JPS63100713A - Substrate heating device for molecular beam epitaxial system - Google Patents

Abstract

PURPOSE:To increase the efficiency of heating and to make the temperature of a substrate uniform by a method wherein a heating plate, arranged opposing to the substrate in order to heat the substrate, is formed in such a manner that its inner circumferential side is thickly formed and the outer circumferential side is thinly formed. CONSTITUTION:The heating plate 11 arranged opposing to a substrate 1 is made of the material such as pyrolytic boron nitride, for example, and the heating plate 11 is thickly formed on the inner circumferential side and thinly formed on the outer circumferential side. When the heating plate 11 having the above-mentioned plate thickness distribution is used, the quantity of transmitted radiant heat on the outer circumferential part of thin plate thickness becomes larger than that of the inner circumferential part having heavy plate thickness, end the substrate 1 can be heated more on the outer circumference than the inner circumference. As a result, the quantity of heat escaping by the heat transfer through a substrate holder 2 on the outer circumference of the substrate 1 can be compensated, and the temperature distribution of the substrate 1 can be made uniform. Also, as the substrate 1 is heated up by the quantity of transmitted radiant heat of the heating plate 11, the efficiency of heating of the title device can be improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a substrate heating device for a molecular beam epitaxial device, and particularly to a molecular beam heating device that has a uniform temperature distribution on a substrate and is suitable for efficient heating. The present invention relates to a substrate heating device for an epitaxial device.

[Conventional technology]

In the conventional device, as described in Japanese Patent Application Laid-Open No. 60-112691, a heating equalizing member (herein referred to as a heating plate) inserted between a heater and a substrate in order to equalize the temperature of the substrate is a single unit. It had a different thickness. However, when a heating plate is inserted, the radiant heat from the heater heats the heating plate, and the radiant heat from the heating plate also heats the board, so the board is kept at a predetermined temperature compared to when there is no heating plate. This increases power consumption. High power consumption corresponds to an increase in the temperature of the heater, which in turn corresponds to an increase in the amount of gas released from the heater and its surroundings.

Such a conventional technique will be explained with reference to FIGS. 6 and 7.

FIG. 6 is a sectional view of a conventional substrate heating device of a molecular beam epitaxial apparatus, and FIG. 7 is a temperature distribution diagram of the heating plate thereof.

As shown in FIG. 6, the substrate 1 is held by a plate 3 on a substrate holder 2, and this substrate holder 2 is fixed with claws 4, and can be rotated by a drive mechanism not shown in the figure. .

The substrate 1 is heated by thermal radiation from a heating plate 5 arranged opposite to the substrate 1, and the heating plate 5 is heated by a heater 6 arranged opposite to the heating plate 5.

This heater 6 is made of pyrolytic boron nitride (hereinafter referred to as P
It is fixed on a heater base 7 made of an insulating material such as BN).

Temperature control of the substrate 1 is performed by a thermocouple 8. In the example shown in FIG. 6, the insulator 9 of the thermocouple 8 is equipped with a heating plate 5, a heater base 7, and a heat shield plate for improving heating efficiency. It had a structure with a 10th grade attached.

[Problem that the invention seeks to solve]

The temperature diagram of the heating plate in Fig. 7 shows the temperature of the heating plate 5 measured using an infrared thermometer with a wavelength of 0.9 μm without attaching the substrate 1 and substrate holder 2 in the substrate heating apparatus shown in Fig. 6 above. This is the result.

In Figure 7, the horizontal axis represents the radius of the heating plate (mrn), the vertical axis represents the heating plate temperature ("C), and the heating plate 5 is a silicon plate that does not transmit a wavelength of 0.9 μm. The solid line indicates the temperature, and the broken line indicates the temperature when the heating plate 5 is made of PBN which transmits a wavelength of 0.9 μm.

The measurement results shown in FIG. 7 are based on the emissivity of the silicon plate being 0.
6, P B N is set to 0.425.

As can be seen from FIG. 7, the temperature distribution measurement results of the PBN heating plate vary greatly in the radial direction as shown by the broken line.

This is because the wavelength of 0.9 μm emitted from the heater 6 on the back side of the heating plate 5 also passed through the heating plate 5 and was detected by the infrared thermometer. In the case of a wavelength of 0.9 μm, even if the material of the heating plate 5 is PBN, it does not transmit 100%, and it is recognized that the amount of transmission changes depending on the thickness of the PBH.

In the conventional substrate heating device described above, in order to bring the substrate 1 to a predetermined temperature, it is necessary to increase the temperature of the heater 6, which increases power consumption and increases the amount of gas released from around the heater. No consideration was given to the fact that there would be a large number of cases.

Furthermore, sufficient consideration was not given to the loss of heat from the outer circumference of the substrate 1 through the substrate holder 2 by thermal conduction.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and aims to provide a substrate heating device for a molecular beam epitaxial device that can improve heating efficiency and uniformize the temperature of the substrate. That is the purpose.

