JP2590351B2 - Heat treatment furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat treatment furnace.

2. Description of the Related Art In order to form an oxide film on a semiconductor wafer, for example, a silicon wafer, a processing furnace using an electric heater is generally used. This type of processing furnace basically includes an inner tube made of quartz or the like, that is, a furnace core tube, inside an outer tube made of a heat-resistant metal material, and a heat equalizing tube, an electric heater, And a heat insulating layer of ceramic wool or the like having an appropriate thickness is provided on the inner wall of the outer cylinder.

On the other hand, since the formation of an oxide film on a silicon wafer or the like is related to the processing time, temperature and pressure, great care should be taken in controlling these factors. Speaking of temperature, considering the growth rate of the oxide film, the wafer is processed while maintaining the furnace temperature at 1000 to 1200 ° C, and when removing the processed wafer outside the furnace, the temperature is uniformly lowered to about 700 ° C. Thus, control is performed so as not to adversely affect the diffusion processing of the wafer carried into the furnace next. That is, in the temperature range of about 300 to 500 ° C., it is necessary to repeatedly raise and lower the temperature in a short time.

In order to satisfy such demands, a high-temperature type electric heater is disposed around the furnace core tube, and a gas for promoting heat retention or cooling is supplied to the heat insulating layer on the outer peripheral side of the electric heater. Is done. One example of this is disclosed in JP-A-59-176586.
No. 1993.

Problems to be Solved by the Invention In the prior art as described above, a gas having a small thermal conductivity for promoting heat retention and a gas having a large thermal conductivity for promoting cooling,
It is necessary to change the input in the heat insulating layer at the time of wafer processing and loading / unloading. However, in practice, for example, despite the fact that the temperature in the furnace is being lowered, a part of the gas for promoting heat retention remains in the heat insulating layer, and a long time is required for the temperature to be lowered. Therefore, work efficiency is poor. In addition, it is difficult to obtain a uniform cooling rate over the entire length of the furnace, and it is difficult to reduce the uniformity of the product.

Therefore, an object of the present invention is to solve the above-mentioned disadvantages of the related art by providing a novel furnace structure.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention basically engages a hanging pin with a ferrite electric heater supported by a separator, Is extended along the outer peripheral surface of the mold, and further, an air chamber is arranged in a blanket located approximately outside the center in the longitudinal direction of the mold, and cooling air is supplied into the blanket from a hole in a side wall of the air chamber. Use technical means to:

Action The hanging pin transfers the preheating of the electronic heater and the surrounding high temperature to the outer cylinder side, facilitating the temperature drop, preventing the drip of the ferrite electric heater with low high temperature strength, and preventing the broken line of the heater from occurring. prevent. Further, the cooling air supplied from the air chamber into the blanket cools the heat insulating layer while flowing through the heat insulating layer.

In the present invention, the ends of the suspension pins that come into contact with and suspend the electric heater are exposed on the outer surface of the mold that forms the inner layer of the heat insulating layer.

Therefore, the heat in the furnace is easily dissipated out of the mold via the hanging pins, allowing a rapid decrease in the furnace temperature.
During heating of the furnace, the supply of cooling air is interrupted. At this time, the air left in the air chamber is heated by the heat of the heater and forms a part of the heat insulating layer, and does not hinder the temperature rise.

EXAMPLE A heat treatment furnace (1) has an outer cylinder (2) made of a heat-resistant metal material. The outer cylinder (2) is arranged with its longitudinal direction being horizontal, and an air-permeable blanket (3) made of ceramic wool is stretched over the entire inner wall surface of the outer cylinder (2). Inside the blanket (3), there is arranged a cylindrical mold (4) made of a solid material integrally formed by fixing ceramic fibers with a binder. On the inner wall surface of the mold (4) having some air permeability, a plurality of spaced grooves (5) which open inward in the radial direction are provided so as to extend in the longitudinal direction, and these grooves (5) are provided. Then, a separator (6) made of an insulating alumina is fitted. The separator (6) has an opposing side wall of about 15 as shown in FIG.
A groove (7) formed so as to be inclined at an angle,
A spirally wound ferrite-based electric heater (8) is inserted into the groove (7), and the separator (6) holds the electric heater (8). As the electric heater (8), Fe-
A Cr-Al-based Pyromax PXDS material (trade name) is preferred.

