JPH0615437B2 - Thin film growth equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin film growth apparatus for growing a thin film crystal on a substrate by a molecular beam epitaxial growth method, a so-called molecular beam epitaxial apparatus, and more particularly to a molecular beam growth apparatus thereof. The present invention relates to an improvement of a thin film material evaporation device as a ray generation source.

[Conventional technology]

The molecular beam epitaxy apparatus is a thin film growth apparatus that heats and evaporates a thin film material that forms a thin film in an ultrahigh vacuum and causes the material to fly in the form of a molecular beam onto a substrate to grow a thin film crystal. Conventionally, the following method has been proposed as a method for growing a thin film crystal on a substrate by a molecular beam epitaxial growth method. That is, a thin film material evaporation device used in this type of device will be described with reference to FIGS. 6 and 7. This thin film material vaporization apparatus comprises a crucible 2 as a filling chamber for filling the thin film material 1, a thin film material heating heater 3 provided around the crucible 2, a temperature control thermocouple 4, and a substrate of the thin film material. 5 to control the flight to the
And a shaft 6 for rotating the shutter 5, and the shaft 6 is connected to a rotation driving means (not shown).

In order to grow a thin film crystal on a substrate using the thin film material evaporator having such a structure, the thin film material heating heater 3 is usually energized with the shutter 5 closed to bring the thin film material 1 to a desired evaporation temperature. Up to. This temperature is controlled by the electric power supplied to the heating heater 3 based on the voltage signal obtained from the thermocouple 4. After the thin film material 1 reaches the desired evaporation temperature, the opening operation of the shutter 5 causes the evaporated thin film material to fly toward the substrate (not shown) provided facing the thin film material evaporation device, and then to the substrate surface. accumulate. In this way, thin film crystals grow on the substrate surface. Then, when the thin film on the substrate reaches the desired film thickness, the shutter 5 is closed to blow or cut off the thin film material to the substrate. After the thin film is grown, the temperature of the thin film material is lowered, and the desired temperature is maintained with the shutter 5 closed.

[Problems to be solved by the invention]

However, in such a thin film material evaporation device, the shutter 5 is arranged so as to be in contact with or close to the opening of the thin film material evaporation device. When the shutter 5 is closed, the crucible 2 or the thin film material filling chamber is kept in thermal equilibrium.
Further, since the sealed state is close, the pressure difference between the filling chamber and the thin film growth chamber is large. At the moment when the shutter 5 is opened, the pressure in the thin film material filling chamber drops sharply and the thermal equilibrium state collapses. Then, it takes several minutes to reach the equilibrium state again. Therefore, the molecular dose of the thin film material jumping out of the filling chamber changes with time as shown in FIG. Such changes in the molecular beam control the film thickness of the thin film grown on the substrate, or control the doping concentration when doping impurities in the thin film by heating and evaporating by the same means as the film thickness growth, and the steepness of the doping profile. Deteriorates sex.

In addition, for example, when Ga and As are used as thin film materials and a GaAs single crystal is grown on a substrate, it is shown in the document T. Ito et al. Jpn. J. Appl. Phys. 23, L702 (1984). As described above, at the moment when the shutter provided in the opening of the filling chamber of the Ca vaporizer is opened, Ga spitting generated by the dissociation of Ga oxide formed on the molten Ga surface is scattered on the substrate. , Surface defects called oval defect occur. Further, at the moment of opening the shutter, fine particles such as As and CaAs adhering to the vicinity of the outlet of the filling chamber fly toward the substrate, and minute surface defects occur. Most of these surface defects are generated from fine particles that fly from the thin film material filling chamber or the vicinity of the outlet of the filling chamber at the moment when the shutter is opened.

In order to solve the above problems, it is conceivable to install a shutter at a certain distance from the opening of the thin film material evaporator, but in this case, after the thin film growth, the thin film material is kept at a desired temperature. There is a drawback that impurities are mixed into the thin film material filling chamber when the thin film material is stored, which lowers the purity of the thin film material and eventually deteriorates the quality of the grown thin film.

