JP2008244409A - Heat treatment method and heat treatment apparatus - Google Patents

Abstract

An object of the present invention is to provide damage to a peripheral part of a furnace port due to a direct contact between a lid and a peripheral part of a furnace port due to an airtight member being crushed between the lid and the peripheral part of the furnace port during decompression. Prevents rubbing of the periphery of the furnace mouth.
A holder 20 on which a workpiece w is mounted in multiple stages is placed, and a lid 17 that opens and closes the furnace port 3a, and loading / unloading of the holder 20 into and out of a processing vessel 3 and a lid 17 are performed. In the heat treatment apparatus 1, which includes an elevating mechanism 18 that opens and closes and an annular airtight member 26 that is provided on the lid body 17 and seals between the furnace port peripheral portion 3 f of the treatment container 3. The pressing force reducing means 37 is provided for reducing the pressing force of the pressure difference between the inside and outside due to the pressure reduction when the pressure inside the pressure reducing device 3 is reduced.
[Selection] Figure 1

Description

  The present invention relates to a heat treatment method and a heat treatment apparatus.

  In the manufacture of semiconductor devices, various types of processing apparatuses (semiconductor manufacturing apparatuses) are used to perform processing such as oxidation, diffusion, and CVD (Chemical Vapor Deposition) on an object to be processed such as a semiconductor wafer (hereinafter also referred to as a wafer). Is used. As one of the processing apparatuses, a batch type heat treatment apparatus capable of performing heat treatment on a large number of objects to be processed at one time, for example, a vertical heat treatment apparatus is known (for example, see Patent Document 1).

  This heat treatment apparatus has a furnace port at the bottom, and places a processing vessel (process tube) that can accommodate a wafer and can perform a predetermined heat treatment under reduced pressure, and a holder (boat) on which the wafers are mounted in multiple stages. And a lid for opening and closing the furnace port, a lifting mechanism for loading and unloading the holder into the processing container, and opening and closing the lid, and a periphery of the furnace port of the processing container provided on the lid And an annular hermetic member (O-ring) for sealing.

  The lid is connected to the lifting mechanism via the lid base in order to make the lid uniformly adhere to the peripheral edge of the furnace port, and the lid is closed between the lid and the lid base. A spring for biasing and a regulating member for regulating the gap between the lid body and the lid body base portion at a predetermined distance against the biasing force of the spring are interposed.

JP 2001-237238 A

  However, in the heat treatment apparatus, due to the structure described above, a pressure difference between the inside and outside acts on the lid body in addition to the biasing force (pressing force) of the spring when the inside of the processing container is depressurized. Since it is proportional to the pressure receiving area (πr2) and increases as the diameter of the wafer increases (increase in diameter), the hermetic member is excessively crushed by an increase in the pressing force of the lid, and the durability of the hermetic member is reduced. And the lid body is in direct contact with and pressed against the periphery of the furnace port. When the lid body is made of metal and the periphery of the furnace port is made of quartz, an excessive force is applied to the periphery of the furnace port. There was a problem that damage such as cracks or breakage occurred in the peripheral edge of the mouth. In addition, when the lid is made of metal and the periphery of the furnace port is also made of metal, there is no such problem, but rubbing occurs due to the difference in thermal expansion between the two, and this rubbing causes the metal contamination of the wafer. There is a risk of becoming.

  The present invention has been made in consideration of the above circumstances, and can prevent the airtight member from being excessively crushed during decompression, improve the durability of the airtight member, and directly contact the peripheral portion of the lid and the furnace port. It is an object of the present invention to provide a heat treatment method and a heat treatment apparatus capable of preventing damage to the peripheral edge of the furnace port and occurrence of rubbing between the lid and the peripheral edge of the furnace port due to the above.

