodiment of a semiconductor radiation detector of the present invention, FIG. 2 is a cross-sectional diagram of a second embodiment of a semiconductor radiation detector of the present invention, and FIG. 3 is a diagram of a conventional semiconductor radiation detector. FIG. 2 is a cross-sectional configuration diagram of a semiconductor radiation detector. 1... Single crystal Si substrate, 2... Amorphous semiconductor film, 3
...Metal electrode, 4...Metal electrode, 5...Amorphous B
N film, 6...Platinum, 11...N-type single crystal Si substrate,
12... P type layer, 13... Boron coating. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1/Single crystal, Sδ

Claims (5)

[Claims] (1) A semiconductor radiation detector characterized in that it has an electrical junction on the surface of a single crystal semiconductor substrate, and an insulating film containing at least boron is provided on top of the electrical junction. (2) forming an amorphous semiconductor film on a single crystal semiconductor substrate;
A semiconductor radiation detector characterized in that an insulating film containing at least boron is provided on at least the single crystal semiconductor substrate and the amorphous semiconductor film to cover them. (3) The insulating film containing boron is made of amorphous boron nitride (B
N) The semiconductor radiation detector according to claim 1 or 2, wherein the semiconductor radiation detector is a film. (4) The semiconductor radiation detector according to claim 3, wherein the insulating film containing boron contains hydrogen. (5) forming an amorphous semiconductor film on at least a partial region of a single crystal semiconductor substrate; A method for manufacturing a semiconductor radiation detector, comprising the step of forming a boron nitride film covering a crystalline semiconductor substrate and the amorphous semiconductor film.