JPS6050917A - Wafer temperature controller of molecular ray epitaxial device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 incident on the sea urchin/2 in the form of a molecular beam. Material supply sources such as Ga, Ag, As, etc.
6 is a heater wire, 7 is an electron gun, 8 is a mass spectrometer, and 9 is an RHKED screen. FIG. 2 is a partially cutaway perspective view of the chamber 1. In Figure 2, Ll
-j: knob for operating the shutter 6, 10 is a liquid nitrogen container, 11 is a wafer loading hole 12 of chamber 1 to chamber 1;
This knob is used for operations such as directing the wafer 2 loaded therein toward the molecular beam incidence side. 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 coated on the surface 14 of the molybdenum broth 13 as shown in FIG. A material such as indium is loaded into the chamber 1 in a state where it is pasted through a member 15. On the other hand, inside the chamber 1, there are provided a member 16 that supports the molybdenum block 13 in the loading position, a heater 3, and a thermocouple 17 as a temperature sensing element. Therefore, when the molybdenum block 13 is loaded at 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 its detection output to a temperature control circuit (not shown). Also,
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 between 550°C and 00°C.
It is maintained at a predetermined temperature of about °C.

By the way, the thermal emissivity of the molybdenum block 13 is 0.2.
8, whereas GaA e growing on Ueno-2
That of the growing layer is 0.7. Further, a GaAs growth layer is also generated on the surface of the molybdenum block 13 except for the wafer 2. Therefore, the wafer temperature at the start of growth is
As the GaA growth layer is formed on the surface 14 of the molybdenum block 13, the temperature decreases to 40'C to 50'C or more compared to the temperature at the end of growth. However, the thermocouple 17 is located on the back side of the molybdenum block 13 and
The local temperature of No. 3 is taken as the wafer temperature. This is no good,
Since the local temperature of the molybdenum block 130 remains constant even though the actual wafer temperature has significantly decreased, there is a risk that the wafer temperature may be controlled assuming that the wafer temperature is also constant. Such unstable temperature control has the disadvantage that it is impossible to obtain a GaA[] growth layer on the wafer that satisfies predetermined growth characteristics. In addition, it is difficult to load molybdenum blocks and thermocouples so that the mutual positional relationship is always constant for every molybdenum block, and in any case, devices that use thermocouples do not provide stable temperature control. There were some difficulties in doing so.

The main object of the present invention is to enable constant and stable control of temperature.

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 through which infrared rays 19 from a wafer bonded to molybdenum pass. One end side of a cylindrical body 21 having a predetermined length is attached to this window 20 . A quartz window 22 is provided at the other end of this cylinder 21.
is formed. An infrared radiation thermometer 23 for detecting Ueno temperature is arranged on the other end in the cylinder length direction. Cylindrical body 2
1 includes a quartz plate 24 that prevents the quartz window 22 from getting dirty.
is attached so that it can 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. In this case, it is housed in the bulge 25.

In this embodiment, the bulging portion 25 is made by bulging out a part of the cylindrical body 21, but it is also possible to form a side structure with the cylindrical body 21 and provide it between the window 20 and the cylindrical body 21. You can also do it. When this side structure is adopted, the term cylindrical body 21 is defined to include this side structure. In this embodiment, first, with the quartz plate 24 retracted to the position indicated by the chain line in the bulge 25, infrared rays 19 are passed through the cylinder 21 and are made to enter the infrared radiation thermometer 23 through the quartz window 22. The infrared radiation thermometer 23 measures the radiation temperature due to the incident infrared rays 19. Let the measured temperature at this time be TloC. 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 12°C. This difference in measured temperature is defined as ΔT°C. This temperature difference Δ
Corresponding to T° C., the temperature measured by the thermometer 23 is 12° C., and the correction volume of the thermometer 23 is adjusted so that this is read as TloC.

However, since the quartz plate 24 becomes contaminated with As in the chamber 1, the measured temperature T2°C changes. However, since the quartz window 22 is prevented from getting dirty by the quartz plate 24, it will hardly get dirty to the extent that it will affect the measured value, for example, for several months, and therefore the measured temperature T1°
C may be considered to be approximately constant. Therefore, when the difference in measured temperature changes from ΔT'C to 277°C, the correction volume is further adjusted to ΔT/°C based on the difference in temperature.
Adjust accordingly. Therefore, even if the quartz plate 24 becomes dirty, the temperature read by the thermometer 23 can accurately correspond to the temperature of the sea urchin. However, the reference measurement temperature T1°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 Ueno bonded to molybdenum pass, and one end of a cylinder having a predetermined length is placed in the window. A quartz window is formed on the other end of the cylinder, and an infrared radiation thermometer for detecting sea urchin temperature is placed on the other end of the cylinder.
A quartz plate that prevents the quartz window from becoming dirty is attached so that it can move back and forth between the outside and 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 used as the correction value for the reading temperature, so there is no need to use a thermocouple to control the wafer temperature, and a quartz plate is additionally provided to prevent the quartz window from getting dirty. It is now possible to eliminate this through correction, allowing accurate and stable Ueno/temperature control.
It is possible to improve the quality of the growth film on Ueno.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a 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 cross-sectional view of a conventional example, and Fig. 4 is a diagram of the present invention. FIG. 2 is a cross-sectional view of an embodiment of the invention. 1...-f-ya7) Z, 19...infrared, 20・g, 2
1. Cylindrical body, 22.. Quartz window, 23.. Infrared radiation thermometer, 24.. Quartz plate. Applicant: ROHM Co., Ltd. Agent: Kazuhide Okada, patent attorney

Claims (1)

[Claims] (1) A window is formed in an ultra-high vacuum chamber that allows infrared rays from the sea urchin attached to molybdenum to pass through.
One end side of a cylinder having a predetermined cylinder length is attached to this window, and a quartz window is formed on the other end side of this cylinder, and an infrared radiation thermometer for detecting wafer temperature is placed on the cylinder length direction line on this other end side. A quartz plate is attached to a part of the cylinder so that it can move back and forth between the outside of the cylinder and the inside of the cylinder to prevent the quartz window from getting dirty. A wafer temperature control device for a molecular beam epitaxial apparatus, which uses a change in a temperature difference measured by an infrared radiation thermometer between the steps as a correction value for the measured temperature.