JPH07169989A - Semiconductor radioactive rays detector and its manufacture - Google Patents

Abstract

PURPOSE:To ensure connection between one electrode and an electrode lead part with a simplified process without deteriorating the characteristics of a detector by basically fixing a compound semiconductor and the electrode lead part, and directly connecting the one electrode and the electrode lead part with a conductive bonding agent. CONSTITUTION:A substrate 1 comprises a chlorine-doped high resistance CdTe semiconductor single crystal. An anode electrode 2 and a cathode electrode 3 are formed on opposite principal surface of the substrate 1. Then, the substrate 1 is bonded and fixed to an aluminum substrate 4 being an insulting substrate. A first electrode lead pattern 5 is formed on the surface side of the alumina substrate 4, and the anode electrode 2 and the first electrode lead pattern 5 are oppositely electrically connected with a conductive bonding agent 6 and are simultaneously mechanically directly fixed. A second electrode lead pattern 8 and the anode electrode 3 are directly electrically connected with a connection part 9 through a conductive bonding agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode lead-out structure of a semiconductor radiation detector and a connecting method thereof, and is particularly applied to an array type detector in which a large number of semiconductor portions which are individual detecting portions are arranged. .

[0002]

2. Description of the Related Art A semiconductor radiation detector measures a photocurrent generated in a semiconductor due to radiation through an electrode provided on its surface. When a compound semiconductor such as CdTe or HgI ₂ is used, it can operate at room temperature because of its wide bandgap, and has a large absorption coefficient for X-rays and γ-rays due to the large atomic number of the constituent elements, resulting in high sensitivity. can get. Such detectors are used for monitors of radiation facilities, spectrum survey meters, and the like. Further, the detectors can be downsized and arrayed, and the arrayed detectors are beginning to be applied to medical diagnostic equipment, industrial nondestructive inspection devices, and the like.

Conventionally, in a detector using only one detecting element consisting of a semiconductor portion and an electrode provided on the surface thereof,
The flexible metal wire for wiring allows the relatively lightweight semiconductor portion to be held in the air without any other support. Further, it is also possible to fix the semiconductor portion to a base portion such as an insulating substrate or a can package. At this time, the wiring is taken out from the electrode by wire bonding such as thermocompression bonding or a conductive adhesive (for example, conductive particles such as metal powder are dispersed in an insulating adhesive made of an organic polymer material). It was done by connecting a thin metal wire to the electrode. In particular, in an array-type detector in which a large number of detection elements are arranged, the spatial positional accuracy of each element is required, so each semiconductor portion is fixed to the base portion and the wiring is taken out in the same manner. It was

[0004]

However, such extraction of the wiring from the electrode deteriorates the characteristics of the detection element or complicates the manufacturing process, resulting in poor reliability. That is, when the metal thin wire is connected to the electrode by wire bonding, the connection portion of the electrode is pressed, so that the characteristics of the detection element deteriorate. Alternatively, such a connection, which does not apply sufficient mechanical pressure, is vulnerable to mechanical vibration and is unreliable. Further, connecting metal thin wires with a conductive adhesive without applying mechanical pressure requires skill and is difficult to automate.

An object of the present invention is to provide a highly reliable connection structure and a connection method for connection to an electrode of a semiconductor radiation detection element, which can be connected by a simple process without deteriorating the characteristics of the detector. It is a thing.

[0006]

The structure of a semiconductor radiation detector according to the present invention comprises: (a) a compound semiconductor to which radiation is incident; and (b) a pair of compound semiconductors provided on two opposing surfaces of the compound semiconductor. An electrode, (c) an electrode lead-out portion that is provided adjacent to the edge of at least one of the electrodes, and is a substantially rigid body; and (d) a base portion to which the compound semiconductor and the electrode lead-out portion are fixed. And (e) a conductive adhesive that directly connects the one electrode and the electrode lead-out portion. In addition, it is preferable that (f) an insulator is filled between the electrode lead-out portion and the surface of the compound semiconductor between the pair of electrodes. further,
The compound semiconductor is made of a crystal containing CdTe as a main component, the electrode covers almost the entire surface on which the electrode is provided, and / or a plurality of the semiconductor radiation detectors are arranged adjacent to each other. It is desirable to do.

The method for manufacturing a semiconductor radiation detector according to the present invention comprises: (a) a first step of forming a pair of electrodes on two opposing surfaces of a compound semiconductor to which radiation is incident; and (b) a substantial step. A second step of arranging the compound semiconductor so that the edge of one of the electrodes is adjacent to the electrode lead-out portion that is a rigid body; and (c) a conductive adhesive between the one electrode and the electrode lead-out portion. And a third step of connecting with. It is desirable that an insulator is filled between the surface of the compound semiconductor between the electrodes and the electrode lead-out portion, and in particular, the insulator is made of an insulating adhesive.

