JPS62106616A - Molecular beam epitaxial deposition device - Google Patents

Abstract

PURPOSE:To identify the component and the density of the molecule radiated from the crystal thin film to be formed by growth by a method wherein a mass spectrometer of a molecular beam epitaxial deposition device is arranged at a position at which the molecule radiated from a semiconductor substrate can be measured. CONSTITUTION:The substrate supporting stand 2, with which a heating source provided for the purpose of attaching a semiconductor substrate 4, is provided in the container 1 which is maintained in a vacuum state. A mass spectrometer 11 is provided on the molecular beam epitaxial deposition device consisting of a plurality of molecular beam generators 5, 6 and 7 which are attached to the spherical-shaped side wall plate 1a, opposing to each side wall plate in the container 1, in such a manner that said molecular beams can be made to irradiate on the semiconductor substrate 4. At this time, a box 12 to be used for the mounting of the mass spectrometer is provided on the spherical side wall plate 1a, and the mass spectrometer 11 is provided in said box 12 in such a manner that the molecular beam 13 radiated from the semiconductor substrate 4 can reach the ionizing part of the mass spectrometer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Application Field The present invention relates to an improvement in a molecular beam epitaxial growth apparatus (MBE apparatus) for depositing a crystal thin film on the surface of a semiconductor substrate.

[Conventional technology]

When forming a crystalline a film on the surface of a semiconductor substrate, a so-called method has recently been developed in which a crystal thin film is grown on the surface of the substrate by irradiating the surface of the substrate with molecular beams of raw materials such as Ga, As, and AN in a high vacuum. Molecular beam epitaxial growth is widely used.

An apparatus for carrying out this molecular beam epitaxial growth method, that is, a molecular beam epitaxial growth apparatus, consists of a heating source 3 in a container 1 maintained in a high vacuum, as shown in FIG.
While the semiconductor substrate 4 is attached to the substrate holding stand 2 with a holder 2, a plurality of molecular beam generating means 5.6.7 are attached to the container 1.
, 6a.

7a is attached so as to face the semiconductor substrate 4. However, in the figure, reference numerals 8, 9. ．． Reference numeral 10 denotes a shutter that can be opened and closed for each molecular beam generating means 5, 6.7. , 5a
, 7a is irradiated onto the surface of the semiconductor substrate 4.

In this conventional molecular beam epitaxial growth apparatus, the mass spectrometer 11 is
The above-mentioned molecular beam generating means 5.
The structure is such that the intensity of the molecular beam emitted from the container 6.7 and the atmospheric concentration within the container 1 are measured.

[Problem that the invention seeks to solve]

However, by arranging the mass spectrometer 11 near the substrate holder 2 in this way, the mass spectrometer 11 cannot detect the molecular components emitted from the surface of the semiconductor substrate 4. Since the properties of the crystal thin film grown and formed on the surface of the semiconductor substrate are obtained by adjusting the temperature and time based on the molecular beam intensity and atmospheric concentration detected by the mass spectrometer 11, the semiconductor substrate There is a problem in that it is extremely difficult to achieve the desired properties of the crystal thin film that grows on the surface of the semiconductor laser. When manufacturing using a molecular beam epitaxial growth apparatus, there are problems as described below.

The present inventors have filed an earlier patent application (Japanese Patent Application No. 59-165334)
No. 1), when manufacturing a semiconductor laser, a lower cladding layer of N-type AβGaAs is formed on the surface of the semiconductor substrate 4,
A7! A first layer formed in the form of a seedling layer includes an active layer of GaAs, a first upper clad FFi of P-type AeGaAs, a light absorption layer of N-type GaAs, and an evaporation prevention layer of N-type AβGaAs.
Growth layers are sequentially formed in the container 1 of the molecular beam eviaxial growth apparatus, and the semiconductor substrate 4 is placed in the container 1.
The first photo-etching process is carried out in the next photo-etching process.
Stripe grooves are formed in the evaporation prevention layer and the light absorption layer in the growth layer, leaving a thin part of the light absorption layer, and then this semiconductor substrate 4 is placed in the container 1 again, and its surface is As described above, the semiconductor substrate 4 is heated by the heat source 3 while being irradiated with an As molecular beam from one of the molecular beam generating means 5, 6.7. The remaining light absorbing layer is removed by evaporation to expose the surface of the first upper cladding layer within the stripe groove, and then each molecular beam generating means 5, 6 .
We have proposed a method of forming a second growth layer consisting of a second upper craft layer of P-type ffGaAs and a cap layer of P-type GaAs using molecular beams irradiated from the substrate.

In the thermal etching step of this method, in the conventional molecular beam epitaxial growth apparatus described above, the molecular components of the light absorption layer emitted from the surface of the first upper cladding layer of the semiconductor substrate 4 are arranged in the vicinity of the semiconductor substrate 4. Since the light absorption layer left on the surface of the first upper cladding layer cannot be detected by the mass spectrometer 11, the light absorption layer left on the surface of the first upper cladding layer is thermally removed by heating the substrate 4 while irradiating the semiconductor substrate 4 with an As molecular beam. In the etching process, the thermal etching of the remaining light absorption layer is controlled by the BOW degree and time. Since there is an error in the thickness of the stripe, controlling thermal etching by heating temperature and time will result in excessive etching or insufficient etching. As the shape of the etching changes, the first upper cladding layer is attacked, and if etching is insufficient, a light absorption layer remains. Therefore, controlling the etching by heating temperature and time will affect the performance of the semiconductor laser. There was a problem with being harassed.

