JPH11163310A - Semiconductor radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor radiation detector through which the breakdown strength of an insulating film can be increased. SOLUTION: A semiconductor radiation detector D1 has a semiconductor substrate 1, in which isolation regions 1 electrically isolating a plurality of cathode or anode regions 1k, 1a, from which signal currents are extracted in response to the incidence of radiation, are formed, and an insulating film 2 covering the isolation-region surfaces 11 of the semiconductor substrate 1. In the semiconductor radiation detector D1, the electric field concentration of the adjacent sections 1io of the isolation regions 1 by the irradiation of radiation such as high energy line can be inhibited because at least parts of the adjacent sections 1io of the isolation regions l are covered with electrodes 3 through the insulating film 2, and the deterioration of the breakdown strength of bias voltage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor radiation detector for detecting radiation.

[0002]

2. Description of the Related Art Semiconductor radiation detectors are used for physical experiments and detection of high energy rays in outer space.
A conventional semiconductor radiation detector is disclosed in Japanese Unexamined Patent Publication No. 1-220867.
(US Pat. No. 4,896,201). The detector includes a semiconductor substrate having an isolation region formed therein for electrically isolating a plurality of anode or cathode regions from which a signal current is extracted in response to the incidence of radiation, and an insulating film covering the surface of the isolation region of the semiconductor substrate. And

[0003]

However, in such a semiconductor radiation detector, an electric field concentrates on the vicinity of the isolation region of the semiconductor substrate due to the incidence of a high energy ray or the like, and the breakdown voltage of the bias voltage deteriorates. The present invention has been made to solve such a problem, and an object of the present invention is to provide a semiconductor radiation detector capable of improving the withstand voltage of a bias voltage.

[0004]

SUMMARY OF THE INVENTION In a semiconductor radiation detector according to the present invention, an isolation region for electrically isolating a plurality of anode or cathode regions from which a signal current is extracted in accordance with the incidence of radiation is formed. A semiconductor radiation detector including a semiconductor substrate and an insulating film covering the surface of the isolation region of the semiconductor substrate, further comprising an electrode that covers at least a part of the vicinity of the isolation region via the insulation film. In the present semiconductor radiation detector, since the electrode covers at least a part of the isolated region adjacent portion via the insulating film, electric field concentration in the isolated region adjacent portion due to irradiation of high energy rays or the like can be suppressed, and the bias voltage can be reduced. Withstand voltage deterioration can be prevented.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor radiation detector according to an embodiment will be described below. The same reference numerals are used for the same elements or elements having the same functions, and overlapping descriptions are omitted.

(First Embodiment) FIG. 1, FIG. 2 and FIG.
Plan view of a semiconductor radiation detector D1 according to the first embodiment,
AA 'arrow sectional view and BB' arrow sectional view are shown, respectively. The semiconductor radiation detector D1 includes a plurality of cathode regions 1k formed in a stripe shape on the surface side of the semiconductor substrate 1.
And an anode region 1 formed on the back side of the semiconductor substrate 1
a. The cathode region 1k and the anode region 1a are made of high-concentration n-type and p-type semiconductors, respectively.

A reverse bias is applied between the cathode region 1k and the anode region 1a, that is, for example, a positive potential is applied to the n-type cathode region 1k via the cathode electrode 4 and a positive potential is applied to the p-type anode region 1a via the anode electrode 5. When a negative potential is applied, a depletion layer spreads in the low-concentration semiconductor substrate 1 from the junction surface with the cathode or anode regions 1k and 1a. When radiation enters the detector D1, electrons and holes generated inside the semiconductor substrate 1 flow into the cathode region 1k and the anode region 1a, respectively, according to the internal electric field. And from the anode electrode 5.

A plurality of isolation regions 1i of the opposite conductivity type, ie, p-type, are arranged between the cathode regions 1k to form a stripe. The isolation region 1i has an outer frame region surrounding the entire stripe region, and further isolates each cathode region 1k from other cathode regions 1k. Most of the electrons generated by the incidence of the radiation flow into the neighboring cathode region 1k, but the flow of electrons into the other cathode region 1k is suppressed by the isolation region 1i.

