JPH0611027B2 - Molecular beam epitaxy system - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a molecular beam epitaxy apparatus, and more particularly to a molecular beam epitaxy apparatus suitable for accurately controlling the temperature of a substrate.

[Background of the Invention]

Conventionally, for the temperature control of the substrate in the molecular beam epitaxy apparatus, the method shown in "Molecular beam epitaxy technology" (published by the Industrial Research Group, 1984) is known. Referring to FIG. 4, the substrate 2 is attached to the susceptor 3 in the vacuum container 1 and attached to the sample rotation holder 4. The sample rotation holder 4 includes a heater 5 for heating the substrate 2 and the substrate 2
The thermocouple 6 for measuring the temperature is fixed. Thermocouple 6
Since its tip cannot contact the rotating susceptor 3, it is fixed near the center of the susceptor 3. In such a mounting structure, since the temperature cannot be measured absolutely, the indicated value of the thermocouple 6 is calibrated by the radiation thermometer 8 via the window 7 of the vacuum container 1 at any time. The temperature of the substrate 2 is controlled by feeding back the indicated value of the thermocouple 6 and controlling the output of the heater 5 by the temperature controller 9.

However, in the temperature measurement and control method with the above configuration, the molecular beam 10 that has flown from the molecular beam cell adheres to the surface of the substrate 2 and the emissivity of the substrate 2 changes, so the overall heat balance is lost and the substrate 2 Since the relative relationship between the temperature of 1 and the indicated value of the thermocouple 6 is not constant, the correct temperature of the substrate 2 cannot be measured. Therefore, there is a problem that the temperature cannot be controlled.

Even if the temperature of the substrate 2 is measured not by the thermocouple 6 but by the radiation thermometer 8, the emissivity of the substrate 2 changes with time, so that the correct temperature cannot be measured.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a molecular beam epitaxy device which eliminates the drawbacks of the conventional molecular beam epitaxy device and enables accurate temperature measurement and temperature control of the substrate.

[Outline of Invention]

The molecular beam epitaxy apparatus of the present invention utilizes the property that the substrate is specularly reflected, arranges a black body radiation source and a radiation thermometer in symmetrical positions with respect to a vertical line of the substrate surface, and measures the temperature of the substrate and the black body radiation source. The temperature of the substrate surface can be detected by detecting the amount of heat from the black body radiation source reflected by the substrate surface and the amount of heat radiated from the substrate surface by the radiation thermometer. In addition, the temperature can be accurately controlled to the crystal growth temperature.In particular, the means for independently controlling the temperature of the substrate and the temperature of the blackbody radiation source measures and adjusts the temperature of the substrate. Substrate temperature control system that controls the temperature of the substrate by adjusting the heater with a controller, and a black body radiation source that measures the temperature of the black body radiation source and adjusts the heater with the controller to control the temperature of the black body radiation source Equipped with a temperature control system, the temperature of the substrate Characterized in that it is configured to control the heating temperature of the substrate while feeding back the temperature of the black body radiation source calculating unit for calculating.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. Fourth
The same symbols as those in the figures indicate the same parts.

In FIG. 1, 11 is a black body radiation source, 17 is a thermocouple for measuring the temperature of the black body radiation source 11, and 13 is a heater for heating the black body radiation source 11. Reference numeral 14 is a perpendicular line erected on the surface of the substrate 2, and the radiation thermometer 8 and the black body radiation source 11 are arranged symmetrically with respect to the perpendicular line 14 at an angle θ. Reference numeral 15 is a molecular beam cell for generating the molecular beam 10, 16 is a vacuum pump for vacuuming the inside of the vacuum container 1, and 17 is a thermocouple for measuring the temperature of the black body radiation source 11.

In the above configuration, when the substrate 2 is completely specularly reflected, the heat quantity Q per unit area detected by the radiation thermometer 8 is detected.
Is expressed by the following equation.

Q = ε · σT _W ⁴ + (1−ε) · σT _B ⁴ (1) where ε is the emissivity of the substrate 2, T _W is the temperature of the substrate 2,
T _B is the temperature of the black body radiation source 11, and σ is the Stefan-Boltzmann constant. The temperature T _B of the blackbody radiation source 11 is the thermocouple 1.
It is a value measured by 7. Therefore, if the temperature T _B of the blackbody radiation source 11 is independently changed in two ways by the heater 13 and the heat quantity Q at that time is measured by the radiation thermometer 8,
The temperature T _{W of the} substrate 2 and the emissivity ε can be obtained from the equation (1). In this way, it is possible to measure the absolute temperature of the substrate 2 and feed back this temperature to control the output of the heater 5.