  In order to achieve the above object, among the present inventions, the invention according to claim 1 is such that the object to be processed is mounted in multiple stages on a holder placed on the upper part of the lid that opens and closes the furnace port at the lower part of the processing container. In the heat treatment method in which the lid body is raised by an elevating mechanism, the holder is carried into a heat treatment furnace, the furnace port is closed with a lid body through an airtight member, and the object to be treated is heat-treated under a predetermined reduced pressure. Further, the pressing force of the pressure difference between the inside and outside due to the reduced pressure among the pressing force acting on the lid when the pressure in the processing container is reduced is reduced.

  The invention according to claim 2 has a furnace opening in the lower part, and places a processing container capable of performing a predetermined heat treatment under reduced pressure and containing a processing object, and a holder on which the processing objects are mounted in multiple stages. And a lid for opening and closing the furnace port, a lifting mechanism for loading and unloading the holder into the processing container, and opening and closing the lid, and a periphery of the furnace port of the processing container provided on the lid In a heat treatment apparatus comprising an annular hermetic member for sealing, pressing for reducing the pressing force of the pressure difference between the inside and outside due to the reduced pressure out of the pressing force acting on the lid body when the pressure in the processing container is reduced A force reducing means is provided.

  According to a third aspect of the present invention, the lid body is connected to the elevating mechanism via the lid base portion, and a spring that biases the lid body in the closing direction between the lid body and the lid base portion, A regulating member for regulating the gap between the lid and the lid base portion at a predetermined interval against the biasing force of the spring is provided.

  According to a fourth aspect of the present invention, the pressing force reducing means includes a stepping motor that drives the lifting mechanism, a closing position sensor that detects that the lid is closed, and the lid is closed by the closing position sensor. And a controller that reversely rotates the stepping motor by a predetermined angle so as to urge the lid in the opening direction when the inside of the processing container is decompressed.

  The invention according to claim 5 is characterized in that the pressing force reducing means is provided in at least one of the fixing portion for fixing the peripheral edge of the furnace port of the processing vessel, the fixing portion and the lid body, and And a movement preventing member that prevents the lid from further moving in the closing direction from the closed position when the pressure in the processing container is reduced.

  The invention according to claim 6 is characterized in that the pressing force reducing means is provided in at least one of the fixing portion for fixing the peripheral edge of the furnace port of the processing vessel, and the fixing portion and the lid body, and A fluid pressure expansion / contraction mechanism is provided that takes the reaction force to separate the lid from the furnace port when the processing container is depressurized.

  The invention according to claim 7 is characterized in that the pressing force reducing means is provided between the lid body and the lid body base portion, and the space between the lid body and the lid body base portion when the inside of the processing container is decompressed. An interval fixing mechanism for fixing the lid to the interval when the lid is closed is provided.

  According to the present invention, the pressing force of the pressure difference between the inside and outside of the pressing force acting on the lid during pressure reduction in the processing vessel is reduced, so that the airtight member can be prevented from being excessively crushed during pressure reduction. It is possible to improve the durability of the hermetic member and to prevent damage to the peripheral part of the furnace port and rubbing of the peripheral part of the furnace port due to the direct contact between the cover and the peripheral part of the furnace port. it can.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view schematically showing a heat treatment apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic view showing a method for reducing the surface pressure at which the lid presses the furnace port by controlling the height position of the lid. FIG.

  In FIG. 1, reference numeral 1 denotes a vertical heat treatment apparatus which is one of semiconductor manufacturing apparatuses. This heat treatment apparatus 1 accommodates a large number of semiconductor wafers w to be processed at one time, for example, heat treatment such as reduced pressure diffusion. A vertical heat treatment furnace 2 is provided. The heat treatment furnace 2 includes a processing container 3 for storing wafers w in multiple stages and performing a predetermined heat treatment, a cylindrical heat insulating material 4 surrounding the processing container 3, and an inner peripheral surface of the heat insulating material 4. A heating resistor (also referred to as a heater wire) 5 arranged mainly in a spiral or meandering manner is mainly provided. The upper end portion of the tubular heat insulating material 4 is closed. A heater (heating device) 6 is constituted by the heat insulating material 4 and the heating resistor 5.

