JPH0152891B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] In a molecular beam crystal growth apparatus that grows a crystal using a molecular beam emitted from a raw material in a molecular beam source cell, the raw material is introduced into the molecular beam source cell in the form of a molecular beam. By providing a second molecular beam source cell for replenishment, it is possible to stabilize the intensity of the molecular beam used to grow crystals over a long period of time.

[Industrial application field]

The present invention relates to a molecular beam crystal growth apparatus, and in particular,
Concerning a configuration that stabilizes the intensity of molecular beams.

Molecular beam crystal growth (MBE) equipment is capable of controlling the thickness of the grown film formed on the substrate, for example, to around 10 Å, and is said to be capable of continuously growing multilayered films. It has outstanding characteristics.

For this reason, in recent years it has come to be used for crystal growth of compound semiconductors and mixed crystal semiconductors used in the formation of semiconductor devices, but it is also useful for controlling film thickness and stabilizing the composition of grown films when growing multiple crystal films. Therefore, it is desirable to maintain the stability of the molecular beam intensity for crystal growth over a long period of time.

[Conventional technology]

FIG. 3 is a side cross-sectional view showing the main part configuration of a conventional MBE apparatus, and FIG. 4 is a side cross-sectional view of a molecular beam source cell section in the apparatus.

In Figure 3, 1 is a growth chamber that is kept under ultra-high vacuum during growth, and 2 is a plurality of growth chambers in which raw materials M of different elements (shown in Figure 4) constituting the grown film are placed and heated to release molecules from the raw material M. A molecular beam source cell 3 irradiates the growth substrate S held by the substrate holder 6 with the beam B, and a shutter 3 opens and closes the irradiation of the substrate S with the molecular beam B.

Moreover, in FIG. 4, 2 is the above-mentioned molecular beam source cell;
2a is an opening of the cell 2, 2b is a heater for heating the cell 2, 2c is a liquid nitrogen shroud for heat shielding, and 3 is the above-mentioned shutter.

Molecular beams B emitted from the raw material M placed in the cell 2 and heated by the heater 2b pass through the opening 2a directed toward the substrate S, and when the shutter 3 is released, the substrate S is irradiated to grow a crystal film. .

[Problem that the invention seeks to solve]

In the apparatus with the above configuration, the raw material M in the cell 2 is gradually reduced by emitting the molecular beam B, and accordingly, the raw material M
The intensity of the molecular beam B changes depending on the remaining amount of .

The intensity of this molecular beam B controls the amount of elements supplied to the growth of the crystal film.

For this reason, when growing crystal films of compound semiconductors or mixed crystal semiconductors such as gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs),
When the number of growth processes increases, the change in the intensity of the molecular beam B becomes noticeable, and there is a problem that it becomes difficult to control the thickness and composition ratio of the grown film.

Further, during the initial period after the growth chamber 1 is made into an ultra-high vacuum, impurities contained in the gas adsorbed in the molecular beam source cell 2 and the raw material M are released, making it impossible to grow a high-quality crystal film. For this reason, prior to growth, the cell 2 is heated to a high temperature to remove 10 to 30% of the raw material M, thereby increasing the purity of the raw material M. However, since it is not possible to replenish the raw material M in an ultra-high vacuum, this apparatus has a small amount of raw material M that can be used for growth.

[Means for solving problems]

FIG. 1 is a side cross-sectional view showing the main structure of an embodiment of an MBE apparatus according to the present invention.

The above problem is solved by the substrate S as shown in FIG.
a first molecular beam source cell 2 containing a molecular beam raw material and having a first opening facing the substrate holder 6; The first molecular beam source cell 2 includes a second molecular beam source cell 4 that accommodates the cell and has a second opening diagonally opposite to the first opening.
The contained raw material is heated with a heater and a molecular beam is irradiated from the first opening toward the substrate holder 6 to release the substrate S.
A crystal is grown on the second molecular beam source cell 4,
The MBE of the present invention heats the stored raw material with a heater and injects the molecular beam from the second opening toward the first opening to replenish the raw material in the first molecular beam source cell 2.
This is solved by the device.

[Effect]

The remaining amount of the raw material on which the intensity of the molecular beam B in question depends is the remaining amount in the first molecular beam source cell 2.

Therefore, by replenishing the raw material from the second molecular beam source cell 4 to the first molecular beam source cell 2, changes in the remaining amount of raw material in the first molecular beam source cell 2 can be reduced, and the Changes in the intensity of line B can be reduced.

Furthermore, since the above replenishment is carried out in the form of molecular beams, it is possible without releasing the ultra-high vacuum in the growth chamber 1, and the supply of molecules with reduced intensity changes is possible until the raw material in the second molecular beam source cell 4 is exhausted. Line B can be obtained.

Thus, by using this apparatus, it is possible to grow a large number of high-quality crystal films having desired film thicknesses and composition ratios without releasing the ultra-high vacuum in the growth chamber 1.

〔Example〕

Hereinafter, an example will be described using FIG. 1 and a side sectional view of FIG. 2 showing a molecular beam source cell section in the example.

FIGS. 1 and 2 are views corresponding to FIGS. 3 and 4 showing conventional devices.

