JPS61137373A - Manufacture of semiconductor radiation detector - Google Patents

Abstract

PURPOSE:To obtain a detector of low Schottky barrier by coating a reverse conductive type amorphous Si layer from the surface to the side of one conductive type high impurity Si single crystal substrate, forming one metal electrode on the surface, and diffusing one conductive type high impurity density layer in the surface layer of the back surface of the substrate having no amorphous Si layer, and forming other electrode thereat. CONSTITUTION:An N type amorphous Si layer 2 is coated from one surface to the side of a P type high purity Si single crystal substrate 1 having 10kOMEGAcm or higher of specific resistance, and one aluminum electrode 3 is formed on the surface portion. Then, an aluminum film 6 is coated on the back surface of the substrate having no layer 2, heat treated in Ar plasma, aluminum in the film 6 is diffused to form a P<+> type layer 61 in the surface layer of the back surface of the substrate 1, and other aluminum electrode 4 is coated thereon. Thus, the height of a Schottky barrier produced in a boundary between the substrate 1 and the electrode 4 is reduced to improve the detecting efficiency of the detector.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a method for manufacturing a semiconductor radiation detector using a heterojunction formed between a high-purity single crystal semiconductor substrate and an amorphous semiconductor layer thereon. [Prior art and its problems]

As a means of forming a depletion layer in a detector that detects radiation by carriers generated by the incidence of radiation into a depletion layer in a semiconductor, for example, a high-purity single crystal silicon substrate and an amorphous silicon film deposited thereon are used. A semiconductor radiation detector using a heterojunction formed between
It has been filed under No. xoz3st and Japanese Patent Application No. 156031/1983. As shown in the cross-sectional structure of FIG. 2, this detector has an amorphous silicon layer 2 deposited on one surface and side surfaces of a single-crystal silicon base [1], and metal electrodes 3 and 4 provided on both sides. Semiconductor single crystal l by applying a voltage between
A depletion layer 5 is spread inside the depletion layer, and radiation is incident into the depletion layer to generate electron-hole pairs to detect a signal. However, in such a detector, especially when the silicon single crystal 1 and the amorphous silicon layer 2 have high voltage resistance, Schiff (Schiff) that occurs at the interface between the metal electrode 3.4 and the single crystal silicon and the amorphous silicon Due to the large voltage drop at the key barrier, the voltage applied to the original heterojunction of amorphous silicon and single crystal silicon is not sufficiently applied, and as a result, the depletion layer does not spread sufficiently into the crystalline silicon. It had In addition, the Schottky barrier part is
It also has the disadvantage that it is not desirable as a semiconductor radiation detector because it becomes a source of noise when extracting signals. FIG. 3 shows the energy distribution in the semiconductor radiation detector shown in FIG. 2, and the positions of various parts are indicated by the symbols written in FIG. 2 below. is the Fermi level energy, C and B are the conduction band, and V and B are the valence span, respectively. In FIG. A Schottky barrier occurs at the junction 23 with 1tFi3, and a heterojunction 22 exists at the interface between single crystal silicon 1 and amorphous silicon 2. The Schottky barrier is caused by the energy difference between the work functions of a semiconductor and a metal, and it is a well-known technique that the Schottky barrier can be reduced by reducing this energy difference. In order to reduce this Schottky barrier, that is, to form an ohmic contact, there is a method of forming a p° layer on a p-type semiconductor substrate and forming a metal electrode thereon, or a method of forming an n° layer on an n-type semiconductor substrate. A method of forming a layer and forming a metal electrode thereon is a technique widely used in current semiconductor processing. However, the currently used p layer and 10 layer formation technology, that is, the ohmic contact formation technology is 10
These methods include a thermal diffusion method at 00° C. or higher and an ion implantation method that requires post-treatment at 800° C. or higher. Since these methods all involve high-temperature processes of 800° C. or higher, they pose little problem with conventional low-resistance silicon, but are not suitable processes for semiconductor radiation detectors using high-purity silicon substrates. The reason for this is that exposing a high-purity silicon substrate to high temperatures causes thermal defects in the silicon substrate itself, resulting in a reduction in rough time and a drastic deterioration of the electrical characteristics of the device.

