JPH0732135B2 - Method for manufacturing heterojunction element - Google Patents

Description

Description: TECHNICAL FIELD The present invention mainly relates to a method for manufacturing a semiconductor heterojunction device for sensing light in a specific wavelength region or radiation in a specific energy range and converting it into an electric signal. Regarding

2. Description of the Related Art Conventionally, junction type devices using semiconductors have been widely used as devices for converting visible light, infrared light, radiation, etc. into electric signals, but they are mainly used for thermal diffusion and ion implantation on single crystal silicon substrates. The depletion layer when a reverse bias is applied to a diode having a pn junction or a pin junction formed by the method is used as a sensing layer. However, the process of forming such a pn or pin junction requires a high temperature treatment of 900 ° C. or higher, which causes thermally-induced defects, and in the case of the ion implantation method, substrate damage due to implantation generated during implantation is not caused. In many cases, it cannot be removed even by heat treatment. As a result, recombination leakage current increases and S /
There was a problem that it was difficult to obtain the N ratio. Therefore, to avoid this problem, recently, instead of forming a junction by impurity diffusion, a high frequency or DC plasma CV is formed on single crystal silicon.
Amorphous silicon carbide was deposited and formed by the D method by a relatively low temperature process of 200 to 300 ° C, and it was attempted to reduce the induction of defects by adopting a heterojunction diode structure and to reduce the leakage current by the hetero effect. There is.

Problems to be Solved by the Invention However, in such a conventional plasma CVD method, the distribution of energy in plasma is from a low energy of several eV to 10
Levels that cause recombination at the interface between crystalline silicon and amorphous silicon carbide due to damage to the interface with the substrate due to ions accelerated by high energy because the energy covers a wide range up to high energies above 0 eV Will be formed. Further, a substrate heating step at the time of formation is required, and good quality amorphous silicon carbide cannot be obtained without this substrate heating. Therefore, the generation of stress due to film formation while still applying heat forms a level that causes recombination at the interface between crystalline silicon and amorphous silicon carbide, and the hetero effect cannot be utilized. There is also a problem that such a heterojunction element is prevented from being put to practical use.

The present invention aims to solve such problems.

Means for Solving the Problems In order to solve the above problems, in the present invention, amorphous silicon carbide formed by a conventional high-frequency or direct-current plasma CVD method is used for microwave electron cyclotron resonance absorption (ECR). It has been found that the above problems can be solved by forming using the plasma CVD method. The present invention provides a high performance heterojunction device by the above means.

Action The action of the present invention produced by using the above means is as follows. First of all, conventional plasma
In the CVD method, the energy distribution in the plasma covers a wide range from low energies of several eV to high energies of 100 eV or higher, so the ions accelerated by high energies damage the interface with the substrate. Due to the characteristics of the plasma in the discharge, the energy of 10 to 30 eV is aligned, and therefore damage due to such high energy ions is reduced. Secondly, in the conventional method, the interface state generated because it was necessary to heat the substrate to 200 ° C. or higher,
It can be further reduced by using the microwave ECR plasma CVD method that can obtain a good quality amorphous silicon carbide regardless of the formation temperature, and a good interface characteristic can be obtained. Thirdly, the energy band gap of conventional amorphous silicon carbide produced by plasma CVD is 2.
Although it was about 0 eV, the hetero effect increases because the ECR method has a very wide range of 2.4 ev or more. Particularly in the low temperature formation film, a wide band gap is easily obtained, and the hetero effect is further increased. Such an action solves the poor interface characteristics and the bad reverse leakage current of the device, which have been problems in the past.

Examples Representative examples of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a heterojunction device having a structure of gold electrode layer / single crystal silicon substrate / amorphous silicon carbide layer / metal electrode layer as one embodiment of the present invention. 11
Is a single crystal silicon substrate, and 12 is an amorphous silicon carbide film formed by the ECR plasma CVD method. For example, a mixed gas of silane (SiH ₄ ) and methane (CH ₄ ) is used as a source gas, for example, SiH ₄ vs. CH ₄ Set the ratio to about 5: 1, for example 100 ℃
The substrate temperature is about 500 A to 1 μm. Reference numeral 13 is a first metal electrode, which is formed of a metal such as Al by, for example, a vacuum deposition method. A second metal electrode 14 is formed of a metal such as Al by, for example, a vacuum deposition method. In this way, the heterojunction element of the present invention is formed.

