JPH035396A - Method for growing crystal - Google Patents

Abstract

PURPOSE:To eliminate noise and to control crystal growth in atomic order by regulating the irradiation of the surface of a substrate with molecular beams for crystal growth in accordance with the rate of crystal growth calculated by the Fourier transformation of the detected signal of the intensity of diffracted electron beams from the surface of the substrate. CONSTITUTION:The surface of a substrate 2 is irradiated with molecular beams from crucibles 3, 4, 5 to grow a crystal. During this crystal growth, the surface of the substrate 2 is irradiated with electron teams 10 and the oscillation of diffracted electron beams 10a from the surface is detected through a phosphor 11, a photomultiplier 13, etc., The rate of crystal growth is calculated by the Fourier transformation of the detected signal and the irradiation of the surface of the substrate 2 with electron beams from the crucibles 3-5 is regulated in accordance with the calculated rate of crystal growth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is suitably implemented in, for example, the manufacture of semiconductor devices such as semiconductor laser devices having a superlattice structure, and is suitable for the production of semiconductor devices such as semiconductor laser devices having a superlattice structure. It relates to a crystal growth method.

[Conventional technology]

A superlattice element in which the crystal is controlled on an atomic layer basis, for example, several dozen different atomic layers are alternately stacked, has an optical forbidden band width that changes depending on the applied voltage.

It has unique characteristics such as negative resistance and high mobility, and is applied to semiconductor laser devices and high mobility transistors.

Conventionally, MBE (molecular beam epitaxial) method has been used to grow semiconductor crystals for producing such superlattice elements, and crystal growth is controlled for each atomic layer. The configuration for this crystal growth is shown in FIG.

Group #H held in the vacuum container 1 by a structure not shown,
A plurality of crucibles 3, 4.5 for melting and vaporizing different substances are arranged opposite to the crucibles 2. Shutters 6.7.8 are arranged in association with the crucible 3.4.5, and the substance deposited on the surface of the substrate 2 is controlled by opening and closing each shutter.

The surface of the substrate 2 facing the crucibles 3, 4.5 is irradiated with an electron beam 10 from the IF gun 9, and the diffracted electron beam 10a from the surface of the substrate 2 enters the fluorescent plate 11.
A corresponding image of the atoms on the surface of the substrate 2 is formed.

This image is the so-called R HE E D (Reflec
tion High Energy Electron
Diffraction: reflection high-speed electron beam diffraction) image.

The light at the brightest point near the center of this RHEED image is guided to the photomultiplier tube 13 via the optical fiber 12 and detected, and the output of the photomultiplier tube 13 (rRH
EEDRHEED image) to a recorder 14 to record its changes, and the RHEED signal to a control means (not shown) to calculate the crystal growth rate;
The opening/closing control of the shutter 6.7.8 is performed in accordance with this growth rate.

The RHEED signal from the photomultiplier tube 13 corresponds to the intensity of the diffracted electron beam 10a;
The signal changes as shown in FIG. That is, RHE
The intensity of the diffracted electron beam 10a, which forms the brightest point near the center of the ED image, oscillates with a period equal to the formation of one atomic layer.

The second vibration is called RHEED vibration.

FIG. 5 is a simplified cross-sectional view showing the formation of an atomic layer on the surface of the substrate 2 in chronological order, and FIG. 6 is an explanatory diagram showing the recording H in the recorder 14 in chronological order. 5 (1) to (5) The recording state of the recorder 14 corresponding to each time in the illustrated state is shown in FIG. 6 (1) to (5).
are shown respectively.

In the state shown in FIG. 5(1) before crystal growth begins, the surface of the substrate 2 is flat, and therefore the electron beam 10 from the electron gun 9 is reflected toward the center of the fluorescent screen 11. Therefore, the intensity of the diffracted electron beam 10a in this case is high, and the RHEED signal is relatively large.

When crystal growth starts, crystals 15 begin to grow in the form of islands on the flat surface of the substrate 2, and the electron beam 10 comes to be scattered on the surface of the substrate 2. As a result, as the crystal grows, the intensity of the diffracted electrons kiA 10a toward the center of the fluorescent screen 11 decreases, and after passing through the state shown in FIG. 5(2),
FIG. 5(3) When the crystal 15 grows in the area of the surface of the substrate 2 shown in the diagram, the crystal 15 reaches a minimum. If the crystal 15 grows further from the state shown in FIG. 5(3), the surface of the substrate 2 On the contrary, the flatness increases, and therefore the intensity of the diffracted electron beam 10a directed toward the center of the fluorescent screen 11 increases. In this way, after passing through the state shown in FIG. 5(4), the RHE is
The ED signal increases and reaches its maximum value when the growth of one atomic layer is completed.

In this way, one period of RHEED vibration corresponds to the period of one atomic layer. Therefore, by monitoring the recording of the recorder 14, it is possible to count the atomic layers and determine the growth rate, and by controlling the opening and closing of the shutter 6.7°8 corresponding to this growth rate, the superlattice can be It is possible to obtain a semiconductor crystal of the structure.