The surface of the semiconductor substrate 1 is covered and protected by an insulating film 2 such as an oxide film, so that the insulating film 2 is located on the surfaces of the cathode region 1k and the isolation region 1i. A plurality of cathode electrodes 4 are provided on each cathode region 1k via an insulating film 2, and an electrode 3 is provided on the isolated region 1i via the insulating film 2. Although the isolation region 1i alone has an electron isolation function, in the present embodiment, a potential lower than the potential of the cathode region 1k is applied to the electrode 3 so that internal electrons generate an electric field from the isolation region 1i to the cathode region 1k. Improve the isolation function.

Electrons are generated in a proximity portion 1io (a region several μm from the edge of the isolation region 1i) outside the isolation region 1i of the semiconductor substrate 1 by electrostatic attraction due to positive charges generated in the insulating film 2 by irradiation of radiation. The electric field tends to be accumulated, whereby the electric field is concentrated on the proximity portion 1io outside the isolation region 1i. Such electric field concentration degrades the withstand voltage of the bias voltage. In the semiconductor radiation detector D1 according to the present embodiment, the electrode 3 provided on the isolation region 1i is arranged such that the electrode 3 provided on the outer edge of the isolation region 1i, that is, the proximity portion 1io adjacent to the edge.
, The accumulated electrons are expelled from the vicinity of the outer edge of the isolation region 1i of the semiconductor substrate 1 by applying a negative potential to the electrode 3, thereby suppressing the electric field concentration and preventing the withstand voltage from deteriorating. Further, the stored electrons constitute an n-type layer, and n
Although the parasitic capacitance is increased by shortening the n-type interlayer distance including the cathode region 1k, the detector D1 can suppress the increase in the parasitic capacitance due to the ejection of the accumulated electrons.

The semiconductor substrate 1 has a low concentration of p
Although it may be a type semiconductor, it is preferably a low concentration n-type semiconductor. When the semiconductor substrate 1 is continuously irradiated with radiation, for example, protons or neutrons, the p-type carrier concentration increases, and the function as a detector cannot be sufficiently performed.
Therefore, the semiconductor substrate 1 is made to be an n-type semiconductor in advance, and
It compensates for the increase in the type dopant concentration and improves the life of the detector.

In the detector D1, since the plurality of cathode regions 1k are individually isolated, the detector D
When radiation is incident on the cathode electrode 1, an alternating current is output from the cathode electrode 4 which is capacitively coupled to the corresponding cathode region 1 k via the insulating film 2, and a direction orthogonal to the direction in which the stripe extends, that is, the direction in which the cathode electrodes 4 are aligned Can be detected. Some of the cathode electrodes 4 may be in contact with the cathode region 1k as electrodes for applying a DC reverse bias voltage. Further, the detector D1 may be improved as follows.

FIG. 4 is a longitudinal sectional view of the improved semiconductor radiation detector cut in a direction perpendicular to the direction of extension of the individual cathode regions 1k arranged in stripes. Note that the above-described proximity portion 1io is a region at a distance L within a few μm from the edge of the electrode 3. In this detector, the surface of the anode region 1a is covered with an insulating film 5x, and the anode electrode 5 is brought into contact with the anode region 1a through an opening formed in a partial region of the insulating film 5x to stabilize the back surface of the semiconductor substrate 1. I have. Further, a buffer insulating layer 2x is formed between the insulating film 2 and the cathode electrode 4 to improve the stability of the cathode electrode 4. Here, the cathode and anode electrodes 4 and 5 are made of aluminum,
The buffer insulating layer 2x is made of silicon nitride, the insulating film 2 is made of a silicon oxide film, and the semiconductor substrate 1 is made of silicon.

