JPH057252Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

This invention relates to a molecular beam epitaxy device.
Specifically, the present invention relates to an improved shutter that is openable and closable in front of each evaporation source in order to start and stop crystal formation using each growth material.

[Conventional technology]

Molecular beam epitaxy is attracting attention as a method for epitaxially growing - group elements on a single crystal substrate in the process of manufacturing - group compound semiconductors. This is a type of vacuum evaporation method that uses group elements such as gallium Ga, aluminum Al, and indium In, and group elements such as arsenic As and phosphorus P as growth materials in an ultra-high vacuum of 10 ^-11 torr. irradiate these in the form of atomic or molecular beams.
Ga is deposited on a single crystal substrate such as GaAs or InP.
This is a method of epitaxially growing - group compound semiconductor crystals such as As, Al Ga As, In P, or In Ga As P. According to this molecular beam epitaxy method, because the deposition is carried out in an ultra-high vacuum, there is very little contamination of impurities from residual gas, and the substrate surface can be kept clean, uniformly and over a large area. A multi-component film that can obtain a flat film at the atomic level, the deposition rate can be extremely slow and precisely controlled, and the film thickness can be controlled with high precision on the order of a single atomic layer of several angstroms. The mixed crystal thin film of the system can also be easily obtained by simply increasing the number of evaporation sources, and it is possible to dope various impurities while controlling the amount by simultaneous evaporation. FIG. 3 shows a schematic configuration of a molecular beam epitaxy apparatus for performing such a molecular beam epitaxy method. A substrate holder 3 is placed in the center of a growth chamber 2 connected to an ultra-high vacuum pump 1, and is designed to rotate in order to uniformly grow crystals on the substrate. Further, a heater is provided to raise the temperature of the substrate held by the substrate holder 3 to a desired temperature. On one side of the growth chamber 2, a plurality of evaporation sources 5 are arranged, each of which is formed by filling a crucible 4 opening toward the substrate holder 3 with each growth material. This evaporation source 5 is also heated to a desired temperature by a heater controlled based on the temperature detected by the temperature sensor. Note that each evaporation source 5 is surrounded by a liquid nitrogen shroud 6 so that each evaporation source is not affected by heat or pollution from each other. Crystal growth is started and stopped by opening and closing shutters 7 arranged in front of the opening of each crucible 4. For example, to grow a GaAs layer on a GaAs single crystal substrate, an evaporation source 5 filled with Ga and
While heating the evaporation source 5 filled with As to a predetermined temperature and setting the temperature of the substrate holder 3 to an appropriate temperature, the shutter 7 of each evaporation source 5 is kept open for a predetermined time. Note that when Al is evaporated together, a Ga _x Al _1-x As layer grows. At this time, Ga and Al
The composition x can be controlled by controlling the ratio of the evaporation amounts. In addition, to make the growth layer n-type, Si, Sn, etc. are evaporated at the same time, and to make it p-type, Be, Mg, etc.
It is necessary to evaporate etc.

[Problem that the invention attempts to solve]

As shown in FIG. 3, the shutter 7 in the conventional molecular beam epitaxy apparatus supports a rotating shaft 7a on the outer wall of the growth chamber 2 with its tip protruding into the growth chamber. A rotary shutter in which a shutter plate 7b is attached to the evaporation source 5 is common, and by controlling the rotation of the rotating shaft 7a, the shutter plate 7b is attached to the crucible 4 of the evaporation source
A closed state in which the opening is covered, and an open state in which the opening is retracted to the side of the opening can be selected. By the way, when growing crystals of various semiconductors using the molecular beam epitaxy method described above, it is possible to dope a large number of impurities by simultaneous evaporation. There is a tendency to set a number that can accommodate growth. In this case, when using a rotary shutter as described above, the following problem arises. In other words, in conventional molecular beam epitaxy equipment, the interference of the rotation locus around the axis of each shutter with the rotation locus around the axis of other shutters is not taken into consideration. When increasing the number of shutters, it is necessary to provide sufficient spacing between the evaporation sources to avoid interference between the shutters, resulting in an unnecessarily large growth chamber. It is also possible to reduce the size of the shutter plate in order to avoid increasing the size of the growth chamber, but this causes another problem in that the molecular beam blocking function of the shutter decreases and the reproducibility of epitaxial growth also decreases. This idea was devised under the above-mentioned circumstances, and while it uses a rotary shutter that is easy to control, it reduces the molecular beam blocking function of the rotary shutter even when the number of evaporation sources increases. It is an object of the present invention to provide a molecular beam epitaxy apparatus in which the growth chamber is arranged without increasing the size of the growth chamber more than necessary.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides the following technical means: In a molecular beam epitaxy apparatus including a growth chamber connected to an ultra-high vacuum pump, a substrate holder disposed inside the growth chamber, a plurality of evaporation sources disposed on one side of the growth chamber with their axes facing the substrate holder, and a shutter for covering and opening the opening of the evaporation source, the shutter includes a shaft rotatably supported on the inner wall of the growth chamber near the opening of the evaporation source, and a shutter plate attached to the tip of the shaft so as to cover the opening of the evaporation source in a closed state, and the axis of the shutter shaft of each adjacent evaporation source is inclined in the same direction as the adjacent direction of each evaporation source, so that the rotation locus of each shutter plate does not interfere with each other.