The MBE device shown in FIG. 1 uses the molecular beam source cell 2 of the conventional device shown in FIG. 3 as the first molecular beam source cell, and has a second molecular beam source cell 4, a shutter 5, etc. It is something. The second molecular beam source cell 4 has the sole purpose of supplying raw materials to the first molecular beam source cell 2, and the growth of the crystal film is
Similar to the conventional apparatus, the molecular beam B from the first molecular beam source cell 2 is used.

Therefore, the difference from the conventional device is the molecular beam source cell section shown in FIG.

In FIG. 2, a first molecular beam source cell 2, an opening 2a, a heater 2b, a liquid nitrogen shroud 2c,
Shutter 3 remains the same as before. 4 is a second molecular beam source cell, 4a is an opening of the cell 4, and 4 is a second molecular beam source cell;
b is a heater that heats the cell 4; 4c is a liquid nitrogen shroud for heat shielding the cell 4; 5 is a shutter for the cell 4; M1 is the raw material in the cell 4 (same as the raw material M in the cell 2); B1 is raw material M1
It is a molecular beam from .

The opening 4a, which serves as a passage for the molecular beam B1, has a cylindrical shape, diagonally facing the opening 2a, and so that the molecular beam B1 hits the opening 2a with directionality.

The heater 4b is arranged so as to heat not only the raw material M1 accommodating portion in the cell 4 but also the opening 4a up to its tip.

The shutter 5 opens and closes the molecular beam B1 to advance to the opening 2a.

The operation will be described below, taking as an example the case where gallium (Ga) is used as the raw materials M and M1.

The crystal film is grown at 1000°C using the raw material M as before.
This is done by heating the shutter to a predetermined temperature and opening the shutter 3. Needless to say, the aforementioned raw material M has already been purified. At this time, the raw material M1 is heated to about 100° C. and the shutter 5 is closed. Therefore, the presence of the second molecular beam source cell 4 has no effect on the growth of the crystal film.

After growing the raw material M to an appropriate amount to the extent that the decrease in the raw material M is not excessive and the change in the intensity of the molecular beam B is not noticeable, the raw material is supplied from the second molecular beam source cell 4 to the first molecular beam source cell 2. (Transferring a part of raw material M1 to raw material M) is performed.

This raw material replenishment is carried out by bringing the raw material M to a temperature such as about 700°C that does not generate molecular beams B, and at the same time
1 at a temperature sufficient to emit the molecular beam B1, e.g. about 1100
℃, and open both shutters 3 and 5. At this time, since the opening 4a is also heated to its tip, the molecular beam B1 does not become liquid and adhere to the opening 4a. Moreover, since the impurities contained in the raw material M1 are mainly diffused outside the cell 2, the raw material M is hardly contaminated with the impurities.

Then, when the amount of raw material M returns to the amount at the start of growth, shutters 5 and 3 are closed, the temperatures of raw materials M and M1 are returned to the temperature at the time of growth, and growth is started again.

This cycle can be continued until the raw material M1 is used up, and during that time the change in the intensity of the molecular beam B can be maintained within a range that is lower than before.

Note that the above-mentioned supply of raw materials by the second molecular beam source cell 4 is characterized by less trouble because the only movable parts are the shutters 3 and 5.

In addition, even if the second molecular beam source cell 4 is installed only to correspond to the first molecular beam source cell 2 that contains the raw material M that consumes a large amount, it is possible to install a large number of cells having the desired film thickness and composition ratio. A sufficient effect for growing a high-quality crystal film can be obtained.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in an MBE apparatus that grows crystals using molecular beams emitted from raw materials in a molecular beam source cell, the intensity of the molecular beams used to grow crystals can be stabilized over a long period of time. This has the effect of making it possible to grow a large number of high-quality crystal films having desired film thicknesses and composition ratios.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing the main part configuration of an embodiment of the present invention, Fig. 2 is a side sectional view of the molecular beam source cell section in the embodiment, and Fig. 3 shows the main part structure of a conventional MBE apparatus. FIG. 4 is a side sectional view of the molecular beam source cell section in the device. In the figure, 1 is a growth chamber, 2 is a first molecular beam source cell, 4 is a second molecular beam source cell, 2a is an opening (first opening), and 4a is an opening (second opening). ),
2b and 4b are heaters, 2c and 4c are liquid nitrogen shrouds, 3 and 5 are shutters, 6 is a substrate holder,
B and B1 are molecular beams, M and M1 are raw materials, and S is a growth substrate.

Claims (1)

[Claims] 1. A substrate holder 6 that holds a growth substrate S;
a first molecular beam source cell 2 containing a molecular beam raw material and having a first opening facing the substrate holder 6;
A second molecular beam source cell 4 containing the same raw material as the first molecular beam source cell 2 and having a second opening diagonally opposite to the first opening; The molecular beam source cell 2 heats the contained raw material with a heater and irradiates the molecular beam from the first opening toward the substrate holder 6 to grow a crystal on the substrate S, and grows a crystal on the substrate S. The radiation source cell 4 replenishes the raw material in the first molecular beam source cell 2 by heating the contained raw material with a heater and injecting the molecular beam from the second opening toward the first opening. A molecular beam crystal growth apparatus characterized by: 2. The molecular beam crystal growth apparatus according to claim 1, wherein the second opening has a cylindrical shape and is heated up to the tip of the cylindrical portion by a heater.