JPS586911B2 - Multichannel semiconductor radiation detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation detector for X-rays, gamma rays, etc., and particularly to a multi-channel semiconductor radiation detector useful when applied to an X-ray tomography apparatus using a computer.

Conventionally, scintillator photomultiplier tubes and ionization chamber detectors have often been used in the detection section of computerized X-ray tomography apparatuses, but these have the drawbacks of being extremely large in size and weight.

On the other hand, the use of semiconductor radiation detectors has recently been considered as a means of reducing the size and weight.

FIG. 1 is an example of a detector previously proposed by the present inventors.

In the figure, 1 is a semiconductor radiation detection element, and this detection element 1 is mounted on a U-shaped insulating mounting base 2 and fixed with an adhesive.

An output terminal electrode layer 3 is deposited on the surface of the detection element 1 on which the rectifying bonding layer is formed, and a portion thereof extends onto the mount base 2 to form an output terminal 4.

Further, on the other side of the detection element 1, there is a metal back plate 5 which covers the mount base 2 and which also functions as a collimator and protrudes upward.
is covered.

A hole is pre-drilled in the area of the metal back plate 5 facing the detection element 1, and after the metal back plate 5 is attached to the detection element 1, a hole is formed on the back surface of the detection element 1 so as to cover the hole. A contacting ground terminal electrode layer is deposited.

A large number of detector units configured in this manner are arranged and housed in the housing 6 to form a multi-channel radiation detector having positional resolution.

An electrically insulated connector 7 is provided on the bottom plate of the housing 6.
is provided, and when the output terminal 4 comes into pressure contact with this connector 7, the output is guided to an external sense amplifier 8.

When measuring X-rays passing through a subject using a detector such as the one described above, unless the scattered X-rays from the subject are sufficiently removed, the measured values for the same input value between each detector unit may differ. have different values even if the sensitivity of each detector unit is equal.

That is, it greatly affects the quality of the tomographic image of the subject that is finally obtained.

In this sense, it is important to limit the incident angle of the scattered X-rays by using the metal back plate 5 as a collimator.
A molybdenum plate with a length of 50-70 mm was required.

However, a detector having such a structure has the following problems.

That is, when making a detector unit, after fixing the detection element to an insulating mount and attaching a metal back plate that also serves as a collimator, metal evaporation of Au, Al, etc. is performed in the final step.

In this case, as described above, the metal back plate has a large area in order to obtain a large collimation effect, so if the size of the vapor deposition apparatus is limited, the number of sheets that can be vapor-deposited at one time is greatly limited.

In addition, storing a large metal plate in a high-vacuum evaporation device causes gas generation, lowering the quality of the vacuum, causing impurities to adhere to the semiconductor surface, and deteriorating the voltage-current characteristics of the detector. .

Deterioration of the voltage-current characteristics of the detector causes an increase in noise, which ultimately leads to deterioration of the image quality of the tomography apparatus.

This invention was made in view of the above-mentioned points, and has excellent workability during manufacturing, mass productivity, and excellent electrical characteristics, and also controls the incident angle of scattered X-rays by changing the collimator length as necessary. The present invention provides a multi-channel semiconductor radiation detector that makes it possible to

In this invention, the detector unit itself is made smaller by configuring the detector unit and the collimator plate as separate bodies.

Then, the height of the detector unit is set to be equal to or less than the length of the sliding groove of the housing, and collimator plates fixed to the insulating support are arranged and housed in each sliding groove of the housing in which the detector units are arranged and housed.

An embodiment of the present invention will be described below.

FIG. 2 is an exploded perspective view showing the overall configuration, and FIG. 3 is a side sectional view of the detector unit and collimator portion.

In the figure, 11 is a semiconductor radiation detection element, for example, using a high-resistance Si wafer, with a rectifying bonding layer on one side,
An ohmic contact layer is provided on the other side.

The detection element 11 is mounted on a U-shaped insulating mount 12 and fixed with an adhesive.

Further, an output terminal electrode layer 13 is provided on the surface of the detection element 11 on which the rectifying bonding layer is formed by vacuum deposition or the like.

A portion of the output terminal electrode layer 13 extends onto the mount base 12 to form an output terminal 14.

A metal back plate 15 is attached to the ohmic contact layer side of the detection element 11.

This metal back plate 15 has a smaller area than the mount base 12 so as not to come into electrical contact with the housing when it is housed in the housing, which will be described later.
It is designed to be located at a lower position than the top of 2.

