JPH0113214B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is a molecular beam epitaxial method in which a wafer is loaded in an ultra-high vacuum chamber, and materials such as Ga, Al, and As are incident on the wafer in the form of molecular beams to grow a film. The present invention relates to a wafer temperature control device in an apparatus.

A molecular beam epitaxial apparatus is generally designed in principle as shown in FIG.

In Figure 1, 1 is a chamber with an ultra-high vacuum inside, 2 is a GaAs wafer loaded in this chamber 1, 3 is a heater for heating the wafer, and 4 is a molecular beam incident on the wafer 2. A material supply source such as Ga, Al, As, etc., 5 is a heater wire, 6 is a shutter, 7 is an electron gun, 8 is a mass spectrometer, and 9 is an RHEED screen. FIG. 2 is a partially cutaway perspective view of the chamber 1. In FIG. 2, 9 is a knob for operating the shutter 6, 10 is a liquid nitrogen container, and 11 is an operation for directing the wafer 2 loaded into the chamber 1 from the wafer loading hole 12 of the chamber 1 toward the molecular beam incidence side. This is a knob for use. Such a molecular beam epitaxial apparatus is capable of precisely controlling the thickness of the film grown on the wafer 2, but conventionally, the wafer 2 is grown on the surface 14 of a molybdenum block 13, as shown in FIG. It is loaded into the chamber 1 in a state where it is pasted through a pasting member 15 made of indium or the like. On the other hand, inside the chamber 1 is a member 1 that supports the molybdenum block 13 in the loading position.
6, heater 3, and thermocouple 17 as a temperature sensing element.
and is provided. Therefore, when the molybdenum block 13 is loaded into a predetermined position in the chamber 1, the heater 3 and the thermocouple 17 are arranged on the back surface 18 side of the molybdenum block 13.
This thermocouple 17 detects the temperature of the wafer 2 heated by the heater 3, and provides the detection output to a temperature control circuit (not shown). In addition, this temperature control circuit controls the heating operation of the heater 3 in response to this detection output, so that the wafer 2 is always kept at 550°C to 700°C.
so that the temperature is maintained at a certain level.

By the way, the thermal emissivity of the molybdenum block 13 is 0.28, whereas the thermal emissivity of the molybdenum block 13 is 0.28.
That of the GaAs growth layer is 0.7. In addition, GaAs is also formed on the surface of the molybdenum block 13 except for the wafer 2.
A growth layer is generated. Therefore, the wafer temperature at the start of growth decreases as the GaAs growth layer is formed on the surface 14 of the molybdenum block 13, and becomes 40°C compared to the temperature at the end of growth.
The temperature will drop to ~50℃ or more. However, the thermocouple 17 is located on the back surface of the molybdenum block 13 and uses the local temperature of the molybdenum block 13 as the wafer temperature. Therefore, since the local temperature of the molybdenum block 13 is constant, the wafer temperature may be controlled assuming that the wafer temperature is also constant, even though the actual wafer temperature has significantly decreased. With such unstable temperature control, it is difficult to satisfy the specified characteristics on the wafer.
A drawback was that it was not possible to obtain a GaAs growth layer. Furthermore, it is difficult to load molybdenum blocks and thermocouples in such a way that the mutual positional relationship is always constant for every molybdenum block, and in any case, devices that use thermocouples do not allow stable temperature control. There were some difficulties in doing so.

The main object of the present invention is to enable stable control of wafer temperature at all times.

Hereinafter, the present invention will be explained in detail based on an embodiment shown in the drawings.

