JPS61125123A - Molecular beam crystal growth device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a molecular beam crystal growth apparatus, and particularly to a molecular beam crystal growth apparatus capable of monitoring molecular beam intensity during crystal growth.

2. Description of the Related Art Substrates in which a required single crystal layer is epitaxially grown on a single crystal substrate are widely used in semiconductor devices and the like.

Various methods are used for epitaxial growth, but
The molecular beam crystal growth method (MB2 method) is a method in which constituent elements and impurity elements of a single crystal layer are evaporated from a cell in a high vacuum of about 10-'' Torr, and the substrate is irradiated with a beam to perform epitaxial growth. .

In the MB2 method, the number of molecules of each element that reaches the substrate is uniquely determined by the geometric shape of the evaporation system and the evaporation source temperature. Therefore, it is possible to accurately control the crystal growth rate, the composition ratio of the mixed crystal, the amount of impurity doping, etc., and is suitable for the most precise crystal growth such as a superlattice structure.

However, in order to perform this control accurately, it is necessary to monitor the intensity of the molecular beam during crystal growth, and conventional molecular beam crystal growth apparatuses are still inadequate in this respect.

[Problems to be solved by the prior art and the invention] The molecular beam intensity monitor during crystal growth in a molecular beam crystal growth apparatus requires
Conventionally, methods have been used such as directly receiving the molecular beam with a vacuum gauge and reading it as the degree of vacuum, or reading the intensity of the molecular beam with a four-electrode mass spectrometer.

However, with these methods, the readings vary depending on the degree of vacuum in the growth chamber, and the sensitivity of vacuum gauges and mass spectrometers changes over time due to filament wear, etc., so it is difficult to measure molecular beams with sufficient accuracy. It is difficult to measure the strength, and in order to obtain the desired epitaxial growth layer using the molecular beam crystal growth method,
There is a strong need for improved methods of measuring molecular beam intensity during crystal growth.

[Means for solving problems]

The above problem is that during the epitaxial growth of the required single crystal, a film is formed by the molecular beam to be measured on a monitoring member provided in the growth chamber, and the transmittance of light transmitted through the monitoring member by the film is reduced. This problem is solved by the molecular beam crystal growth apparatus according to the present invention, which is equipped with means for monitoring the intensity of the molecular beam based on changes in the molecular beam.

[For production]

In the molecular beam crystal growth apparatus of the present invention, only the molecular beam to be measured enters the growth chamber for the required time, other molecular beams are blocked, and the molecular beam to be measured is placed on a monitoring member mounted here. A structure capable of forming a film,
It is equipped with a light source and a light detection device or an optical system equivalent thereto for measuring the light transmittance of the monitoring member.

This monitoring member is made of a material such as quartz that transmits the light from the light source, and is usually processed into a plate shape.

At a required time point, the molecular beam to be measured is irradiated onto the monitoring member for a required period of time to form a film.

Next, the light transmittance of the monitoring member is compared before and after the film formation, or between the area where the film is formed and the area where the film is not formed, based on the calibration data obtained in advance. The thickness of the membrane, the intensity of the molecular beam that formed it, etc. can be easily monitored.

〔Example〕

The present invention will be specifically explained below using examples.

FIG. 1(a) is a schematic diagram showing a growth chamber of an embodiment of the molecular beam crystal growth apparatus according to the present invention, and FIG. 1(b) is a schematic diagram showing the molecular beam intensity monitoring device portion thereof.

In the figure, 1 is the wall of the growth chamber, 2 and 3 are cells that serve as molecular beam sources, 4 is a substrate holder, 5 is a substrate for epitaxial growth, 6 and 7 are molecular beam shield plates, 8 is a shutter, and 9 is the operation of the shutter. axis, 10 is optical fiber, 11
1 is a photodetector, 12 is a monitor member holder, 13 is an operating shaft of the monitor member holder, and 14 is a monitor member.