[0008]

According to the present invention, the edge portion of the electrode provided on the surface of the compound semiconductor on which radiation is incident is provided adjacent to the electrode lead-out portion which is a substantially rigid body. The structure is such that the surface of the compound semiconductor and the electrodes can be electrically connected to each other without mechanical pressure, and the electrode lead-out part has a flexible structure. It is not mechanically stable. In addition, it is possible to connect by a simple process of only applying a conductive adhesive. Therefore, it is possible to manufacture the semiconductor radiation detector with good reproducibility by a simple manufacturing process suitable for automation without degrading the characteristics of the radiation detector such as energy resolution.

In particular, by filling the surface of the compound semiconductor between the electrodes and the space between the electrode lead-out portions with an insulator, it is possible to prevent the conductive adhesive from flowing between the electrodes and short-circuiting between the electrodes. It enables high-density mounting and enables a simpler manufacturing process. When a crystal containing CdTe as a main component is used as the compound semiconductor, high detection sensitivity can be obtained, but it is susceptible to deterioration due to mechanical pressure, and the effect of the present invention becomes remarkable. Further, in order to obtain high sensitivity, the electrode is usually provided on almost the entire surface on which the electrode is provided. By arranging a plurality of such semiconductor radiation detectors adjacent to each other, an array type detector having high positional accuracy can be manufactured by a manufacturing process suitable for mass production.

[0010]

EXAMPLE A manufacturing process of a CdTe radiation detector which is an example of the present invention will be described below with reference to FIG.

Substrate 1 (thickness: 2 mm, width: 2 mm, length: 2
The 0 mm rectangular parallelepiped) is made of chlorine-doped high-resistance CdTe semiconductor single crystal. After the opposite main surfaces of the substrate 1 are polished and etched, the anode electrode 2 and the cathode electrode 3 are formed. The cathode electrode 2 is a Pt (platinum) electrode formed by electroless plating, and the barrier height for electrons (0.9 eV) is the barrier height for holes (0.6 e).
Higher than V). The anode electrode 3 is an In (indium) electrode formed by vacuum evaporation, and the height of the barrier against electrons (0.1 eV) is lower than the height of the barrier against holes (1.4 eV). Although both electrodes can be made of the same material, dark current can be reduced and detection accuracy can be improved by using two types of electrodes having different height relationships of barriers for electrons and holes. improves. Further, other compound semiconductors such as GaAs can be used instead of the CdTe semiconductor single crystal, but CdT has a high absorption coefficient of radiation.
It is desirable to use a crystal containing CdTe as a main component such as e or CdZnTe. In addition, its shape is flat so that the electric field between the electrodes is uniform when an external bias is applied,
The depth in the radiation incident direction may be a thickness that allows the incident radiation to be sufficiently absorbed.

Next, the substrate 1 is an alumina substrate 4 (thickness: 0.5 mm, width: 3 mm, length: 50 m) which is an insulating base portion.
Adhere to m) and fix. A first electrode lead-out pattern 5 is formed by a screen-printed AgPd layer on the surface side of the alumina substrate 4, and the cathode electrode 2 and the first electrode lead-out pattern 5 face each other and a conductive adhesive (Ag epoxy) is used. That is, electrically conductive silver particles are dispersed in an epoxy resin adhesive) 6 to be electrically connected and simultaneously mechanically directly fixed.

A convex portion 7 having substantially the same width as that of the substrate 1 is provided on the end portion on the front surface side of the alumina substrate 4. Substrate 1 is convex 7
The height of the convex portion 7 is almost the same as the thickness of the substrate 1. Then, on the upper surface of the convex portion 7, a second electrode lead-out pattern 8 which becomes a part of the electrode lead-out portion is formed by an AgPd layer by screen printing. The second electrode lead-out pattern 8 extends to the vicinity of the anode electrode 3 and electrically connects them directly by a connecting portion 9 made of a conductive adhesive (Ag epoxy). The width of the second electrode lead-out pattern 8 is almost the same as the width of the anode electrode 3, and almost the entire width is connected by a conductive adhesive, so that the connection is reliable.
Further, since the electrode lead-out pattern and the surface of the electrode connected thereto are close to each other, it is possible to easily connect with the conductive adhesive. The heights of the upper surfaces of the electrode and the electrode lead-out portion are substantially the same for facilitating the connection by the conductive adhesive, and if the electrode lead-out portion projects above the electrode, the assembly becomes difficult, which is not desirable. The electrode lead-out portion is composed of the convex portion 7 and the second electrode lead-out pattern 8. The mechanical protrusion 7 is a rigid body for sufficient mechanical stability, and the second electrode lead-out pattern 8 is electrically conductive. Has been achieved by

Then, the external leads 10 are electrically connected to the first electrode lead-out pattern 5 and the second electrode lead-out pattern 8 by soldering or ultrasonic wire bonding. A bias power supply 11 and an ammeter 12 are connected to the external lead 10. By these connections, a bias voltage can be applied to the cathode electrode 2 and the anode electrode 3, and the signal output proportional to the radiation intensity can be measured. The cathode electrode 2 and the anode electrode 3 may be arranged upside down, and a pulse height analyzer or the like may be connected as usual.