The present invention has been made to solve the above problems, to grow a thin film of excellent quality with few defects,
Further, the present invention provides a thin film growth apparatus having excellent controllability of film thickness and impurity doping concentration.

[Means for solving problems]

The thin film growth apparatus according to the present invention is a molecular beam epitaxial apparatus for heating and evaporating a thin film material forming a thin film to grow a thin film crystal on a substrate, and a shutter for controlling the deposition of the thin film material on the substrate. The first shutter, which is installed in contact with or close to the opening through which the thin film material of the thin film material vaporizer pops out, is connected to the same rotary drive shaft as the core first shutter, and the thin film material filling material is in the closed state. And a second shutter installed at a position distant from the opening to the extent that leakage of the thin film material occurs from the opening, and the opening and closing operation of the first shutter controls the leakage from the filling material of the thin film material. , Second with the first shutter open
By controlling the opening and closing of the shutter, the splashing of the thin film material onto the substrate is controlled.

[Action]

In the present invention, when the thin film material is heated to a desired evaporation temperature, or when the evaporation temperature is lowered to a desired thin film material holding temperature, and when the thin film material is held at the holding temperature, thin film material evaporation is performed. By closing the first shutter placed in contact with or close to the opening of the device, contamination of impurities into the thin film material is prevented. Then, until the thin film material reaches the desired evaporation temperature and until the growth of the thin film on the substrate is completed, the first shutter is opened and the thin film material is separated from the opening to the extent that leakage of the thin film material occurs. It is possible to control the deposition of the thin film on the substrate by the opening / closing operation of the second shutter installed at the different position.

〔Example〕

 Hereinafter, the present invention will be described based on embodiments shown in the drawings.

FIG. 1 is a schematic sectional view showing a thin film material evaporation apparatus according to an embodiment of the present invention. In the figure, 11 is a thin film material,
12 is a crucible as a filling material for filling the thin film material 11, 13 is a heater for heating the thin film material provided around the crucible 12, 14 is a thermocouple for temperature control, and 15 is a thin film material sprayed on the substrate. First shutter 15A to control the
And a second shutter 15B, a shutter 16
Is a rotary shaft that drives the rotation of the shutter 15,
The rotary shaft 16 is connected to a rotary drive means (not shown). FIG. 2 shows the shutter 15 viewed from the opening side of the crucible 12 from which the thin film material is ejected, that is, the thin film material filling chamber. In the shutter 15 shown in FIG. 2,
The first shutter 15A is installed in contact with or close to the opening, and shows a closed state. Also, the second
The shutter 15B is installed at a distance such that the thin film material can leak from the opening even in the closed state, and shows the open state. And these shutters 15A
And 15B are connected to the same rotary shaft 16.

FIG. 3 shows a cross section perpendicular to the XY axis of the shutter 15 shown in FIG. 2 and passing through the Y point, and shows a state in which the shutter 15 shown in FIG. 2 is rotated 90 ° counterclockwise. It is shown in FIG. This corresponds to FIG. 1, in which the first shutter 15A is in the open state and the second shutter 15B is in the closed state. Further, FIG. 5 shows a state in which the shutter 15 shown in FIG. 4 is rotated 90 ° counterclockwise. At this time, both the first and second shutters 15A and 15B are in the open state.

Next, a thin film growth method using the thin film material evaporation apparatus having the above-described embodiment will be described with reference to FIGS. First, as shown in FIG. 2, the thin film material is heated to a desired evaporation temperature with the first shutter 15A closed. Then, after reaching the desired evaporation temperature, the first shutter 15A is opened and the second shutter 15B is closed (FIG. 4). In this state, the temperature is maintained until the thin film material temperature (thin film molecular dose) becomes stable.
Next, when the thin film is to be deposited on the substrate, the second shutter 15B is opened as shown in FIG. When the film thickness on the substrate reaches the desired value, the second shutter 15B is closed as shown in FIG. Then, when the temperature of the thin film material is lowered to a desired holding temperature, or when the thin film material is held at that temperature after reaching the desired holding temperature, the first shutter 15A is closed as shown in FIG. .

