JPS636830A - Molecular beam crystal growth apparatus - Google Patents

Abstract

PURPOSE:To reduce the variation in the depositing area of the liquid surface of a source material by altering the inclination from the horizontal surface of a molecular beam source to 0-90 deg., and regulating the inclining angle corresponding to the area of the liquid surface of the source material in a crucible. CONSTITUTION:When the temperature of a heater 14 and hence a crucible 13 is constant, a molecular beam intensity is proportional to the depositing surface of a source. Then, when gallium Ga to become a molecular beam source is filled in the crucible 13, Ga molecular beam is produced by the deposition from the melted liquid surface. A vacuum chamber 11 integrated with the crucible container 12 for containing the crucible 13 is so inclined at 45 deg. of inclining angle from the horizontal surface 18 of the liquid surface by utilizing vacuum bellows 17. As the Ga source is consumed, the inclining angle is reduced to finally 30 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This is a molecular beam crystal growth apparatus in which the inclination angle of the molecular beam source from the waterside surface can be adjusted according to the area of the liquid surface of the source in the molecular beam source.

[Industrial application field]

The present invention relates to a molecular beam crystal growth apparatus, and more specifically, to an apparatus configured to maintain a constant molecular beam intensity (amount) and a constant crystal growth rate.

[Conventional technology]

In the growth of compound semiconductors, for example, GaAs, Aj! When manufacturing a semiconductor device by sequentially growing GaAs or the like, a molecular beam crystal growth apparatus as shown in the cross-sectional view of FIG. 2 is used. Crucible storage section, 1
3 is a crucible (molecular beam cell), 14 is a heater that heats the crucible, and 15 is a source of semiconductor elements placed in the crucible (
(e.g. Ga), 16 is a semiconductor single crystal substrate (e.g. a GaAs substrate, which has been heated to some suitable temperature) on which the crystal is grown.

When the Ga source 15 is heated in the crucible 13, it melts. Here, since the vacuum chamber 11 is maintained at an ultra-high vacuum of about 10-'6 Torr, Ga molecules jump out from the liquid surface 19 of the source 15, become a molecular stream, and irradiate the substrate 16. Crystals grow. The crucible 13 is configured in the shape of a mirror so that the above-described molecular flow irradiates the substrate 16, and is tilted at a certain angle so as to have a constant angle of incidence with respect to the substrate 16.

[Problem that the invention seeks to solve]

Referring to FIG. 3, which shows the crucible 13 and the substrate 16 in more detail, in addition to the fact that the crucible 13 has a square shape as described above, the heater 14 has a temperature distribution outside the crucible as shown by the dotted line. and is highest at the opening of the crucible.

The crucible is set at a constant angle of incidence with respect to the substrate, but the angle of inclination with respect to the horizontal plane 18 is fixed. In this method, as the source material stored (charged) in the crucible is consumed, the liquid level (evaporation area) A decreases to liquid level a as shown in FIG. The resulting molecular beam intensity (amount of molecular beam) becomes small, and as a result, the crystal growth rate cannot be kept constant, causing the problem that crystal growth cannot be performed with good reproducibility.

In conventional molecular beam crystal growth equipment, in order to grow crystals with good reproducibility, methods such as (1) measuring the molecular beam intensity with a molecular beam intensity monitor, or (2) performing crystal growth specifically to check the growth rate are used. However, either method was not accurate or required complicated work.

The present invention was created in view of these points, and is capable of reducing changes in the evaporation area of the liquid level of the source due to consumption, stabilizing the molecular beam intensity, and achieving crystal growth with good reproducibility. The purpose of the present invention is to provide a molecular beam crystal growth apparatus that can perform the following steps.

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention.

In the present invention, a plurality of semiconductor elements (source 14) are heated in an ultra-high vacuum, and the same elements are extracted as molecular beams and irradiated onto the semiconductor single crystal substrate 16 which has been appropriately heated. In a molecular beam crystal growth apparatus for growing semiconductor single crystals, the inclination of the molecular beam source (crucible 13) from the horizontal plane 18 can be changed from Oo to 90°, and this inclination angle can be changed to The structure can be adjusted according to the area of the liquid surface 19 (evaporation area).