Instead of changing the temperature T _B of the black body radiation source 11 by the heater 13, as shown in FIG.
A chopper 18 is provided between the substrate 2 and the substrate 2, the temperature of the black body radiation source 11 is kept constant, and the amount of heat radiated from the surface of the substrate 2 by rotating the chopper 18 ε · σT _W ⁴ and the black body radiation source 11 The amount of heat radiated and reflected on the surface of the substrate 2 (1-ε)
The temperature T _W of the surface of the substrate 2 and the emissivity ε can also be measured by separately detecting σT _B ⁴ and the sum of the amount of heat ε · σT _W ⁴ radiated from the substrate surface.

Next, when the emissivity ε of the substrate 2 changes with time as during crystal growth, the temperature T _B of the black body radiation source 11 is changed by the heater 13 to set the temperature of the substrate 2 (crystal growth temperature). Set equal to T _WS . Between the set temperature T _BS of the black body radiation source 11 and the set temperature T _WS of the substrate 2, Q = ε · σT _WS ⁴ +, as in the previous equation (1) when the emissivity ε does not change. (1-ε) · σT _BS ⁴ (2) holds, and T _BS = T _WS , so that Q = σT _WS ⁴ = σT _BS ⁴ (3), and the amount of heat detected by the radiation thermometer 8 Q is equal to the amount of heat radiated by the black body radiation source 11 regardless of the emissivity ε of the substrate 2. In other words, by setting the temperature of the black body radiation source 11 to the temperature of the substrate 2 to be set, the detected heat quantity Q of the radiation thermometer 8 is the heat quantity σT _WS radiated by the black body radiation source 11.
By changing the output of the heater 5 so as to be equal to ⁴ or σ T _B ⁴ , accurate temperature control of the substrate 2 becomes possible.

Next, FIG. 3 shows a block diagram of a control system for independently controlling the temperatures of the substrate 2 and the black body radiation source 11. The set values T _WS and T _BS of the substrate temperature and the black body radiation source temperature are set in advance in the controller 9, and the respective temperatures are detected by the radiation thermometer 8 and the thermocouple 17, and the set values T _WS and T _{BS are set.} The output signals of the controller 9 are used to change the outputs of the heaters 5 and 13 according to the deviations ΔT _W and ΔT _S from the temperature control. At this time, since the detected amount detected by the radiation thermometer 8 is the amount of heat Q, the temperature T _W is calculated by the equation (1) or the equation (3). Therefore, the black body radiation source temperature T _B is also fed back to the temperature calculation unit of the substrate temperature control system.

In the above invention, the radiation thermometer for detecting a specific wavelength or wavelength range may be used instead of the radiation thermometer 8 to detect radiation intensity in this wavelength or wavelength range, and the same effect can be obtained. Needless to say.

〔The invention's effect〕

As described above, according to the present invention, the radiation thermometer and the black body radiation source are arranged at symmetrical positions with respect to the perpendicular line erected on the surface of the substrate, and the temperature of the black body radiation source and the temperature of the substrate are independently controlled. By doing so, not only when the emissivity of the substrate is constant, but also when the emissivity changes with time, it is possible to accurately measure the temperature of the substrate and control the temperature, and as a result, a crystal with excellent quality can be obtained. There is an effect.

[Brief description of drawings]

FIG. 1 is an explanatory view of a molecular beam epitaxy apparatus of the present invention, and FIG.
FIG. 4 is an explanatory view of another embodiment of the molecular beam epitaxy apparatus of the present invention, FIG. 3 is a block diagram of a control system for temperature control in the molecular beam epitaxy apparatus of the present invention, and FIG. 4 is a conventional molecular beam epitaxy apparatus. FIG. 1 ... vacuum container, 2 ... substrate, 5,13 ... heater, 8
...... Radiation thermometer, 11 ...... Black body radiation source, 17 ...... Thermocouple, 18 ...... Chopper.

Claims (1)

[Claims] 1. A molecular beam epitaxy apparatus for detecting a temperature of a substrate surface and irradiating the substrate with a molecular beam to epitaxially grow while controlling a heating temperature of the substrate, in a position symmetrical with respect to a perpendicular line erected on the substrate surface. A black body radiation source and a radiation thermometer are arranged in the, and the temperature of the substrate and the temperature of the black body radiation source are controlled independently, and the radiation thermometer is the amount of heat emitted from the black body radiation source and reflected on the substrate surface. And means for measuring the temperature of the substrate surface by detecting the amount of heat radiated from the substrate surface, controlling the substrate surface temperature, and independently controlling the substrate temperature and the blackbody radiation source temperature. Is a substrate temperature control system that measures the temperature of the substrate, controls the temperature of the substrate by adjusting the heater with a controller, and measures the temperature of the blackbody radiation source,
It is equipped with a black body radiation source temperature control system that controls the temperature of the black body radiation source by adjusting the heater with a controller, and the computing unit that computes the temperature of the substrate heats the substrate while feeding back the temperature of the black body radiation source. A molecular beam epitaxy device characterized by controlling temperature.