JP3031724B2 - Multi-element radiation detector and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-element radiation detector for use in an X-ray CT apparatus or the like in which a photodiode array in which a plurality of light receiving elements are arranged on a substrate and a scintillator are fixed to each other by bonding. The present invention relates to a manufacturing method, and is particularly suitable for improving sensitivity of each light receiving element of a photodiode array and improving the processing accuracy of a groove separating the light receiving elements to make it uniform.

[0002]

2. Description of the Related Art In a multi-element radiation detector used in an X-ray CT apparatus, an X-ray baggage inspection apparatus, etc., the variation in sensitivity among the respective light receiving elements of the detector causes the quality of an X-ray CT image to be superior. In order to directly influence the sensitivity, it is necessary to keep the sensitivity as low as possible. In particular, in the X-ray CT apparatus, even if the sensitivity distribution of each light receiving element itself varies in the thickness direction, it adversely affects the image quality, such as artifacts. Has been requested.

As a conventional multi-element radiation detector, in order to reduce the amount of crosstalk of a multi-channel photodiode and to improve the electrical insulation between channels,
The light receiving area of each light receiving element of the radiation detector formed by joining the scintillator elements arranged at the same pitch and the light receiving elements arranged and formed at predetermined intervals in the longitudinal direction on the semiconductor substrate is determined by the light of the corresponding scintillator element. A configuration in which the output area is smaller than the output area (for example, Japanese Patent Application Laid-Open No. Sho 60-42671). Also, in order to improve the uniformity of the sensitivity distribution of the X-ray detection element and improve the image quality of the X-ray CT apparatus, An X-ray CT apparatus having an X-ray detector configured by combining a phosphor element having a larger area than the sensitive part of the conversion element and a photoelectric conversion element (for example, JP-A-63-154158); By a simple manufacturing process, it is possible to extremely reduce light leakage between adjacent channels with high accuracy, and to insert a partition plate for preventing the light leakage on a substrate on which photoelectric conversion elements are formed. And a multi-element radiation detector for an X-ray CT apparatus having a configuration in which a partition plate penetrates between each scintillator element and its tip reaches the inside of the substrate on which the photoelectric conversion element is formed (for example, Japanese Patent Laid-Open No. 1-191
No. 085) has been proposed.

On the other hand, as a conventional method of manufacturing a multi-element radiation detector in which each scintillator can be easily and accurately adhered to a photodiode at a predetermined interval, a plate-like scintillator is adhered to a jig and a plurality of scintillators are attached. A scintillator is cut and divided, and each of the divided scintillators is fixed to a jig, and a light shielding adhesive is filled between the scintillators and adhered to each other, and the bonded scintillators are peeled off from the jig. A method of manufacturing a scintillation-type detector for an X-ray CT apparatus comprising a step of forming a detector by polishing the surface and then bonding the same to a photodiode (for example, Japanese Patent Application Laid-Open No. Sho 60-6889). .

[0005]

The variation in sensitivity between the respective light receiving elements of the radiation detector is caused as a result of a variation in the correspondence between the position of the light emitting surface of the scintillator and the sensitive part of each light receiving element of the photodiode array. However, in order to prevent variations in sensitivity, it is necessary to eliminate variations in the corresponding positions. However, in the above-mentioned conventional multi-element radiation detector, there is a proposal that deterioration of sensitivity does not occur by appropriately setting the scintillator element and each light receiving element so that a certain relationship is established, and a groove for inserting a partition plate. Is formed at the center position of the dead zone between the light receiving surfaces of the photodiodes, etc., but there is a specific method for determining the fixed relationship, or a specific configuration for forming the groove at the center position of the dead zone. No proposal has been made. In any case, immediately before and after bonding the scintillator to the photodiode, the shape and dimensions of the sensitive portion cannot be visually checked, so that it is extremely difficult to accurately match the correspondence of the positions, and the photodiode array Even when the groove is formed at the center position of the dead zone after the scintillator plate is bonded thereon, it is difficult to accurately process and form the groove at the center position of the dead zone because the center position of the dead zone is not visible. Therefore, there is a problem that the sensitivity distribution among the respective light receiving elements is not eliminated and uniform, as well as the sensitivity distribution in the thickness direction of each light receiving element itself.