[Purpose of the invention]

The present invention relates to an electrode of a semiconductor radiation detector that has been previously applied for, in which an amorphous semiconductor layer is deposited on one surface of a high-purity semiconductor single crystal, and metal electrodes are provided on each surface of the semiconductor single crystal and the amorphous semiconductor layer. An object of the present invention is to provide a manufacturing method that prevents the formation of a Schottky R wall at the interface between a single crystal semiconductor substrate and a semiconductor, and that does not cause thermal defects by exposing a single crystal semiconductor substrate to high temperatures.

[Key points of the invention]

According to the present invention, after depositing an amorphous semiconductor layer of an opposite conductivity type covering at least one main surface of a high-purity single crystal semiconductor substrate of one conductivity type, the single crystal semiconductor substrate is heated in an inert gas plasma. Impurities are introduced from the other main surface of the semiconductor substrate or the surface of the amorphous semiconductor layer to form a layer with the same conductivity type and high impurity concentration as the original semiconductor substrate or semiconductor layer, and then a metal layer is formed on top of that layer. The above objective is achieved by providing iti. Embodiment of the Invention] Figures 1 (♂) to (11) show most of the steps of an embodiment of the present invention. An undoped amorphous silicon layer 2 exhibiting a weak mouth shape due to monosilane gas is deposited on the upper surface of a pure silicon single crystal substrate l by a known plasma CVD method (b
Figure) Metal type ff13 on the surface of the zero-order amorphous silicon layer 2.
(Fig. 0), followed by the first step.
As shown in Figure 1dl, the top and bottom are replaced and 0. (
An aluminum film 6 having a thickness of 11-0.1 .mu.- is formed by vacuum evaporation (Figure 6). The device 1G that has undergone these steps is placed in the reaction tank 11 of the apparatus shown in FIG. 4, and placed on the lower electrode plate 12 with the aluminum film 6 facing down. In addition, the device shown in FIG. 4 has an upper electrode plate 13. DC voltage power supply 14. Exhaust system 15. Pulp for adjusting displacement 16. Vacuum gauge 17. It is equipped with a heater for heating the lower electrode plate, a power source 19 for the heater, and a reaction tank 11.
An inert gas cylinder 31 is connected to a pressure reducing valve 32 and a gas flow rate regulator 33. It is connected via a gas flow meter 34. Using the apparatus shown in FIG. 4, plasma is generated under the following conditions to cause aluminum to penetrate from the aluminum film 6 into the silicon crystal. 1st group 1 (lower sii pole Fi) temperature: 300”C2
) Vacuum degree: 0.1 to 0.5 Torr3) Applied voltage: DC 400 to 1G (IOV4) Inert gas used
: Explain the intrusion process of aluminum below argon. First, the element 10 shown in Figure 1 (@)! ! After the lower electrode chamber is set, the argon pressure in the reaction chamber 11 is reduced to 0°1 using the exhaust volume adjustment valve 16 and the gas flow rate adjustment valve 33.
A DC voltage of 400 to 1000 V is applied between the electrode plates 12 and 13 using an electric conductor A14. This causes a glow discharge between the electrodes in the reaction tank, and as a result, a Crookes dark area with an extremely strong electric field exists above the lower electrode plate. FIG. 5 is an enlarged view of the vicinity of the element 10 in FIG. 4. Here, ionized argon 35 is applied to the cathode electrode 1.
2, aluminum penetrates into silicon single crystal 1 due to the action of colliding with aluminum 6, and
Since aluminum, which is a group element, acts as an acceptor, it is considered that the p° layer 61 is formed. Furthermore, the argon ions 35 colliding with the surface of the aluminum film 6 can be considered to have the effect of repelling aluminum from the aluminum film 6. After forming the p° layer 61 in this manner, aluminum was again deposited on the surface of the p° layer by vacuum evaporation to form the electrode 4. Most of the energy is applied to the heterojunction between single crystal silicon and amorphous silicon, which not only makes it possible to sufficiently expand the depletion layer in the crystal silicon, but also eliminates the noise that conventionally occurs in the shifted key barrier. As a result, the detection efficiency of γ-rays and β-rays was improved by 15% and 12%, respectively, compared to a semiconductor radiation detector in which a metal electrode was directly formed. The Sittky barrier indicated by the reference numeral 23 in the figure, that is, a reduced Sittky barrier between amorphous silicon and a metal electrode will be described.
tal, (in BL, after depositing an undoped amorphous 2937 layer 2 on a p-type wheel crystal substrate 1 with a specific resistance of 10 kQas or more in the same process as in FIG. 1, As shown, antimony 1 to 1 on the surface of the amorphous silicon layer 2
A film 7 of gold containing 10% is vacuum deposited. Next, gold containing antimony is infiltrated into the amorphous silicon M2 by argon plasma using the apparatus shown in FIG. 4 in the same manner as in the above embodiment. As a result, the amorphous silicon surface layer becomes an n'' layer due to the addition of antimony, a metal-n'' layer-weak n amorphous silicon layer junction is formed, and the shift key barrier is reduced. Thereafter, gold is further deposited on the gold-antimony film 7 to form the electrode 3. However, it is also possible to make the gold-antimony film thicker and use it as it is as one electrode.Semiconductor radiation detectors fabricated in this way are compared with detectors in which an aluminum electrode is provided directly on the amorphous silicon layer. The γ-ray and β-ray detection efficiency were improved by 5% and 7%, respectively. In this example, the amorphous silicon M2 is formed of undoped amorphous silicon, but if the n-type is strengthened by doping with an appropriate impurity, or if p-type amorphous silicon is formed on an n-type silicon single crystal. Even if debris is deposited,
According to the present invention, each n4
layer or p. It is also effective to form an amorphous silicon surface layer.

