JP2002118064A - Crystal growth method of semiconductor at low temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify controlling for decreasing of the temperature in crystal growth, and to inhibit automatic doping. SOLUTION: When an amorphous semiconductor material is subjected to crystal growth, light is applied, thus decreasing temperature in the crystal growth. The energy of light to be applied exceeds a band gap specific to a semiconductor material to be subjected to crystal growth. In the manufacture of a semiconductor device, the automatic doping is inhibited for making clear the boundary of a doping region, thus manufacturing an electronic device, having single atom layer doping and modulation doping layers, and superior functions according exactly as designed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a semiconductor crystal, and more particularly to a method for lowering the crystal growth temperature of an amorphous semiconductor.

[0002]

2. Description of the Related Art Semiconductor materials such as silicon, gallium arsenide, and gallium nitride are electronic device materials that support the present highly developed information and electronics society. It is necessary to lead the energy-saving society. For this purpose, a modulation doping or a monoatomic (delta) doping H
An EMT (High Electron Mobility Transistor, ultra-high-speed transistor element), a three-dimensional structure device, and the like have been considered.

[0003]

However, a problem in achieving the high doping required for such a high-performance electronic device is that a dopant (Dopant) diffuses from a doped region to another region. This causes a phenomenon that the dopant which has flowed out or has flowed out as a gas is taken in again during crystal growth. As a result, a high doping profile is broken, thereby causing a problem that a desired function cannot be achieved.

[0004] This is a phenomenon called auto-doping, and minimizing the auto-doping is one of the necessities in producing a high-performance electronic device. Since auto-doping is caused by thermal diffusion, the most effective way to suppress this is to lower the crystallization temperature. Particularly, in a high-performance electronic device that performs monoatomic layer doping or modulation doping, a desired dopant is attached to the surface of a single crystal semiconductor, and an amorphous semiconductor layer is temporarily deposited and heated thereon to grow solid phase crystals. Accordingly, a manufacturing method of single-crystallizing the amorphous semiconductor layer is used. In this case, it is necessary to suppress the auto doping by lowering the temperature required for solid phase crystal growth.

[0005] In the growth of undoped amorphous semiconductors and single crystal semiconductors using molecular beam epitaxy or vapor phase chemical vapor deposition, high-temperature crystal growth generally involves the formation and transfer of vacancies, It induces the occurrence of stacking faults and the like, thereby deteriorating the quality as an electronic device material. Therefore, lowering the crystal growth temperature has become a very important issue not only in the crystallization of a doped amorphous semiconductor but also in the application fields described above.

The temperature required for solid-phase crystal growth greatly depends on the cleanliness of the underlying surface of the crystal growth and the proportion of impurities such as hydrogen, water, oxygen, etc., which are exhaust gas remaining in the crystal growth atmosphere in vacuum. . Therefore, it is necessary to make the degree of vacuum in the atmosphere during the deposition of the amorphous layer very good, and to minimize the concentration of impurities taken into the deposited amorphous. In particular, since elements such as hydrogen and oxygen have an adverse effect on the growth of amorphous solid phase crystals, it is desired to remove these elements from the residual gas.
In a hypernomial vacuum apparatus of about 0 to 10 Torr, hydrogen and water are ultimately left, and reducing these requires more cost and more precise control of the apparatus.

Furthermore, when a relatively long time is required for depositing an amorphous semiconductor layer, the amount of impurities taken into the amorphous phase gradually increases, and the crystal growth temperature fluctuates (increases) accordingly. I had to. For this reason, development of a method for lowering the solid-phase crystal growth temperature by a method that is very dense and generally simpler than these complicated and complicated controls for low-temperature growth has been desired.

