JPH0476234B2 - - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention [Field of Industrial Application] The present invention relates to a multi-channel radiation detector using a P-type cadmium tellurium (hereinafter simply referred to as CdTe) crystal substrate; It relates to its manufacturing method. More specifically, the present invention relates to improving isolation characteristics between channel elements.

[Conventional technology]

FIG. 3 is a diagram showing a conventional multichannel surface barrier radiation detector formed in an array. In the same figure, is a perspective view and a cross-sectional view showing an example in which each element is completely cut and separated and lined up, and is a perspective view and its cross-sectional view showing an example in which electrodes 3 are formed in an array on the same semiconductor substrate. FIG. In this FIG. 3, 1 is a support stand. Reference numeral 2 denotes a substrate, which is made of semiconductor crystal.
Reference numeral 3 represents an electrode, which has shot barrier bonding characteristics. 4 is an ohmic electrode. Reference numeral 5 denotes a radiation sensitive layer, which consists of a depletion layer created by the electrode 3 and a carrier diffusion layer.

[Problem that the invention seeks to solve]

The conventional example shown in FIG. 3 has the following drawbacks.

Although the separation characteristics of each radiation detection element in FIG. 3 are good, there is a drawback that the process of forming each element as shown in the figure or the process of arranging them as an array becomes complicated.

FIG. 3 shows a case in which electrodes 3 are formed after surface treatment such as chemical etching and ion sputter cleaning has been performed on a semiconductor substrate 2. As shown in FIG.
Here, if the substrate 2 is made of a high resistivity crystal, the radiation-sensitive layer 5 will be connected to the adjacent radiation-sensitive layer, resulting in poor separation characteristics of the radiation detection element.
Particularly in the case of a highly sensitive detector, it is necessary to increase the specific resistance of the substrate crystal and widen the sensitive layer 5, which further deteriorates the separation characteristics of the elements.

Figure 4 shows the element separation characteristics of a multichannel radiation detector when the configuration shown in Figure 3 is used as is, the substrate 2 is a P-type CdTe crystal, and the shot barrier junction electrode 3 is aluminum Al. This is a diagram. In the figure, the vertical axis shows the radiation response signal, and the horizontal axis shows the electrode position. Further, in the figure, the characteristic is the signal of the detector having the configuration shown in FIG. 3, and the characteristic is the signal of the detector having the configuration shown in FIG. 3. As can be seen from FIG. 4, the radiation detector having the configuration shown in FIG. 3 has poor element separation characteristics.

B "Structure of the Invention" [Means for Solving the Problems] In the radiation detector according to the present invention, in the process of surface treatment of the CdTe crystal, after chemical etching,
Only the electrode part of the shot barrier junction is subjected to ion sputter etching to remove the chemical etching layer, and then an electrode having shot barrier bonding characteristics is formed by vacuum evaporation on the surface treated with ion sputter etching. The structure is such that they are sufficiently electrically independent and the radiation response signals are well separated, and a chemically etched surface layer remains between each element (between electrodes).

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The radiation detector according to the present invention will be described below with reference to FIGS. 1 and 2 based on the order of its manufacturing process.

In FIG. 1, a is a mask having a slit of a predetermined width, and is made of metal. b is a crystal substrate, in which a high-resistivity P-type CdTe crystal is cut and polished to a thickness of, for example, 0.5 to 2 mm;
Chemically etched with a bromine methanol solution. c is a chemically etched portion (layer) of the crystal substrate b.

In this way, the chemically etched crystal substrate b
As shown in FIG. 1, a mask a is placed on top of the film, and argon ion sputter etching is performed from direction A as shown in the same figure. As a result, the chemically etched layer c of the crystal substrate b corresponding to the slit portion of the mask a is removed by Ar ion sputter etching, as shown in FIG.

Next, electrodes are provided as shown in FIG. In FIG. 2, b and c are the same as those explained in FIG. d is an electrode, and by vacuum evaporation method,
This is a thin film shot barrier bonding made of Al, Pt, etc. Then, this electrode d is formed by patterning using a mask a. At this time, the chemically etched surface layer remains between each element (between electrodes d).

On the other side, for example, an ohmic electrode e is formed using a thin Au film by electroless plating with gold chloride.

The P-type CdTe crystal substrate b under the electrode d of the radiation detector shown in FIG. f is formed. Therefore, when radiation is incident from the direction of the electrode d, carriers generated within the radiation-sensitive layer f become a response signal as an ionization current. Figure 5 shows
It shows the separation characteristics of each element of the response signal when a line is incident.

In FIG. 5, the dotted line indicates the response signal for the configuration shown in FIG. 3, which is the same as in FIG. On the other hand, solid line A shows a response signal of the radiation detector (configuration shown in FIG. 2) according to the present invention. As can be seen from this data, the radiation detector of the present invention is close to the one in FIG. 3 (dotted line data) in which the elements are completely separated, indicating that the elements are sufficiently separated.

The reason for this improved separation property is the chemically etched surface (chemically etched layer c in Figure 2).
However, it is a layer that is far away from the stoichiometric ratio of CdTe, and has a very high deep trap level concentration, which prevents the depletion layer and carrier diffusion layer from spreading between the elements. This is because the chemically etched surface layer is removed, so the shot barrier bonding properties are improved.

C. ``Effects of the present invention'' As described above, according to the present invention, in a CdTe crystal in which heat treatment and formation of a diffusion layer are not easy to control, a P-type high-resistance CdTe crystal is used, and after chemical etching, a metal mask is etched. Therefore, by using a continuous method of forming Ar ion sputter etching surface treatment and vacuum evaporation of metal (Al, Pt, etc.) thin film shot barrier bonding electrodes, we have created multi-channel radiation with sufficient independent isolation of each element. A detector can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the removal of the chemical etching layer c by argon ion sputter etching in the radiation detector according to the present invention, and FIG. 2 is a diagram showing an example of the configuration of the radiation detector according to the present invention. Figure 3 is a diagram showing a conventional multi-channel type surface barrier radiation detector formed in an array.
The figure uses the configuration shown in Figure 3 as it is, and the board 2 is P-shaped.
CdTe crystal and shot barrier junction electrode 3
Fig. 5 is a diagram showing a comparison of the element separation characteristics of the radiation detector according to the present invention and the detector shown in Fig. 3. It is. a...mask, b...crystal substrate, c...chemical etching layer, d...electrode, e...ohmic electrode, f...radiation sensitive layer.

Claims (1)

[Claims] 1. A multi-channel radiation detector using a P-type CdTe crystal substrate b, including a plurality of slit regions arranged adjacent to each other in the longitudinal direction on one surface of the crystal substrate b. a chemically etched layer (c) uniformly provided on the slit, and an electrode having shot barrier bonding properties, provided on the region of the slit, and a crystal substrate (b) below the surface on which it is provided. radiation sensitive layer f
A radiation detector comprising: an electrode d forming an electrode d; 2 In a multi-channel radiation detector using a P-type CdTe crystal substrate, a mask with slits is placed on a CdTe crystal plate whose surface has been chemically etched, and CdTe is removed in the area corresponding to the slit. The chemical etching layer on the surface of the crystal is removed by ion sputter etching, and then electrodes having shot barrier bonding characteristics are formed on the surface of the CdTe crystal at each portion where the chemical etching layer has been removed, and A method for manufacturing a radiation detector, characterized in that a chemically etched layer remains between each of the electrodes.