A hole is pre-drilled in the portion of the metal back plate 15 facing the detection element 11, and a ground terminal electrode layer 16 is deposited by vacuum deposition or the like so as to cover the hole.

A portion of the ground terminal electrode layer 16 extends onto the mount base 12 to serve as a ground terminal 17.

The detector unit configured in this way is housed in the housing 18.
is stored in an array.

Electrically insulated connectors 19 and 20 are provided on the bottom plate of the housing 18, and when the output terminal 14 and the ground terminal 17 of the detector unit come into pressure contact with the connectors 19 and 20, respectively, the output signal is sensed. The signal is taken out to an amplifier 21.

When the detector unit is housed along the sliding groove 22 of the housing 18, the metal back plate 15 does not come into contact with the housing 18, as described above, and is electrically maintained one position above the housing 18.

A collimator plate 23 is made of a metal plate having a high X-ray absorption effect such as molybdenum or tungsten, and supports 24a are made of the same insulating material as the mount base 12 and are disposed with the same width as the mount base 12. 24b.

The lower ends of the collimator plate 23 are insulating supports 24a and 24b.
It protrudes slightly downward from the bottom edge of the.

The height of the detector unit, that is, the height of the mount base 12 is set to be less than or equal to the length of the sliding groove 22 of the housing 18, and the detector unit is inserted into the sliding groove 22 of the housing 18, and then Collimator plates 23 fixed to supports 24a and 24b are inserted.

At this time, a small gap of, for example, about 0.5 mm is created between the collimator plate 23 and the metal back plate 15 of the detector unit, so that the two are kept electrically insulated.

This is necessary in order to prevent the signal current from the detector from leaking to others as much as possible since the metal back plate 15 forms a part of the signal circuit of the detector.

Furthermore, when the collimator plate 23 is housed in the housing 18, it is brought into electrical contact with the housing 18.

This increases the electrical shielding effect of the detector.

For convenience, only one detector unit and one collimator plate each are shown in the figure, but a large number of similar detector units and collimator plates are arranged and housed in the housing 18 to constitute a multi-channel radiation detector. .

With the above configuration, the collimator part and the detection element part are separated from each other in the groove of the housing, and the collimator plate and the ground side metal back plate of the detector unit are set on the same plane. There will be no misalignment.

This means that the space between adjacent elements is extremely small.
For T detectors and the like, this is important in order to improve measurement accuracy for the same amount of incident radiation, and as a result it greatly contributes to uniformity of image quality.

Further, since the collimator section is separated from the detector unit, a collimator of a length suitable for the scattered radiation generation situation of the subject can be used regardless of the detector unit.

This prevents the collimator length from becoming longer than necessary and lowering the count value, making it possible to set the signal (count value) to noise (contamination of scattered radiation) ratio under conditions that suit the subject. Become.

Furthermore, when manufacturing the detector, the collimator section is separated, which reduces the surface area of the metal plate and insulating material that are likely to degas inside the evaporation equipment, which reduces the quality of the vacuum and improves the characteristics of the detector. The risk of deterioration is reduced.

This greatly improves the yield rate during manufacturing.

As explained above, the multi-channel semiconductor radiation detector according to the present invention has excellent reliability during manufacture and stability of characteristics, and can set optimal measurement conditions according to the object to be examined. The setting accuracy of the instrument and the collimator section is high, and it is very useful especially when applied to a computer-based X-ray tomography apparatus used in the medical field.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the multi-channel semiconductor radiation detector proposed earlier, FIG. 2 is a diagram showing the configuration of an example of the multi-channel semiconductor radiation detector according to the present invention, and FIG. 3 is a diagram showing its outline. FIG. 3 is a diagram showing a partial cross-sectional structure. 11... Semiconductor radiation detection element, 12...
...Insulating mount base, 13...Output terminal electrode layer, 14...Output terminal, 15...Metal back plate, 16...Ground terminal electrode Layer, 17...
...Grounding terminal, 18...Housing, 19,2
0...Connector, 21...Sense amplifier, 22...Sliding groove, 23...Collimator plate, 24a, 24b...Insulation sexual support.

Claims (1)

[Claims] 1 Fix the semiconductor radiation detection element on an insulating mount,
In a multi-channel semiconductor radiation detector configured by arranging and housing a detector unit having an output terminal electrode layer on one surface and a ground terminal electrode layer on the other surface along a sliding groove of a housing, the detector The height of the unit is equal to or less than the length of the sliding groove of the housing, and collimating plates fixed to an insulating support are arranged and housed in each sliding groove of the housing in which the detector units are arranged and housed. Channel type semiconductor radiation detector.