JPH0669141A - Heat treatment furnace - Google Patents

Abstract

PURPOSE:To provide a heat treatment furnace for depositing a thin film through vapor phase epitaxial growth on the surface of a substrate inserted into a reaction tube having one closed end by introducing reaction gas into the reaction tube while heating through a tubular electric furnace disposed coaxially therewith, wherein the electric furnace has a structure facilitating regulation of energy density in the axial direction required for making uniform the temperature in the reaction tube over a range where the substrate exists. CONSTITUTION:A tubular electric furnace 20 is mainly constituted of a group of a large number of annular heaters 50 stacked around a reaction tube 10 in the axial direction thereof wherein each annular heater 50 is provided with a heater terminal 5OA connected on the outside thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment apparatus for chemically vapor-depositing a thin film on the surface of a silicon wafer or the like used as a substrate for an integrated circuit or the like, one of which is in a sealed cylindrical shape. While the substrate inserted in the reaction tube is heated by a cylindrical electric furnace arranged outside the reaction tube coaxially with the reaction tube, a reaction gas is introduced into the reaction tube to vapor-deposit a thin film on the surface of the substrate. The present invention relates to a configuration for easily adjusting the axial temperature distribution of the cylindrical electric furnace of the heat treatment apparatus.

[0002]

2. Description of the Related Art In the chemical vapor deposition method (CVD method), a volatile compound containing an element to be formed into a film is gasified and uniformly fed onto a substrate heated to a high temperature to cause thermal decomposition on the substrate. Form a thin film. In this case, since the reaction gas is diffused largely, a low pressure chemical vapor deposition method (L
PCVD) is widely used.

FIG. 6 is an explanatory sectional view of a conventional vapor phase growth apparatus, and is a schematic sectional view of an apparatus generally called vertical LPCVD. An electric furnace 2 is arranged so as to surround a cylindrical reaction tube 1 made of quartz, and a wafer group 4 is arranged in the reaction tube 1 via a support 3 and the reaction tube is a vacuum chamber (not shown). It is evacuated by the exhaust device. For example, when forming a polysilicon thin film, the wafer group 4 is the electric furnace 2
It is heated to about 600 to 650 ° C., and a reaction gas such as SiH ₄ is supplied to the reaction tube. Reaction gas Si
H ₄ is thermally decomposed into SiH ₄ → Si + 2H ₂ and a silicon film is formed. The film forming rate changes depending on the wafer temperature, the reaction gas pressure, the flow rate, and the like.

In this apparatus, in order to uniformly heat the wafer group inserted into the reaction tube, the heater of the electric furnace installed outside the reaction tube is usually divided into three parts in the axial direction and divided into heaters 5a, 5b and 5c. The temperature of the entire wafer is soaked by the control. More specifically, the heating by the central heater is basically used, the heaters at both ends are adjusted while measuring the temperature distribution in the furnace, and a soaking zone (a predetermined range in the axial direction where the temperature is uniform) is secured. There is. The heater control is performed by temperature detection by the thermocouples 6a, 6b, 6c shown in FIG. The electric furnace 2 is composed of heaters 5 a to 5 c and a heat insulating material 7.

[0005]

In the above-mentioned electric furnace, due to variations in the manufacturing dimensions of the heater, variations in the shape of the bricks forming the heat insulating material, blocks made of ceramics, asbestos, etc. However, it is unavoidable that individual differences occur, and in the past, it took a lot of time to improve the soaking performance, that is, to secure the soaking zone by partially maintaining the heat of each part or adjusting the insulation performance such as removing the heat insulating material. It required labor.

The heating of the wafer is mainly performed by radiation from the heater. Therefore, the wafer placed in the center of the furnace is also subjected to radiant heating from the upper and lower heaters, and the wafer placed above is also subject to radiant heating from the middle and lower heaters. For example, when the temperature of the wafer installed on the upper part is low, simply controlling the heater on the upper part interferes with the wafer installed on the center to change the temperature, which complicates the control.

An object of the present invention is to provide an electric furnace structure in which it is easy to adjust the temperature distribution in the axial direction in order to ensure uniform heating performance in the axial direction of the electric furnace.

