JPH0517143Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is mainly used to investigate the physical and chemical properties of various materials under high vacuum and high temperature conditions, research and development of new materials, such as heat treatment of wafers, etc. This is particularly excellent for transparent electric furnaces used for various purposes such as crystal growth, vapor phase growth while observing the surface condition of samples during high-temperature gas flow, and production furnaces that require rapid temperature rise and stable temperature maintenance. The present invention provides an improved type of high-vacuum heat treatment equipment that is suitable for energy saving and employs a gold mirror tube that has excellent heat uniformity characteristics.

(Conventional technology) In the past, the physical and chemical properties of various materials were investigated under high vacuum and high temperature conditions, and high vacuum heat treatment equipment was used to conduct research and development of new materials. This required a long soaking zone and the overall size of the device to be simplified.

In addition, the electric furnace 1 shown in Figure 1 used in this type of conventional equipment does not use ordinary heat insulating material, but instead uses a gold mirror tube with a thin gold film coated on the inner surface of cylindrical Pyrex glass. Special measures were taken to extend the soaking period of the electric furnace by making the pitches of the spiral-shaped Inconel sheath heater tighter at both ends.

However, since this transparent electric furnace uses a transparent quartz cylinder over the entire length L0 as the furnace core tube ₂ , the heat from the transparent electric furnace 1 is transferred by heat conduction through the transparent quartz tube material.
Radiation in the quartz tube, convection conduction in the gas atmosphere, etc. raise the temperature of the vacuum-sealed metal flange 3, causing leaks from there and lowering the degree of vacuum.

The temperature distribution characteristics in the furnace at this time are as shown by the dotted line in FIG. 4 when the vertical axis is the temperature inside the furnace (° C.) and the horizontal axis is the distance inside the furnace (mm). Therefore, even if measures are taken to prevent this drawback, such as by making the distance between the electric furnace 1 and the metal flange 3 sufficiently long, or by providing a water-cooled structure for the metal flange, the entire device will require a lot of space and the structure will become complicated. Naturally, the soaking zone in the electric furnace 1 was shortened due to the loss of heat.

(Technical Issues) The present invention was developed in view of the shortcomings of the prior art, and it prevents the temperature increase due to heat conduction, radiation, convection, etc. to the metal flange part and the accompanying decrease in the degree of vacuum, and The technical challenge is to propose an electric furnace in which even if a short furnace core tube is adopted, the temperature rise at the metal flange part is small, heat loss is reduced, and the soaking zone inside the electric furnace can be set sufficiently long. It is something.

(Technical means) In order to solve the above-mentioned technical problem, the present invention has created a core tube, which is a normal transparent quartz tube inserted into an electric furnace, with a conventional configuration, and both ends of the core tube. By using an opaque quartz material with low thermal conductivity for the metal flange part, the temperature rise in the metal flange part is reduced. The configuration is as follows.

Reference numeral 10 denotes a high vacuum heat treatment apparatus, which is roughly divided into a high vacuum exhaust unit 11, a furnace core tube 12, and a transparent electric furnace 1.
3 and a temperature controller 14.

The high vacuum exhaust unit 11 has a vacuum degree of approximately 10 ^-6
A rotary diffusion pump 15 capable of evacuation up to Torr is employed, and a gasket 16 of the high vacuum evacuation unit 11 and a metal flange 17 attached to the furnace core tube 12 with a vacuum seal are connected via a flexible pipe 18. be. 19 and 20 are vacuum valves.

The transparent electric furnace 13 uses a gold mirror tube 21, which is a transparent Pyrex tube coated with a thin gold film on the inner wall, so that it reflects approximately 95% or more of infrared rays on the inside, and at the same time transmits visible rays to the outside. The total length between the supporting portions 22 and 23 at both ends thereof is approximately L.

Reference numeral 24 denotes a heating element heater which is inserted into the transparent electric furnace 13 and wound in a spiral manner. Appropriate measures have been taken to improve heat uniformity, such as by making the sample heating area denser in the vicinity and roughly changing the pitch of the sample heating area in the center.

The heating element heater 24 employs a nichrome wire or the like sheathed in a heat-resistant metal Inconel, insulated with magnesium oxide in the middle, and welded the heater part and Inconel at the tip to form a non-inductively wound structure. .

Therefore, the infrared rays emitted from the heating element heater 24 of the transparent electric furnace 13 enhance the heating and soaking effect of the sample placed in the furnace core tube 12, and even during heating, changes in the shape and color of the sample inside the furnace can be observed with the naked eye. It is made for observation. Further, the part where the furnace core tube 12 is inserted into the transparent electric furnace 13 is made of transparent quartz material, and the supporting portion 22 of the transparent electric furnace 13 of the furnace core tube 12,
Opaque furnace core tubes 25A and 25B made of opaque quartz are formed with both end portions projecting outward from 23, and the furnace core tube 12 made of transparent quartz is heated at the positions of the supports 22 and 23, which are fixed to a pedestal 26. They are integrated by welding or the like. The total length of each of the opaque furnace core tubes 25A and 25B at both ends, that is, the distance from the support part 22 to the metal flange 17, has a length l, and the distance from the metal flange 27 at the other end to the support part 23. have substantially the same length l.