【Effect of the invention】

The present invention provides a radiation detector that utilizes an electrical signal generated by the incidence of radiation into a depletion layer based on a heterojunction between a single crystal semiconductor and an amorphous semiconductor. In order to reduce the Schittky barrier at the interface and bring it closer to ohmic contact, a highly concentrated impurity layer is formed by infiltrating metal into a single crystal semiconductor film or an amorphous semiconductor layer using the energy of plasma generated at low temperatures. be. As a result, the adverse effects of high-temperature processing on high-purity semiconductor single crystals can be avoided, and the detection efficiency of semiconductor radiation detectors can be improved at low cost with short processing times and simple equipment.

[Brief explanation of drawings]

Fig. 1 is a sectional view sequentially showing the steps of an embodiment of the present invention, Fig. 2 is a sectional view of a semiconductor radiation detector which is the object of the present invention, Fig. 3 is its energy level diagram, and Fig. 4 is a sectional view showing the steps of an embodiment of the present invention. A configuration explanatory diagram of an example of a plasma generating device used for carrying out the present invention, FIG. 5 is an enlarged cross-sectional view of a part of the device shown in FIG. 4, and FIG. 6 sequentially shows the steps of another embodiment of the present invention. FIG. 1: P-type wheel crystal silicon plate, 2: Amorphous silicon layer, 3
．． 4: metal electrode, 6: aluminum film, 61: p'' layer,
7: gold-antimony film, 10: element, 11: reaction tank, 1
2, 13: electrode plate, 15: exhaust system, 31: inert gas cylinder. Sai 1 Ward Sai 2 Diagram Sai 3 Diagram + 4 Diagram

Claims (1)

[Claims] 1) After depositing an amorphous semiconductor layer of the opposite conductivity type covering at least one main surface of a high purity single crystal semiconductor substrate of one conductivity type, the other main surface of the single crystal semiconductor substrate is deposited in an inert gas plasma. It is characterized by infiltrating impurities from the surface or the surface of an amorphous semiconductor layer to form a surface layer having the same conductivity type as the original semiconductor substrate or semiconductor layer and having a high impurity concentration, and providing a metal electrode on the layer. A method for manufacturing a semiconductor radiation detector.