[Means for solving problems]

In order to achieve the above object, the structure of the substrate heating device for a molecular beam epitaxial apparatus according to the present invention includes a heating plate disposed opposite to the substrate to heat the substrate held by the substrate holder; In a molecular beam epitaxial apparatus equipped with a heater for heating the heating plate, the thickness of the heating plate is changed so that the amount of transmitted radiant heat of the heating plate is higher on the outer periphery side than on the inner periphery side of the heating plate. It has been established.

In addition, the above object is achieved by changing the thickness of the heating plate along the radial direction of the heating plate so that it is thicker on the inner peripheral side and thinner on the outer peripheral side.

Further, by providing a large number of irregularities on the surface of the heating plate, the effective emissivity of the heating plate can be improved.

[Effect]

When the material fft of the heating plate is, for example, pyrolytic boron nitride (PBN), PBN transmits infrared rays having a wavelength of about 1 μm or more.

Therefore, part of the radiant heat from the heater passes through the PBN heating plate and reaches the substrate, and part of it is absorbed by the heating plate and heats the heating plate, resulting in thermal radiation from the heating plate. The substrate is heated. The amount of heat transmitted through a PBH heating plate depends on the thickness of the heating plate. The amount of radiant heat from the heating plate depends not on the thickness of the heating plate but on the temperature distribution of the heating plate. Therefore, by controlling the amount of radiant heat that passes through the heating plate by appropriately changing the thickness of the heating plate, the temperature distribution of the substrate can be made uniform. Further, since the temperature of the heater is higher than the temperature of the heating plate, the intensity of infrared rays transmitted through the heating plate is stronger than the intensity of infrared rays of the same wavelength emitted from the heating plate, so that the substrate can be heated efficiently.

Further, by providing the surface of the heating plate with irregularities, the effective emissivity of the heating plate can be improved, and heating efficiency can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

First, FIG. 1 is a cross-sectional view of a substrate heating device of a molecular beam epitaxial device according to an embodiment of the present invention.
Components with the same reference numerals as those in the drawings are the same parts as in the prior art, so their explanation will be omitted.

In FIG. 1, reference numeral 11 denotes a heating plate placed opposite to the substrate 1. The material of the heating plate 11 is pyrolytic boron nitride (r'BN), which has high emissivity and high thermal conductivity. The plate thickness is such that the inner peripheral side of the heating plate 11 is thicker and the outer peripheral side is thinner.

If a heating plate 11 having such a plate thickness distribution, in other words, a variable plate thickness is used, the amount of transmitted radiant heat at the outer circumference where the plate is thinner will be larger than at the inner circumference where the plate thickness is large, and the substrate 1 will be heated. The outer periphery of the substrate 1 is heated more. Therefore, the amount of heat escaping from the outer periphery of the substrate 1 through the substrate holder 2 by thermal conduction is guaranteed, and the temperature distribution of the substrate 1 can be made uniform. Furthermore, since the substrate 1 is heated by the amount of transmitted radiant heat from the heating plate, heating efficiency is also improved.

According to this embodiment, the temperature distribution of the substrate can be made uniform, heating efficiency can be improved, and power consumption can be reduced.
This has the effect of increasing the area on the substrate where normal crystal growth can occur. Furthermore, as power consumption decreases, the temperature of the heater and the temperatures of peripheral components decrease. Therefore, the amount of released gas is also reduced, which has the effect of reducing the amount of impurity gas that adversely affects crystal growth.

Next, another embodiment of the present invention will be described with reference to FIGS. 2 and 3.

FIG. 2 is a perspective view of a heating plate provided in a substrate heating apparatus according to another embodiment of the present invention, and FIG. 3 is a sectional view thereof.

The heating plate 12 shown in FIG. 2.3 is a PBN heating plate having a uniform thickness, but is provided with a plurality of concentric grooves 12a.

Generally, the emissivity of a heating plate changes depending on the surface condition of the heating plate, so providing concentric grooves increases the emissivity. Therefore, the pitch of the grooves on the outer circumferential side of the heating plate 12 should be narrowed (more grooves on the outer circumferential side).

If the groove pitch on the inner circumferential side is widened (the number of grooves on the inner circumferential side is decreased), the thickness of the heating plate is substantially changed between the inner circumferential side and the outer circumferential side, and the transmission of the heating plate 12 is reduced. The heat radiation area is higher on the outer circumferential side of the heating plate 12 than on the inner circumferential side. Therefore, the same effects as the previous embodiment shown in FIG. 1 are expected.

Note that the substrate temperature can be made uniform by appropriately selecting the groove width and groove depth in addition to the interval between the grooves 12a.

Although not particularly shown, the grooves are not limited to concentric circles.

A similar effect can be expected even if spiral grooves are provided, with a wide groove pitch on the inner circumferential side and a narrow groove pitch on the outer circumferential side.