The molecular beam intensity monitoring device of this embodiment is installed near the substrate holder 4, but the light transmittance measurement part is shielded from all molecular beams by the molecular beam shield plate 7, and the film forming part is shielded from all molecular beams. The molecular beam 3R from the cell 3 is shielded by the ray shield plate 6, and the molecular beam 2 from the cell 2 is
Only B enters the film forming portion when the shutter 8 is opened as shown in FIG.

When epitaxially growing a GaAs layer on, for example, a gallium arsenide (GaAs) substrate using the molecular beam crystal growth apparatus of this embodiment, the cell 2 is a gallium (Ga) molecular beam source that controls the epitaxial growth rate of the GaAs layer. 3 is an arsenic (As) molecular beam source.

In this example, a quartz plate is used as the monitoring member 14, but at any time during crystal growth or during preparation for crystal growth, the shutter 8 is opened for a certain period of time, and Ga is deposited on the monitoring member 14. A Ga film is formed by irradiating the molecular beam 2B.

Next, this Ga film-formed portion is moved between the optical fiber 10 and the photodetector 11, and its light transmittance to, for example, helium-neon (He-Ne) laser light is measured.

As schematically shown in FIG. 2, for example, the correlation between the intensity of the Ga molecular beam 2B, which is determined by the thickness of the Ga film, and the light transmittance, with the film formation time constant, is determined in advance, and the correlation between the light transmittance and the Ga film formation time is determined in advance. The light transmittance of the monitoring member 14 is
The intensity of the Ga molecular beam 2B can be monitored from the difference in light transmittance obtained here. Furthermore, from the intensity of the Ga molecular beam 2B, it is possible to monitor and control the growth rate of the GaAs epitaxial growth layer.

When the epitaxially grown single crystal layer is, for example, aluminum gallium arsenide (^l zGa , -, As), the molecular beam intensity monitor is
^l) and gallium (Ga),
Either two monitoring devices are provided, or one monitoring device is provided with means for separately irradiating two types of molecular beams. The same applies to quaternary compound single crystals and the like.

The formation area of the film on the monitoring member 14 may be small, and by using a method such as shielding with a mask, a large number of monitoring measurements can be performed with one monitoring member 14, and management can be easily and thoroughly carried out. . In addition, the monitor member 14
It is also possible to provide a portion shielded by a mask, a notch, etc. to facilitate comparison with a state in which the film is not formed.

In the embodiment described above, a quartz plate is used for the monitoring member 14, but other materials such as silicon (Si), sapphire, and glass may also be used.

Further, as the measurement light source, a semiconductor laser, a light emitting diode, or the like having a longer wavelength than in this embodiment may be used.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to accurately and stably monitor the molecular i intensity during epitaxial growth using the molecular beam crystal growth method, and to make good use of the characteristics of this growth method, the superlattice structure etc. can be precisely formed. can be grown with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the present invention, and FIG. 2 is a schematic diagram of the correlation between molecular beam intensity and light transmittance. In the figure, l is the growth chamber wall, 2 and 3 are cells that serve as molecular beam sources, 4 is a substrate holder, 5 is a substrate for epitaxial growth, 6 and 7 are molecular beam shield plates, 8 is a shutter, and 9 is shutter operation 10 is an optical fiber, 11 is a photodetector, 12 is a monitor member holder, 13 is an operating shaft of the monitor member holder, and 14 is a monitor member. % 1 figure

Claims (1)

[Scope of Claims] 1. During the epitaxial growth of a required single crystal, a film is formed by the molecular beam to be measured on a monitoring member provided in the growth chamber, and the film is transmitted through the monitoring member. 1. A molecular beam crystal growth apparatus comprising means for monitoring the intensity of the molecular beam based on changes in transmittance caused by the change in transmittance. 2. The molecular beam crystal growth apparatus according to claim 1, wherein a difference in the transmittance due to the presence or absence of the film is detected as the change in the transmittance.