FIG. 4 is a sectional view of the main parts of this embodiment. In this embodiment, a chamber 1 of the molecular beam epitaxial apparatus shown in FIGS. 1 and 2 has a cylindrical window 20 for passing infrared rays 19 from a wafer bonded to molybdenum. In this window 20,
One end side of a cylinder 21 having a predetermined cylinder length is attached. A quartz window 22 is formed at the other end of the cylinder 21 . An infrared radiation thermometer 23 for detecting wafer temperature is arranged on the other end in the cylinder length direction. A quartz plate 24 that prevents the quartz window 22 from becoming dirty is attached to a part of the cylinder 21 so as to be able to reciprocate inside and outside the cylinder (up and down in the figure). That is, a part of the cylindrical body 21 is bulged in the radial direction to form a bulged portion 25, and the quartz plate 24 can be reciprocated between the solid line and the chain line by the support shaft 26, and the quartz plate 24 can be moved back and forth between the solid line and the chain line. It is designed to be housed within the bulge 25. Note that in this embodiment, the bulging portion 25 is
The cylinder body 21 is made by bulging out a part of the cylinder body 21.
It is also possible to have a separate structure and provide it between the window 20 and the cylindrical body 21. In the case of such a different structure, the term cylindrical body 21 is defined to include this different structure. In this embodiment, first, the quartz plate 2
The infrared rays 19 are passed through the cylinder body 21 while the infrared rays 19 are retracted to the position indicated by the chain line inside the bulge 25, and the quartz window 22
The light is input to the infrared radiation thermometer 23 through the infrared radiation thermometer 23. The infrared radiation thermometer 23 measures the radiation temperature due to the incident infrared rays 19. The measured temperature at this time
T ₁ ℃. Next, the radiation temperature is similarly measured with the quartz plate 24 moved to the solid line position.
The measured temperature at this time is T ₂ °C. This difference in measured temperature is defined as ΔT°C. Corresponding to this temperature difference ΔT°C, the temperature measured by the thermometer 23 is T ₂ °C,
Thermometer 23 so that this is read as T ₁ °C
Adjust the correction volume.

However, the quartz plate 24 is
Because it becomes dirty due to etc., the measurement temperature T ₂ ℃
is changing. However, the quartz window 22 is
Since contamination is prevented by step 4, the contamination hardly affects the measured value for several months, for example, and therefore the measured temperature T ₁ °C can be considered to be approximately constant. Therefore, when the difference in measured temperature changes from ΔT'°C to ΔT'°C, the correction volume is further adjusted according to this difference in temperature. Therefore, even if the quartz plate 24 becomes dirty, the temperature read by the thermometer 23 can accurately correspond to the temperature of the wafer. However, the reference measurement temperature T ₁ °C was measured taking into consideration the thermal emissivity of GaAs and the quartz window 22.

As described above, according to the present invention, a window is formed in an ultra-high vacuum chamber through which infrared rays from a wafer bonded to molybdenum pass, and one end side of a cylinder having a predetermined length is inserted into the window. A quartz window is formed on the other end of the cylindrical body, and an infrared radiation thermometer for detecting wafer temperature is placed along the longitudinal direction of the cylindrical body. A quartz plate that prevents contamination is attached so that it can move back and forth between the outside of the cylinder and the inside of the cylinder, and the change in temperature difference read by an infrared radiation thermometer between when the quartz plate is inside the cylinder and when it is not is read. Since the temperature is used as a correction value, it is no longer necessary to control the wafer temperature using a thermocouple, and a quartz plate is additionally provided to prevent the quartz window from becoming dirty. This makes it possible to accurately and stably control the wafer temperature and improve the quality of the grown film on the wafer.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the molecular beam epitaxial apparatus used to explain the principle of the apparatus, Fig. 2 is a partially cutaway perspective view of the chamber of this apparatus, Fig. 3 is a sectional view of a conventional example, and Fig. 4 is a schematic diagram of the apparatus. FIG. 2 is a cross-sectional view of an embodiment of the invention. 1... Chamber, 19... Infrared, 20...
Window, 21... Cylindrical body, 22... Quartz window, 23... Infrared radiation thermometer, 24... Quartz plate.

Claims (1)

[Claims] 1 A window is formed in an ultra-high vacuum chamber to allow infrared rays from a wafer attached to molybdenum to pass through, one end of a cylindrical body having a predetermined length is attached to this window, and the other end of this cylindrical body is attached to the window. A quartz window is formed, and an infrared radiation thermometer for detecting wafer temperature is placed on the other end of the cylinder in the longitudinal direction of the cylinder, and a quartz plate is placed outside the cylinder in a part of the cylinder to prevent the quartz window from getting dirty. A molecular beam that is attached so as to be able to reciprocate between the quartz plate and the cylinder, and uses the change in the temperature difference measured by the infrared radiation thermometer between when the quartz plate is inside the cylinder and when it is not inside the cylinder as a correction value for the measured temperature. Wafer temperature control device for epitaxial equipment.