JPH03115191A - Molecular beam generator - Google Patents

Abstract

PURPOSE:To provide the molecular beam generator which more surely prevents the generation of oval defects by providing a heater on the outer side of a side wall which is reduced in the thickness near the aperture of a crucible contg. a molecular beam source consisting of a group III metals. CONSTITUTION:The molecular beam source 8 is heated to evaporate in the crucible 21 by the heat generated from a heater wire 22 and is passed through the aperture 21a to arrive at a substrate 3. The part near the aperture 21a is wound with the heater wire 22 and is reduced in the thickness and is, therefore, heated to the temp. higher than in the other parts; in addition, the temp. difference from the bottom increases. The adhesion of the liquid drops of the molecular beam 8, such as Ga, near to the aperture 21a is, therefore, more surely prevented. The oval defects are thus decreased to a lower level than a conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a molecular beam generating apparatus, for example, a molecular beam generating apparatus used in a molecular beam epitaxial growth apparatus.

[Prior Art] FIG. 3 is a block diagram showing a conventional molecular beam epitaxial growth apparatus.

In the figure, symbol (1) is a growth chamber whose interior is evacuated (2) is a liquid nitrogen shroud provided in the growth chamber (1), and (3) is a growth chamber (
(1) is a substrate held in the interior; (4) is a heater for heating the substrate (3);

(5) is the first molecular beam generator provided facing the substrate (3), and (6) is the first molecular beam generator provided opposite the substrate (3) along with the first molecular beam generator (5). This is the second molecular beam generator.

In the molecular beam epitaxial growth apparatus as described above, G a A heated by the substrate heating heater (4)
An epitaxial layer is formed on the substrate (3) by irradiating the substrate (3) of S or InP with molecular beams generated by the first and second molecular beam generators (5) and (6). .

Here, FIG. 4 is an enlarged sectional view of the first molecular beam generator (5), and in the figure (7) is a cylindrical crucible having an opening (7a) and a cap (7b). , (8) is a molecular beam source made of a group II metal such as Ga or In (hereinafter, for example Ga
The case will be explained below. ), (9) is a heater wire evenly wound around the entire outer circumference of the crucible (7), (10) is a thermocouple provided so as to be in contact with the bottom of the crucible (7),
(11) is a radiation prevention plate.

In such a first molecular beam generator (5), G
When the molecular beam a is irradiated from the crucible (7), the opening (
7a) Ga droplets adhering to the vicinity fly out and touch the substrate (3)
Oval defects occur on the substrate (3) due to the adhesion to Ga and the influence of impurities contained in Ga.

The oval defect is
MBE (Molecular Beam Epitax)
y) These are surface defects that occur due to growth specific to the method.

On the other hand, FIG. 5 is an enlarged sectional view of the second molecular beam generator (6), and as shown in the figure, the second molecular beam generator (6) has an opening on the outer periphery of the crucible (7). ()a) The heater wire (9) is wound only in the vicinity (top heat type), so the vicinity of the opening (7a) is heated, making it difficult for Ga droplets to adhere to this area. , oval defects will be reduced.

[Problems to be Solved by the Invention] In the conventional device as described above, by adopting a top heat type, oval defects can be reduced to some extent, but Ga droplets cannot be evaporated sufficiently, so oval defects occur. There is also a problem that the reduction in the amount of carbon is not sufficient, and there is a problem that such a problem must be solved.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a molecular beam generator that can more reliably prevent the occurrence of oval defects.

[Measures to Solve the Problems: 1] In the molecular beam generator according to the present invention, the wall thickness of the side wall near the opening of the crucible is made thinner than the wall thickness of other parts of the side wall. A heater is installed outside the thinner part.

[Function] In the present invention, the side wall near the opening of the crucible is made thinner, and a heater is provided outside that portion, thereby effectively heating the vicinity of the opening.

[Example] Hereinafter, the present invention will be explained based on the drawings showing one example thereof.

FIG. 1 is a sectional view of a main part of a molecular beam generator according to an embodiment of the present invention, and the same or equivalent parts as in FIGS. 4 and 5 are designated by the same reference numerals, and the explanation thereof will be omitted.

