JPH03164496A - Substrate heater for molecular beam epitaxial device - Google Patents

Abstract

PURPOSE:To uniformize a heating temp. by setting the epitaxial growth surface of a substrate in a gravity direction and increasing the radiation heat quantity of a heater for heating a substrate placed and held on a substrate holder in the central part of the substrate. CONSTITUTION:The molecular beam epitaxial device is constituted of the substrate 1 held by the holder 2, the heater 6 fixed to a heater base 7, a heat shielding plate 10 and a thermocouple 8, etc., for measuring the temp. of the substrate 1, etc., as shown in Fig. l. Methods of increasing the thickness of the central part of the heater base 7a to shorten the distance from the substrate 1 as shown in Fig. 2, disposing a material having a higher radiation rate in the central part of the substrate 1 as shown in Fig. III, increasing the density of the heater 6C in the central part as shown in Fig. IV, increasing the resistance of the heater 6d in the central part as shown in Fig V, discriminating the supply electric power to the heater 6 to the central part 6e and the outer peripheral part 6f and increasing the electric power in the central part 6e as shown in Fig. VI, or mounting a cooling mechanism 13 to a central part holding member 3 and controlling temp., as shown in Fig. VII, etc., are adopted to increasing the radiation heat quantity of the heater 6 in the central part so that the substrate 1 can be uniformly heated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a substrate heating device for a molecular beam epitaxial device, and in particular, to a substrate heating device for a molecular beam epitaxial device. The present invention relates to a substrate heating device for a line epitaxial device.

[Conventional technology]

Conventional devices are disclosed in Japanese Patent Application Laid-Open Nos. 57-30320 and 1983.
As described in Japanese Patent No. 112691, a heating equalizing member (referred to as a heating plate) is provided between a heater and a substrate in order to uniformly heat the substrate. 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 maximum possible heating temperature of the board is lower than when there is no heating plate. As a result, the power consumption to bring the board to a predetermined temperature increases.

As a result, when a heating plate is used to maintain the substrate surface at a predetermined temperature, the relative temperature of the heater needs to be higher than when no heating plate is used. As a result, more gas is released from the heater and its surroundings.
The released gas adheres to the substrate surface, causing problems such as surface defects. Another problem is that the heater material is gradually deposited on the heating plate, and the transmittance and reflectance of the heating plate itself change, causing the heating efficiency to change over time, making it impossible to control the substrate temperature with good reproducibility. Figure 2 is a cross-sectional view of a conventionally used molecular beam epitaxial apparatus described in JP-A No. 63-116419, and Figure 3 is a cross-sectional view of a conventional molecular beam epitaxial apparatus described in JP-A-63-116419. A temperature distribution diagram of the substrate when heated is shown.

As shown in FIG. 2, the substrate 1 is securely held by the substrate holding frame 19. The substrate is heated by heaters 6a and 6b placed opposite the substrate. These heaters are made of pyrolytic boron nitride (hereinafter referred to as PBN).
It is fixed on a heater base 7 made of an insulating material such as. The position of the heater 6a and the heater 6b are such that they do not overlap with respect to the substrate on the substrate projection plane. Temperature control of the board is performed by a thermocouple 8. In the example shown in FIG. 2, the insulator 9 of the thermocouple 8 is placed in the center, and the heater base 7, heating plate 5, and heat shield plate 10 are used as pillars and spacers. It had a fixed structure. The characteristic of the heater of this substrate heating device is that in a single heater system, a low temperature region and a high temperature region are generated on the substrate facing the heat generating section, so the heating plate is connected to the part of the substrate facing the low temperature region. Some devices are equipped with a heater and have a dual heater structure, allowing the two systems of heaters to heat the substrate uniformly.

In addition, as described in Japanese Patent Application Laid-open No. 63-242993, heat is released from the outer circumference of the substrate to the member holding the substrate, so a heater for heating the substrate is used to uniformly heat the temperature of the substrate. Separately, there is also an example in which the outer periphery of the substrate is heated by an electron beam. Furthermore, JP-A-59-3921, JP-A-59-3922, and JP-A-59-3934.