As described above, in the present semiconductor radiation detector D1, since the electrode 3 covers at least a portion of the isolation region 1i adjacent portion 1io via the insulating film 2, the radiation 3 such as a high energy beam is applied. The concentration of the electric field in the isolation region 1i adjacent portion 1io can be suppressed, and the withstand voltage degradation of the bias voltage can be prevented. In addition, since the cathode region 1k and the isolation region 1i are arranged in a stripe shape, it is possible to perform one-dimensional radiation incident position detection along the alignment direction of the cathode region 1k.

(Second Embodiment) FIGS. 5, 6 and 7 show
Plan view of a semiconductor radiation detector D2 according to the second embodiment,
AA 'arrow sectional view and BB' arrow sectional view are shown, respectively. The detector D2 is different from the detector D1 of the first embodiment in that the electrode 3 has an isolated region 1i through the opening of the insulating film 2.
The only difference is that they are in contact. In addition, as shown in FIG. 24, this contact may be indirectly electrically connected via an Al electrode 3 '. That is, the polysilicon electrode 3 covers the isolation region 1i, the upper left portion 1io in the drawing, and the upper right portion 1io in the drawing.
And the isolation region 1 i are connected to the insulating film 3 on the polysilicon electrode 3.
The connection is made by an Al electrode 3 ′ via a contact hole provided in x, thereby suppressing an increase in contact resistance. in this case,
The electrode 3 has the same potential as the isolation region 1i, but has the effect of suppressing the electric field concentration in the vicinity of the isolation region 1i as in the first embodiment. A negative potential is applied to the electrode 3 in a DC manner. Further, the detector D1 may be improved as follows.

FIG. 8 is a longitudinal sectional view of the improved semiconductor radiation detector cut in a direction perpendicular to the direction of extension of the individual cathode regions 1k arranged in stripes. In this detector, compared to the detector shown in FIG.
Only in that it is in contact with the isolation region 1i through the opening and has a conductive potential with the isolation region 1i.

(Third Embodiment) FIGS. 9, 10, 11 and 12 show a semiconductor radiation detector D according to a third embodiment.
3 is a plan view, a bottom view, an AA 'arrow sectional view, and BB'.
The arrows show cross-sectional views, respectively. This detector D3 is different from the detector D1 of the first embodiment in that the anode region 1
a in a plurality of anode regions 1a '
And the surface of the anode region 1a 'of the semiconductor substrate 1 is covered with an insulating film 2', and the anode electrode 5 is provided on the insulating film 2 'corresponding to each anode region 1a'. The alignment direction of each anode region 1a 'is orthogonal to the alignment direction of the cathode region 1k or has an arbitrary angle.

When radiation enters the semiconductor substrate 1 in a state where a reverse bias is applied to the detector D3, electrons and holes generated inside the cathode region 1 near the generating position are respectively generated.
k and the anode region 1a '. Therefore,
From the cathode region 1k and the anode region 1a 'at the position where these charges have flowed in, signal current is extracted from the respective cathode electrode 4 and anode electrode 5. Since the alignment direction of each anode region 1a 'has a predetermined angle with respect to the alignment direction of the cathode region 1k, the detector D3 can perform two-dimensional radiation incident position detection.

(Fourth Embodiment) FIGS. 13, 14, and 15
16 is a plan view, a bottom view, an AA ′ arrow cross-sectional view, and a B-B view of a semiconductor radiation detector D4 according to the fourth embodiment.
B ′ arrow sectional views are respectively shown. This detector D4 is the third
Compared to the detector D3 of the embodiment, the isolation region 1 on the front surface side
The only difference is that the electrode 3 comes into contact with the electrode i through the opening of the insulating film 2 and has the same potential as the isolated region 1i.
4, the two-dimensional radiation incident position can be detected. Further, similarly to the second embodiment, the isolation region 1i may be in indirect electrical contact with the electrode 3.