[0008]

In order to solve the above-mentioned problems, the present invention reduces the crystal growth temperature by irradiating light at the time of crystal growth of a semiconductor material, and the temperature control is simple. Provide a way to Further, the semiconductor crystal layer provides a method for clearing a layer interface of each semiconductor layer and suppressing auto-doping when a semiconductor material is crystal-grown on the semiconductor crystal layer as a doping layer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to FIGS. FIG. 1 shows the fabrication of an amorphous silicon layer,
1 schematically shows an ultra-high vacuum vapor deposition apparatus for performing the crystal growth method of the present invention. In the figure, 1 is an ultra-high vacuum deposition apparatus, 2 is a substrate, 3 is an electron beam heating deposition apparatus that irradiates a substrate 2 with semiconductor material, for example, silicon ions, 4 is a light irradiation apparatus that generates light, and 5 is a substrate. A substrate holder for holding, 6 a heater for heating the substrate 2 at a desired temperature, 7 a chamber, 8 a vacuum pump, 9 a surface for controlling the surface of the substrate 2 held by the substrate holder 5 in a predetermined direction and angle 6 Represents a shaft sample manipulator.

Further, reference numeral 10 denotes an ion accelerator for irradiating ions for observing and evaluating the crystal state of the substrate 2, and 11 denotes an ion detector for detecting ions scattered from the irradiated surface of the substrate 2. I have. Although not shown in FIG. 1, a RHEED (Reflection Hight Energy Elect) having an electron gun and a fluorescent screen is provided in the vertical direction of the drawing.
ron Diffraction (reflection high-speed electron diffraction) device is provided.

The prepared sample is subjected to low-energy time-of-flight ion scattering spectroscopy 10 and a RHEED device connected to the ultra-high vacuum deposition apparatus 1 without breaking the vacuum in-situ, and the amorphous thickness and crystallinity are maintained. Etc. can be evaluated. The evaluation of the substrate 2 by the low energy time-of-flight ion scattering spectrometer 10 is performed at the position of the substrate 2 indicated by a dotted line in FIG.

An amorphous layer is formed by the ultra-high vacuum evaporation apparatus 1 shown in FIG. The surface is cleaned before being put into the chamber 7 in advance, and the silicon single crystal substrate whose surface is covered with an extremely thin oxide film is used as the substrate 2 and attached to the 6-axis sample manipulator 9 in the ultra-high vacuum evaporation apparatus 1. The silicon single crystal substrate 2 is set on the substrate holder 5 in the chamber 7 by the 6-axis sample manipulator 9.

Using a vacuum pump 8, the inside of the chamber 7 is 1 ×
Evacuate to about 10-10 Torr. When the heater 6 of the substrate holder 5 is energized, the silicon substrate 2
C. to evaporate a very thin oxide film covering the surface to clean the surface of the silicon substrate 2. The production of the clean surface can be confirmed by the pattern of the phosphor screen of the RHEED device. Thereafter, silicon ions are removed at room temperature by, for example, clean silicon (001) using an electron beam heating evaporation apparatus 3 using a rod-shaped silicon evaporation source having a diameter of 2 mm.
Deposit on the surface to deposit an amorphous silicon layer.

At this time, if the deposition rate of silicon is made very slow, a large amount of residual impurity gas in the atmosphere is taken into the deposited amorphous layer, and the impurity concentration of the amorphous layer is intentionally raised, it is usually necessary to increase the impurity concentration. Thus, an amorphous silicon layer in which solid-phase crystal growth is less likely to occur as compared with amorphous silicon having a low impurity concentration is produced. In our example of producing amorphous silicon, the volume velocity was about 10 Å / hour. Atmospheric pressure during vapor deposition is 9 × 10-10 Tor
r or less.

When the amorphous silicon thus produced is heated in an ultra-vacuum, the amorphous silicon is crystallized. At this time, light of a predetermined intensity is emitted by the light irradiation device 4. It has been found that crystallization can be realized at a lower temperature by irradiation. This will be described below.

