JPH0669147A - Vertical heat treatment furnace - Google Patents

Abstract

PURPOSE:To block intrusion of particles, produced from rotary mechanism for wafer boat, into a treating space. CONSTITUTION:In the vertical heat treatment furnace, a driven side permanent magnet 26 carried on a rotary shaft 52 for supporting a wafer boat is placed in a bearing space 50 isolated from outer air. The driven side permanent magnet 26 is coupled magnetically with a drive side permanent magnet 42 arranged on the outside thus rotating the rotary shaft 52. The driven side permanent magnet 26 is covered hermetically by a stainless steel cover member 66 thus blocking intrusion of produced particles into a treating space S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical heat treatment apparatus.

[0002]

2. Description of the Related Art Generally, when a semiconductor wafer is subjected to heat diffusion such as thermal diffusion or CVD, a large number of wafers are mounted on a wafer boat at predetermined intervals in the vertical direction, and the wafers are mounted on the wafer. The boat is placed on the heat-retaining cylinder, and the boat is loaded into the reaction container through the loading / unloading mechanism. And
By driving a rotating mechanism provided below the wafer boat, the processing gas is introduced into the reaction vessel while the wafer boat is rotated, and each wafer is subjected to desired heat treatment.

This will be described with reference to FIGS. 4 and 5. The processing space S in the quartz reaction vessel 2 having a ceiling and an open bottom has a cylindrical shape. A quartz wafer boat 6 mounted on the heat insulating cylinder 4 is provided. In this wafer boat 6, a large number, for example, 5
About 0 semiconductor wafers W are stacked at a predetermined interval in the vertical direction. A processing gas introduction pipe 8 connected to a processing gas source (not shown) for introducing a processing gas such as HCl gas or CF type gas into the processing container S is provided on one side of the lower portion of the reaction container 2. A gas exhaust pipe 10 connected to the other side and connected to a vacuum pump or the like (not shown)
Are connected. A bottom plate 12 made of, for example, stainless steel is detachably attached to the bottom of the reaction container 2 via an O-ring 14, so that the inside of the reaction container 2 can be sealed. The entire bottom plate 12 can be moved up and down by elevating means 15 such as a ball bearing.

As shown in FIG. 3, in the central portion of the bottom plate 12,
A rotating mechanism 13 for rotating the wafer boat 6 during heat treatment of the wafer is attached. This rotating mechanism 13
It has a bearing casing 16 fixedly attached to the bottom plate 12 by bolts 14, and the inside is configured as a bearing space 18 communicating with the processing space S. This bearing space 18
A rotary shaft 22 is rotatably supported in the inside by two bearings 20 which are vertically spaced apart from each other by a predetermined center-to-center distance L1, and the heat insulating cylinder 4 is mounted on the upper end of the rotary shaft 22. Has been done. And these two bearings 20
Is designed to support the entire load of the wafer and the like.

As the bearing 20, there is no need to use lubricating oil that causes contamination in the processing space S, so that the bearing 2 can be used.
A so-called ceramic bearing in which the outer ring 20A and the inner ring 20B of 0 are formed of stainless steel and the balls 20C are formed of ceramic is used. A magnet mounting shaft 24 extends downward from the lower portion of the rotary shaft 22, and a driven permanent magnet 26 divided into 12 poles along the circumferential direction is fixed to the shaft 24. A magnet casing 28 covering the driven-side permanent magnet 26 is connected to the lower end of the bearing casing 16, and a pulley shaft 30 is attached to the lower end of the magnet casing 28.

A pulley 34 is rotatably attached to the pulley shaft 30 via two pulley bearings 32 having a predetermined center-to-center distance L2. The pulley 34 is rotationally driven by a belt 38 that is interposed between the pulley 34 and the rotation shaft of the motor 36. Also, the pulley 34 has
A container-like drive-side magnet casing 40 is integrally provided so as to cover the side portion of the magnet casing 28 with a slight distance therebetween. A drive-side permanent magnet 42, which faces the driven-side permanent magnet 26 and is magnetically coupled to the driven-side permanent magnet 26, is provided on the inner surface of the casing 40 in the circumferential direction, for example, divided into 12 poles. .

