JP2007221010A - Semiconductor x-ray detecting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability and productivity without occurrence of an undesirable phenomenon caused by electrification of a protective layer. <P>SOLUTION: An element surface that is not covered by an n surface electrode (4) and a p surface electrode (6) are covered by two layers, an oxide layer (7) and a nitride layer (8). The oxide layer (7) and the nitride layer (8) function as protective layers. The oxide layer (7) and the nitride layer (8) can be formed using a method suitable for mass production. Therefore, productivity can be improved. Variations in film quality can be reduced. With only the oxide layer (7), the protective layer tends to become positively charged. With only the nitride layer (8), the protective layer tends to become negatively charged. However, because of the two-layer structure, both charges are neutralized and the protective layer is not electrified. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor X-ray detection element, and more particularly to a semiconductor X-ray detection element with improved productivity and reliability.

Conventionally, a semiconductor X-ray detection element having an n-plane electrode, an n ⁺ layer, an i layer, a p-layer, and a p-plane electrode is known (see, for example, Patent Document 1).
JP 2005-183603 A

In the conventional semiconductor X-ray detection element, the n ⁺ layer not covered with the n-plane electrode, the i layer not in contact with the p-plane electrode, and a part of the surface of the p layer are covered with a protective film.
However, since this protective film (for example, silicon-based resin) has to be baked and hardened after hand-painting the elements one by one, the productivity is low and the film quality tends to vary.
Furthermore, this protective film was easy to be charged, but when the protective film was charged, the surface portion of the i layer became an n ⁺ layer, and an electric field curve (electric field lines) when a reverse bias was applied between the n-plane electrode and the p-plane electrode. ) Is curved and the electric field is not uniformly applied. As a result, undesired phenomena such as a tail on the low energy side of the spectrum peak or an increase in the background may occur. There was a low problem.
Therefore, an object of the present invention is to provide a semiconductor X-ray detection element with improved productivity and reliability.

In a first aspect, the present invention is a semiconductor X-ray detection element having an n-plane electrode, an n ⁺ layer, an i-layer, a p-layer electrode, and a p-plane electrode, which is covered with the n-plane electrode and the p-plane electrode. There is provided a semiconductor X-ray detection element comprising an oxide film covering all non-element surfaces and a nitride film covering the surface of the oxide film.
In the semiconductor X-ray detection element according to the first aspect, the surfaces of the n ⁺ layer not covered with the n-plane electrode, the i layer not in contact with the p-plane electrode, and the p layer are covered with two layers of an oxide film and a nitride film. A protective film is used. Since the oxide film and the nitride film can be formed by a method suitable for mass production, productivity can be improved. In addition, variations in film quality can be reduced. Furthermore, the oxide film alone is easily charged to +, and the nitride film alone is easily charged to-, but due to the two-layer structure of the oxide film and the nitride film, the mutual charges cancel each other and they are no longer charged. Therefore, an undesirable phenomenon due to charging of the protective film does not occur, and the reliability can be improved.

  In the past, the side of the element was sandwiched between tweezers, etc., and the element was held and hand-painted. As a result, a protective film could not be formed on the side of the element. Was incomplete, but no such part occurs and the protection is complete. In the case of a semiconductor X-ray detection element (high purity Si detection element) using a high resistance Si crystal that does not use lithium (Li) or a semiconductor X-ray detection element (high purity Ge detection element) using a Ge crystal, It is particularly effective.

In a second aspect, the present invention provides the semiconductor X-ray detection element according to the second aspect, wherein the oxide film is a SiO ₂ film and the nitride film is a Si ₃ N ₄ film. An X-ray detection element is provided.
In the semiconductor X-ray detection element according to the second aspect, for example, a SiO ₂ film can be formed by immersing in an ammonia hydrogen peroxide aqueous solution at 80 to 90 ° C., and Si CVD by plasma CVD with SiH ₄ and N ₂ gas flowing. _{Since 3} N ₄ film can be formed, it can be manufactured using a stable manufacturing process.

  According to the semiconductor X-ray detection element of the present invention, since the oxide film and the nitride film can be formed by a method suitable for mass production, productivity can be improved. In addition, variations in film quality can be reduced. Furthermore, since the two-layer structure of the oxide film and the nitride film cancels each other's electric charges and becomes uncharged, an undesirable phenomenon due to charging does not occur and reliability can be improved.

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a cross-sectional view illustrating a semiconductor X-ray detection element 100 according to the first embodiment.
The semiconductor X-ray detection element 100 includes an n-plane electrode 4 that collects electrons when a reverse bias is applied, an n ⁺ layer 1 in which majority carriers are electrons, an i layer 2 that is an intrinsic region, and majority carriers A p-layer 3 that is a hole; a p-plane ring electrode 5 and a p-plane electrode 6 that collect holes; and an oxide film 7 that covers an element surface that is not covered by the n-plane electrode 4 and the p-plane electrode 6; A nitride film 8 covering the surface of the oxide film 7 and a light receiving part EW on which X-rays enter are provided.

The oxide film 7 is a SiO ₂ film, and the nitride film 8 is a Si ₃ N ₄ film.

  When X-rays enter the light receiving unit EW, electron-hole pairs proportional to the energy of the X-rays are generated in the i layer 2, so that electric signals are taken out from the n-plane electrode 4 and the p-plane electrode 6.

