JPH0716024B2 - Method for manufacturing semiconductor radiation detecting element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor radiation detecting element for detecting fast neutrons using hydrogen atoms.

[Conventional technology]

The semiconductor radiation detection element has a diode structure such as a pn junction type or a Schottky junction type. A reverse bias is applied to this junction to expand the depletion layer, and the radiation is injected into the depletion layer to reduce the range. The generated electron-hole pairs are counted to detect radiation. With this method, it is possible to detect radiation having ionizing action such as α, β, γ, and x-rays.
However, since neutrons have no charge, they have no effect on the Coulomb field of orbital electrons and nuclei except for nuclear reactions, and thus electron-hole pairs do not occur. Therefore, the semiconductor radiation detection element as described above is not suitable for neutron detection as it is.

Known semiconductor neutron detection elements include those using ¹⁰ B (n, α) conversion with the isotope ¹⁰ B of boron, and those using hydrogen atoms. This is a method to detect fast neutrons by using (n, p) scattering reaction. Neutrons give part of their energy to protons, and utilize the results of ionization and excitation phenomena of protons. Is. However, it is not easy to fix hydrogen atoms for this purpose in the semiconductor substrate.

For example, as a semiconductor neutron detecting element using this principle, there is one in which a plate containing a large amount of hydrogen atoms, for example, a polyethylene plate is placed on the front surface of the semiconductor radiation detecting element. However, this has drawbacks such as a complicated structure and poor detection efficiency. Further, a semiconductor neutron detector using an amorphous semiconductor is disclosed in Japanese Patent Laid-Open Publication No.
No. 56-114382 is known. The publication discloses an embodiment in which a p-i-n structure is made of an amorphous semiconductor using hydrogenated amorphous silicon or amorphous germanium. At present, amorphous silicon is used in various fields such as solar cells and can be made very easily.This amorphous silicon compensates for dangling bonds by hydrogen atoms and creates a large amount of hydrogen atoms. It is taking in. The element focused on this point is a very effective idea, and is also excellent in that hydrogen atoms are fixed in the element itself.

[Problems to be solved by the invention]

However, this amorphous semiconductor has a depletion layer width of about 1 μm.
It is very thin and has a very short lifetime, which is problematic as a semiconductor radiation detecting element. That is, since the number of electron-hole pairs generated in the depletion layer of the amorphous semiconductor due to incident radiation is small and the lifetime is short, the obtained signal is small and it is difficult to distinguish it from the noise component.

An object of the present invention is to provide a semiconductor radiation detecting element which can detect neutrons by utilizing hydrogen atoms contained in an amorphous semiconductor and has a large signal.

[Means for solving problems]

In order to achieve the above-mentioned object, according to the present invention, a step of depositing an amorphous semiconductor layer on at least one surface of a crystalline semiconductor element body on which a junction is formed, and hydrogen plasma in the amorphous semiconductor layer. And the step of exposing to at least 3 times are alternately repeated.

[Action]

Since the number of electron-hole pairs generated by the incidence of radiation into the depletion layer formed by the junction formed in the crystalline semiconductor element body having a long lifetime is large, the radiation detection efficiency is high, and the non-deposited layer deposited on the surface is high. Since the crystalline semiconductor layer has a high hydrogen atom concentration due to the penetration of hydrogen, it has a high probability of causing a reaction between fast neutrons and hydrogen atoms, and has high sensitivity to fast neutrons. In particular, by repeating the amorphous semiconductor layer forming step and the step of exposing this layer to hydrogen, as a whole,
A hydrogenated amorphous semiconductor layer having a large thickness and a higher hydrogen concentration can be obtained.

