JPH08222754A - Semiconductor x-ray detector and manufacturing method thereof - Google Patents

Abstract

PURPOSE: To provide a semiconductor X-ray detector and a manufacturing method capable of low voltage operation with high sensitivity and high density packaging. CONSTITUTION: The side face of a substrate 1 made of a semiinsulating compound is doped with impurities to form a p type, -n type, and -p type structure. Furthermore, an oxide film 2, a metallic film are formed respectively to be a protective film and an electrode 3. Next, these elements are impressed with reverse bias and the substrate surface is with injected X-ray in parallel direction to operate it as an X-ray detector.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to semiconductor photodetection, and in particular to X
The present invention relates to a wire detection device and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a scintillation counter has been used for the detecting section of an X-ray detecting apparatus for industrial and medical purposes. Its structure and operation are described in "Physics Dictionary (Baifukan, 19
1984) ". However, the scintillation counter has the drawback of being spatially large.

In addition to this, there is also a semiconductor X-ray detector using Si as a substrate, but it has a drawback of low quantum efficiency.

Further, using a compound semiconductor substrate, p-type-n
There is also a radiation detector having a type-p type structure, but it has a high operating voltage and is not suitable for detecting X-rays parallel to the substrate surface. Therefore, since the X-ray incidence in the direction perpendicular to the substrate surface is detected, the detection area becomes large and there is a drawback that high-density arrangement becomes difficult.

[0005]

SUMMARY OF THE INVENTION The present invention provides a semiconductor X which is spatially smaller than a conventional scintillation counter.
Provide a line detector.

Further, the present invention provides a semiconductor X-ray detector having high quantum efficiency as compared with the conventional semiconductor X-ray detector using Si as a substrate. Further, the effect is to provide a semiconductor X-ray detector which is thinner than the conventional one, makes the incident direction of X-rays parallel to the substrate surface, and allows the X-rays to be incident from the side surface of the substrate, thereby enabling spatially high-density arrangement.

Further, according to the present invention, by using the low-concentration semi-insulating substrate, the depletion layer generated in the vicinity of the pn junction can be easily expanded, and the semiconductor X which can operate at a low voltage can be obtained.
Provide a line detector.

[0008]

In the present invention, a semiconductor wafer is used as the main substrate of the X-ray detector, and semi-insulating GaAs is used as the substrate material, and p-type impurities are doped from both sides. Further, electrode deposition is performed on a plurality of surfaces.

[0009]

When a bias is applied to the above electrode, one of the pn junctions existing at two places becomes a reverse bias operation and the other becomes a forward bias operation, but the depletion layer spreads by the forward bias in comparison with the expansion of the depletion layer by the reverse bias. Therefore, only the reverse bias operation is required as the function of this detector, and the influence of the forward bias operation is ignored. The depletion layer is widened by the reverse bias, and the carriers generated by the X-ray incidence are extracted as current from the electrode to detect the X-ray incidence amount.

[0010]

1 is a top view of a semiconductor X-ray detector according to an embodiment of the present invention. 2 is a sectional view taken along line AA of FIG. The substrate portion 1 is made of semi-insulating GaAs and has a carrier concentration of about 10 ⁸ to 10 ⁹ / cm ³ . AlO ₃ /
Using the diffusion pattern mask 2 of SiO ₂ , Zn is diffused and doped at 5 to 10 μm from both the upper surface and the lower surface to form a p-type diffusion region 4. Add TiPtAu to the top and bottom electrodes 3
As a vapor deposition.

The carrier concentration in the diffusion region is sufficiently higher than the carrier concentration in the substrate, and can be considered to be a step junction. When the concentration of the semi-insulating GaAs substrate is 10 ⁹ / cm ³ , the following formula is established between the depletion layer extension W [mm] and the reverse bias Vr [V].

[0012]

[Equation 1] W = 3.81 × √ (0.089 + Vr / 10) [mm] (Equation 1) Therefore, with a target bias of about 25 V, the depletion layer becomes about 6 mm, and the device thickness is 0.4 mm. Will be long enough.
In addition, since the depletion layer spreads about 1 mm even without bias, 1
A low voltage operation of about V is possible. Table 1 shows an example of the relationship between the reverse bias and the extension of the depletion layer.

[0013]

[Table 1]

[0014]

According to the present invention, the main body can operate at a low voltage even when the main body has a thickness of several mm. By utilizing this thickness, the X-rays can be incident from the direction parallel to the substrate surface, and therefore, the X-rays can be arranged at a high density when incorporated in the system. Since GaAs having a high absorptivity is used as the substrate material, X-rays can be detected with high sensitivity. In terms of process, the steps can be shortened by performing doping on both sides at once.

[Brief description of drawings]

FIG. 1 is a top view of an X-ray detection element according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

1 ... Semiconductor substrate, 2 ... Oxide film, 3 ... Electrode, 4 ... Impurity diffusion region.

Claims (5)

[Claims] 1. A compound semiconductor substrate having a p-type-n-type-p-type or n-type-p-type-n-type layer structure in which an impurity element is doped on both sides, and a single-layer or multi-layer electrode. And a semiconductor X-ray detector. 2. The compound semiconductor substrate according to claim 1, wherein the compound semiconductor substrate is undoped or Cr-doped semi-insulating GaAs.
A semiconductor X-ray detector using. 3. The substrate according to claim 1, wherein at least one of the upper surface, the lower surface and the side surface of the substrate has at least one layer of an oxide film and a nitride film, or a plurality of layers including these two kinds of films. X-ray detector having a. 4. The X parallel to the substrate surface according to claim 1.
A semiconductor X-ray detector capable of injecting a ray from a side surface or an upper surface or a lower surface of a substrate. 5. The method of manufacturing a semiconductor X-ray detector according to claim 1, wherein a pn junction is manufactured by diffusing impurities in an ampoule and simultaneously forming pn junctions on both surfaces of the substrate.