(Fifth Embodiment) FIGS. 17, 18 and 1
9 shows a plan view, an AA ′ arrow sectional view, and a BB ′ arrow sectional view of the semiconductor radiation detector D5 according to the fifth embodiment, respectively. This detector D5 is the detector D of the first embodiment.
1, the isolation region 1i on the surface side of the semiconductor substrate 1 is arranged so as to form a lattice having two or more opening regions in each of the vertical and horizontal directions, and the cathode region 1 is arranged in each opening region of the isolation region 1i. The only difference is that electrodes 3 and 4 are provided on the isolation region 1i and the cathode region 1k, respectively.

When radiation enters the semiconductor substrate 1 in a state where a reverse bias is applied to the detector D5, electrons and holes generated inside the cathode region 1 near the generating position are respectively generated.
k and the anode region 1a. Each cathode region 1k is 2 × 2 in a state of being isolated by the isolation region 1i.
Since these detectors are arranged in a matrix,
Reference numeral 5 can perform two-dimensional radiation incident position detection.
The present detector D5 can reduce the parasitic capacitance per single pixel as compared with the above-mentioned detector having the stripe structure, and can improve the response speed and the noise resistance.

(Sixth Embodiment) FIGS. 20, 21 and 2
2 shows a plan view, an AA 'arrow cross-sectional view, and a BB' arrow cross-sectional view of the semiconductor radiation detector D6 according to the sixth embodiment. This detector D6 is the detector D of the second embodiment.
2, the isolation region 1i on the front surface side of the semiconductor substrate 1 is arranged so as to form a lattice having two or more opening regions in the vertical and horizontal directions, and the cathode region 1k is arranged in each opening region of the isolation region 1i. The only difference is that electrodes 3 and 4 are provided on the isolation region 1i and the cathode region 1k, respectively.

When radiation enters the semiconductor substrate 1 in a state where a reverse bias is applied to the detector D6, electrons and holes generated inside the cathode region 1 near the generating position are respectively generated.
k and the anode region 1a. Each cathode region 1k is 2 × 2 in a state of being isolated by the isolation region 1i.
Since these detectors are arranged in a matrix,
5, a two-dimensional radiation position detection can be performed.

As described above, the semiconductor radiation detectors D1 to D6 according to the above embodiment electrically connect the plurality of cathode or anode regions 1k and 1a (1a ') from which signal currents are taken out in accordance with the incidence of radiation. The semiconductor device includes a semiconductor substrate in which an isolation region for isolating the semiconductor substrate is formed, and an insulating film covering an isolation region surface of the semiconductor substrate. The detector D1 is provided with the isolation region 1i and the proximity portion 1io via the insulating film 2.
And an electrode 3 that covers at least a portion of the electrode 3. In the semiconductor radiation detectors D1 to D6 according to the above embodiment, since the electrode 3 covers at least a part of the isolated region 1i adjacent portion 1io via the insulating film 2, pinch-off due to irradiation of radiation such as high energy rays or reverse bias. And the like, it is possible to suppress the electric field concentration in the isolated region 1i adjacent portion 1io portion due to
Deterioration of the withstand voltage of the bias voltage can be prevented.

The cathode electrode 4 and the anode electrode 5
Is not limited to the above, and may be circular or triangular as long as a signal current can be extracted. Further, the cathode electrode 4 and the anode electrode 5
May be brought into contact with the cathode region 1k and the anode region 1a, respectively, to read out the charges generated inside the semiconductor substrate 1 in a DC manner. Further, each of the semiconductor regions 1a, 1k, 1
i can be formed using an ion implantation method, an epitaxial growth method, or the like in addition to the impurity diffusion method.

Finally, evaluation was made on the deterioration of the breakdown voltage of the insulating film 2 due to the irradiation of radiation. One semiconductor radiation detector D2 of the second embodiment (Example), one in which the electrode 3 does not cover the isolation region 1i and the proximity portion 1io, that is, the electrode 3 is located inside the isolation region 1i than the proximity portion 1io. Two things
(Comparative Examples 1 and 2), a total of three samples were produced.
FIG. 23 shows the relationship between the bias voltage and the leakage current of each sample after irradiation. The radiation dose is 1.33 × 10 ¹⁴ P / cm ² and the measurement temperature is -8 ° C.
It is. As is clear from the figure, the semiconductor radiation detector D2 having the structure according to the example has a small leak current even after irradiation, and the deterioration of the breakdown voltage is suppressed.