In the figure, the symbol (21) is a crucible that is provided inside the radiation prevention plate (11) and houses the molecular beam source (8).
This crucible (21) has an opening (21m) and a cap (
211)), and the wall thickness of the side wall near the opening (21a) is made thinner than the wall thickness of other portions of the side wall. A heater wire (22) is wound around the thinner side wall of the crucible (21).

In the above-mentioned molecular beam generator, a molecular beam source (8
) is heated in the crucible (2) by the heat generated from the heater wire (22).
1) It is heated inside and evaporates. Evaporated molecular beam source (8)
passes through the opening (21m) and reaches the substrate (3).

At this time, the heater wire (22
) is rolled up, and the wall thickness is thinner, so it gets hotter than other parts, and the temperature difference with the bottom part becomes large.

Therefore, adhesion of droplets of the molecular beam source (8) such as Ga to the vicinity of the opening (21a) is more reliably prevented. As a result, oval defects are also reduced compared to the prior art.

Next, FIGS. 2(a) to (c) show the crucible (21) shown in FIG. 1! ! FIG. 3 is a schematic cross-sectional view showing an example of a method of manufacturing the product in the order of steps.

When manufacturing the crucible (21) as described above, first a mold (23) as shown in FIG. 2(a) is manufactured.

Next, PB was added to the mold (23) by the CVD method.
N (pyrolytic boron n1trid
A crucible material (24) consisting of e) is attached. At this time,
The outer shape of the crucible material (24) is as shown in FIG. 2(b).
Since the shape follows the outer shape of the mold (23), the crucible material (
24) The outer periphery of the side wall, especially the part where you want to make the wall thinner,
After grinding, the final crucible (21
) shape.

Also, the thickness of the thin part of the side wall of the crucible (21) is 0.5z
Preferably, the thickness of the other portions of the side wall is approximately 0.9zz. In addition, the thin wall thickness of the side wall
It is preferable to provide it in a range of about 173 to 172 overall from the end on the opening (21m) side.

In addition, PBN used as the crucible material (24) in the above example
has anisotropy with respect to heat conduction, making it difficult to conduct heat in the circumferential direction.

Note that the shape, material, etc. of the crucible (21) are not limited to those in the above embodiment.

Furthermore, although the heater wire (22) is shown as the heater in the above embodiment, any other heater may be used as long as it can evaporate the molecular beam source (8).

[Effects of the Invention] As explained above, in the molecular beam generator of the present invention, the wall thickness of the side wall near the opening of the crucible is made thinner than the wall thickness of other parts of the side wall. Since the heater is installed outside the opening, the area near the opening can be effectively heated.
In addition, it is possible to increase the temperature gradient with the bottom, and it is possible to more reliably prevent droplets of the molecular beam source from adhering to the vicinity of the opening.
This has the effect that the occurrence of oval defects can be more reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a molecular beam generator according to an embodiment of the present invention, and FIGS. 2(a) to (c) are schematic cross-sectional views showing an example of a method for manufacturing the crucible shown in FIG. 1 in the order of steps. , FIG. 3 is a block diagram showing an example of a conventional molecular beam epitaxial growth apparatus,
FIG. 4 is an enlarged sectional view of the first molecular beam generator shown in FIG. 3;
FIG. 5 is an enlarged sectional view of the second molecular beam generator shown in FIG. 3. In the figure, (8) is a molecular beam source, (21) is a crucible, and (2
1a) is an opening, and (22) is a heater wire (heater). In each figure, the same reference numerals indicate the same or corresponding parts. 21 - Indication of the Crucible Kō 2 Figure Cold 3 Helmet 5 Procedural Amendment Case Patent Application No. 252078 Name of the invention Relation to the old case in which the molecular beam generator was amended Patent Applicant Address 2 Marunouchi, Chiyoda-ku, Tokyo Chome 2-3 Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki

Claims (1)

[Claims] A crucible in which the wall thickness of the side wall near the opening is thinner than the wall thickness in other parts of the side wall and which houses a molecular beam source made of a group III metal; A molecular beam generator characterized in that it is equipped with a heater provided outside of a portion where the molecular beam is exposed.