JPH069254B2 - Method for manufacturing semiconductor radiation detecting element - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor radiation detecting element for detecting radiation including thermal neutron rays.

[Conventional technology]

As shown in FIG. 2, a semiconductor radiation detecting element has a typical n-type region 22 formed on a p-type high resistivity silicon plate 21 by phosphorus diffusion using an oxide film 23 as a mask. The radiation is detected by the current flowing between the electrodes 24 and 25 on both sides, based on the electron-hole pairs generated when the radiation enters the depletion layer 10 caused by the application of. However, since the neutron beam has no charge, it has no effect on the Coulomb field of orbital electrons and nuclei except for the case reaction, and therefore electron-hole pairs do not occur. Therefore, a neutron beam is transmitted through a substance having a large neutron absorption cross section, an α ray is generated by a neutron transmutation reaction, and an electron-hole pair is generated in the depletion layer by the α ray.

FIG. 3 shows a cross-sectional structure of a semiconductor radiation detecting element capable of detecting thermal neutrons, which is disclosed in Japanese Patent Laid-Open No. 61-17477. The n-type silicon substrate 1, the boron coating 2, the electrodes 31, 3 are shown.
It consists of two. A p-type doping layer 4 is formed on a portion of the substrate 1 which is in contact with the boron film. When a thermal neutron beam 11 is incident on the detection element with a reverse voltage −V _B applied to the pn junction, ¹⁰ B + n →
⁷ Li + alpha particles 12 and ⁷ Li nucleus 13 by neutron transmutation reaction of alpha is generated, electrons in the depletion layer 10 by the alpha particles and ⁷ Li nucleus -
Hole pairs are generated, which are detected through the amplification circuit 15.

[Problems to be solved by the invention]

4 (a) to 4 (e) show an outline of the manufacturing process of the detection element shown in FIG. 3, in which a thermal oxide film or a CVD oxide film 23 is deposited on the surface of the n-type silicon substrate 1. After that (FIG. A), the window 26 is opened by a photo-etching process (FIG. B), and the boron film 2 is formed on this window through the mask 27 by the plasma CVD method (FIG. C). Then, this silicon substrate is inserted into an infrared irradiation annealing furnace, and is annealed in dry nitrogen at 900 ° C. for 10 seconds, for example, and boron is immersed in the silicon substrate 1.
28 is further electrically activated to form P ⁺ region 4 (d
(Figure). Next, an electrode 31 is formed on the surface of the boron coating 2 and an electrode 32 is formed on the back surface of the silicon substrate 1 by, for example, a vacuum evaporation method of aluminum through a mask 29 having a diameter of 100 to 200 μm smaller than that of the mask 27 (e figure). ).

The above-described manufacturing process requires at least an oxide film generation device for forming a thermal oxide film or a CVD oxide film, an infrared irradiation annealing furnace, a photoetching device, a plasma CVD device, and a vacuum deposition device. Therefore, the manufacturing of the radiation detecting element requires many steps and days, and in addition, the expensive oxide film generating apparatus and photoetching apparatus have a drawback that a high technique is required for handling them.

The object of the present invention is to provide a method for manufacturing a semiconductor radiation detecting element which is capable of detecting thermal neutron rays and has good characteristics, with relatively simple manufacturing equipment and short-term technical education, except for the above-mentioned drawbacks. To do.

[Means for solving problems]

In order to achieve the above object, the method of the present invention comprises depositing a boron film on a predetermined region of one surface of an n-type semiconductor substrate and providing the semiconductor substrate with a p-type region in contact with the boron coating. In forming a pn junction with the original portion of the semiconductor substrate, an amorphous silicon film is deposited on one surface of the n-type semiconductor substrate by a plasma CVD method using a silicon compound gas, and then an etching gas is used. The amorphous silicon film is selectively removed through a mask by plasma etching, and then plasma CV is performed using a boron compound gas.
A boron film is deposited on the removed portion of the amorphous silicon film on the substrate surface by the D method, and boron atoms are allowed to penetrate into the substrate to p
A layer shall be formed.

[Action]