COMPARATIVE EXAMPLE 1 The inventors deposited an amorphous silicon layer having a thickness of 29 angstroms on a clean silicon (001) single crystal surface by using the above-described vapor deposition method, and heated the substrate 2 with a heater 6 at a temperature of 600 Å. ℃,
A single crystal was grown by heating for 5 minutes. The low energy time-of-flight ion scattering spectroscopy spectrum which observed the scattering of the hydrogen ion irradiated by the ion accelerator 10 with the detector 11 before and after heating is shown. The horizontal axis is the flight time, and the vertical axis is the scattered ion intensity (the amount of hydrogen ion atoms counted per hour,
Relative value). In the figure, a spectrum curve A shows an ion scattering spectrum observed before heating, and a spectrum curve B.
Is an ion scattering spectrum observed after heating at 600 ° C. for 5 minutes. Spectral curve C is a random spectrum curve. Ion scattering spectrum observed in a silicon single crystal layer in which the incident direction of ions does not match any crystal axis. It is a spectrum.

The peak width of the spectrum curve A measured before heating from the flight time of 220 nsec to 230 nsec is a signal due to the scattered ions from the amorphous silicon layer. By calculating the number of scattered ions within this width, the amorphous width is calculated. The thickness of the layer can be calculated. Here, the fact that the deposited silicon layer is amorphous means that the peak value of the spectrum curve B is smaller than the peak value of the spectrum curve C of “random” and that the RHEE
It can be confirmed from the pattern of the fluorescent screen of the D apparatus.

The peak value of the spectrum curve B after heating is very small, and complete solid phase crystal growth of the amorphous layer occurs by heating at 600 ° C. for 5 minutes, and single crystallization occurs to the surface. It is confirmed that. The crystal growth up to the surface is RH
This was confirmed by the pattern of the phosphor screen of the EED device.

Comparative Example 2 A single-crystal silicon layer was formed by heating a 100 angstrom amorphous silicon layer formed in the same manner as in Comparative Example 1 at 500 ° C. lower than the heating temperature of 600 ° C. in the comparative example for 30 minutes. Tried to grow. FIG. 3 shows low energy time-of-flight ion scattering spectroscopy of hydrogen ions observed before and after this example. In the figure, a spectrum curve D is an ion scattering spectrum observed before heating, and a spectrum curve E is 500.
The ion scattering spectrum and the spectrum curve F observed after heating at 30 ° C. for 30 minutes show a random spectrum curve. In this example, there is almost no difference between before and after heating, and it can be seen that no crystal growth occurred in the amorphous silicon layer by heating at 500 ° C.

Example 1 Next, the inventors heated the substrate 2 at the heating temperature of 500 ° C. of Comparative Example 2 and simultaneously irradiated the substrate 2 with ultraviolet light having a wavelength of 172 nm by the light irradiation device 4. FIG. 4 shows a spectrum curve measured before and after heating and irradiation in this example. In the figure, a spectrum curve G is an ion scattering spectrum observed before heating and irradiation, a spectrum curve H is an ion scattering spectrum observed after heating and irradiation, and a spectrum curve I is a random spectrum curve. From FIG. 4, the peak value of the spectrum curve H due to the scattered ions from the amorphous layer was smaller than the curve G before heating due to the heating with the irradiation of the ultraviolet light, and solid phase crystal growth of the amorphous layer occurred. You can see that.

The energy of this ultraviolet light is larger than the band gap of silicon, 1.1 eV, and it is important that many electrons are excited in the semiconductor material by light irradiation. In this case, the energy of the ultraviolet light of 172 nm was 7.2 eV, which was sufficiently larger than the band gap of silicon, so that many electrons were excited. This was confirmed by the current flowing through the sample by the irradiation of the ultraviolet light. The intensity of ultraviolet light is 1.
8 × 1015 pieces / cm2sec (1.3 × 1016 eV / cm2se
c).