[Problems to be Solved by the Invention] However, in the above configuration, the photomultiplier tube 1
Since the RHEED signal from 3 contains various noises,
When determining the evaporation rate, errors caused by the noise pose a problem, and as a result, it has become difficult to control crystal growth on the atomic order.

An object of the present invention is to provide a crystal growth method that solves the above-mentioned technical problems and allows crystal growth of a fine structure to be carried out in a much better manner.

[Means to solve the problem]

In the crystal growth method of the present invention, a detection signal of the diffracted electron beam intensity from the substrate surface is Fourier-transformed, a crystal growth rate is determined from this Fourier-transformed signal, and the molecular beam irradiation is adjusted in accordance with this growth rate. It is characterized by controlling.

[Function] According to the configuration of the present invention, the detection signal of the diffracted electron beam intensity, which oscillates with a period equal to the growth of the atomic layer, is converted into a frequency by Fourier transform. It becomes possible to determine the frequency of vibration while excluding the influence of noise.

In other words, it is now possible to accurately determine the crystal growth rate from the Fourier-transformed signal, and therefore, if the molecular beam irradiation is controlled in accordance with this growth rate, the crystal growth can be controlled on the atomic order. becomes possible.

〔Example〕

FIG. 1 is a conceptual diagram showing the basic structure for implementing a crystal growth method according to an embodiment of the present invention.

In FIG. 1, parts corresponding to those shown in FIG. 3 described above are designated by the same reference numerals. In this embodiment, the RHEED signal from the photomultiplier tube 13 is input to a signal processing computer 16, where it is Fourier transformed. The RHEED signal from the photomultiplier tube 13 changes as shown in FIG. 4 above, but by Fourier transforming this RHEED signal, it is converted into a signal with a peak P as shown in FIG. can do.

The frequency f0 at this peak P is the frequency of vibration of the RHEED signal, and as is clear from FIG. 2,
Noise components are clearly separated. Therefore, if the crystal growth rate is determined based on the frequency r0 at the peak P, it is possible to obtain a growth rate that is one order of magnitude more accurate than the conventional method.

In FIG. 1, 17 is a display device such as a CRT (cathode ray tube), and 18 is a printing device. For example, the display device 17 displays the Fourier-transformed signal shown in FIG. is the RH from the photomultiplier tube 13.
The waveform of the EED signal may also be output.

As mentioned above, by determining the crystal growth rate based on the frequency f0 at the peak P of the signal obtained by Fourier transforming the RHEED signal, an accurate growth rate can be determined. Based on the thus determined crystal growth rate, By controlling the opening and closing of the shutter 6.7°8, the crucible 3
By controlling the irradiation of each molecular beam from , 4.5,
A semiconductor crystal or the like having a superlattice structure or the like that is precisely controlled on the atomic order can be formed on the surface of the substrate 2.

〔Effect of the invention〕

As described above, according to the crystal growth method of the present invention, the detection signal of the intensity of the diffracted electron beam, which oscillates with a period equal to the growth of the atomic layer, is converted into a frequency by Fourier transform. It becomes possible to determine the frequency of vibration of line intensity while excluding the influence of noise. That is,
It is now possible to accurately determine the crystal growth rate from the Fourier-transformed signal, and therefore, by controlling molecular beam irradiation according to this growth rate, it is possible to control crystal growth on the atomic order. becomes.

As a result, crystal growth of a fine structure can be performed well, and good characteristics can be obtained, for example, in a semiconductor crystal having a superlattice structure.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the basic configuration for carrying out a crystal growth method according to an embodiment of the present invention, FIG. 2 is a diagram showing a Fourier-transformed RHEED signal from a photomultiplier tube 13, and FIG. Figure 3 is a conceptual diagram showing the basic configuration of the conventional technology.
FIG. 4 is a diagram showing the RHEED signal from the photomultiplier tube 13, FIG. 5 is a simplified cross-sectional view showing the state of crystal growth on the surface of the substrate 2, and FIG. 6 is a simplified diagram showing the recording mode of the recorder 14. It is an explanatory diagram. 2...Substrate, 9...Electron gun, 10...Electron beam, 1
0a... Diffracted electron beam, 11... Fluorescent screen, 13...
Photomultiplier tube, 16...signal processing computer 10
a.-me Yari Denjin 16...Signal processing computer Fig. t. Deep attack□

Claims (1)

[Claims] The substrate surface is irradiated with a molecular beam to grow a crystal, and the substrate surface is irradiated with an electron beam, and vibrations in the intensity of the diffracted electron beam from the substrate surface are detected, and the detection result is obtained. In the crystal growth method in which the molecular beam irradiation is controlled based on the above, the detection signal of the diffracted electron beam intensity is Fourier transformed, and the crystal growth rate is determined from the Fourier transformed signal,
A crystal growth method characterized in that irradiation of the molecular beam is controlled in accordance with the growth rate.