The amorphous silicon film formed by plasma CVD and then patterned by plasma etching acts as a mask for forming a p-layer instead of a conventional oxide film, and a boron film is deposited by plasma CVD and at the same time a substrate is formed by glow discharge. Boron is doped by increasing the temperature. Therefore, each process can be performed by the same plasma reactor.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 5 shows a plasma reactor used for carrying out the present invention, in which electrodes 52 and 53 facing each other are arranged in a vacuum chamber 51.
Connected to power supply 54. Below the one electrode 53, a power supply 55 is provided so that the semiconductor substrate 1 placed on the electrode can be heated.
And a heater 56 connected to the. The vacuum evacuation system 57 is connected to the vacuum container 51 through a valve 58 for adjusting the pressure inside the container, which is measured by a vacuum gauge 59.
61, 62, 63 are adjusting circuits for adjusting gas pressure and flow rate
It is connected to the vacuum vessel via 64. A manufacturing process using this apparatus is shown in FIGS. 1 (a) to (d). First, the specific resistance 10
Negative electrode 53 with 00Ωcm n-type silicon substrate 1 with the mirror surface facing up
Placed on the top of the container, for example, SiH ₄ gas diluted with hydrogen to 10% is introduced into the vacuum container 51 from the cylinder 61, and the gas pressure is 1 to 10 Torr.
Then, a voltage of 600 to 800 V is applied between the electrodes 52 and 53 to generate glow discharge, and a 1 μm thick amorphous silicon film 5 is deposited on the surface of the substrate heated to 200 ° C. by the heater 56 ( (Figure a). Next, a metal mask 6 having a predetermined shape is placed on the amorphous silicon film 5, SF ₆ gas is introduced from the cylinder 62 into the vacuum vessel 1, and a glow discharge is performed at a gas pressure of 0.2 Torr and a discharge voltage of 800 V. Is generated, the portion of the window which is not covered with the metal mask reacts with SF ₆ gas and the region 7 of the amorphous silicon film 5 is removed by dry etching (FIG. 7B). Then, for example, boron isotope ₁₀ B is added to 94%
Gas containing diborane (B ₂ H ₆ ) contained above diluted to 1000 ppm with hydrogen is introduced into the vacuum vessel 51 from the cylinder 63 and the gas pressure is set to 2
Glow discharge is similarly generated by a discharge voltage of 400 to 700 V at -6 torr, and the boron coating 2 having a thickness of 0.6 μm is heated at a temperature of 200 ° C.
On the area 7 of the silicon substrate 1. At the time of forming the boron film, boron atoms penetrate into the n-type silicon substrate 1 and have a surface concentration of 1 to 3 × 10 ¹⁵ atoms / cm ³ and a depth of about 0.3 μm.
A P-type doping layer 4 of m is formed to form a pn junction.
(Figure c).

Next, the n-type silicon substrate 1 is taken out of the vacuum chamber 51 and the mask 8 is used to form, for example, an aluminum layer on the boron film 2 and the substrate 1 by vacuum vapor deposition as in the case of FIG.
Then, the electrodes 31 and 32 are obtained by forming the electrodes on the back surface (FIG. 3D). Before introducing each reaction gas into the vacuum vessel 51, each step was performed after the vacuum degree was kept at 1 × 10 ⁻⁶ Torr by the vacuum exhaust system 57.

The structure of the device thus manufactured is the same as that of the device of FIG. 3 manufactured in the process of FIG. 4, except that an amorphous silicon film is used instead of the oxide film as the surface protection film. The difference is that the window opening process of the crystalline silicon film is performed by dry etching using a metal mask instead of photoetching. The resistivity of an amorphous silicon film formed by plasma CVD is 1 to 3 × 10 ¹⁰ Ωcm, which is lower than 10 ¹⁴ to 10 ¹⁵ Ωcm of a thermal oxide film or a CVD oxide film. It is possible to obtain an element that is hard to be accumulated in the film and has high radiation resistance. Especially when it is used for neutron ray detection, its effect is great because many r rays are mixed.

〔The invention's effect〕

According to the present invention, an amorphous silicon film that can be formed by the plasma CVD method is used as a surface protection film, and a plasma CV is formed in a window opened in the film by plasma etching.
By forming a boron film containing an isotope and doping at the same time by the D method to form a PN junction in the N-type silicon substrate, the plasma reaction is continuously utilized in the same device to expose the element substrate to the atmosphere. Each step can be performed without exposing. Therefore, the boron film can be formed on the surface of a clean silicon substrate with good reproducibility of the film thickness and good adhesion, and the photo-etching process is not required due to the dry etching using the mask, which is not necessary for the oxide film forming process. This has made it possible to reduce manufacturing equipment, greatly simplify the manufacturing process, and reduce the manufacturing cost of semiconductor radiation devices that can detect neutron rays and have strong radiation resistance.

[Brief description of drawings]

1 (a) to 1 (d) are sectional views sequentially showing a manufacturing process of an embodiment of the present invention, FIG. 2 is a sectional view of a semiconductor radiation detecting element, and FIG. 3 is a semiconductor radiation detection capable of detecting neutron rays. Sectional views of the element, FIGS. 4 (a) to 4 (e) are sectional views sequentially showing the conventional manufacturing process of the element of FIG. 3, and FIG. 5 is a configuration diagram of a plasma reactor used in one embodiment of the present invention. Is. 1: n-type silicon substrate, 2: boron film, 4: p-type doping layer, 5: amorphous silicon film, 6: mask.

Claims (1)

[Claims] 1. A boron film is deposited on a predetermined region on one surface of an n-type semiconductor substrate, and p is brought into contact with the boron film of the semiconductor substrate.
In forming a pn junction with the original portion of the semiconductor substrate by providing the shaped region, an amorphous silicon film is deposited on one surface of the n-type semiconductor substrate by a plasma CVD method using a silicon compound gas. The amorphous silicon film is selectively removed through a mask by plasma etching using an etching gas, and then the amorphous silicon film removal portion on the substrate surface is formed by a plasma CVD method using a boron compound gas. A method for manufacturing a semiconductor radiation detecting element, comprising depositing a boron film on the substrate and infiltrating boron atoms into the substrate to form a p-layer.