[Effect]

By rotating the shutter plate by controlling the rotation of the shaft, the shutter can select between a closed position where the shutter plate covers the opening of the evaporation source and an open position where the shutter plate is retracted laterally from the opening of the evaporation source. In the present invention, the axes of the rotation shafts of the shutters are inclined in the same direction adjacent to each evaporation source, so that the rotation trajectories of the shutter plates do not interfere with each other. In this way, even if the evaporation sources are formed close to each other, the openings of the evaporation sources can be opened and closed by the rotary shutter without any problem. Furthermore, since the rotational trajectories of each shutter plate do not interfere with each other, the shutter plates in the closed position can be arranged so that their adjacent ends overlap vertically, which limits the size of the shutter plate. This is no longer necessary, and each shutter plate can be made large enough to provide a molecular beam shielding effect.

[Effect of the idea]

From the above, according to the molecular beam epitaxy device of the present invention, even if the number of evaporation sources increases, it is possible to arrange them relatively close together and to easily control the shutter that covers the opening of each evaporation source. It can be composed of a rotating shutter. Moreover, there is no need to limit the size of the shutter plate of each shutter in consideration of interference of their rotational trajectories, and the molecular beam shielding function of each shutter is not diminished. Further, from the above, even if the number of evaporation losses increases, there is an effect that the growth chamber does not become unnecessarily large.

[Explanation of Examples]

