JPH0325401Y2 - - Google Patents

Description

[Detailed description of the invention] [Summary] In a molecular beam crystal growth apparatus, the shutter for the molecular beam source has a structure in which metal plates are stacked with a space provided so that the shutter faces the growth film forming substrate in the shutter. This improves the purity of the grown film by reducing the release of impurity gas from the surface and the re-evaporation of dopants.

[Industrial application field]

The present invention relates to a molecular beam crystal growth apparatus, and particularly to an improvement of the shutter for the molecular beam source.

Molecular beam crystal growth (MBE) equipment is unique in that it is possible to control the thickness of the grown film formed on the substrate by, for example, about 10 Å, and it is also possible to continuously grow multilayered films. Because of these characteristics, in recent years it has come to be used for crystal growth of compound semiconductors used in the formation of semiconductor devices.

It is also desired to reduce as much as possible the mixing of unnecessary impurities into the grown film.

[Conventional technology]

FIG. 3 is a plan view showing the main part configuration of a conventional MBE device.

In the same figure, 1 is a chamber for ultra-high vacuum;
2 is a molecular beam cell, which has a plurality of cells, in which different raw material elements constituting a grown film are heated and emitted from the molecular beam; 3 is a molecular beam source shutter placed just before the radiation port of each cell 2; , 4 is a thermocouple that monitors the temperature of the raw material, and 5 is a shroud that blocks heat around the cell 2.

Crystal growth is performed by arranging the substrate S at a position facing the radiation opening of the cell 2 in the chamber 1, selectively opening and closing the shutter 3, and irradiating the substrate S with the molecular beam from the opened cell 2. At this time, the closed shutter 3 blocks the molecular beam from the cell 2. That is, for example, when growing non-doped gallium arsenide (GaAs), the shutters 3 of the two cells 2 that emit gallium (Ga) and arsenic (As) are opened, and n-type GaAs with tin (Sn) as a dopant is grown. When growing, the shutters 3 of three cells 2, which are the two cells 2 mentioned above plus the cell 2 that emits Sn, are opened.

Molecular beam source shutter 3 used in this way
As shown in the front view a and the side sectional view b of FIG. 4, it is composed of a single metal plate (approximately 0.2 mm thick and approximately 70 mmφ in diameter) made of tantalum (Ta), for example. In the figure, shutter 3 is fixed by 6.
is, for example, a rod-shaped shaft that moves in the direction of the arrow to open and close the shutter 3.

[Problem that the invention attempts to solve]

In the MBE apparatus having the above configuration, when the temperature of the molecular beam reaches a high temperature of, for example, 1300°C, the shutter 3 reaches a high temperature of nearly 1000°C in the closed state.

Therefore, there is a problem that impurities such as carbon C contained in the material of the shutter 3 are released as a gas, fly to the growth surface, and are taken in, thereby deteriorating the purity of the grown film.

In addition, there is a problem in that molecular beams such as dopants reevaporated from the growth surface adhere to the high-temperature shutter 3, where they evaporate again and are incorporated into, for example, a non-doped grown film that is being grown, deteriorating the purity of the grown film. .

[Means for solving problems]

FIG. 1 is a plan view showing the main part configuration of the MBE device according to the present invention.

The above-mentioned problems are solved by the molecular beam crystal growth apparatus of the present invention, which includes a molecular beam source shutter 7 having a structure in which metal plates are stacked with a space provided therebetween, as shown in FIG.

[Effect]

In the conventional examples shown in FIGS. 3 and 4, the high temperature of the shutter 3 is due to radiant heat from the molecular beam cell 2 side, and the purity of the grown film is mainly affected by the grown film of the shutter 3. This is the surface facing the formation substrate S.

The present invention focuses on this point and changes the shutter 3 to the shutter 7 having the above structure. The temperature rise of the plate is moderated, and the problematic release of impurity gases and re-evaporation of dopants are reduced, improving the purity of the grown film.

〔Example〕

Hereinafter, an embodiment will be described with reference to FIG. 1 and a front view a side sectional view b of FIG. 2 showing an embodiment of a shutter for a molecular beam source included in the apparatus shown in FIG. Note that the same reference numerals indicate the same objects throughout the figures.

The MBE apparatus shown in FIG. 1 is obtained by replacing the molecular beam source shutter 3 of the MBE apparatus shown in FIG. 3 with a molecular beam source shutter 7 according to the present invention, and other than that, the structure and method of use are the same as before.

As shown in FIG. 2, the shutter 7 has a thickness of approximately
A plurality of protrusions 7b having a height of about 1 mm are provided on a metal plate 7a made of Ta, for example, with a diameter of 0.15 mm and a diameter of about 70 mmφ, and two plates are stacked with the protrusions 7b shifted in position, similar to the conventional method (as shown in Fig. 4). is fixed to the shaft 6.

Therefore, a space 7c of approximately 1 mm is provided between the two metal plates 7a. This space 7c becomes a thermal cross-section between the molecular beam cell 2 side and the growth film forming substrate S side described above.

The inventor of the present application uses an MBE apparatus shown in FIG. 3 equipped with a shutter 3 and an MBE apparatus shown in FIG.
When an Sn-doped n-type GaAs film was grown on top of the Sn-doped n-type GaAs film and a non-doped GaAs film was grown on top of it, the carrier concentration of the non-doped GaAs film was compared; the former was about 3 x 10 ¹⁵ /cm ³ , but the latter So about 1×
10 ¹⁵ /cm ³ , confirming that the present invention has the desired effect.

In the shutter 7 of the above embodiment, the number of metal plates 7a is two, but in view of the principle of the present invention, this number may be three or more. In addition, the protrusion 7b
As for the metal plate 7a, which faces outward from the shutter 7, the protrusion 7b may not be provided. Further, in the embodiment, a plurality of independent circular metal plates 7a are stacked one on top of the other, but they may be made into a polygonal shape or the like and have a folded structure.

[Effect of idea]

As explained above, according to the configuration of the present invention, in a molecular beam crystal growth apparatus, it is possible to reduce the release of impurity gas and the re-evaporation of dopants from the surface of the molecular beam source shutter facing the growth film formation substrate. This has the effect of improving the purity of the grown film.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the main structure of an MBE device according to the present invention, FIG. 2 is a front view a and a side sectional view b of a shutter embodiment included in the device shown in FIG. 1, and FIG. 3 is a conventional MBE device. Plan view showing the main part configuration of the device, No. 4
The figure is a front view a of the shutter included in the device shown in Figure 3.
and side sectional view b. In the figure, 1 is a chamber, 2 is a molecular beam cell,
3 and 7 are molecular beam source shutters, 7a is a metal plate, 7
b is a projection, 7c is a space, and S is a growth film forming substrate.

Claims (1)

[Scope of utility model registration request] The shutter for the molecular beam source in front of the radiation port of the molecular beam cell, which is installed in the chamber at a position facing the substrate on which the grown film is formed, is made up of multiple metal plates stacked one on top of the other with a space interval between them, and is integrally formed. A molecular beam crystal growth apparatus characterized by having a structure that can open and close a radiation aperture.