Reference numerals 28 and 29 denote support frames in which the metal flanges 17 and 27 are supported and fixed on the frame 26, respectively, and hold the furnace core tube 12 substantially horizontally.

Reference numeral 30 denotes a sample inlet/outlet provided in the metal flange 27, and the metal flange 27 is attached to the opaque furnace core tube 25B with a vacuum seal applied thereto.

The temperature controller 14 has a built-in microcomputer, and the transparent electric furnace 1 is controlled by its program circuit.
3, the temperature is automatically controlled according to a desired program such as heating, holding, and cooling.

Next, a comparison between the case where a conventional transparent quartz material is used for both ends of the furnace core tube 12 and the case where an opaque quartz material is used as in this embodiment will be explained.

The thermal conductivity of transparent quartz material and opaque quartz material (both manufactured by Toshiba Ceramics) is 0.057 cal/cm sec°C (800°C) for transparent quartz material and 0.053 cal/cm sec°C (800°C) for opaque quartz material. At this time, the temperature rise of the metal flanges 19 and 27 is approximately 100°C at a furnace temperature of 800°C, in the case of transparent quartz material, total length 1000 mm, l = 200 mm, and in the case of opaque quartz material, total length 800 mm, l = 100 mm. Therefore, if opaque quartz material is used, even if the length l of both ends is short, the metal flange 1
9 and 27, the temperature rise is small and water cooling is not necessary.

In addition, the length of the soaking zone in the transparent electric furnace 14 having length L is 48% of the furnace length in the case of transparent quartz material when the furnace length L = 508 mm when the controller keep temperature is 800°C in the air atmosphere. is ±5℃, 30% of the furnace length is ±2℃, and in the case of opaque quartz material, at furnace length L = 508 mm, 70% of the furnace length is ±5℃,
and 50% of the furnace length is within the range of ±2°C. (See Figure 4) (Operation) The above technical means operates as follows.

First, the sample inlet/outlet 30 is opened and a heating sample is placed therein approximately in the center of the furnace core tube 12, and then the sample inlet/outlet 30 is closed.

Next, the vacuum valves 19, 20, etc. are opened, and the rotary diffusion pump 15 of the high vacuum exhaust unit 11 is opened.
etc. to create a high vacuum inside the furnace core tube 12.
Exhaust to 10 ^-6 Torr. At this time, the furnace core tube 1
In order to set the inside of 2 to another gas atmosphere, a rare gas or the like may be filled.

Thereafter, the vacuum valves 19, 20, etc. are closed, and the temperature controller 14 is operated to cause current to flow through the heating element heater 24, and the sample is heated by radiant heat such as infrared rays.

At this time, the radiant heat is reflected inside by the gold mirror tube 21 and does not pass through to the outside, so the sample can be heated efficiently.Also, all visible light is transmitted to the outside, so the sample inside the furnace is heated. You can observe changes in shape and color.

On the other hand, since the radiant heat from the heating element heater 24 that irradiates the opaque furnace core tubes 25A, 25B formed at both ends of the furnace core tube 12 has poor thermal conductivity, the radiant heat from the opaque furnace core tubes 25A, 25B is transferred from the metal flange 17
Less heat is transferred to 27.

Therefore, the short opaque furnace core tube 25A, 2 with a total length l
Even if 5B is adopted, the temperature rise of the metal flanges 17, 27 is small and there is little heat loss, so the soaking zone in the transparent electric furnace 13 can be widened and a constant degree of vacuum can be maintained at all times. I can do it.

In addition, the water cooling device is specially equipped with metal flanges 17, 27.
There is no need to add it to the part.

(Effects) The present invention has the following unique effects.

In particular, since a furnace core tube made of opaque quartz material with low thermal conductivity is adopted at both ends of the furnace core tube 12, heat conduction of the furnace core tube 12, radiant heat in the furnace, convection in the gas atmosphere, It is possible to prevent the temperature rise of the metal flanges 17, 27 due to heat conduction, etc.
There are great advantages such as less heat loss in the furnace and the soaking zone can be set to be sufficiently long.

[Brief explanation of the drawing]

FIG. 1 shows the prior art. Fig. 2 to Fig. 4 show an embodiment of the present invention, Fig. 2 is an overall configuration diagram of a high vacuum heat treatment equipment, Fig. 3 is a structural diagram of main parts of a transparent electric furnace, and Fig. 4 is a vertical axis. Furnace temperature (℃)
FIG. 2 is an explanatory diagram showing temperature distribution characteristics with the distance within the furnace (mm) taken on the horizontal axis. 12...Furnace core tube, 13...Transparent electric furnace, 25
A, 25B... Opaque furnace core tube, 17, 27... Metal flange.

Claims (1)

[Scope of utility model registration request] The part of the furnace core tube 12 inserted into the transparent electric furnace 13 is made of transparent quartz material, and the parts extending outside from the transparent electric furnace 13 that connect to the metal flanges 17 and 27 at both ends are heated. High vacuum heat treatment equipment made of opaque quartz material with low conductivity.