The portion of the i layer 2 that is continuous with the n ⁺ layer 1 is referred to as an i layer body portion 21, and the cross-sectional area of the i layer body portion 21 is referred to as a “light receiving area”. Further, the portion of the i layer 2 extending to the p layer 3 is referred to as an i layer edge portion 22.

  According to the semiconductor X-ray detection element 100 of the first embodiment, the oxide film 7 and the nitride film 8 function as a protective film. Since the oxide film 7 and the nitride film 8 can be formed by a method suitable for mass production, productivity can be improved. In addition, variations in film quality can be reduced. Furthermore, although the oxide film 7 alone is easily charged to + and the nitride film 8 alone is easily charged to-, the two-layer structure of the oxide film 7 and the nitride film 8 cancels each other out of charge. Therefore, an undesirable phenomenon due to charging of the protective film does not occur, and the reliability can be improved.

FIG. 2 is a flowchart illustrating a process of manufacturing the semiconductor X-ray detection element 100 according to the first embodiment.
In step S1, Li is vapor-deposited on the upper surface of the p-type semiconductor crystal PC as shown in FIG. The p-type semiconductor crystal PC is, for example, a silicon crystal doped with an impurity such as boron (B).

In step S2, as shown in FIG. 4, Li is thermally diffused to form the n ⁺ layer 1a.

  In step S3, as shown in FIG. 5, Ni / Au is vapor-deposited to form the n-plane electrode 4a.

In step S4, the n-plane electrode 4a, the n ⁺ layer 1a, and a part of the p-type semiconductor crystal PC are removed by, for example, an ultrasonic cutting machine so as to form a top hat shape, and as shown in FIG. And n ⁺ layer 1 is formed.

  In step S5, as shown in FIG. 7, a voltage is applied while the temperature is increased to diffuse Li, thereby forming the i layer 2 including the i layer body portion 21 and the i layer edge portion 22.

  In step S6, as shown in FIG. 8, the p-side bottom surface 31 is polished until the i-layer edge 22 has the same light receiving area.

  In step S7, as shown in FIG. 9, a p-plane Au electrode 5a is deposited on the bottom surface.

In step S8, for example, the substrate is immersed in an aqueous ammonia hydrogen peroxide solution set at 80 to 90 ° C. to form an oxide film 7 of a SiO ² film as shown in FIG. In this step, a large number of elements can be processed at once by batch processing.
Note that, in the semiconductor X-ray detection element 100 according to the first embodiment, the high temperature process cannot be applied to prevent reheat diffusion because Li is used. Therefore, the oxide film 7 uses a chemical oxide film formed in a chemical solution.

In step S9, a Si ₃ N ₄ nitride film 8 is formed as shown in FIG. 11, for example, by plasma CVD using SiH ₄ and N ₂ gas. In this step, a large number of elements can be processed at once by batch processing.

  In step S10, as shown in FIG. 12, the p-plane Au electrode 5a and a part of the i-layer 2 are etched on the bottom surface to form the light receiving part EW and the p-plane ring electrode 5, for example.

  In step S11, as shown in FIG. 1, Ni is vapor-deposited on the bottom surface to form the p-plane electrode 6.

  According to the above method for manufacturing a semiconductor X-ray detection element, the semiconductor X-ray detection element 100 according to the first embodiment can be preferably manufactured.

FIG. 13 is a cross-sectional view illustrating a semiconductor X-ray detection element 200 according to the second embodiment.
The semiconductor X-ray detection element 200 is basically the same as the semiconductor X-ray detection element 100 of the first embodiment, but the area of the n-plane electrode 4 and the n ⁺ layer 1 is larger than the light receiving area in order to reduce the capacitance of the element. Is also getting smaller.

  The semiconductor X-ray detection element of the present invention can be used as a detector of an energy dispersive X-ray analyzer.

1 is a cross-sectional view showing a semiconductor X-ray detection element according to Example 1. FIG. FIG. 3 is a flowchart showing a method for manufacturing a semiconductor X-ray detection element according to Example 1. It is explanatory drawing which shows the vapor deposition process of Li. It is explanatory drawing which shows the thermal diffusion process of Li. It is explanatory drawing which shows the formation process of an n-plane electrode. It is explanatory drawing which shows the process shape | molded in a top hat shape. It is explanatory drawing which shows the drift process of Li. It is explanatory drawing for the grinding | polishing process of the p side bottom face. It is explanatory drawing which shows the formation process of a p-plane electrode (Au). Is an explanatory view showing the step of forming the oxide film (SiO _2). It is an explanatory view showing the step of forming the nitride film (Si ₃ N _4). It is explanatory drawing which shows the formation process of a light-receiving part. 6 is a cross-sectional view showing a semiconductor X-ray detection element according to Example 2. FIG.

Explanation of symbols

1 n + layer 2 i layer 3 p layer 4 n-plane electrode 5 p-plane ring electrode 6 p-plane electrode 7 oxide film 8 nitride film 100, 200 semiconductor X-ray detection element

Claims (2)

a semiconductor X-ray detection element having an n-plane electrode, an n ⁺ layer, an i-layer, a p-layer, and a p-plane electrode, and an oxide film covering the element surface not covered with the n-plane electrode and the p-plane electrode; A semiconductor X-ray detection element comprising a nitride film covering a surface of an oxide film. In the semiconductor X-ray detector according to claim 1, wherein the oxide film is a SiO ₂ film, a semiconductor X-ray detector elements, wherein the nitride film is a Si ₃ N ₄ film.

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