Further, when fixing the substrate 1 to the alumina substrate 4, the insulating adhesive 2 is provided between the substrate 1 and the side surface of the convex portion 7.
Fixed by 0. As the insulating adhesive 20, an organic polymer resin adhesive such as an epoxy resin adhesive or a silicone resin adhesive is used. By this fixing, it is possible to reliably prevent the conductive adhesive from flowing along the side surface of the substrate 1 and reaching the cathode electrode 2 when the connecting portion 9 is formed by the conductive adhesive. A short circuit due to the conductive adhesive can also be prevented by sandwiching an insulating sheet such as a silicone resin in place of the insulating adhesive 20. However, by using the insulating adhesive 20, the substrate 1 and the alumina substrate 4 can be firmly fixed, so that the connection is not disconnected even by mechanical vibration and the reliability is further improved. From desirable.

An array type detector can be constructed by arranging a large number of the above CdTe radiation detectors. In this case, by arranging the side surfaces of the alumina substrate 4 so as to be in close contact with each other, it is possible to set the interval of the substrate 1 which is the detection portion with high accuracy. By using a material such as an alumina substrate 4 that can be precision processed for the base portion that determines the precision, the position precision as an array type detector can be improved regardless of the precision of the substrate 1 which is difficult to process.
Further, the connection method according to the present invention can be used when a large number of semiconductors are arranged on one substrate to form an array. In this case, since the connection is simple, it is possible to improve the uniformity of the detection sensitivity among the respective elements and form a high-density array.

The present invention is not limited to this embodiment described above, but various modifications such as the following are possible. In order to prevent the deterioration of the electrode characteristics due to the fixing of the substrate 1, it is desirable to fix the substrate to the substrate via the surface of the CdTe substrate surface on which no electrode is provided. In this case, an ordinary non-conductive adhesive may be used as the fixing means, and the two electrodes 2 and 3 may be taken out by a conductive adhesive through two electrode take-out portions provided on both sides of the substrate 1. You may connect directly.

Further, in this embodiment, the electrode lead-out portion is
Although it is formed on a part of the base body, it may be fixed independently of the base body such as a metal projection.
Further, the shape may be a shape that is adjacent to the electrode and can obtain an area necessary for connection. Further, the gap between the electrode on the CdTe substrate and the electrode lead-out portion is determined as an appropriate value depending on the viscosity of the conductive adhesive used for connection.
If it exceeds 1.0 mm, the viscosity of a suitable conductive adhesive becomes high and the workability is significantly deteriorated.
m or less.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a CdTe radiation detector according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate (compound semiconductor) 2 Cathode electrode 3 Anode electrode 4 Alumina substrate (base part) 5 First electrode extraction pattern 6 Conductive adhesive 7 Convex portion 8 Second electrode extraction pattern (electrode extraction part) 9 Conductive adhesion Connection part with adhesive 10 External lead 11 Bias power supply 12 Ammeter 20 Insulating adhesive

Claims (8)

[Claims] 1. A compound semiconductor on which radiation is incident, (b) a pair of electrodes respectively provided on two opposing surfaces of the compound semiconductor, and (c) at least an edge portion of the one electrode. An electrode lead-out portion which is provided adjacently and is substantially rigid, (d) a base portion to which the compound semiconductor and the electrode lead-out portion are fixed, (e) one of the one electrode and the electrode lead-out portion A semiconductor radiation detector, comprising: a conductive adhesive that directly connects the two. 2. The semiconductor radiation detector according to claim 1, further comprising an insulator filling a space between the surface of the compound semiconductor between the pair of electrodes and the electrode lead-out portion. 3. The semiconductor radiation detector according to claim 1, wherein the compound semiconductor is a crystal containing CdTe as a main component. 4. The semiconductor radiation detector according to claim 1, wherein the one electrode covers substantially the entire surface on which the one electrode is provided. 5. A semiconductor radiation detector comprising a plurality of semiconductor radiation detectors according to claim 1 arranged adjacent to each other. 6. (a) A first step of forming a pair of electrodes on two opposing surfaces of a compound semiconductor to which radiation is incident, and (b) one of the electrodes at a substantially rigid electrode extraction portion. A second step of arranging the compound semiconductor so that the edge portions of the electrode are adjacent to each other, and (c) a third step of connecting the one electrode and the electrode lead-out portion with a conductive adhesive. Manufacturing method of semiconductor radiation detector. 7. The method for manufacturing a semiconductor radiation detector according to claim 6, wherein an insulator is filled between the surface of the compound semiconductor between the electrodes and the electrode lead-out portion. 8. The method of manufacturing a semiconductor radiation detector according to claim 6, wherein the insulator is made of an insulating adhesive.