JPH035054B2 - - Google Patents

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,
More specifically, it relates to an apparatus configured to keep the molecular beam intensity (amount) constant and the crystal growth rate constant.

[Conventional technology]

In the growth of compound semiconductors, for example, when manufacturing a semiconductor device by sequentially growing GaAs, AlGaAs, etc. on a GaAs substrate, a molecular beam crystal growth apparatus as shown in the cross-sectional view of Figure 2 is used. , 11 is a chamber maintained in an ultra-high vacuum, 12
Crucible storage section, 13 crucible (molecular beam cell),
14 is a heater that heats the crucible; 15 is a source of semiconductor element (e.g. Ga) placed in the crucible; 1
6 is a semiconductor single crystal substrate (for example a GaAs substrate, heated to a certain suitable temperature) on which a crystal is grown.

When the Ga source 15 is heated within the crucible 13, it melts. Here, the vacuum chamber 11 is 10 ^-10 Torr
Since the vacuum is kept at an extremely high vacuum, Ga molecules jump out from the liquid surface 19 of the source 15 and irradiate the substrate 16 in the form of a molecular stream, so that Ga crystals grow on the substrate 16. The crucible 13 has a substrate 16 where the molecular flow described above is
The beam is arranged in a tapered shape so as to irradiate the area, 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 crucible 13 having a rippled shape as described above, the heater 14 has a temperature distribution outside the crucible as shown by the dotted line. It is the highest point 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 measuring molecular beam intensity with a molecular beam intensity monitor or performing crystal growth specifically to check the growth rate are used. However, none of these methods were 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 0° to 90°, and this inclination angle Face 19
The structure can be adjusted according to the area (evaporation area).

[Effect]

In the apparatus of the present invention, the source 1 in the crucible
Taking advantage of the fact that the area of the liquid surface in step 5 can be freely changed by changing the inclination angle from the horizontal surface of the crucible, when the amount of source 15 is large and the evaporation area is large, the area of the liquid surface in step 5 is set at a deep angle from the horizontal surface, and the amount of source 15 is changed. If the evaporation area becomes smaller as the amount 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 any 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, so 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 is consumed, the evaporation surface of the source will become farther away from the opening, as shown in Figure 3. Since (in addition to reducing the evaporation area) the temperature of the source evaporation surface decreases and the molecular beam intensity decreases, it is most desirable that the evaporation surface of the source be located near the opening to compensate for this. 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 will be explained using an example in which a Ga source is used as the molecular beam source 15. The Ga molecular beam is extracted by evaporation from the molten liquid surface, and the inclination angle of the Ga molecular beam liquid from the horizontal plane 18 was set to 45° in the initial Ga source charge state. This angle of inclination was made shallower as the Ga source was consumed, and finally reached an angle of 30°.

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

If Ga consumption progresses by the same amount using the conventional method, the evaporation area will change from 100% to 25%, and Ga
The molecular beam intensity changed 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, crucible 1
It is preferable to use the vacuum bellows 17 to tilt the vacuum chamber 11 in which the crucible housing part 12 in which the crucible 3 is housed is integrated. When the inclination of the crucible changes as shown in FIG. 1, the amount of molecular beam irradiated to the substrate changes, so a holder for the substrate 16 is placed in the vacuum chamber 11 so that when the crucible is tilted, the substrate is also tilted. When fixed, the crucible and substrate maintain a constant molecular beam incidence angle.

In FIG. 2, if a GaAs crystal is to be grown on the substrate, an As source is put into the crucible placed in the upper crucible housing. 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 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 the drawing]

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 storage section, 13 is a crucible, and 14
15 is a heater, 15 is a source, 16 is a substrate, and 17 is a vacuum bellows.

Claims (1)

[Claims] 1. Heating a plurality of semiconductor elements 15 in vacuum and extracting the same elements as molecular beams semiconductor single crystal substrate 16
In an apparatus for growing a semiconductor single crystal on the same substrate 16 by irradiating it upward, a horizontal plane 1 of a molecular beam source containing a semiconductor element 15 is used.
A molecular beam crystal growth apparatus characterized in that the slope from 8 to 8 is changed in accordance with the consumption of the same element 15.