JPS5964594A - Crucible for molecular beam epitaxy (mbe) - Google Patents

Abstract

PURPOSE:Parts are set on the opening for emitting molecular beam so that these cover the peripheral part of the opening to inhibit condensed drops from falling down to the source surface, thus decreasing the oval defects caused by a crucible for MBE. CONSTITUTION:The inner cover 17a is set on the wall surface of the crucible 11 so that the cover has its opening at a depth Sa from the top edge of the crucible opening and the other outer cover 17b is set thereon so that its opening is at a depth Sb. Both covers have a cap shape, respectively and are fitted to the crucible 11 so that their openings are coaxial. When such a crucible provided with such covers is used, Ga source 13 is heated with a heater 12 to form Ga molecules 13', which pass through the openings to form an epitaxial layer on the base 15. Even when Ga drops 16 condensed on the outer cover 17b fall down, they are inhibited from falling down to the Ga source 13 by the inner cover 17a. Thus, the Ga source 13 and GaAs membrane surface are free from disturbance.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to the structure of a crucible that houses a molecular beam source used in molecular beam growth, and particularly relates to the structure of a crucible that houses a molecular beam source used in molecular beam growth. This invention relates to a crucible for molecular beam growth that reduces oval defects formed on a substrate to be processed due to a temperature drop near the tip of a discharge opening.

(2) Prior art and problems Conventionally, a cylindrical or conical crucible has been commonly used as a crucible for a gallium (Ga) source used in molecular beam crystal growth (hereinafter referred to as MBE). .

FIG. 1 is a schematic cross-sectional view of a conventional cylindrical crucible used when performing MBE.

As shown in FIG. 1, a cylindrical crucible 1 containing a Ga source 3 is heated by a coil heater 2 disposed around its outer periphery.
Since heat radiation to the outside is greater than that to the inside, the temperature becomes lower than that inside the crucible. Usually, the Ga molecules vaporized inside the crucible 1 form GaA on the GaAs substrate with As molecules.
s is grown as a single crystal. However, due to the lower temperature near the open end of the crucible 1 mentioned above, the Ga molecular groups vaporized inside the crucible 1 KGa near the open end of the crucible 1
≧1.4 concretions as droplet 6. These droplets or dew condensates 6 often fall onto the Ga source and QaAs film 14 inside the crucible 1 during molecular crystal growth and disturb the liquid level. Therefore, from the Ga source 3, clusters of molecules that are relatively large compared to the molecules are released, and some of them propagate onto the grown epitaxial layer 1 of the substrate 5 to be processed, resulting in oval defects on the growth surface. The GaAs film 4 in the crucible 1 is formed by As entering the Ga source crucible 1 when growing a QaAs crystal on a substrate.

(3) Purpose of the Invention In view of the above disadvantages, the purpose of the present invention is to provide an improved crucible structure 'f' that reduces oval defects caused by crucibles for molecular pure growth devices.

(4) Structure of the Invention The object of the present invention is to provide a molecular beam emitting opening of a crucible for molecular beam crystallization with a member that covers a part of the opening and prevents dew condensation from dropping onto the source surface. υ is achieved by establishing

(5) Examples of the invention The present invention will be described in detail below based on examples.

FIG. 2 is a schematic sectional view showing one embodiment of the MBE crucible according to the present invention.

According to FIG. 2, an ordinary MBE source crucible 11 containing a GIL source 13 is surrounded by a coil heater 12 having a conventional structure.

The crucible of this example has a length S of about 6 [ctIT], a diameter at the tip of the opening for molecular beam emission of 3 [m], and a diameter at the straight body part of 2 to 2 m.
It is 2.5 [CJ++]. An inner lid member 17a having an opening of 3 to 5 diameters is disposed on the wall of the crucible 11 at a depth Sa (=3.5 [c1n]) from the tip of the opening. Depth 5b (=2.5[c] from the tip
111]), an outer lid member 17b having an opening of 3 to 5 diameters is disposed. The centers of the two openings are arranged on concentric axes, and the lid members 17a and 17b are attached to the crucible 11 in the form of caps. If the crucible 11 provided with such a lid member is used, Ga molecules 13' generated from the Ga source 13 heated to a temperature of 900 to 1100 [°C] by the heater 12 will pass through the opening provided in the lid member and reach the substrate 15. grown on the surface of At this time, there is a possibility that the GaO droplets 16 may form dew condensation on the back surface of the outer M portion 4d' 17b on the low temperature side. However, in the present invention, even if the Ga tan aggregates 16 settled on the outer cover member 17b fall, the Ga source 1 is removed by the next inner cover member 17&.
3 is prevented from falling. Therefore, Ga source 13 and G
The surface of the aAs film 14 is not disturbed. Therefore, no giant molecular clusters are released, and it is possible to prevent over-defects from occurring on the surface of the substrate 15. Note that the humidity near the outer lid member 17a is lower than that of the inner lid member 17.
Since the temperature is higher than that of the outer lid member 17alC ("the first G'a droplet does not form dew condensation, the molecular beam emission opening of the crucible 11 is
The temperature inside the crucible improves uniformity because the parts are cuckooed.

The material of the lid member according to the present invention is the same as the material of the crucible.
f ylolytic y) pron nitride) is preferred. Furthermore, in this embodiment, a lid member 17a.

Since 17b is removable, the crucible 11 can be easily cleaned. In this embodiment, the lid member 17'a.

In order to make 17b removable, it was formed separately from the crucible, but
It may be formed integrally with the crucible.

3 and 4 are schematic sectional views showing other embodiments of the present invention.

In FIG. 3, as in FIG. 2, the lid member disposed at the molecular beam emitting opening of the crucible has a double structure, but the feature of this embodiment is that the inner lid member 17a' and the outer lid This is because the position of the hole provided in part 17b' is shifted from the concentric 1 lilo.
The outside of the crucible 11 can be seen from the Ga source 13, and the heat retention efficiency is higher than in the case shown in FIG.
Since the structure has an inner lid member 17b'' and an outer lid member 17c'', it is effective when heat retention is insufficient.

It should be noted that other reference numerals in FIGS. 3 and 4 are the same as in the previous example.

In this embodiment, the lid members are provided in double or triple layers, but it is easily understood that if the moisture retention is complete, it is effective even if only one lid member is removed.

(6) Effects of the Invention From the above explanation, the molecular beam crystal growth according to the present invention can make the temperature in the crucible uniform or improve the heat retention efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view for explaining the prior art.
2, 3, and 4 are schematic sectional views showing embodiments of the present invention. 1.11... Crucible, 2,12... Heater, 3゜1
3-Ga source, 3', 13'-Ga molecule, 14
...GaAs B'A, 5.15...Ga substrate, 6
, l 6·=Ga droplet, 17a , 17b , 17
a', 17b', 17a'. 17b#+17c'-Lid member 11♀Applicant Fujitsu Limited Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yukio Uchida Patent attorney Akira Yamaguchi

Claims (1)

[Claims] During molecular crystal growth, the molecular beam emitting opening is provided with a member that prevents dew condensation from dropping onto the source surface by blocking a part of the opening.