There is also a method of heating the outer periphery of the substrate with a lamp or the like, as described in Japanese Patent Application Laid-Open No. 59-3935.

These methods are effective on the precondition that the temperature around the substrate is lowered, as described in Japanese Patent Application Laid-Open No. 59-243816. Therefore, in the conventional method of holding a board, the board is tightened and fixed from both sides of the board, but in the holding method of simply placing the board on a member that holds the board, heat is passed from the outer periphery of the board through the member that holds the board. The release of will be reduced. As a result, the temperature of the portion of the substrate facing the member holding the substrate becomes higher than the temperature of the central portion of the substrate. Therefore, the temperature at the outer periphery of the substrate is higher than the temperature at the center, and there is a problem that the entire substrate cannot be uniformly heated.

[Problem to be solved by the invention]

The conventional substrate heating device for molecular beam epitaxial equipment described above focuses on uniformly heating the substrate, but when a substrate holding method is adopted in which the substrate is simply placed on a member that holds the substrate, , the temperature drop at the center of the board was not taken into account. That is, in the conventional substrate heating device.

Since the substrate is tightened and fixed from both sides of the substrate, heat is released from the outer periphery of the substrate to the member holding the substrate, as described in Japanese Patent Application Laid-Open No. 63-242993. As a result, in order to uniformly heat the substrate, it was necessary to heat the outer peripheral portion of the substrate with an electron beam, in addition to the heater for heating the substrate. However, with the board holding method where the board is simply placed on a member that holds the board, the amount of heat released from the outer periphery of the board is small, and the temperature of the outer periphery of the board is higher than that of the center of the board. , which causes defects in film quality during epitaxial growth.

In addition, in the prior art, there are examples in which the heater density at the outer periphery of the heater used for heating the substrate is improved or another heating mechanism is attached to the outer periphery, but this does not address the temperature drop at the center of the substrate.

An object of the present invention is to provide a substrate heating device for a molecular beam epitaxial device that uniformly heats a substrate.

[Means to solve the problem]

In order to achieve uniform heating temperature of the substrate, in the substrate heating device of the molecular beam epitaxial apparatus according to the present invention, the amount of heat radiated from the heater for heating the substrate facing the substrate is increased in the central part on the substrate projection surface. In this way, the distance between the substrate and the heater is reduced at the center of the substrate, a material with a higher weight than the substrate is attached to the back surface of the center of the substrate, and the area of the heater facing the substrate is increased with respect to the center of the substrate. This is achieved by increasing the resistance of the heater facing the center of the substrate, and by dividing the power supply of the heater into two or more systems, one for the center and the other for the outer periphery.

In addition, by attaching a cooling mechanism to the member that holds the board and cooling it, the temperature of the member that holds the board is lowered, and by constantly emitting a constant amount of heat from the outer periphery of the board, the temperature of the center of the board can be adjusted relative to the temperature of the center part of the board. By increasing the distance between the board and the board, reducing the contact area between the board and the board, and widening the distance between the board and the board, the external part of the board can be treated as well as the center of the board. It becomes possible to radiate heat by radiation, and the purpose of efficiently and uniformly heating the substrate on the substrate projection surface is achieved.

[Effect]

In the present invention, the heater density on the substrate projection surface of the heater that heats the substrate is increased in the central portion. When the resistance of the heater is increased at the center, the distance between the heater and the substrate is shortened at the center, so the amount of heat radiated from the heater to the substrate is increased at the center of the substrate. Also, if the amount of heat radiated from the heater to the substrate is (Qhν), then Qhw follows the first equation, and the amount of heat radiated from the heater to the substrate is the surface area of the heater.