The present invention has been made in view of the above-mentioned problems of the prior art,
It is an object of the present invention to provide a multi-element radiation detector capable of uniformizing the sensitivity between light receiving elements of a photodiode array by improving the processing accuracy of a groove separating the light receiving elements, and a method of manufacturing the same. .

[0007]

In order to achieve the above object, a multi-element radiation detector according to the present invention comprises: a photodiode array in which a plurality of light receiving elements are arranged in parallel on a substrate at a predetermined pitch; In a multi-element radiation detector in which a sensitive portion of each light receiving element and a scintillator which has an area covering a dead zone existing between the sensitive portions and absorbs and emits radiation and emits light are bonded and fixed to each other, On the extension of the dead zone of each light receiving element, and on the surface of the photodiode array at a position deviated from the sensitive part, a boundary line between the sensitive part for groove processing separating the light receiving elements and the dead zone is shown. The mark is provided.

Further, the method of manufacturing a multi-element radiation detector according to the present invention is directed to a photodiode array in which a plurality of light receiving elements are arranged in parallel on a substrate at a predetermined pitch, a sensitive portion of each light receiving element of the photodiode array, and A scintillator having an area covering the dead zone existing between the sensitive parts and absorbing and emitting radiation is bonded and fixed to each other, and a groove is formed along the dead zone from the bonded and fixed scintillator side. In the method of manufacturing a multi-element radiation detector that separates the light receiving elements, a sensitive element provided on a surface of the photodiode array at a position deviating from the sensitive part on an extension of a dead zone of each light receiving element. The processing is performed with reference to the mark indicating the boundary between the section and the dead zone.

[0009]

With the above construction, when a scintillator having an area covering a sensitive portion of a photodiode array and a dead zone between the sensitive portions is adhered and fixed on the photodiode array, an extension of the dead zone of the photodiode array is required in advance. Above, and at a position deviated from the sensitive part, a mark indicating the boundary line between the sensitive part and the dead zone is provided, so that it is covered with a scintillator even after bonding, as well as when bonding. It becomes possible to visually check the pattern shapes of the sensitive part and the dead zone, which become invisible. For this reason, the groove separating each light receiving element can be processed with reference to the mark, and the groove width dimension, the center position of the groove, and the like can be processed with high accuracy, and the scintillator and the photodiode array can be processed. Variations in sensitivity among the light receiving elements due to misalignment of the light receiving elements with the sensitive part, irregularities in the shape of the scintillator, and the like can be prevented and uniformized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view of a radiation detector before processing a groove when a photodiode array having six light receiving elements is used, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. Fig. 4 is an enlarged view of the "" part during groove processing.
It is IV sectional drawing.

In the drawing, 1 is a substrate, 2 is a photodiode array in which a plurality of light receiving elements are arranged in parallel on a substrate 1 at a predetermined pitch, 3 is a sensitive part of each light receiving element, 4 is an adjacent sensitive part 3 The dead zone having a width B existing between them is arranged alternately with the sensitive portion 3. Reference numeral 5 denotes a plate-shaped scintillator having an area covering the sensitive portion 3 and the dead zone 4 of each light-receiving element and absorbing radiation to emit light. The scintillator 5 is adhered and fixed on the photodiode array 2 with an optical adhesive. A multi-element radiation detector is formed. Numeral 6 indicates a boundary line between the sensitive part 3 and the dead zone 4, and a groove processing mark formed on the surface of the photodiode array 2 by vacuum deposition or etching for separating the light receiving elements. Is a mark indicating the center line of the width B of the dead zone 4, and similarly to the mark 6, a pattern is formed on the surface of the photodiode array 2 by vacuum evaporation or etching. The mark 7 is provided for facilitating the positioning of the cutter before the groove processing, and the positioning can be performed using the mark 6. The mark 7 disappears by the groove processing. As shown in FIG. 1, the marks 6 are formed on the extension of the dead zone 4 of each of the light receiving elements and at both ends of the position deviating from the sensitive portion 3, and each of the grooves 8 separates the light receiving elements. It is used as a reference for measurement of the parallelism of the processing machine, the finished state of the groove 8 after processing, and the like when processing (width b). 9 is a hole for mounting a multi-element radiation detector, and 10 is a signal terminal.