[0027]

As described above, in the semiconductor radiation detector of the present invention, since the electrode covers at least a part of the vicinity of the isolation region via the insulating film, the isolation region is irradiated by high energy rays or the like. It is possible to suppress the electric field concentration in the portion, prevent deterioration of the withstand voltage of the bias voltage, and improve the life of the detector.

[Brief description of the drawings]

FIG. 1 is a plan view of a semiconductor radiation detector according to a first embodiment.

FIG. 2 is a view A- of the semiconductor radiation detector according to the first embodiment;
A 'arrow vertical sectional view.

FIG. 3 is a diagram illustrating a semiconductor radiation detector according to the first embodiment;
B 'arrow vertical sectional view.

FIG. 4 is a longitudinal sectional view of an improved semiconductor radiation detector according to the first embodiment.

FIG. 5 is a plan view of a semiconductor radiation detector according to a second embodiment.

FIG. 6 is a view A- of the semiconductor radiation detector according to the second embodiment;
A 'arrow vertical sectional view.

FIG. 7 is a diagram illustrating a semiconductor radiation detector according to a second embodiment;
B 'arrow vertical sectional view.

FIG. 8 is a longitudinal sectional view of an improved semiconductor radiation detector according to the second embodiment.

FIG. 9 is a plan view of a semiconductor radiation detector according to a third embodiment.

FIG. 10 is a bottom view of the semiconductor radiation detector according to the third embodiment.

FIG. 11 illustrates a semiconductor radiation detector according to a third embodiment.
-A 'arrow longitudinal section.

FIG. 12 is a view B of the semiconductor radiation detector according to the third embodiment;
-B 'arrow longitudinal section.

FIG. 13 is a plan view of a semiconductor radiation detector according to a fourth embodiment.

FIG. 14 is a bottom view of the semiconductor radiation detector according to the fourth embodiment.

FIG. 15 illustrates a semiconductor radiation detector according to a fourth embodiment.
-A 'arrow longitudinal section.

FIG. 16 is a view B of the semiconductor radiation detector according to the fourth embodiment;
-B 'arrow longitudinal section.

FIG. 17 is a plan view of a semiconductor radiation detector according to a fifth embodiment.

FIG. 18 illustrates a semiconductor radiation detector according to a fifth embodiment.
-A 'arrow longitudinal section.

FIG. 19 is a view B of the semiconductor radiation detector according to the fifth embodiment;
-B 'arrow longitudinal section.

FIG. 20 is a plan view of a semiconductor radiation detector according to a sixth embodiment.

FIG. 21 illustrates a semiconductor radiation detector according to a sixth embodiment.
-A 'arrow longitudinal section.

FIG. 22 shows B of the semiconductor radiation detector according to the sixth embodiment.
-B 'arrow longitudinal section.

FIG. 23 is a graph showing a relationship between a bias voltage and a leakage current after irradiation.

FIG. 24 is a longitudinal sectional view of a modified example of the radiation detector shown in FIG. 8;

[Explanation of symbols]

1k: Cathode region, 1a: Anode region, 1i: Isolation region, 1 ... Semiconductor substrate, 2 ... Insulating film, 1io ... Proximity.

Claims (1)

[Claims] 1. A semiconductor substrate having an isolation region formed therein for electrically isolating a plurality of anode or cathode regions from which a signal current is extracted in response to the incidence of radiation, and covering a surface of the isolation region of the semiconductor substrate. A semiconductor radiation detector comprising: an insulating film; and an electrode that covers at least a part of the isolation region adjacent portion via the insulating film.