Table 1 summarizes the difference in the amount of crystal growth between Comparative Example 1 and Example 1 depending on the presence or absence of ultraviolet light irradiation. The solid phase growth, which was not caused by heating at 500 ° C. without irradiation with ultraviolet light, was caused by irradiation with ultraviolet light. As described above, it was confirmed that irradiation of ultraviolet light of a predetermined intensity induced solid-phase growth, and the temperature for crystal growth, which was a required temperature of 600 ° C., could be lowered to 500 ° C.

[0023]

[Table 1]

In the crystallization of the semiconductor amorphous layer according to the present invention, the bonds between the atoms at the interface between the amorphous layer and the crystal layer are broken once, and the atoms on the amorphous layer side are replaced with the atoms on the crystal layer side. By rearranging according to the sequence of Irradiation of light to the amorphous layer is promoted by the electrons excited by the light irradiation to break the bonds between atoms at the interface between the amorphous layer and the crystal layer of the semiconductor material, and the subsequent rearrangement process is performed. make it easier.
When the energy of the light to be irradiated is smaller than the band gap inherent to the semiconductor material to which the light is irradiated, few electrons are effectively excited in the semiconductor. Therefore, it can be said that in the present invention, the crystal growth temperature can be lowered when the energy of the light applied is larger than the band gap inherent to the semiconductor material to which the light is applied.

The low-temperature crystal growth method of the first embodiment is an example in which an amorphous semiconductor material is formed on a semiconductor crystal layer and crystal growth is performed, but an amorphous semiconductor material is formed on another material layer. Materials can be formed and crystals can be grown.

Embodiment 2 The crystal growth method of Embodiment 1 can be applied to the manufacture of a high-performance electronic device having a monoatomic layer doping layer and a modulation doping layer. If a device for supplying a dopant material to the substrate 2 is added to the ultra-high vacuum vapor deposition device 1 of FIG. 1, a semiconductor device to which a dopant is applied can be manufactured. In the step of manufacturing a high-performance electronic device, a doped semiconductor material layer, for example, an amorphous semiconductor film formed on a silicon layer, a predetermined intensity having energy equal to or more than the band gap inherent to the amorphous semiconductor film. By irradiation with light, the crystal growth temperature of the amorphous semiconductor film can be reduced. The monoatomic layer doping and the modulation doping layer are suppressed by lowering the crystal growth temperature. By repeatedly doping the single-crystallized semiconductor layer and the like, a high-performance electronic device having a profile as designed highly can be manufactured.

[0027]

According to the method of the present invention, single crystal growth of an amorphous semiconductor can be achieved by simple heating temperature control without the need for laborious and costly management and reduction of residual gas in a vacuum chamber. can do. In addition, by lowering the heating temperature for single crystal growth of amorphous semiconductors, it is possible to suppress autodoping and clear each semiconductor region, and as designed for high-performance electronic devices that perform monoatomic layer doping or modulation doping. In this way, a highly functional electronic device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view conceptually showing an apparatus for performing a crystal growth method of the present invention.

FIG. 2 is a view showing a spectrum curve measured before and after heating by the method of Comparative Example 1.

FIG. 3 is a view showing a spectrum curve measured before and after heating by the method of Comparative Example 2.

FIG. 4 is a view showing a spectrum curve measured before and after heating by the method of Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultra-high vacuum vapor deposition apparatus 2 Silicon substrate 3 Electron beam heating vapor deposition apparatus 4 Light irradiation apparatus 6 Heating apparatus 10 Ion accelerator 11 Ion detector

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Claims (3)

[Claims] 1. A low-temperature crystal growth method for a semiconductor, comprising irradiating light during crystal growth of a semiconductor material to lower the crystal growth temperature. 2. A low-temperature crystal growth method for a semiconductor, comprising irradiating light to grow a semiconductor material on a semiconductor crystal layer to lower the crystal growth temperature. 3. The method according to claim 2, wherein the semiconductor crystal layer according to claim 2 includes a doping layer.