Furthermore, regarding the cross-sectional shape of the groove, although rectangular square grooves are shown in the embodiments shown in FIGS. 2 and 3, V-shaped grooves, U-shaped grooves, or irregularly shaped grooves may also be effective. Needless to say.

Next, still another embodiment of the present invention will be described with reference to FIGS. 4 and 5.

FIG. 4 and FIG. 5 are both perspective views of a heating plate used in a substrate heating apparatus according to still another embodiment of the present invention.

The heating plate 13 shown in FIG. 4 is a PBN heating plate having a uniform thickness, but is provided with radial grooves 13a. These radial grooves 13a are formed by forming shallow grooves on the inner circumferential side of the heating plate 13 and deep grooves on the outer circumferential side, thereby substantially reducing the plate thickness between the inner circumferential side and the outer circumferential side of the heating plate 13. As a result, the amount of transmitted heat radiation of the heating plate 13 becomes higher on the outer circumferential side than on the inner circumferential side of the heating plate 13.

Therefore, the same effects as the previous embodiment shown in FIG. 1 are expected.

Note that the cross-sectional shape of the groove is similar to the embodiment shown in FIGS. 2 and 3 above.
It may be rectangular, V-shaped, U-shaped, or irregularly shaped. Although not shown, radial grooves may be provided only on the outer periphery of the heating plate.

The heating plate 14 shown in FIG. 5 is a PBNIl heating plate having a uniform thickness, but is provided with a large number of irregularities 14a. These unevenness 14a are not limited to the shape, and may be, for example, point-like scratches such as those made with a drill. By forming the heating plate 14, the amount of transmitted radiation of the heating plate 14 becomes higher on the outer circumferential side than on the inner circumferential side. Therefore, the same effects as the previous embodiment shown in FIG. 1 are expected.

Note that the shape of the unevenness may be irregular, and although it is not shown in FIG.

Moreover, if a large number of irregularities, for example, dot-like scratches, are provided on the surface of each heating plate 11, 12, 13, etc., which faces the heater 6, as explained in the embodiments of FIGS. 1 to 4, Since the heating plate is easily heated by the heater, the heating efficiency is improved, and as a result, it is also possible to reduce the power consumption of the heater.

This also leads to lower emission gas,
Beneficial for crystal growth.

In each of the above-described embodiments, PBN, which is commonly used as a material for the heating plate, has been described, but the present invention is not limited thereto.

Does not prevent the use of other materials.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a substrate heating device for a molecular beam epitaxial device that can improve heating efficiency and also make the temperature of the substrate uniform.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a substrate heating device for a molecular beam epitaxial apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of a heating plate provided in a substrate heating device according to another embodiment of the present invention. 3 is a sectional view thereof, FIGS. 4 and 5 are perspective views of a heating plate provided in a substrate heating apparatus according to still another embodiment of the present invention, and FIG. 6 is a sectional view thereof. A cross-sectional view of a substrate heating device of a conventional molecular beam epitaxial device, FIG.
It is a temperature distribution diagram of the heating plate. 1... Substrate, 2... Substrate holder, 6... Heater,
11゜12.13.14...Heating plate, 12a, 13a
...Groove, 14a...Irregularities.

Claims (1)

[Claims] 1. A molecular beam epitaxial device comprising a heating plate placed opposite to the substrate to heat the substrate held in the substrate holder, and a heater for heating the heating plate. A substrate heating device for a molecular beam epitaxial apparatus, characterized in that the thickness of the heating plate is varied so that the amount of transmitted radiant heat of the heating plate is higher on the outer periphery side than on the inner periphery side of the heating plate. 2. A substrate heating device for a molecular beam epitaxial device according to claim 1, wherein the heating plate is made of pyrolytic boron nitride. 3. In the product described in claim 1, the thickness of the heating plate is formed so that the thickness of the heating plate is thicker on the inner circumferential side and thinner on the outer circumferential side along the radial direction of the heating plate. Equipment substrate heating device. 4. In the item described in claim 1, the thickness of the heating plate is such that the heating plate is provided with a spiral groove or a plurality of concentric grooves, and the groove pitch on the inner circumference side is widened on the outer circumference side. A substrate heating device for a molecular beam epitaxial device, which is changed by narrowing the groove pitch. 5. In the item described in claim 1, the thickness of the heating plate is such that the heating plate is provided with a plurality of radial grooves, and these grooves are shallow on the inner circumferential side and deep on the outer circumferential side. This is a modified substrate heating device for molecular beam epitaxial equipment. 6. In the item described in claim 1, the thickness of the heating plate is such that a plurality of irregularities are provided on the surface of the heating plate, and these irregularities are formed sparsely on the inner circumferential side and densely on the outer circumferential side. A substrate heating device for molecular beam epitaxial equipment that has been changed by 7. A substrate heating device for a molecular beam epitaxial device according to any one of claims 3 to 6, wherein the heating plate has a plurality of projections and depressions on the surface facing the heater. .