〔Example〕

FIG. 1 shows an embodiment of the present invention. For example, electrodes 2 and 3 are provided on both surfaces of a silicon substrate 1 having a pn junction inside,
Lead wires 21 and 31 are connected to each. The amorphous silicon layer 41, 42, 43 is formed on one surface of the substrate 1 so as to cover the electrode 2.
Are stacked. Each amorphous silicon layer has a hydrogen atom penetration layer 5 on the side far from the substrate. The electrode 2
The lead wire 21 connected to the above is drawn out from the window 6 opened in the amorphous silicon layers 41 to 43. FIG. 2 shows an apparatus for producing an amorphous silicon layer having such a hydrogen atom penetration layer 5. This is an ordinary plasma generator, which introduces monosilane-containing hydrogen gas or hydrogen gas into the reaction tank to generate plasma by a DC voltage. For that purpose, the upper electrode plate 12 and the lower electrode plate 13 are arranged in the reaction tank 11 and connected to the DC power source 14, and the reaction tank 11 also includes a monosilane-containing hydrogen gas cylinder 15 and a hydrogen gas cylinder 16 and an exhaust system 1.
7. A vacuum gauge 18 is connected, and a heater 19 is provided on the lower electrode plate 13. The silicon substrate 1 on which a pn junction or the like is formed in advance is placed on the lower electrode 13, and the heater 19 is used to
Heat to ℃. In order to set the internal pressure of the reaction tank 11 that has been evacuated by the exhaust system 17 to, for example, 4 torr, the gas cylinder 15
Then, hydrogen gas containing 10% of monosilane (SiH ₄ ) is introduced and 800 V, for example, is applied between the electrodes 12 and 13 by using a power supply 14. By applying this voltage, monosilane plasma is generated, and an amorphous silicon layer 41 is deposited on the surface of the silicon substrate 1 as shown in FIG. Next, the supply of monosilane gas from the monosilane-containing hydrogen gas cylinder 15 was stopped, hydrogen gas was introduced from the hydrogen gas cylinder 16, and the reaction tank
The internal pressure of 11 is set to, for example, 4 torr and 80 between the electrodes 12 and 13.
Apply 0V. By applying this voltage, hydrogen plasma is generated between the electrodes 12 and 13, and a large amount of hydrogen atoms penetrate from the surface of the amorphous silicon layer 41. Next, after the supply of hydrogen gas to the reaction tank 11 is stopped, the monosilane gas is again introduced into the reaction tank 11 from the gas cylinder 15, and the amorphous silicon layer 42 is formed on the surface of the amorphous silicon layer 42 by the above-described method. Deposit on the crystalline silicon layer 41. After the formation of the amorphous silicon layer 42, hydrogen gas is again introduced by the above method to inject a large amount of hydrogen on the amorphous silicon layer 42. Electrodes like this
By alternately generating plasma of monosilane and plasma of hydrogen gas between 12 and 13, a hydrogenated hydrogenated amorphous silicon layer having an extremely high hydrogen atom concentration can be easily obtained with a thickness of several μm or more. In the present embodiment, the monosilane-containing hydrogen gas cylinder 15 and the hydrogen gas cylinder 16 are provided with an on-off valve (not shown) which is operated by compressed air by an electric signal so that the gas can be introduced a predetermined number of times automatically. For example, after opening the valve of the gas cylinder 15 for 10 minutes and supplying monosilane gas into the reaction tank 11, the gas cylinder 15
The valve of the gas tank 16 is closed for 30 minutes, and then the valve of the gas cylinder 16 is opened for 10 times.
When the voltage was kept at 800 V, a hydrogenated hydrogenated amorphous silicon layer having a thickness of about 2 μm was obtained.

FIG. 3 shows the results of measuring the hydrogen atom concentration contained in the hydrogenated hydrogenated amorphous silicon layer thus obtained, using a secondary ion mass spectrometer (SIMS). The hydrogenated amorphous silicon layer formed by using the above monosilane gas (10% SiH ₄ hydrogen base) contains about 5 × 10 ²⁰ atoms / cm ³ of hydrogen atoms. Is further exposed to hydrogen gas plasma, a high-concentration hydrogen penetration layer 5 can be obtained. As can be seen from FIG. 3, the surface of the amorphous silicon layer is about 2 × 10 ²² atoms / cm ³ , and the average is about 9 × 10.
An amorphous silicon layer containing ²¹ atoms / cm ³ of hydrogen atoms is obtained.