FIG. 2 is a schematic diagram of the ECR plasma CVD apparatus used in the present invention. A vacuum chamber 20 is evacuated to a vacuum through an exhaust hole 21. Microwaves are introduced into the plasma generation chamber 24 from the microwave oscillator 23 through the waveguide 22. A magnetic field is applied to the plasma generation chamber 24 by the electromagnet 25. Reference numeral 26 is a gas inlet, into which raw material gases such as SiH ₄ and CH ₄ are introduced. By setting the magnetic field strength of the plasma generation chamber so as to satisfy the electron cyclotron resonance condition, plasma with a high degree of dissociation can be obtained.
27 occurs. The generated plasma 27 is a plasma extraction window
After passing through 28, it reaches the substrate holder 29 and is deposited on the single crystal silicon substrate 30 as an amorphous chamber silicon carbide film. FIG. 3 shows the current-voltage characteristics of the heterojunction device realized at the forming temperature of 100 ° C. according to this embodiment. For comparison, the characteristics of the device manufactured by the conventional plasma CVD method at the formation temperature of 200 ° C. are also shown by the dotted line. As is clear from the figure, in the device of the present invention, the forward current rise is good, and the reverse leakage current is 1/100 times that of the conventional method.
It is reduced to 5 or less. This is because in the conventional plasma CVD method, the energy distribution in the plasma covers a wide range from low energies of several eV to high energies of 100 eV or higher, so that the ions accelerated by high energy damage the interface with the substrate. However, in the ECR discharge, the damage is reduced because the energy of 10 to 30 eV is aligned due to the characteristics of the plasma. Secondly, in the conventional method, the microwave ECR plasma CVD method that can obtain high-quality amorphous silicon even if the formation temperature is low is used as the interface state, which is generated because it is necessary to heat the substrate to 200 ° C. or higher. This is the result of being able to further reduce it by using it and obtaining good interface characteristics.

FIG. 4 shows changes in the reverse leakage current when the formation temperature of amorphous silicon carbide is changed. At 50 ° C., water and the like adsorbed on the surface of the crystalline silicon of the substrate are likely to remain, and there are many leaks.
When the formation temperature is further increased, the hydrogen content in the amorphous silicon carbide is reduced, the band gap is reduced, and the hetero effect is reduced.
On the contrary, the leak current increases.

In this embodiment, the case of amorphous silicon carbide to which no impurities are added has been described. However, in the case of a p-type substrate, an n-type amorphous silicon carbide is used, and in the case of an n-type substrate, a p-type amorphous silicon carbide is used. The forward current rise is further improved by using crystalline silicon carbide. However, in this case, an amorphous silicon carbide having a relatively low resistance is formed. Therefore, if the amorphous silicon carbide is made larger than the electrode, there is a problem that the leak current in the lateral direction increases.

Effects of the Invention The effects of the present invention are as follows.

First of all, as shown in FIG. 3, in the device of the present invention,
The forward current rise is good, and the reverse leakage current is reduced to less than 1/3 of that of the conventional method. The so-called leak current was reduced, and the characteristics preferable for practical use as a heterojunction diode device were obtained.

The second effect is that the substrate heating temperature during the fabrication of the device is lowered, and the process time is shortened. For this reason, the productivity is improved, and it can be said that it is very advantageous when it is put into practical use as a device.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the heterojunction device of the present invention,
FIG. 2 is a schematic view of a microwave ECR plasma CVD apparatus used to form the heterojunction device of the present invention, and FIG. 3 is a comparison diagram of current-voltage characteristics of the heterojunction device of the present invention and a conventional heterojunction device. FIG. 4 is a diagram showing changes in the reverse leakage current when the formation temperature is changed. 11 …… single crystal silicon substrate, 12 …… amorphous silicon carbide film, 13,14 …… metal electrode film, 20 …… vacuum chamber, 21 …… exhaust hole, 22 …… waveguide, 23 …… Microwave oscillator, 24 ... Plasma generation chamber, 25 ... Electromagnet, 26 ... Raw material gas inlet, 27 ... Plasma, 28 ... Plasma extraction window, 29 ... Substrate holder, 30 ... Substrate.

Front page continuation (72) Inventor Takashi Hirao 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-58-25226 (JP, A) JP-A-62-73622 (JP, A) JP 62-86165 (JP, A) JP 62-222074 (JP, A) Actual development JP 62-89874 (JP, U)

Claims (3)

[Claims] 1. A first electrode layer contacting at least one amorphous silicon carbide layer on a single crystal silicon substrate, contacting with the single crystal silicon, and a second contacting contact with the amorphous silicon carbide layer. In the production of a heterojunction device having a structure in which the electrode layers are sequentially laminated, the amorphous silicon carbide layer is formed by a plasma CVD method using microwave electron cyclotron resonance absorption (ECR) for 50 to 150
A method for manufacturing a heterojunction device, characterized in that the heterojunction device is formed at a forming temperature of ° C. 2. A mixed gas of at least silane (SiH ₄ ) and methane (CH ₄ ), a mixed gas of silane and ethylene (C ₂ H ₄ ), a silane and acetylene (C ₂ ) as a raw material gas for the amorphous silicon carbide layer. The method for producing a heterojunction device according to claim 1, wherein a mixed gas of H ₂ ) and further these mixed gases are used. 3. The heterojunction device according to claim 1, wherein n-type or P-type amorphous silicon carbide formed by ECR plasma CVD is used for the amorphous silicon carbide layer. Production method.