Thus, at the time of raising the temperature of the thin film material to the desired evaporation temperature,
The first shutter placed in contact with or close to the opening from which the thin film material jumps out when the temperature is lowered from the evaporation temperature to the desired holding temperature and when the holding temperature is maintained.
By closing 15A, it is possible to prevent impurities from the inner wall of the vacuum chamber from entering the thin film material filling chamber.
In addition, it is possible to prevent the fine particles from splashing on the substrate by cutting off the fine particles that fly out of the thin film material filling chamber at the moment when the first shutter 15A is opened by the second shutter 15B. A thin film with few defects can be grown.
Further, even when the second shutter 15B is closed, the thin film material evaporates through the gap (L shown in FIG. 3) between the opening and the shutter 15B, so that the thin film material filling chamber is not sealed. Therefore, there is no temporal change in the molecular dose emitted from the filling chamber toward the substrate after opening the second shutter 15B, and a constant and stable molecular dose can be obtained. As a result, the control of the film thickness of the thin film and the control of the doping amount and doping profile in the thin film are improved. In the above embodiment, the first shutter 15A and the second shutter 15B are used.
Is connected to one rotary shaft 16, there is an advantage that the number of rotary drive systems is the same as that of the conventional method.

It should be noted that in the above-described embodiment, the case where the first shutter 15A and the second shutter 15B are connected to each other by the XY axis is used as the shutter 15 for controlling the deposition of the thin film material on the substrate. However, the same effect as that of the above-described embodiment can be obtained even if those shutters are separated or the shape of each shutter is arbitrary such as circular or rectangular.

〔The invention's effect〕

As described above, according to the present invention, the first shutter installed in contact with or in close proximity to the opening through which the thin film material of the thin film material evaporation device pops out, and the same rotary drive shaft as the first shutter. The splashing of the thin film material to the substrate is controlled by the shutter having the structure including the second shutter that is connected to the above and is installed at a distance that allows the thin film material to leak even when the thin film material is closed from the opening. By doing so, the conventionally used rotary drive system can be applied. Further, there is an advantage that a thin film having few defects and excellent film quality can be grown, and a thin film having excellent controllability of the film thickness, the doping amount, the doping profile and the like can be grown.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a thin film material evaporation apparatus according to an embodiment of the present invention, and FIG. 2 is a view showing a shutter portion of the thin film material evaporation apparatus of FIG. FIG. 3 is a sectional view of the shutter shown in FIG. 6 taken along a plane perpendicular to the XY axis and passing through the Y point, and FIG. 4 is when the shutter shown in FIG. 2 is rotated 90 ° counterclockwise. Fig. 5 is a diagram when the shutter of Fig. 2 is rotated 180 ° counterclockwise, Fig. 6
FIG. 7 is a schematic cross-sectional view showing a conventional thin film material evaporation device, FIG. 7 is a view seen from the opening side of the thin film material evaporation device of FIG. 6, and FIG. It is a figure which shows the time change of the material molecular dose after opening a shutter. 11 ... Thin film material, 12 ... Crucible for filling thin film material, 1
3 ... Heater for heating thin film material, 14 ... Thermocouple for temperature control, 15 ... Shatter, 15A ... First shatter, 15B
…… Second shutter, 16 …… Rotary drive shaft.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-42815 (JP, A) JP-A-61-191591 (JP, A) JP-A-61-236688 (JP, A)

Claims (2)

[Claims] 1. A thin film material constituting a thin film is heated and evaporated,
In a molecular beam epitaxy apparatus for growing thin film crystals on a substrate, a shutter that controls the deposition of thin film material on the substrate was placed in contact with or in close proximity to the opening of the thin film material vaporizer from which the thin film material jumped out. A first shutter and the same rotary drive shaft as the first shutter,
A thin film growth apparatus comprising a second shutter installed at a distance such that the thin film material can leak from the opening even in the closed state. 2. A shutter for controlling the splashing of a thin film material onto a substrate, the leakage of the thin film material from a thin film material evaporator is controlled by the opening / closing operation of the first shutter, and the first shutter is opened. 2. The thin film growth apparatus according to claim 1, wherein the deposition of the thin film material on the substrate is controlled by opening and closing the shutter of item 2.