It is proportional to the view factor of radiation from the heater to the substrate, the radiation coefficient of the heater, and the radiation coefficient of the substrate, and is also proportional to the fourth power difference between the temperature of the heater and the temperature of the substrate. Also, the view factor from the heater to the substrate is as shown in the second equation:
The closer the distance between the heater and the substrate, the greater the value, and the closer the distance between the heater and the substrate, the greater the amount of radiated heat Qhυ.

Qhw=Ah*Fhw* the aw14.88”
((Th/100)' (Twh/100)
')■Ah (a): Surface area of the heater Fhw: View coefficient of heat radiated from the heater to the substrate εh; Emissivity of the heater εν: Emissivity of the substrate Th (K): Temperature of the heater Tti (K): Temperature of the substrate Fh oath=1/2R1[R1”+R22+L2=((R1
"+R2Z+L")"-4R1 umbrella R2)"/2] @
R1 (m): Radius of the heater R2 (m): Radius of the substrate L (m): Distance between the heater and the substrate Therefore, the heater density on the substrate projection plane of the heater that heats the substrate, the resistance of the heater, and the heater and the substrate By making the distance between the substrate higher, larger, or closer at the center, it is possible to increase the amount of heat radiated from the center of the substrate, which is insufficient with conventional heating methods using heaters, and the distance between the substrate and the substrate on the projection surface can be increased. It has the effect of making the temperature uniform.

Also, consider heat release from the board.

If the amount of heat released from the substrate to the shroud is Qtzs, it can be calculated in the same way as the first equation. There is no problem with heat release from the board to the shroud as it is almost constant per unit area, but at the outer periphery of the board, the amount of heat released from the board to the member holding the board is because the member holding the board is at a high temperature. In addition, the amount of heat released from the center of the board to the shroud is extremely small. Therefore, by minimizing the area of the contact area between the board and the member that holds the board, and by making the shroud visible from the outer periphery of the board, heat release due to radiation from the board can be made almost uniform over the entire board.
This has the effect of reducing the temperature distribution of the substrate on the substrate projection surface.

〔Example〕

Embodiments of the present invention will be described below from FIGS. 1 and 3.
This will be explained using Figure 0.

First, FIG. 1 is a longitudinal sectional view when the substrate heating device of the present invention is installed in a sample holder of a molecular beam epitaxial device. The substrate 1 is placed on a member 3 that holds the substrate, and the member that holds the substrate is held by the substrate holder 2 and further fixed by a holder holder 4, and is rotated (rotated) by a drive mechanism not shown in the figure. ) Exercise is possible. The heater 6 is made of a high melting point metal such as tungsten, tantalum, or carbon, and is fixed to a heater base 7 made of an insulator such as PBN. Also, a heat shield plate 1 made of high melting point metal such as tantalum is provided for the heater base.
0 is placed. Further, a thermocouple 8 for measuring temperature in order to control the temperature of the substrate is attached to the center of the sample holder via an insulator 9. An example for increasing the amount of heat radiated from the center of the substrate will be described below.

In FIG. 4, by increasing the thickness of the heater base 7a to which the heater 6 is fixed at the center, it is possible to reduce the distance between the heater and the substrate. As a result, the purpose of increasing the amount of heat radiated from the heater to the substrate at the center of the substrate is achieved, and it becomes possible to make the temperature distribution of the substrate uniform on the substrate projection surface.

In FIG. 5, a material 12 such as carbon having a higher emissivity than the substrate is placed in the center of the substrate 1 to be heated, so that the amount of heat radiated by the heater is increased in the center of the substrate. As a result, the purpose of increasing the amount of heat radiated from the heater to the substrate at the center of the substrate is achieved, and it becomes possible to make the temperature distribution of the substrate uniform on the substrate projection surface. By varying the heater density with respect to the substrate 1 on the substrate projection surface and increasing it at the center of the substrate, the purpose of increasing the amount of heat radiated from the heater to the substrate at the center of the substrate is achieved. It becomes possible to make the temperature distribution of the substrate uniform.

