JPS62165318A - Device for molecular beam crystal growth - Google Patents

Abstract

PURPOSE:To enable an excellent crystalline film with a specified thickness and composition ratio to grow by a method wherein the material in a first molecular beam source cell 2 is supplied from a second molecular beam cell 4. CONSTITUTION:Crystalline films are grown by heating material M up to specified temperature before operating a shutter 3. Proper quantity of material M reduced moderately is grown to the extent of molecular beams with inconspiculous fluctuation in intensity to be supplied from the second molecular beam source cell 4 to the first molecular beam source 2. This material M is supplied at the temperature not transmitting molecular beams B e.g. around 700 deg.C while the other material M1 is supplied at the temperature sufficient for discharging molecular beams B1 e.g. around 1,100 deg.C by opening shutters 3 and 5. When the quantity of material M is restored to the quantity at the starting time of growing process, the shutters 3 and 5 are closed to restore the temperature of materials M and M1 to the temperatures in growing process for starting the growing process again.

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 in the molecular beam source cell is grown 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 for growing crystals over a long period of time.

[Industrial application field]

The present invention relates to a molecular beam crystal growth apparatus, and particularly to a configuration for stabilizing the intensity of molecular beams.

Molecular beam crystal growth (MBE) equipment is capable of controlling the thickness of a grown film formed on a substrate by, for example, about 10 people, and is capable of continuously growing a multilayered film. It has the following distinctive characteristics.

For this reason, in recent years, attention has been focused on the crystal growth of compound semiconductors and mixed crystal semiconductors used in the formation of semiconductor devices. 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 sectional view showing the main part configuration of a conventional MBE device;
Figure 4 is a side sectional view of the molecular beam source cell section in the device;
It is.

In Fig. 3, 1 is a growth chamber that is under ultra-high vacuum during growth;
2 is a plurality of raw materials M of different elements constituting the grown film;
A molecular beam source cell 3 is a cell in which a growth substrate S held in a substrate holder 6 is irradiated with a molecular beam B emitted from a raw material M by heating (as shown in FIG. 4); It is a shutter that opens and closes the

Further, in FIG. 4, 2 is the molecular beam source cell, 2a is the 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 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 configured as described above, the raw material M in the cell 2 is gradually reduced by emitting the molecular beam B, and the intensity of the molecular beam B, which depends on the remaining amount of the raw material M, changes accordingly.

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

For this reason, compound semiconductors and mixed crystal semiconductors such as gallium arsenide (GaAs) and aluminum gallium arsenide (A]Ga
When growing a crystalline film such as As), as 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 10-30% of the raw material M.
is skipped to improve the purity of 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 as shown in FIG. 2, and a second molecular beam source cell 4 which accommodates the same raw material as the first molecular beam source cell 2 and has 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 molecular beams from the first opening toward the substrate holder 6 to grow crystals on the substrate S. 4 is an MBE apparatus of the present invention that replenishes the raw material in the first molecular beam source cell 2 by heating the stored raw material with a heater and injecting the molecular beam from the second opening toward the first opening. solved by.

[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, the first molecular beam source cell 2
It is possible to reduce the change in the remaining amount of the raw material in , and reduce the change in the intensity of the molecular beam B.

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 apparatus shown in FIG. 1 uses the molecular beam source cell 2 of the conventional apparatus shown in FIG. is added. The second molecular beam source cell 4 has the sole purpose of replenishing raw materials to the first molecular beam source cell 2, and the crystal film is grown in the first molecular beam source cell 2 in the same way as in the conventional device. This is done with molecular beam B from .

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,
The heater 2b, liquid nitrogen shroud 2C, and shutter 3 remain the same as before. 4 is a second molecular beam source cell, 4a is an opening of the cell 4, 4b is a heater for heating the cell 4, 4C is a liquid nitrogen shroud for heat shielding the cell 4, 5 is a shutter for the cell 4, Ml is the raw material in the cell 4 (same as the raw material M in the cell 2), and B1 is the molecular beam from the old raw material.

The opening 4a, which serves as a passage for the molecular beam B1, has a cylindrical shape that faces diagonally to the opening 2a 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 storage part 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 material M and Ml.

The crystal film is grown by heating the raw material M to a predetermined temperature of about 1000° C. and opening the shutter 3, as in the conventional method. 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. (Transfer part of raw material old to raw material M).

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 the molecular beam B, and at the same time bringing the old raw material to the molecular beam B1.
The temperature is set to a temperature sufficient to release the gas, for example, about 1100° C., and both shutters 3 and 5 are opened. At this time, since the opening 4a is also heated up to its tip, the molecular beam B1 does not adhere to the opening 4a in a liquid state. 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 the raw material M returns to the amount at the start of growth, the shutters 5 and 3 are closed, the temperature of the raw material M and the old material is returned to the temperature at the time of growth, and growth is started again.

This cycle can be continued until the raw material 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.

1. The above raw material supply by the second molecular beam source cell 4 is as follows:
Since the only movable parts are the shutters 3 and 5, it is characterized by less trouble.

In addition, even if the second molecular beam source cell 4 is only installed 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 a 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 a crystal using a molecular beam emitted from a raw material in a molecular beam source cell, the intensity of the molecular beam for growing a crystal is 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 is a side sectional view showing 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), 4a is an opening (second opening) ), 2b and 4b are heaters, 2c and 4c are liquid nitrogen shrouds, 3.5 is a shutter, 6 is a substrate holder, B, , Bl are molecular beams, M, and Ml are raw materials, S is a growth substrate, .

Claims (1)

[Scope of Claims] 1) A substrate holder (6) holding a growth substrate (S), and a first substrate holder (6) containing a molecular beam raw material and having a first opening facing the substrate holder (6). a second molecular beam source cell (2) and a second molecular beam cell 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 first 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). The second molecular beam source cell (4) heats the contained raw material with a heater and directs the molecular beam from the second opening to the first opening. A molecular beam crystal growth apparatus characterized in that the raw material in the first molecular beam source cell (2) is replenished by injecting the raw material into the first molecular beam source cell (2). 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. .