[Effect]

In the apparatus of the present invention, the area of the liquid surface of the source 15 in the crucible can be freely changed by changing the inclination angle from the horizontal plane of the crucible. From a deep angle, sauce 1
If the evaporation area becomes smaller as the amount of 5 decreases, the crucible is tilted horizontally to increase the evaporation area, thereby keeping the molecular beam intensity constant.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The inventor of the present application conducted the following analysis to solve the above problem.

First, assuming that the temperature of the heater 14 and therefore the crucible 13 is constant without temperature distribution, the molecular beam intensity is proportional to the evaporation area of the source. Therefore, as the source is consumed and the amount decreases as shown in Figure 3, the molecular beam intensity decreases accordingly.In order to compensate for this, the crucible is tilted as shown in Figure 1. It is best to make the evaporation area of the sauce as large as possible.

Next, considering only the temperature of the crucible, if the temperature is highest at the opening as in the conventional example, as the source continues to be consumed,
As shown in Figure 3, the evaporation surface of the source becomes farther away from the aperture (in addition to a decrease in the evaporation area), the temperature of the source evaporation surface decreases and the molecular beam intensity decreases. Most preferably, the evaporation surface of is located near the opening. Therefore, if the evaporation area becomes smaller as the source is consumed, the crucible may be tilted so that the evaporation surface of the source is located near the opening, as shown in FIG.

The present invention according to the above analysis is applied to a molecular beam source (source) 1
5, an example using a Ga source will be explained.

Although the Ga molecular beam is extracted by evaporation from the molten liquid surface, the inclination angle of the Ga molecular beam liquid from the horizontal plane 18 was set to 45° in the initial Ga source charging state.

This angle of inclination was made shallower as the Ga source was consumed, and finally reached around 30°.

In this example, the area of the evaporation surface of the Ga source changed (reduced) from 100 to 30%, but since the liquid level of the Ga source is always near the opening of the crucible where the temperature is highest, the
The change in a molecular beam intensity could be suppressed to about -10%.

If Ga consumption progresses by the same amount using the conventional method,
The evaporation area varied from 100% to 25%, and the Ga molecular beam intensity varied by about -20%.

Thus, according to the present invention, fluctuations in molecular beam intensity could be reduced to about 1/2 compared to the conventional method.

To tilt the crucible as described above, it is preferable to tilt the vacuum chamber 11 in which the crucible storage section 12 in which the crucible 13 is housed is integrated, using the vacuum bellows 17.

When the inclination of the crucible changes as shown in FIG. 1, the amount of molecular beam irradiated to the substrate changes. Therefore, when the crucible inclines, the holder for the substrate 6 is placed in the vacuum chamber 11 so that the substrate also inclines. When fixed at , the angle of incidence of the molecular beam between the crucible and the substrate is always kept constant.

In Fig. 2, if a GaAs crystal is to be grown on the substrate, A
Add the s sauce. Since the upper crucible storage section is also integrated with the vacuum chamber 11, when the vacuum chamber 11 tilts as described above, the crucible containing As also tilts in the same way.

〔Effect of the invention〕

As described above, according to the present invention, reduction in molecular beam intensity can be suppressed by adjusting the area and position of the molecular beam evaporation surface, so crystal growth can be performed with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a sectional view of an embodiment of the present invention, and FIG. 3 is a diagram showing problems in the conventional example. 1 to 3, 11 is a vacuum chamber, 12 is a crucible housing, 13 is a crucible, 14 is a heater, 15 is a source, 16 is a substrate, and 17 is a vacuum bellows. Kozo Iizuka Patent applicant Director of the Agency of Industrial Science and Technology

Claims (1)

[Claims] A plurality of semiconductor elements (15) are heated in vacuum, the elements are extracted as molecular beams, and irradiated onto a semiconductor single crystal substrate (16) to grow a semiconductor single crystal on the same substrate (16). In a device that uses a horizontal plane (18
1. A molecular beam crystal growth apparatus characterized in that the inclination from ) is changed in accordance with the consumption of the same element (15).