Therefore, the bearing casing 16, the magnet casing 28 and the pulley shaft 30 are fixed to the bottom plate 12 side and do not move, and by rotating the pulley 34, the drive side permanent magnet 42 is integrally formed with the bottom casing 12 in the circumferential direction. Rotate to
At the same time, the driven permanent magnet 26 magnetically coupled to the magnet 42 also rotates to rotate the wafer boat 6. Therefore, by using the magnetic coupling, the rotating shaft 2 is kept in a state where the inside of the bearing space 18 is sealed from the outside air.
The rotational driving force is transmitted to the motor 2. Although not shown, a heater for heating is arranged on the side of the reaction vessel 2.

[0008]

By the way, the heat treatment of a wafer is usually carried out at a high temperature of about 1000 ° C. in a high vacuum state, and a corrosive gas such as HCl or CF is used as a processing gas. Therefore, the vicinity of the bearing 20 and the permanent magnet 26 for coupling also becomes a high temperature of about 200 ° C. Therefore, as the driven-side permanent magnet 26, a magnet made of, for example, a rare earth element having excellent heat resistance and strong magnetic force is used. However, since this type of magnet has a relatively hard but brittle characteristic, particles generated are generated in the bearing. There is a case where the metal flows from the space 18 to the processing space S to cause metal contamination. In order to prevent metal contamination of the wafer by the magnet, the driven permanent magnet 26 is entirely coated with nickel plating, for example.

However, even if the permanent magnet 26 is coated as described above, the coating peels off when the magnet receives some impact or when the driven side permanent magnet 26 is assembled, and particles are generated and metal contamination occurs. It had the improvement point that it caused. In particular, when the magnet material is exposed due to peeling of the coating, the magnet is corroded by the corrosive processing gas that enters the bearing space 18, and particles are further generated. The present invention has been made to pay attention to the above problems and to solve them effectively. An object of the present invention is to provide a vertical heat treatment apparatus capable of preventing particles generated from a rotating mechanism from entering the processing space.

[0010]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a rotating shaft for supporting a wafer boat accommodated in a processing space in a bearing space provided below the processing space. Rotatably supported by the bearing of the drive shaft, a driven-side permanent magnet is formed on the rotation shaft, and a drive-side permanent magnet for magnetically coupling the driven-side permanent magnet and rotating the driven-side permanent magnet is arranged outside the bearing space. In the vertical heat treatment apparatus, the covering member for covering the driven permanent magnet in the bearing space in a sealed state is formed.

In order to solve the above-mentioned problems, a second aspect of the present invention enables a rotating shaft, which supports a wafer boat accommodated in a processing space, to be rotated by a bearing in a bearing space provided below the processing space. A vertical heat treatment apparatus that supports and forms a driven-side permanent magnet of the rotating shaft, and arranges a drive-side permanent magnet that is magnetically coupled to the driven-side permanent magnet and rotates the driven-side permanent magnet outside the bearing space. In the above, the bearing space closer to the processing space than the bearing and the driven permanent magnet is introduced, and an inert gas inlet is introduced into the bearing space, and the introduced inert gas is accompanied by particles in the bearing space. And an inert gas discharge port for discharging the same.

[0012]

According to the first aspect of the present invention, the driven permanent magnet in the bearing space, which is magnetically coupled to the driving permanent magnet and is driven,
For example, since it is covered with a covering member made of stainless steel foil or the like in a completely sealed state, even if the coating or the like is peeled off from the permanent magnet and particles are generated, it is possible to prevent the particles from entering the processing space side. Become. According to the second aspect of the invention, in the bearing space that accommodates the bearing that supports the rotary shaft, the inert gas inlet and the inert gas outlet are provided closer to the processing space than the bearing and the driven permanent magnet. , The particles generated from the permanent magnet and the bearing are discharged from the inert gas discharge port together with the inert gas introduced into the bearing space, and therefore, the particles are prevented from entering the processing space side. Is possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the vertical heat treatment apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a rotating mechanism of a vertical heat treatment apparatus according to the present invention, and FIG. 2 is a schematic sectional view showing a vertical heat treatment apparatus according to the present invention. Incidentally, FIG.
The same parts as those shown in FIG. 5 are designated by the same reference numerals. First, the entire vertical heat treatment apparatus has the same configuration as that shown in FIG. 4, and the overall configuration will be described with reference to FIG.