Further, when manufacturing an rn-v group compound semiconductor laser using the conventional molecular beam epitaxial growth apparatus,
While heating the A6GaAS active layer in the first growth layer, an A6 molecular beam, a G
When grown by simultaneous irradiation with a molecular beam and As, the deposition rate of Ga with respect to the surface temperature T('c) of the lower cladding layer has a relationship with the dotted line curve in FIG. Aj!The laser wavelength λ (nm) of the GaAs active layer with respect to the surface temperature T (t) of the layer is:
It is well known that the relationship shown by the solid line curve B in FIG. 3 exists.

However, in the conventional molecular beam epitaxial growth apparatus, a thermometer is installed on the substrate holder 2 on which the semiconductor substrate 4 is mounted, and the temperature is controlled by the thermometer. There is a temperature difference between T and T when the semiconductor substrate 4 is attached to the substrate support assembly 2 due to the condition etc., and this temperature difference differs each time the semiconductor substrate 4 is replaced and is not constant. A/ that grew and formed from! The laser wavelength λ (nm) emitted from the GaAs active layer is different for each product.
It has been difficult to obtain products with a constant laser wavelength.

The present invention aims to solve such problems.

[Means for solving problems]

For this reason, the present invention provides a molecular beam comprising a substrate holding stand provided in a container maintained in a high vacuum, and a plurality of molecular beam generating means for irradiating a semiconductor substrate attached to the substrate holding stand with molecular beams. In the epitaxial growth apparatus, instead of installing the mass spectrometer in the vicinity of the substrate holding table, the mass spectrometer is placed at a position where it can measure molecules emitted from the surface of the semiconductor substrate. It was established.

〔Example〕

That is, as shown in FIG.
1, a substrate holding stand 2 with heating tAS provided for mounting the semiconductor substrate 4 in the container 1, and the container "I5I".
Molecular beams 5a are applied to the semiconductor substrate 4 on a spherical side wall plate 1a facing the substrate holding table 2 among the side wall plates.
, 6a, 7a, a molecular beam epitaxial growth apparatus comprising a plurality of molecular beam generating means 5°6.7 installed to irradiate the rays 6a, 7a, is equipped with a molecular beam epitaxial growth apparatus, for example, disclosed in Japanese Patent Application Laid-Open No.
When installing the mass spectrometer 11 as described in Japanese Patent No. 160423, the spherical side wall plate 1a is provided with:
A box 12 is provided for mounting the mass spectrometer, and the mass spectrometer 11 is placed in the box 12 so that the molecular beam 13 emitted from the semiconductor substrate 4 can reach the ionization section of the mass spectrometer 11. establish.

In addition, in FIG. 1, the reference numeral 14 indicates the mass spectrometer 11.
It is a shutter that can be opened and closed freely.

In this molecular beam epitaxial growth apparatus, in order to carry out the thermal etching step in manufacturing the semiconductor laser according to the invention of the prior application, one molecule of each molecular beam generating means 5, 6, 7 is applied to the surface of the semiconductor substrate 4. When the remaining N-type GaAs light absorption layer is evaporated by heating while irradiating an As molecular beam from the beam generating means, the Ga emitted from the semiconductor substrate 4 is transferred to the mass spectrometer 11.
The thermal etching step is completed when the mass spectrometer 11 no longer detects Ga, and the mass spectrometer 11 no longer detects Ga when the entire light absorption layer has evaporated. Therefore, thermal etching for evaporating and removing the light absorption layer can be carried out in just the right amount, and variations in the performance of the product semiconductor laser can be reduced.

In addition, in the molecular beam epitaxial growth apparatus, AβGaA in the first growth layer of the semiconductor laser is used as described above.
When growing the active layer of s, the Ga molecular beam emitted from the semiconductor substrate 4 without being able to adhere to the semiconductor substrate 4 is detected by the mass spectrometer 11, and the adhesion rate of Ga to the semiconductor substrate 4 is determined by For example, in FIG. 3, by adjusting the heating temperature of the semiconductor substrate 4 so that the Ga deposition rate (80%) corresponds to the laser wavelength λ of 780 nm,
A semiconductor laser having a laser wavelength λ of 80 nm can be manufactured.

[Action/effect of the invention]

As described above, according to the present invention, the properties of a crystal thin film grown on the surface of a semiconductor substrate can be determined using a mass spectrometer, and the composition and/or concentration of molecules emitted from the crystal thin film during its growth or etching can be sequentially measured. Since it is possible to ascertain the properties of the obtained crystal thin film, it is possible to bring the properties of the obtained crystal thin film closer to the required properties by using a mass spectrometer to detect the intensity of the molecular beams emitted from each molecular beam generating means, as in the conventional method. This has the effect of being simpler and easier than adjusting the temperature and time based on this.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view showing an embodiment of the present invention, Fig. 2 is a longitudinal sectional front view of a conventional apparatus, and Fig. 3 is the relationship between temperature, Ga deposition rate, and laser wavelength when growing an AβGaAs active layer. FIG. 1... Container, 2... Substrate holding stand, 3... Heat source,
4... Semiconductor substrate, 5, 6.7... Molecular beam emission means, 8, 9.10... Shutter, 11... Mass spectrometer, 13... Box, 14... Shutter.

Claims (1)

[Claims] (1) Molecular beam epitaxial growth apparatus consisting of a substrate holder provided in a container maintained at high vacuum and a plurality of molecular beam generating means for irradiating molecular beams onto the semiconductor substrate attached to the substrate holder. A molecular beam epitaxial growth apparatus characterized in that a mass spectrometer provided therein is disposed at a position such that molecules emitted from the surface of the semiconductor substrate can be measured by the mass spectrometer.