FIG. 4 shows another embodiment of the present invention, which is a hydrogenated amorphous silicon layer 44, 45, which also has a hydrogen penetration layer 5 on the back surface of the silicon substrate.
Formed 46 has the advantage that hydrogen with higher fast neutron sensitivity can be obtained.

The silicon substrate 1 shown in FIG. 1 and FIG.
Even if a surface barrier junction or a heterojunction was formed instead of the pn junction, no change was observed in the characteristics of the finished detection element. This is because the hydrogenated hydrogenated amorphous silicon layer is formed at a low temperature of 200 ° C.

FIG. 5 is a spectrum diagram when the device obtained by the present invention is irradiated with fast neutrons. The spectrum 51 is for two amorphous silicon layers, and the spectrum 52 is for 10 amorphous silicon layers, and the fast neutrons are almost proportional to the thickness of the amorphous silicon layer, that is, the content of hydrogen atoms. It can be seen that the sensitivity of is higher. In addition, the fast neutron standard radiation source used here is ²⁵² Cf, and since γ-rays are simultaneously emitted in addition to neutrons, the γ-ray component is also observed, but it can be distinguished from the fast neutron component. I also understand that.

Since the detection element according to the present invention has the same structure as a normal semiconductor radiation detection element except that it has an amorphous semiconductor layer containing a large amount of hydrogen atoms on the semiconductor surface,
It is obvious that α, β, γ, x-rays can be detected in addition to fast neutrons. Not only single crystal silicon but also GaAs, CdTe
It is also possible to manufacture using a crystal of a compound semiconductor such as.

〔The invention's effect〕

According to the present invention, as a result of adopting the above method, a layer having a high hydrogen atom concentration is formed on an element body, and a radiation detector for detecting fast neutrons with high sensitivity can be made into a semiconductor. Although amorphous germanium or the like can be used as the amorphous semiconductor, in particular, amorphous silicon has a depth of penetration of hydrogen atoms that is 2-3 times deeper than that of single crystal silicon. Since a large amount of hydrogen atoms can be fixed, the sensitivity can be increased. Since the detection element according to the present invention does not need to install a hydrogen-containing substance such as paraffin or polyethylene around the semiconductor detection element like a conventional semiconductor neutron detector, a very lightweight and simple structure can be obtained. . As a result, it has become possible to obtain a radiation exposure dosimeter that can detect pocket-type fast neutrons, which was conventionally impossible in terms of weight. In addition, since the deposition of the amorphous semiconductor layer is performed at a low temperature of 200 ° C., the characteristics of the junction previously formed on the semiconductor element body hardly deteriorate. Therefore, it has an advantage that hydrogen can be fixed on the surface of any element.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a sectional view of a plasma generator used for carrying out the present invention, and FIG. 3 is a hydrogen atom-introduced amorphous silicon layer according to the present invention. FIG. 4 is a hydrogen concentration distribution diagram in the thickness direction, FIG. 4 is a sectional view of another embodiment of the present invention, and FIG. 5 is a spectrum diagram when the device according to the present invention is irradiated with fast neutrons. 1: Silicon substrate, 2, 3: Electrode, 41 to 46: Amorphous silicon layer, 5: Hydrogen atom penetration layer.

Claims (1)

[Claims] 1. A step of depositing an amorphous semiconductor layer on at least one surface of a crystalline semiconductor element body having a junction, and a step of exposing the amorphous semiconductor layer to hydrogen plasma at least three times. , A method for manufacturing a semiconductor radiation detecting element, characterized in that the method is repeated alternately.