The vertical heat treatment apparatus 44 has a ceiling portion, a bottom portion is opened, and the reaction container 2 is formed into a cylindrical shape.
The processing space S in the reaction container 2 is provided with the quartz wafer boat 6 mounted on the quartz heat insulating cylinder 4. In the wafer boat 6, for example, about 50 semiconductor wafers W are stacked and housed in the vertical direction with a predetermined space therebetween. A processing gas introduction pipe 8 connected to a processing gas source (not shown) for introducing a processing gas such as HCl gas or CF-based gas into the processing space S is connected to one side of the lower portion of the reaction vessel 2. On the other side, a gas discharge pipe 10 connected to a vacuum pump or the like (not shown) is connected. A heater 11 for heating is arranged on the side of the reaction container 2 so that the wafer W in the container 2 can be heated.

A bottom plate 12 made of, for example, stainless steel or the like is detachably attached to the bottom of the reaction vessel 2 through an O-ring 14 so that the inside of the reaction vessel 2 can be sealed. The entire bottom plate 12 can be moved up and down by elevating means 13 such as a ball bearing. As shown in FIG. 1, a rotation mechanism 46, which is a feature of the present invention, is attached to the center of the bottom plate 12 for rotating the wafer boat 6 during the heat treatment of the wafer.

More specifically, the rotating mechanism 12 includes the bottom plate 1
2 has a bearing casing 46 made of, for example, stainless steel attached and fixed by a bolt 14, and the inside thereof communicates with the processing space S. This bearing casing 46
A magnet casing 48 made of, for example, stainless steel for accommodating the driven-side permanent magnet 26 is integrally formed in the lower part of the same so as to communicate the inside thereof, and the lower part is sealed. Therefore, inside the bearing casing 46 and the magnet casing 4
The interior of 8 is communicated to form a bearing space 50. A rotary shaft 52 on which the heat insulation cylinder 4 is placed is vertically inserted into the bearing space 50. The rotary shaft 52 is inserted between the upper portion of the rotary shaft 52 and the inner wall of the bearing casing 46 and the rotary shaft 52. Bearings 54 and 56 are respectively provided between the lower portion and the inner wall of the magnet casing 48 to rotatably support the rotary shaft 52. in this case,
The upper large bearing 54 receives the entire load of the upper structure such as a wafer. By thus setting the distance between the two ceramic bearings 54, 56 large, it is possible to reduce the rattling of the rotary shaft 52.

As the bearings 54 and 56, the outer rings 54A and 56A and the inner rings 54B and 56B are made of stainless steel so that the lubricating oil that causes the contamination in the processing space S does not have to be used, and the balls are formed. A so-called ceramic bearing in which 54C and 56C are made of ceramic is used. On the rotary shaft 52 between the two ceramic bearings 54 and 56, the driven permanent magnet 26 divided into, for example, 12 poles along the circumferential direction thereof is fixed. A pulley shaft 58 is attached to the lower end of the permanent magnet casing 48, and a pulley 63 is rotatably attached to the shaft 58 via a pulley bearing 60. The pulley 63 is rotationally driven by a belt 38 provided between the pulley 63 and the rotation shaft of the motor 36. The pulley 63 is integrally provided with a container-like drive-side magnet casing 62 which covers the side portion of the magnet casing 48 with a slight distance therebetween. A drive-side permanent magnet 42, which faces the driven-side permanent magnet 26 and is magnetically coupled to the driven-side permanent magnet 26, is provided in the circumferential direction of the casing 62, for example, divided into 12 poles. .

Therefore, the bearing casing 46, the magnet casing 48, and the pulley shaft 58 are fixed to the bottom plate 12 side and do not move, and by rotating the pulley 63, the drive side permanent magnet 42 is integrated with this in the circumferential direction. As a result, the driven permanent magnet 26 magnetically coupled to the magnet 42 also rotates and rotates the wafer boat 6. Therefore, by using magnetic coupling, the rotational driving force is transmitted to the rotary shaft 52 in a state where the bearing space 50 is sealed from the outside air. An ordinary pulley receiving shaft 64 is provided between the upper portion of the drive-side magnet casing 62 and the outer periphery of the bearing casing 46, and the distance between the two pulley receiving shafts 60, 64 is increased. By taking such measures, the drive-side magnet casing 62 is configured to suppress rotational shake and the like.

A covering member 66, which is a feature of the first invention, is formed to cover the driven permanent magnet 26 in a sealed state. Specifically, the cover member 66 is attached to the upper and lower rotary shafts 52 of the driven-side permanent magnet 26, and is made larger than the radius of the magnet 26, for example, a pair of ring plates 68 made of stainless steel, It is composed of a cover foil 70 made of, for example, a stainless steel foil, which is connected by welding or the like across the outer peripheral sides of the upper and lower ring plates 68, completely seals the driven permanent magnet 26, and the inside and the bearing. Ventilation with the space 50 is blocked so that particles and the like generated inside do not float in the bearing space 50. The material of the covering member 66 is not limited to stainless steel, and can withstand high temperatures.
Moreover, any material may be used as long as it has excellent corrosion resistance.

The bearing casing 46 faces the bearing space 50A located above the upper ceramic bearing 54 and the driven permanent magnet 26, that is, on the side of the processing space S.
And an inert gas inlet 72 which is a feature of the second invention,
An inert gas outlet 74 is provided. Specifically, an inert gas introducing pipe 76 made of stainless steel, for example, having a diameter of about 6 mm is horizontally connected to the inert gas introducing port 72, and a gas source (not shown) is connected to the introducing pipe 76. The gas is introduced in the direction perpendicular to the rotary shaft 52. As the inert gas, for example, nitrogen gas (N ₂ ) can be used, but argon gas or helium gas can also be used, and for example, a flow rate of about 0.5 liter / min can be used. There is.

A pair of annular labyrinth rings 7 are provided above and below the rotary shaft 52 facing the inert gas inlet 72.
8 and 80 are formed, and the diameter of the labyrinth ring 78 on the side of the processing space S, that is, on the upper side is the ceramic bearing 54.
It is set to be slightly larger than the diameter of the labyrinth ring 80 on the side, that is, on the lower side.
A ring-shaped labyrinth space 83 having a slightly high atmospheric pressure is formed in each of the chambers 8 and 80, and the flow rate of the inert gas flowing downward is higher than that in the upward direction.

The inert gas discharge port 74 is positioned 180 ° opposite to the rotary shaft 52 and is positioned a short distance below the lower labyrinth ring 80, and is introduced. The inert gas is configured to be efficiently discharged together with the particles generated from the ceramic bearing 54 and the like. The inert gas exhaust port 78 is connected to an inert gas exhaust pipe 82 made of, for example, stainless steel with a vacuum pump (not shown) interposed therebetween. Further, the rotary shaft 52 is formed with a communication passage 84 for communicating the space at the lower end thereof with the upper bearing space 50A.
The atmosphere of the lower portion of the above can be efficiently discharged from the inert gas discharge port 74.

Next, the operation of this embodiment configured as described above will be described. First, a large number of semiconductor wafers W
The wafer boat 6 carrying the wafer is lifted by the elevating means 15 and carried into the reaction container 2, and the bottom plate 12 is used to move the reaction container 2
Seal the bottom opening of the. The inside of the processing container 2 is maintained at a predetermined heat treatment temperature, for example, 900 to 1200 ° C. by previously operating the heater 11 for heating, and the predetermined processing gas required for oxidation or thermal diffusion from the processing gas introduction pipe 8 For example, an HCl gas, a CF-based gas, and a carrier gas are introduced, and at the same time, the inside of the reaction container 2 is evacuated through a gas exhaust pipe 10 by a vacuum pump (not shown) to maintain the processing space S at a predetermined pressure, The heat treatment is applied to the wafer W.

During this heat treatment, in order to perform the uniform heat treatment of the wafer W, the rotating mechanism 46 provided at the lower portion of the reaction vessel 2 is driven to move the entire wafer boat 6 to, for example, 3 to 5.
Rotate at a rate of times / rpm. That is, by rotationally driving the motor 36 of the rotating mechanism 46, the rotational force is transmitted to the pulley 63 via the belt 38, and the driving side magnet casing 62 to which the pulley 63 and the driving side permanent magnet 42 are attached is moved 3 to 5 times. Rotate at a rate of / rpm. In this case, the casing 62 is supported by the two pulley bearings 60 and 64 that are separated by a relatively large distance, and rotates around the bearing casing 46 and the magnet casing 48 as fixed shafts.

When the drive-side magnet casing 62 rotates, the driven-side permanent magnet 2 magnetically coupled to it rotates.
6 follows and rotates, and as a result, the rotating shaft 52 rotates while being supported by the two ceramic bearings 54 and 56 provided apart from each other.
Will rotate. Also, ceramic bearings 54, 5
6, the bearing space 50 in which the driven side permanent magnet 26 is housed
The inside is communicated with the upper processing space S side, and an inert gas such as nitrogen gas is introduced into the bearing space 50 through an inert gas introducing pipe 76 at a flow rate of, for example, 0.5 liter / min. At the same time, the introduced inert gas is evacuated and discharged from the inert gas discharge pipe 82.

In such a state, even if particles are generated from the driven permanent magnet 26 that has been subjected to the coating treatment during the assembling or due to some impact,
The magnet 26 is completely sealed by a cover member 66 made of stainless steel or the like so that the atmosphere inside the cover member is the bearing space 5
Since the particles are prevented from leaking into the inside of 0, it is possible to reliably prevent the particles generated in the magnet 26 from entering the processing space S side. In addition, the cover member 6
By the action of 6, it is possible to prevent the driven-side permanent magnet 26 from being exposed to the atmosphere in the bearing space 50 in which the corrosive process gas may enter from the process space S side. It is also possible to prevent the magnet 26, which is made of a rare earth element, from being easily corroded.

As described above, since the driven permanent magnet 26 is completely sealed by the covering member 66, the magnet 2
Particles generated due to 6 are the covering members 66.
It can be prevented from being confined inside and affecting the outside, and metal contamination resulting from this can be prevented. On the other hand, as the rotating shaft 52 rotates, the two ceramic bearings 54, 56 cause an outer ring 54 made of stainless steel, which is softer than the ceramic balls 54C, 56C.
Particles tend to be generated from A, 56A and the inner rings 54B, 56B, but since an inert gas such as nitrogen gas is introduced into the bearing space 50A on the processing space S side of these bearings, the generated particles are Since this inert gas is discharged from the inert gas discharge pipe 82, it is possible to prevent the particles from entering the processing space S side and causing metal contamination.
In addition, even if the covering member 66 is damaged and particles from the magnet 26 leak out, the particles are discharged.
Emitted from 2.

In particular, when the inert gas is introduced, an annular labyrinth space 83 is provided in a portion facing the inert gas introduction port 72, so that the atmospheric pressure in this space 83 becomes slightly higher than the ambient pressure. Therefore, as shown by arrows A and B, the labyrinth space 83 is forcibly generated as a flow of the inert gas in the vertical direction. Moreover, since the inert gas discharge port 74 is positioned at a position slightly lower than the lower labyrinth ring 80, the downward gas flow indicated by the arrow B causes the ceramic bearings 54 and 56 to generate. The particles are guided and discharged toward the inert gas discharge port 74, and as a result, the particles are discharged above the processing space S.
It is possible to greatly reduce the possibility of entering the side. Furthermore, the diameter of the labyrinth 80 on the lower side is made equal to that of the labyrinth 78 on the upper side.
Lower labyrinth 8 by setting the diameter smaller than
Since the gap between the peripheral portion of 0 and the inner wall of the bearing casing 46 is set to be larger than the gap on the upper side, the arrow B
The flow rate of the inert gas in the downward direction is increased, and as a result, the intrusion of particles upward can be reliably prevented.

Further, as shown by the arrow A, the bearing space 5 is introduced from the processing space S side by the upward flow of the inert gas.
It is possible to prevent the corrosive process gas from entering the inside. Therefore, it is possible to prevent the metal material in the bearing space 50 from corroding, and in particular, even if the covering member 66 is damaged, it is possible to interrupt the contact between the magnet 26 inside and the processing gas. Can be prevented from corroding. The type and flow rate of the introduced inert gas are selected so that they do not affect the process conditions applied to the wafer W during the heat treatment. Further, in the lower part of the bearing space 50, the atmosphere containing particles generated from the lower ceramic bearing 56 tends to settle, but the air in this part is discharged through the communication passage 84 formed in the rotary shaft 52 with the inert gas. Since it is sucked toward the tube 82 side, it is possible to efficiently discharge the particles generated in the lower ceramic bearing 56.

The various bearings for the rotary shaft 52 and the drive-side magnet casing 62 are, for example, 20 times during heat treatment.
The bearing balls are dimensioned so that they can be accurately tightened at 0 ° C. Therefore, when the bearing is rotated at room temperature such as when transferring a wafer, the bearing itself may be slightly rattled, and the rotary shaft 52 and the drive-side magnet casing 62 may be slightly rattled. To do. However, in the present embodiment, between the two ceramic bearings 54 and 56 and the two ordinary pulley bearings 60 and 6 are used.
4 has a predetermined large span in comparison with the conventional device, and the rotary shaft 52 and the drive side magnet casing 6 are provided.
Since No. 2 is supported, it is possible to significantly suppress the rattling at the time of rotation at room temperature.

In the above embodiment, the covering member 66, which is the feature of the first invention, and the inert gas inlet port 76 and the inert gas discharge port 74, which are the features of the second invention, are both provided. I explained about the case, but any one of these
You may make it provide one structure. Further, in the above-described embodiment, the case where the present invention is applied to the rotating mechanism having a structure in which the respective bearings are vertically separated from each other and a predetermined span is provided, but the present invention is not limited to this and is shown in FIG. As described above, for example, the cover member 66, the inert gas inlet, and the inert gas outlet (not shown) may be provided in the rotating mechanism having the same configuration as that described in the conventional device of FIG.

[0032]

As described above, according to the vertical heat treatment apparatus of the present invention, the following excellent operational effects can be exhibited. According to the first aspect of the invention, since the driven permanent magnet of the magnetic coupling is covered with the covering member, it is possible to confine particles generated from the magnet and prevent the particles from entering the processing space. It is possible to suppress the occurrence of contamination. According to the second invention,
Since the particles generated by introducing the inert gas into the bearing space and discharging the inert gas are removed, it is possible to prevent the particles generated in the bearing space from invading the processing space. It is possible to suppress the occurrence of contamination.

[Brief description of drawings]

FIG. 1 is a sectional view showing a rotating mechanism of a vertical heat treatment apparatus according to the present invention.

FIG. 2 is a schematic sectional view showing a vertical heat treatment apparatus according to the present invention.

FIG. 3 is a sectional view showing a rotation mechanism of a modified example of the invention.

FIG. 4 is a schematic sectional view showing a conventional vertical heat treatment apparatus.

FIG. 5 is a sectional view showing a rotating mechanism of a conventional vertical heat treatment apparatus.

[Explanation of symbols]

 2 Reaction vessel 6 Wafer boat 26 Driven side permanent magnet 42 Driven side permanent magnet 48 Magnet casing 50 Bearing space 52 Rotating shafts 54, 56 Ceramic bearing 62 Driven side magnet casing 66 Covering member 68 Ring plate 70 Covering foil 72 Inert gas Inlet port 74 Inert gas outlet port 76 Inert gas inlet pipe 82 Inert gas outlet pipe 83 Labyrinth space

Claims (2)

[Claims] 1. A rotary shaft for supporting a wafer boat accommodated in the processing space is rotatably supported by a bearing in a bearing space provided below the processing space, and a driven-side permanent magnet is formed on the rotary shaft. In the vertical heat treatment apparatus, in which a drive side permanent magnet that is magnetically coupled to the driven side permanent magnet and rotates the driven side permanent magnet is arranged outside the bearing space, the driven side permanent magnet in the bearing space is sealed. A vertical heat treatment apparatus, wherein a cover member for covering in a state is formed. 2. A rotary shaft for supporting a wafer boat housed in the processing space is rotatably supported by a bearing in a bearing space provided below the processing space to form a driven side permanent magnet. In addition, in the vertical heat treatment apparatus in which a drive side permanent magnet for magnetically coupling with the driven side permanent magnet and rotating the driven side permanent magnet is arranged outside the bearing space, the treatment is performed more than the bearing and the driven side permanent magnet. A bearing space on the space side is provided, and an inert gas inlet is provided in the bearing space, and an inert gas outlet is provided for discharging the introduced inert gas together with particles in the bearing space. A vertical heat treatment apparatus characterized in that