[0008]

In order to solve the above-mentioned problems, in the present invention, a heat treatment apparatus having the structure described in the beginning is provided with the cylindrical electric furnace surrounding the reaction tube and in the axial direction of the reaction tube. A large number of stacked annular heater groups are mainly configured, and a heater terminal is provided on each annular heater, and the terminals are connected outside the annular heater.

Here, the annular heater constituting the electric furnace is
An annular heating element that surrounds the reaction furnace and an adiabatic holding member that is formed in an annular shape so that the cross section is formed in a U shape and the central side of the U shape constitutes an outer wall surface and holds the heating element inside. It is preferable to use it. And, the annular heat insulating holding material that holds the annular heating element inside the U-shaped cross section,
It is preferable that the inner diameter side of the U-shape projects radially inward so that the inner diameter is smaller than that of the annular heating element.

Alternatively, an annular heat insulating holding material for holding the annular heating element is provided inside the U-shaped cross section, and the two opposite sides of the U-shape have an inner diameter that is integral with the central side and has substantially the same inner diameter as the annular heating element. It is also possible to have a ring plate which is formed as a separate body from the integral part of the and the central side and whose inner diameter is smaller than the annular heating element. In this case, it is preferable that the ring plates constituting the opposite sides of the U-shaped cross section of the annular heat insulating holding material are metal plates having a glossy surface.

In addition, it is preferable that the electric furnace mainly composed of a large number of annular heaters is provided with a heat insulating material between the annular heaters. In addition, among the many annular heaters forming the electric furnace, some or all of the annular heating elements of the annular heater may be partially short-circuited.

[0012]

As described above, the cylindrical electric furnace is mainly composed of a large number of annular heater groups that surround the reaction tube and are stacked in the axial direction of the reaction tube, and the heater terminals are provided on the individual annular heaters. By connecting the terminals outside the annular heater, the energy density in the axial direction of the electric furnace can be easily adjusted, and the temperature in the soaking zone of the reaction tube can be made uniform. Can be easily achieved.

Here, the annular heater is formed in an annular shape so that an annular heating element that surrounds the reaction furnace and a U-shaped cross section are formed so that the central side of the U-shape constitutes an outer wall surface. If it is configured by using a heat insulating holding material that holds the heating element, the electric furnace is configured by using a large number of annular heaters, so by using an annular heater of the same design, Since the annular heater has a simple shape, the electric furnace can have a simple structure in which the annular heaters are stacked.

If an annular heat insulating holding material for holding the annular heating element inside the U-shaped cross section is protruded radially inward toward the inner side to make the inner diameter smaller than the annular heating element,
It is possible to effectively prevent thermal interference from a vertical annular heating element with respect to a wafer, which is an object of radiant heating of one annular heating element and is substantially in the same plane as the annular heating element, and to effectively prevent the temperature in the soaking zone from increasing. Adjustment for homogenization becomes easy.

Further, both sides of the U-shape of the annular heat insulating holding material for holding the annular heating element inside the U-shaped cross section are integrated with the central side and have an inner diameter substantially equal to that of the annular heating element. If the integral part and the ring plate are formed separately from the central side and have an inner diameter smaller than the annular heating element, it is easy to adjust the thermal interference prevention effect in the vertical direction. In addition, if both opposite sides of the U-shape are configured with a part integral with the central side and a separate part in this way, the separate part can be configured with a ring plate, and the opposite opposite sides can be integrated with the central side. It is possible to reduce the size of the heat insulating material.

Further, if the electric furnace has a structure in which a heat insulating material is provided between the annular heaters, the energy density in the axial direction of the electric furnace is adjusted by changing the thickness of the heat insulating material depending on the axial position of the electric furnace. Can be done easily. Incidentally, among a large number of annular heaters constituting an electric furnace, if the annular heating elements of some or all of the annular heaters are partially short-circuited, the heating energy of the annular heater itself is adjusted,
It becomes easier to adjust the energy density in the axial direction of the electric furnace.

[0017]

1 is a front sectional view of a first embodiment of the present invention. An electric furnace 20 is arranged so as to surround the cylindrical reaction tube 10 made of quartz, and the support base 3 is provided in the reaction tube 10.
A wafer group 40 is arranged via 0. Here, the electric furnace 20 is configured mainly with a large number of annular heaters 50 surrounding the reaction tube 10 and stacked in the axial direction of the reaction tube 10. Each annular heater 50 has a terminal 5
0A is provided, and these terminals 50A are connected to the annular heater 50.
Connected to each other outside. Reference numeral 60 in the figure is a heat insulating spacer inserted between the annular heaters 50, and
The insertion position and the thickness are adjusted so that the temperature of the soaking zone is uniform.

FIG. 2 shows a first embodiment of the annular heater structure. The annular heater 50 includes an annular heating element 50B that surrounds the reaction tube 10 (FIG. 1), and a heat insulating holding material that is formed in an annular shape so that the central side of the U-shape constitutes an outer wall surface. It consists of 70. The ring-shaped heating element 50B is, for example, a coil made of a tantalum wire, and the coil is put inside the U-shape of the heat insulating material 70 to form a ring. Further, as the material of the heat insulating holding material 70 having a U-shaped cross section, a heat resistant porcelain or an inorganic material such as asbestos is used. The inner diameter of the heat insulating holding material 70 is formed smaller than the inner diameter of the annular heating element 50B so as to prevent thermal interference of the internal heating element in the vertical direction.

FIG. 3 shows a second embodiment of the annular heater structure. In this embodiment, the opposite sides of the U-shape of the heat-insulating holding material having a U-shaped cross section are formed separately from the portion 70A ₁ integrated with the central side and the central side, and the inner diameter is smaller than the inner diameter of the annular heating element 50B. It is composed of a metal ring plate 70A ₂ . The ring plate 70A ₂ has heat insulating properties such as heat-resistant porcelain and asbestos, and the wafer is heated by radiant heat from a heating element. be able to. At this time, the ring plate 7
The inner diameter of 0A ₂ can be made smaller than the inner diameter of the annular heating element 50B, and the opposite sides integrally formed as a U-shape can have the same inner diameter as the inner diameter of the heating element to make the holding material main body small. Further, since the ring plate 70A ₂ is a separate member from the holding material, it is easy to adjust the effect of preventing thermal interference from the vertical direction.

FIG. 4 shows a third embodiment of the annular heater. In this embodiment, a part of the heating element of the annular heater is short-circuited. Adjustments for equalizing the temperature in the soaking zone can be made by changing the thickness of the heat insulating spacer 60 (Fig. 1), but the amount of heat generated from the annular heater is reduced and the thickness of the heat insulating spacer becomes abnormal. By preventing the size from increasing, it is possible to prevent the electric furnace formed by stacking the annular heaters from becoming large. Reference numeral 80 in the figure is a short-circuit conductor, which short-circuits the turns of the coil as shown in FIG.

The above description has been made on the vertical LPCVD apparatus. However, since the substrate is heated by the heat radiation from the heating element of the electric furnace, the present invention is directed to the horizontal LPCVD apparatus in which the reaction tube is placed horizontally. Clearly applicable to

[0022]

According to the present invention, since the heat treatment apparatus having the structure described at the beginning is configured as described above, the effects described below can be obtained. In the apparatus according to claim 1, the cylindrical electric furnace is configured mainly with a large number of annular heater groups surrounding the reaction tube and stacked in the axial direction of the reaction tube, and the heater terminals are provided on the individual annular heaters. Since the terminals are connected outside the annular heater, the heating energy density in the axial direction of the electric furnace can be easily adjusted. This makes it possible to easily achieve temperature uniformity in the soaking zone of the reaction tube.

In the apparatus according to the second aspect, since the annular heater forming the electric furnace is formed in a simple shape, the electric furnace can have a simple structure. In the apparatus according to the third aspect, heat interference in the vertical direction of the heating element held in the annular heat insulating holding material is effectively prevented, and adjustment for temperature equalization in the soaking zone becomes easy.

In the apparatus of claim 4, the selection range of the material is widened depending on whether the separate portion is made of a normal heat insulating material, a metal, or the like. It becomes easy to adjust the thermal interference prevention effect from above and below. In the apparatus according to claim 5, focusing on the fact that the wafer in the reaction tube is heated by heat radiation, the separate parts of the heat insulating holding material form the ring forming the annular heat insulating holding material on opposite sides of the U-shaped cross section. Since it is made of a plate, it is possible to miniaturize the main body of the heat insulation retaining material having a U-shaped cross section.

According to the apparatus of claim 6, the electric furnace is provided with the heat insulating material between the annular heaters. Therefore, by changing the thickness of the heat insulating material depending on the axial position of the electric furnace, the axial direction of the electric furnace is changed. The energy density of can be easily adjusted. In the apparatus of claim 7, the heating energy of the annular heater itself is adjusted, and the adjustment of the energy density in the axial direction of the electric furnace becomes easier.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing an embodiment of a device configuration according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a first embodiment of an annular heater structure which constitutes the main constituent of the electric furnace in the present invention.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the annular heater structure which constitutes the main constituent of the electric furnace in the present invention.

FIG. 4 is an explanatory view showing an embodiment of a method for partially short-circuiting the annular heater heating element according to the present invention.

5 is an enlarged view of a main part of FIG.

FIG. 6 is an explanatory sectional view showing an example of the configuration of a conventional heat treatment apparatus.

[Explanation of symbols]

1 Reaction Tube 2 Electric Furnace 4 Wafer Group (Substrate) 10 Reaction Tube 20 Electric Furnace 40 Wafer Group (Substrate) 50 Annular Heater 50A Terminal 50B Heating Element 60 Insulation Spacer (Insulation Material) 70 Insulation Holding Material 70A ₁ Integrated Part 70A ₂ Ring Board 80 short-circuit conductor

Claims (7)

[Claims] 1. A reaction is carried out in a reaction tube while heating a substrate inserted in a reaction tube in a cylindrical shape with one side sealed by a cylindrical electric furnace arranged coaxially with the reaction tube outside the reaction tube. In a heat treatment apparatus for vapor-depositing a thin film on a surface of a substrate by introducing gas, the cylindrical electric furnace is mainly composed of a large number of annular heater groups surrounding a reaction tube and stacked in the axial direction of the reaction tube. In addition, a heater terminal is provided on each annular heater, and the terminals are connected outside the annular heater so that the energy density in the axial direction of the electric furnace can be adjusted. 2. The apparatus according to claim 1, wherein the annular heater that constitutes the electric furnace includes an annular heating element that surrounds the reaction furnace and a central side of the U-shaped section formed in a U-shaped cross section. A heat treatment apparatus, wherein the heat treatment apparatus is formed to have an annular shape so as to form an outer wall surface, and a heat insulating holding material that holds the heating element inside. 3. The apparatus according to claim 2, wherein the annular heat insulating holding member for holding the annular heating element inside the U-shaped cross section is formed by projecting an inner diameter side of the U-shape toward the inner side in the radial direction to form an inner diameter. A heat treatment device characterized by being made smaller than an annular heating element. 4. The apparatus according to claim 2 or 3, wherein the annular heat insulating holding member for holding the annular heating element inside the U-shaped cross section has two opposite sides of the U-shape and a center side thereof. A heat treatment apparatus comprising: an integral part having an inner diameter substantially equal to that of an annular heating element, and an integral part with a central side; and a ring plate formed separately from the central side and having an inner diameter smaller than that of the annular heating element. 5. The heat treatment according to claim 4, wherein the ring plates constituting the opposite sides of the U-shaped cross section of the annular heat insulating and retaining material are metal plates having a glossy surface. apparatus. 6. The heat treatment apparatus according to claim 1, wherein the electric furnace includes a heat insulating material between the annular heaters. 7. The apparatus according to any one of claims 1 to 6, wherein a part or all of the annular heaters of the plurality of annular heaters constituting the electric furnace are part of the annular heating element. A heat treatment device characterized by being short-circuited.