A hanging pin (9) is engaged in place on the electric heater (8). The hanging pin (9) is made of a material having good heat conductivity, has a substantially U-shape, and is engaged with the electric heater (8) at the bottom of the U-shaped portion to suspend the heater (8). The tip of the hanging pin (9) is extended along the outer peripheral surface of the mold (4),
The electric heater (8) is held together with the hanging pins (9) together with the separator (6). The suspending pin (9) functions to prevent sagging of the ferrite electric heater (8) having a low high-temperature strength at a high temperature beforehand and to radiate heat of the heater to the outside.

A heat equalizing tube (10) and a furnace core tube (11) are arranged inside a spirally wound electric heater (8). The soaking tube (10) receives the heat generated by the electric heater (8), and receives the heating core tube (11).
And heats uniformly, and is formed of a silicon carbide-based material. The furnace core tube (11) is made of quartz, and is also called a reaction tube, in which a wafer is arranged. The furnace core tube is provided with a cap (not shown) at an opening for loading and unloading a wafer, and several ports (not shown) for supplying and discharging a reaction gas such as oxygen and hydrogen therein. Can be

(12) shows a heat seal, and (13) shows a furnace opening sleeve.

A semicircular air chamber (1) having a rectangular cross-section is provided in a blanket located outside the central portion in the longitudinal direction of the mold (4).
4) Embed. The side wall of this air chamber (14) has many holes (1
Cooling air supplied into the room from the central port (16) is provided through the hole (15) into the blanket (3) and the mold (14) to cool and suspend the heat insulating layer. The inside of the furnace is cooled through the pins (9) and the furnace core tube (11)
Allows for rapid cooling of the interior. As shown in FIG. 4, when the furnace body is long, a pipe (17) for introducing auxiliary air is buried in the blanket (3) in the circumferential direction separately from the air chamber, and cooling air is sent to the pipe (17). The cooling air is supplied into the blanket (3) from the small holes of the (1), thereby enabling uniform cooling of the heat insulating layer. A port (not shown) is attached to the pipe (17). A plurality of air discharge holes (18) are drilled upward at appropriate places on the outer cylinder (1).

After processing the wafer while maintaining the temperature in the furnace at 1000 to 1200 ° C., cooling air is supplied to the chamber (14) to cool the blanket (3), the mold (4), and the hanging pins (9) to radiate heat, The furnace temperature is reduced to about 700 ° C. At this temperature, the processed wafer is unloaded and the unprocessed wafer is loaded into the furnace. After loading the unprocessed wafer into the furnace, the supply of cooling air to the chamber (14) is interrupted to form a heat insulating layer of air. Next, electricity is supplied to the electric heater (8) to cause the electric heater (8) to generate heat and heat the soaking tube (10). The furnace core tube (11) is heated by the radiant heat of the soaking tube (10), and the furnace core tube (11) is heated.
The temperature inside is raised to 1000-1200 ° C. Of course, during the wafer diffusion process, the caps of the outer tube (2) and the furnace core tube (11) are closed to shut off the inside from the outside.

The heat equalizing tube (10) is supported by a pipe (19) extending in the longitudinal direction so as to be orthogonal to the electric heater (8), and furthermore, at both ends thereof through a sleeve made of quartz wool insulation (20). (21) is held.

Effect Since the present invention employs the hanging pins and the cooling chamber,
Rapid cooling is possible, and the working efficiency can be improved. In addition, since the cooling chamber is provided in the central part of the furnace in the circumferential direction, the temperature inside the furnace can be uniformly lowered, and uniform heat treatment can be performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an example of the present invention, FIG. 2 is a transverse sectional view taken along line II-II of FIG. 1, FIG. 3 is a perspective view of a cooling chamber,
FIG. 4 is a plan view of a blanket, and FIG. 5 is a partially enlarged view showing a hanging pin. In the figure: 2 ... outer cylinder, 3 ... blanket, 4 ... mold, 6 ... separator, 8 ... electric heater, 9 ... hanging pin, 14 ... cooling chamber, 17 ... pipe.

Claims (1)

(57) [Claims] 1. An outer cylinder made of a heat-resistant metal material, a blanket stretched on an inner wall of the outer cylinder, a mold made of ceramic wool disposed inside the blanket, and a groove formed separately from an inner wall of the mold. A fitted separator, a ferrite-based electric heater spirally wound around the separator, and a plurality of suspensions having a portion engaged with the electric heater and having a tip extending along the outer peripheral surface of the mold. An air chamber circumferentially embedded in a blanket located outside the center of the pin in the longitudinal direction of the mold, and cooling air supplied to the air chamber is supplied through a hole in a side wall of the air chamber. A heat treatment furnace characterized in that it can flow into a blanket and a mold.