FIG. 7 shows that by increasing the resistance of the heater 6d at the center of the substrate on the substrate projection plane relative to the outer periphery, the temperature of the heater 6d at the center of the substrate can be made higher than at the outer periphery. As a result, the purpose of increasing the amount of heat radiated from the heater to the substrate at the center of the substrate is achieved, and it becomes possible to make the temperature distribution of the substrate uniform on the substrate projection surface.

FIG. 8 shows that the temperature of the heater (center) 6e can be adjusted by distinguishing the power supply to the heater into the inner circumferential part and the outer circumferential part, and controlling the power supply to the heater independently from multiple systems on the substrate projection surface. This makes it possible to make the temperature higher than that of the heater (outer periphery) 6f, achieving the purpose of increasing the amount of heat radiated from the heater to the substrate at the center of the substrate, and making the temperature distribution of the substrate uniform on the substrate projection surface. It becomes possible to do so.

FIG. 9 shows a cooling mechanism 13 (for example, Cu, Ag, etc.)
By attaching a metal with high thermal conductivity and controlling the temperature of the member supporting the substrate, it is possible to always release a certain amount of heat from the outer periphery of the board to the member supporting the board. As a result, it is possible to radiate approximately the same amount of heat per unit area at the outer periphery of the board as compared to the center, and it is possible to make the in-plane temperature distribution of the board uniform on the board projection plane. It becomes possible.

In FIG. 10, the area of the contact area with the substrate 1 of the member 3a that supports the substrate held in the substrate holder 2 is minimized so that heat is radiated from all surfaces of the substrate to the shroud. Heat is also released from the outer periphery of the board by radiation. As a result, the amount of radiant heat emitted at the outer periphery of the board is approximately the same per unit area as at the center of the board, making it possible to make the in-plane temperature distribution of the board uniform on the board projection plane. It is.

〔Effect of the invention〕

According to the present invention, in a substrate heating device for a molecular beam epitaxial apparatus, the amount of heat radiated by the heater used for heating the substrate is increased at the center of the substrate, thereby reducing the in-plane temperature distribution of the substrate on the substrate projection plane. This has the effect of reducing defects in film quality during epitaxial growth.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a substrate heating device of a molecular beam epitaxial device according to the present invention, FIG. 2 is a sectional view of a substrate heating device of a conventional molecular beam epitaxial device, and FIG. 3 is a sectional view of a substrate heating device of a substrate heating device on a projection plane of a substrate. FIG. 4 is a cross-sectional view of a substrate heating device in which the heater base on which the heater is fixed is thickened in the center, according to an embodiment of the present invention, and FIG. FIG. 6 is a cross-sectional view of a substrate heating device in which a material with high radiation rate is attached to the center of the substrate. FIG. The figure is a sectional view of a substrate heating device according to an embodiment of the present invention, in which the resistance of the heater is larger in the center than in the outer periphery, and FIG. FIG. 9 is a cross-sectional view of a substrate heating device in which a cooling mechanism is attached to a member that supports a substrate according to an embodiment of the present invention, and FIG. 10 is a cross-sectional view of a substrate heating device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a substrate heating device in which the contact portion of the member supporting the substrate with the substrate is shaped at an acute angle, according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Substrate holder, 3... Member which holds a board, 4... Holder holder, 5... Heating plate,
6... Heater, 7... Heater base, 8... Thermocouple, 9... Insulator, 10... Heat shield plate, 11...
・Current introduction bolt, 12...Material with high load vs. weight, 1
3... Cooling mechanism, 14... Insulating plate, 15... Main body outer frame, 16... Support and spacer, 17... Jig, 1
8... Locking member, 19... Board holding frame.

Claims (1)

[Claims] 1. A substrate heating device for a molecular beam epitaxial apparatus comprising a substrate holder that holds a substrate, a substrate held by the substrate holder, and a heater that heats the substrate, comprising: A substrate heating device for a molecular beam epitaxial apparatus, characterized in that the amount of heat radiated by the heater for heating the substrate held by placing it on the substrate holder is increased at the center of the substrate in the direction of gravity.