When the groove 8 is machined, the groove width b is limited by the distance to the adjacent sensitive portion 3, and when the side surface of the groove 8 approaches 0.05 mm or less from the sensitive portion 3, the groove width b is generated at the time of machining. It has been experimentally confirmed that the dark current of the light receiving element increases due to the micro-crack of the silicon crystal to cause a signal failure, and the width B of the dead zone 4 is, for example, in a PIN type silicon photodiode. It has also been confirmed that 0.2 mm to 0.3 mm is required to suppress the crosstalk amount between light receiving elements to 1% or less. Therefore, when the width B of the dead zone 4 is 0.2 mm, the groove width b is limited to 0.1 mm or less, and the groove 8 is surely parallel to the boundary between the sensitive part 3 and the dead zone 4. Must be processed.

In the processing of the groove 8 in the present invention, first, before processing, the parallelism of the processing machine and the positioning of the cutter are adjusted with reference to the marks 6 formed at both ends of the processing start position and the end position. This is performed so as to be along the center line of the width B of the dead zone 4 from the direction of the arrow 11 shown in FIG. During and after the processing, the finished state of the groove 8 is measured and inspected with reference to the mark 6, and the processing is corrected as needed according to the inspection value to complete the processing. For this reason, the groove 8 can be processed with a high positional accuracy of ± 0.01 mm or less in the center of the groove 8. For example, in the case of a radiation detector having a light-receiving element width of 1 mm, It has been realized that the variation in sensitivity between the elements is reduced to 1% or less. At the same time, it has been confirmed that the dark current of the light receiving element does not increase due to the fact that the side surface of the groove 8 approaches the sensitive portion 3 conventionally. In addition, a not-shown partition plate made of a thin metal plate is inserted into each of the processed grooves 8 in order to enhance the separating ability between the light receiving elements.

In the above embodiment, an example of a radiation detector in which a photodiode array having six light receiving elements is used has been described. However, the number of light receiving elements is not limited to this. For example, an X-ray CT apparatus in which related multi-element radiation detectors are arranged in a large number of arcs to constitute a detector of 500 elements or more, or an X-ray baggage used as a line sensor arranged in a linear manner with a length of 500 mm or more. In an inspection device or the like, a high-quality image free from artifacts can be obtained.

[0015]

Since the present invention is configured as described above, it is possible to improve the processing accuracy of the groove by using the groove processing mark for separating the light receiving elements from each other. There is an effect that the sensitivity between the light receiving elements can be made uniform.

[Brief description of the drawings]

FIG. 1 is a plan view showing a multi-element radiation detector according to an embodiment of the present invention before groove processing.

FIG. 2 is a sectional view taken along the line II-II of FIG. 1 after groove processing.

FIG. 3 is an enlarged view of a portion “A” of FIG. 1 during groove processing.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Photodiode array 3 Sensitive part 4 Dead zone 5 Scintillator 6 Mark (Boundary mark between sensitive part and dead zone) 7 Mark (Center line mark of dead zone width) 8 Groove

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Minoru Yoshida 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Examiner, Central Research Laboratory, Hitachi, Ltd. Shinichi Nagai (56) References JP-A-64-39579 (JP, A) JP-A-59-147289 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/20

Claims (2)

(57) [Claims] 1. A photodiode array in which a plurality of light receiving elements are arranged in parallel at a predetermined pitch on a substrate, and an area covering a sensitive part of each light receiving element of the photodiode array and a dead zone existing between the sensitive parts. In a multi-element radiation detector in which a scintillator that absorbs and absorbs radiation and emits light is adhered and fixed to each other, a photodiode at a position extended from a dead zone of each of the light receiving elements and separated from the sensitive portion. A multi-element radiation detector comprising a mark on a surface of an array, the mark indicating a boundary between a sensitive portion for groove processing for separating the light receiving elements and a dead zone. 2. A photodiode array in which a plurality of light receiving elements are arranged in parallel at a predetermined pitch on a substrate, and an area covering a sensitive part of each light receiving element of the photodiode array and a dead zone existing between the sensitive parts. A multi-element radiation detector for adhering and fixing a scintillator that absorbs and emits light by absorbing radiation and processing a groove along the dead zone from the adhesively fixed scintillator side to separate the light receiving elements from each other In the manufacturing method of the above, with reference to the mark indicating the boundary line between the sensitive part and the dead zone provided on the surface of the photodiode array at a position deviating from the sensitive part on the extension of the dead zone of each light receiving element. A method for producing a multi-element radiation detector, characterized by processing by: