JPH05275339A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a manufacturing method being able to suppress generation of impurity gas from a plasma generator while moreover being able to correctly and easily control an amount of nitrogen to be taken in a II-VI compound semiconductor layer and to manufacture II-VI semiconductor devices of high quality. CONSTITUTION:While piling up a first element, at last one selected from sulfur, celenium and tellurium, and a second element, at least one selected from zinc, mercury, cadmium and magnesium, on a substrate in a vacuum, excited specimen of nitrogen molecules, oxygen molecules, nitrogen atoms or oxygen atoms excited by an electron-cycrotron-resonance(ECR) plasma are irradiated to the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a II-VI group compound semiconductor device exhibiting p-type conductivity.

[0002]

2. Description of the Related Art II-VI group compound semiconductors composed of group II elements such as zinc, mercury, cadmium and magnesium and group VI elements such as sulfur, selenium and tellurium are promising materials for forming light emitting diodes and laser diodes. is there. A method of adding nitrogen (N) as an impurity in order to impart p-type conductivity to the II-VI group compound semiconductor layer is as follows.
For example, Phy. Rev. B27 Vol. 2419-2428 (19
83).

Further, as a method of adding nitrogen, a method of irradiating neutral excited species of nitrogen molecule or ammonia molecule is known, for example, from JP-A-63-303899 and JP-A-63-303889. ing. Also, as a method of adding nitrogen, a method of irradiating with an ionic species is
It is known from JP 63-227027 A. .

[0004]

When nitrogen is added as an impurity to impart p-type conductivity to the II-VI group compound semiconductor layer, it is necessary to control the concentration of nitrogen to an appropriate value. Important for accurate control of conductivity. RF plasma has been conventionally used as a source of the excited species (radical) beam. The power supplied to the RF plasma generator is large, and the heat generated by the RF plasma generator is large.
As a result, when the II-VI group compound semiconductor layer is formed in a high vacuum, impurity gases such as nitrogen, oxygen and H ₂ O adsorbed on the inner and outer walls of the RF plasma generator are separated from the inner and outer walls. There is a problem that it is taken into the -VI compound semiconductor layer as an impurity and adversely affects the electrical characteristics of the semiconductor layer.

Further, it is desirable to control the amount of nitrogen taken into the II-VI group compound semiconductor layer by the electric power supplied to the plasma generator. However, in the RF plasma generator, the change in the amount of nitrogen taken into the II-VI group compound semiconductor layer is small with respect to the change in the power supplied to the plasma generator. Therefore, in the RF plasma generator, there is a problem that it is difficult to control the amount of nitrogen taken into the II-VI group compound semiconductor layer by the electric power supplied to the plasma generator.

Therefore, an object of the present invention is to suppress the generation of an impurity gas from a plasma generator and to accurately and easily control the amount of nitrogen taken into the II-VI group compound semiconductor layer. Capable of high quality I
It is an object of the present invention to provide a method capable of manufacturing a group I-VI semiconductor device.

[0007]

Means for Solving the Problems The above-mentioned object is selected from a first element selected from at least one kind of sulfur, selenium and tellurium and at least one kind selected from zinc, mercury, cadmium and magnesium. While depositing the second element on the substrate in a vacuum, the substrate is irradiated with a nitrogen molecule, an oxygen molecule, a nitrogen atom, or an excited species of an oxygen atom excited by an electron-cyclotron resonance (ECR) plasma. This can be achieved by the method for manufacturing a semiconductor device according to the present invention.

It is desirable to select at least magnesium as the second element.

Further, the irradiation density of the excited species of nitrogen molecules, oxygen molecules, nitrogen atoms or oxygen atoms on the substrate may be 10 ^{−6 to} 10 ⁻³ times the deposition density of the first element on the substrate. desirable. If it is less than 10 ⁻⁶ times, the p-type conductivity required in the II-VI group compound semiconductor layer cannot be obtained. Further, when it exceeds 10 ^-3 times, the obtained II-V
This causes deterioration of the quality of the group I compound semiconductor layer. here,
The irradiation density of the excited species of nitrogen or oxygen molecules or atoms to the substrate means the density of the elements constituting the excited species in the II-VI compound semiconductor layer. The deposition density of the first element on the substrate means the density of the first element in the II-VI compound semiconductor layer.

[0010]

In the method of manufacturing a semiconductor device of the present invention, E
The CR plasma excites nitrogen or oxygen molecules or atoms. In the ECR plasma device, nitrogen or oxygen molecules or atoms can be efficiently excited with a power that is half or less of the power that is input to the RF plasma device.

[0011]

EXAMPLES A method of manufacturing a semiconductor device of the present invention will be described below based on examples. (Example 1) In Example 1, a case is shown in which a p-ZnSe layer made of ZnSe doped with nitrogen (N) as an impurity is formed. That is, selenium (Se) is selected as the first element and zinc (Zn) is selected as the second element,
A nitrogen molecule was used as the excited species. Also, as a substrate,
A substrate made of n-GaAs was used.

FIG. 1 shows a molecular beam epitaxy (MBE) apparatus 10 suitable for use in the method of manufacturing a semiconductor device according to the present invention.
FIG. The MBE device 10 is a kind of vacuum vapor deposition device, and a substrate holding a plurality of molecular beam sources (K cells) 14 and a substrate 30 in a vacuum container 12 equipped with an ultrahigh vacuum exhaust device (not shown). A holder 16 is provided.

The MBE device 10 is characterized in that an ECR cell 20 composed of a permanent magnet 22 and an antenna 24 is provided. That is, the plasma generator is E
The CR cell 20 is provided. The permanent magnet can be replaced with an electromagnet. The magnetic force of the magnet is, for example, 8.7.
It can be 5 × 10 ^-2 T.

Nitrogen (N ₂ ) which is a raw material is highly purified by using an adsorption tube (not shown). Nitrogen is introduced into the ECR cell 20 through a stainless steel tube 26. The 2.45 GHz microwave is guided into the ECR cell 20 by the antenna 24. ECR cell 20
The plasma gas (excited species of nitrogen molecules) generated in the chamber is discharged into the vacuum chamber 12 through the aperture 18.

A method of manufacturing the semiconductor device of the present invention will be described below. First, using the apparatus shown in FIG. 1, a substrate 30 made of n-GaAs whose surface has been cleaned is mounted on a substrate holder 16 and the vacuum container 12 is evacuated to about 10 ⁻⁸ Pa. Based on n-ZnSe
Of the first cladding layer 32 is formed on the substrate 30.
An active layer 34 made of (Cd, Zn) Se was formed on the clad layer 32 (see FIG. 2).

Next, a second cladding layer made of p-ZnSe is formed on the active layer based on the method for manufacturing a semiconductor device of the present invention. High-purity zinc and selenium as raw materials,
Each of them is filled in a separate K cell 14, and the K cell 14 is heated and adjusted so that an appropriate molecular beam intensity can be obtained.
The molecular beam intensity ratio of zinc and selenium was set to 1: 1.2.

The temperature of the substrate 30 is set to 300 ° C. and Se which is the first element and Zn which is the second element are deposited on the substrate 30 (see FIG. 2). That is, a crystal composed of the first element (Se) and the second element (Zn) is grown on the active layer. Simultaneously with this crystal growth, the ECR cell 20 irradiates the substrate 30 with excited species of nitrogen molecules. Thus
A semiconductor device as shown in the schematic sectional view of FIG. 2 could be manufactured.

The irradiated excited species (plasma) is II-VI.
The amount taken into the group compound semiconductor layer depends on the ECR cell 20.
It can be controlled by changing the electric power applied to, or by changing the opening area of the aperture 18. In order to change the area of the aperture opening, it is necessary to break the vacuum of the vacuum container 12 to return it to atmospheric pressure and then replace the aperture. After the aperture is replaced, it is usually 2 to 3 before the vacuum container 12 is made to have a high vacuum.
It takes a week. Therefore, it is necessary to widely change the amount of nitrogen in the II-VI group compound semiconductor crystal by changing the electric power supplied to the ECR cell 20.

As shown in FIG. 3, in the method of manufacturing a semiconductor device of the present invention using ECR plasma, the amount of nitrogen can be controlled over a wide range, and II-VI group compound semiconductor crystals can be formed. An acceptor showing p-type conductivity can be effectively and accurately introduced therein. However, in FIG. 3A, the aperture area of the aperture is 8 × 10 ⁻³ m.
a case of a m ^2, in FIG. 3 (B), the opening area of the aperture 7 × 10 ^- is a case of a ² mm ^2. For example, in a II-VI group compound semiconductor made of ZnSe, Se and N in the ZnSe crystal replace each other. Therefore, as the amount of N in the ZnSe crystal increases, the amount of Se decreases. Therefore, excited species of nitrogen molecule (plasma)
The irradiation density (the density of the N element in the II-VI group compound semiconductor layer) on the substrate 30 of Se is the deposition density of Se on the substrate (II
^{10-6 to} 1 of the density of Se element in the group VI compound layer)
It may be 0 to ³ times.

Moreover, as shown in FIG. 3, the ECR cell 2
The input power to 0 is about half of the input power to the RF plasma generator (usually 150 to 300 W). When the input power to the plasma generator increases, the temperature of the plasma generator increases. As a result, an impurity gas is generated from the plasma generation device, and this impurity gas is taken into the crystal, resulting in deterioration of the quality of the compound semiconductor layer. In the method of the present invention using ECR plasma,
The electric power to be applied to the ECR cell 20, which is the plasma generator, may be small, and the generation of the impurity gas can be suppressed. As a result, as shown in FIG.
A high-quality semiconductor device in which no deep level light emission near 00 nm was observed was obtained.

Example 2 In Example 2, p- (Mg, Zn) (S,
The case where the Se) layer is formed is shown. That is, sulfur (S) and selenium (Se) are selected as the first element, and magnesium (Mg) and zinc (Zn) are selected as the second element,
A nitrogen molecule was used as the excited species. Also, as a substrate,
A substrate made of n-GaAs was used.

Using the apparatus shown in FIG. 1, a substrate 30 made of n-GaAs whose surface has been cleaned is attached to the substrate holder 1.
6 and the vacuum container 12 was evacuated to about 10 ⁻⁸ Pa. Then, according to the conventional method, n- (Mg, Zn) (S, S
e) forming a first cladding layer on the substrate 30,
Further, an active layer made of ZnSe was formed on the first cladding layer.

Next, a second clad layer made of p- (Mg, Zn) (S, Se) is formed on the active layer based on the method for manufacturing a semiconductor device of the present invention. High-purity magnesium, zinc, sulfur, and selenium, which are raw materials, are filled in separate K cells 14, and the K cells 14 are heated so that an appropriate molecular beam intensity can be obtained. The molecular beam intensity ratio of magnesium, zinc, sulfur and selenium is 0.2:
It was set to 1: 0.1: 1.2.

The temperature of the substrate 30 is set to 300 ° C., and the first elements S and Se and the second elements Mg and Zn are deposited on the substrate 30. That is, a crystal composed of the first element (S, Se) and the second element (Mg, Zn) is grown on the active layer. Simultaneously with this crystal growth, the ECR cell 20 irradiates the substrate 30 with excited species of nitrogen molecules. A II-VI group semiconductor device could be manufactured. Note that it is difficult to manufacture a II-VI group semiconductor device containing Mg except for the method of the present invention using ECR plasma. This is because the II-VI group compound semiconductor containing Mg is more easily affected by impurities than the other II-VI group compound semiconductors.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. Instead of a substrate made of GaAs, for example Zn
A substrate made of Se can be used. Instead of the excited species of the nitrogen molecule, the excited species of the nitrogen atom can be used, and further, the excited species of the oxygen molecule or the oxygen atom can be used. That is, p-type conductivity can be imparted to the II-VI group compound semiconductor layer by oxygen.

Instead of depositing various elements on the substrate by the MBE technique, a cracking cell is used to collide the raw material gas with the surface of the substrate to decompose the raw material gas on the surface of the substrate, which is a component of the raw material gas on the surface of the substrate. A technique called gas source MBE, MOMBE or chemical beam epitaxy for depositing an element can also be used.

The structure of the II-VI group compound semiconductor device is as follows.
The invention is not limited to the first embodiment or the second embodiment. For example, the substrate n-GaAs first cladding layer n-ZnSe active layer Zn (S, Se) second cladding layer p-ZnSe, or the substrate p-GaAs first cladding layer p-ZnSe active layer ( Cd, Zn) Se or Zn
(S, Se) Second cladding layer n-ZnSe structure, further substrate p-GaAs first cladding layer p- (Mg, Zn) (S, Se) active layer ZnSe second cladding layer n- A structure of (Mg, Zn) (S, Se) can be exemplified. In these cases, p
The method of the present invention can be applied to the formation of the type compound semiconductor layer.

[0028]

By using ECR plasma,
Since the power input to the plasma generator can be reduced, heat generation in the plasma device can be suppressed. As a result, less impurity gas is generated due to heat generation in a high vacuum, and high quality p-type conductivity II
A -VI compound semiconductor device could be obtained. Also,
The amount of nitrogen in the II-VI group compound semiconductor could be controlled over a wide range by controlling the electric power input to the ECR plasma generator (ECR cell).

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an MBE device suitable for use in a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a schematic cross-sectional view of a semiconductor device manufactured by the method for manufacturing a semiconductor device of the present invention.

FIG. 3 is an input power to the ECR plasma generator, and II
It is a figure which shows the relationship of the amount of nitrogen in a -VI group compound semiconductor crystal.

FIG. 4 is a diagram showing characteristics of the semiconductor device obtained in Example 1;

[Explanation of symbols]

 10 Molecular Beam Epitaxy Apparatus 12 Vacuum Container 14 Molecular Beam Source (K Cell) 16 Substrate Holder 18 Aperture 20 ECR Cell 22 Permanent Magnet 24 Antenna 26 Tube 30 Substrate 32 First Clad Layer 34 Active Layer 36 Second Clad Layer

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Claims (3)

[Claims] 1. At least one of sulfur, selenium, and tellurium.
Electron-Cyclotron-Resonance (ECR) while depositing a first element selected from the type and a second element selected from at least one of zinc, mercury, cadmium and magnesium on a substrate in vacuum. A method for manufacturing a semiconductor device, which comprises irradiating the substrate with an excited species of nitrogen or oxygen molecules or atoms excited by plasma. 2. The method for manufacturing a semiconductor device according to claim 1, wherein at least magnesium is selected as the second element. 3. The irradiation density of the excited species of nitrogen or oxygen molecules or atoms onto the substrate is 10 ^{−6 to} 10 ⁻³ times the deposition density of the first element onto the substrate. A method for manufacturing a semiconductor device according to claim 1 or 2.