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2. In these figures, parts or members that are equivalent to those of the conventional example shown in FIG. 3 are given the same reference numerals. The molecular beam epitaxy apparatus of this example has a vertical growth chamber 2, but the overall basic configuration is the same as that of the conventional example shown in FIG. A boss portion 11 of a rotating cage 10 having a substrate holder 3 at its lower end is rotatably supported on a support shaft 9 that is supported through the ceiling plate 8 of the growth chamber 2 . This rotating cage 10 has a boss portion 11
Rotation is controlled by meshing a pinion 14 of an output shaft of an external motor 13 with a gear 12 fixed to the motor. A heater 10 located behind the substrate holder 3 is provided at the tip of the support shaft 9, and can thereby heat the substrate B held by the substrate holder 3. The inner periphery of the side wall of the growth chamber 2 is surrounded by a liquid nitrogen shroud 15, which adsorbs impurities during degassing and maintains an ultra-high vacuum. Note that the growth chamber 2 is connected to an ultra-high vacuum pump (not shown). The bottom of the growth chamber 2 has a nearly concave shape with the center being the most concave, and several evaporation sources 5 are placed in this part.
... are arranged so that their axes a, b, and c point toward the center of the substrate holder 3. These evaporation sources 5... are a large one filled with arsenic placed at the center of the bottom of the growth chamber, and a small one placed on the circumference around the axis of the central evaporation source. There are things set up. Each evaporation source 5...
is constructed by loading crucibles 4 filled with growth material into a cylindrical container whose upper end is fixed to the bottom wall of the growth chamber 2, and each crucible 4 is placed at the bottom of the container. It is heated to the desired temperature by a hidden heater. A liquid nitrogen shroud 6 is integrally formed in the cylindrical container surrounding each crucible 4, so that the evaporation sources 5 are not affected by heat or contamination. When the growth chamber 2 is placed in an ultra-high vacuum state and the temperature of the substrate B and the evaporation source 5 is raised to a predetermined temperature, the growth material of the evaporation source 5 hits the substrate surface in the form of atoms or molecular beams, forming crystals on the substrate. grows, but the start and stop of this growth is determined by each evaporation source 5...
This is done by opening and closing the openings of the crucibles 4, . . . , with the shutter 7. The shutter 7 is rotatably introduced and supported from the outside on the inner wall of the small evaporation sources 5 disposed on the circumference at a portion adjacent to the radially outward centering on the axis b of the central evaporation source. A shutter plate 7b that can cover the opening in the closed position is fixed to the tip of the shaft 7a. In the present invention, the axis d of the shaft 7a of each shutter 7 is tilted in the same direction as the evaporation sources 5 adjoin, as schematically shown in FIG. 2, and the solid line in FIG. from the closed position shown in the direction of arrow C.
In the rotation trajectory to the open position, which rotates 180 degrees,
The shutter plates 7b are designed not to interfere with each other. Then, the size of each shutter plate 7b is
It is made sufficiently large so that it does not cover the opening of the adjacent evaporation source in the closed position, so that it can fully exhibit its molecular beam shielding function. Then, the second
As shown in the figure, the shutter plate 7 of each shutter
Although the ends of the shutter plates 7b may overlap in the vertical direction, this is possible because the rotation loci of the shutter plates 7b do not interfere with each other as described above. As is clear from FIG. 2, according to the present invention, the shutters for opening and closing the openings of each evaporation source are configured with rotating shutters without causing interference problems while arranging the evaporation sources relatively close to each other. This makes it possible to do so. In this example, the shaft 7 of the shutter 7
In addition to tilting the axis d of each evaporation source in the direction adjacent to each evaporation source, it is also tilted significantly toward the center of the growth chamber, as shown in Figure 1, so that the axis d of each evaporation source is tilted in a side view. It intersects the axis a between the opening of the evaporation source and the substrate holder 3. Then, when the shutter plate 7b centered on the axis 7a assumes the open position shown by the imaginary line in FIG. 1, it will be sufficiently separated from the inner wall of the growth chamber. In this way, the degree of dome-like curvature at the bottom of the growth chamber can be increased, which contributes to miniaturization of the growth chamber. In this example, as shown in FIG. 1, the shaft 7a of the shutter 7 is constructed in two parts, and the cylindrical portion of the motor bracket 16 through which the shaft 7a passes is also connected by flanges 17a and 17b. The first part 7a' on the motor side of the shaft 7a and the second part 7 on the shutter plate side are configured so that they can be connected.
a'' can be connected or separated outside the growth chamber 2 with the flanges 17a and 17b separated.In the conventional rotary shutter 7, a single rotating shaft is inserted through the growth chamber. It was common practice to attach a shutter plate to the tip of the shaft introduced into the growth chamber, so when replacing the shutter plate, it was necessary to enter the inside of the growth chamber through the view port and perform complicated work such as tightening screws. However, in this example, since the shaft 7a can be connected substantially outside the growth chamber as described above, the installation of the shutter plate 7 is extremely easy and safe. Of course, the scope of this invention is not limited to the above-mentioned embodiments.In addition to providing shutters for all of the evaporation sources, it is also possible to adopt the shutter configuration according to the invention for selected evaporation sources. fall within the scope of invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the invention, and FIG. 2 is a schematic diagram showing the main parts of the invention.
FIG. 3, which corresponds to the cross section taken along the line - in the figure, is a schematic configuration diagram of a conventional example. 2...growth chamber, 3...substrate holder, 5...evaporation source, 7...shutter, 7a...(shutter)
Axis, 7b... Shutter plate, a, b, c... Axis line (of the evaporation source), d... Axis line (of the shutter shaft).

Claims (1)

[Scope of claim for utility model registration] A growth chamber connected to an ultra-high vacuum pump, a substrate holder placed inside the growth chamber, and a plurality of substrates arranged on one side of the growth chamber so that their axes face the substrate holder. In a molecular beam epitaxy apparatus comprising an evaporation source and a shutter that shields and opens an opening of the evaporation source, the shutter has a shaft rotatably supported on a growth chamber wall near the opening of the evaporation source; The tip of this shaft is equipped with a shutter plate attached to cover the opening of the evaporation source in the closed state, and the axis of the shutter shaft of each adjacent evaporation source is aligned in the same direction as the adjacent direction of each evaporation source. A molecular beam epitaxy apparatus characterized in that the rotation trajectories of each shutter plate are prevented from interfering with each other by tilting the shutter plates.