  The heat treatment apparatus 1 includes a base plate 7 for installing the heater 6. The base plate 7 is formed with an opening 8 for inserting the processing container 3 from below to above. The opening 8 covers the gap between the base plate 7 and the processing container 3 with a heat insulating material 10. Is provided.

  The processing vessel 3 is also referred to as a process tube (reaction tube) and is made of quartz, and is formed in a vertically long cylindrical shape with the upper end closed and the lower end opened. An outward flange portion 3 f is formed at the open end of the processing container 3, and the flange portion 3 f is supported by the base plate 7 via a flange support member 11. The flange support member 11 includes an annular support frame 12 that supports the lower peripheral edge of the flange portion 3f, a flange presser 13 that is attached to the upper portion of the support frame 12 by screws or the like and presses the upper portion of the flange portion 3f, and A plurality of support rods 14 that support the outer peripheral edge of the support frame 12 from the base plate 7 are included.

The processing container 3 in the illustrated example has an introduction port (introduction port) 15 for introducing a processing gas, an inert gas or the like into the processing container 3 on the lower side and an exhaust port (exhaust gas) for exhausting the gas in the processing container 3. Mouth) 16 is provided. The introduction port 15 is connected to a gas supply source, and the exhaust port 16 is connected to an exhaust system including a vacuum pump capable of pressure reduction control, for example, about 10 to 10 ⁻⁸ Torr.

  Below the processing container 3, a lid body 17 that can be opened and closed in the vertical direction for closing and opening the furnace port 3 a formed of the lower end opening of the processing container 3 is provided so as to be movable up and down by the lifting mechanism 18. On the top of the lid 17, for example, a quartz boat 20, which is a holder for mounting a large number of wafers having a diameter of 300 mm, for example, about 100 to 150 at a predetermined interval in the vertical direction, is a heat retaining means for the furnace port 3 a. For example, it is placed via a heat insulating cylinder 21. The lid body 17 is provided with a rotation mechanism 22 that rotates the boat 20 around its axis. The boat 20 is unloaded from the processing container 3 into the lower loading area 23 by the downward movement of the lid body 17, and is loaded into the processing container 3 by the upward movement of the lid body 17 after the wafer w is transferred. (Loaded).

  In order to maintain the shape of the heat insulating material 4 and reinforce the heat insulating material 4, the outer periphery of the heat insulating material 4 is covered with a metal (for example, stainless steel) outer shell (outer shell) 24. Further, the outer periphery of the outer skin 24 is covered with a water cooling jacket 25 in order to suppress the thermal influence on the outside of the heater.

  An O-ring 26, which is an annular airtight member that seals between the periphery of the furnace vessel (furnace port flange 3 a) of the processing vessel 3, is attached to the upper periphery of the lid body 17. The lid 17 is made of metal, for example, stainless steel (SUS), and the O-ring 26 is made of a heat-resistant resin, for example, a fluorine-based resin. An annular mounting groove 27 [see FIG. 2A] for mounting the O-ring 26 is formed on the peripheral edge of the upper surface of the lid body 17. In order to prevent overheating of the O-ring 26, the support frame 12 is provided with a cooling water passage for indirectly cooling the flange portion 3 f of the processing container 3 by circulating cooling water. Also, a cooling water passage for cooling the O-ring 26 is provided (not shown).

  The lid body 17 is connected to the elevating mechanism 18 via the lid body base portion 28 so that the lid body 17 is brought into close contact with the furnace port peripheral edge portion 3a, and the lid body 17, the lid body base portion 28, and the like. A plurality of coil-shaped springs (springs) 30 for biasing the lid body 17 in the closing direction, and a predetermined distance between the lid body 17 and the lid base portion 28 against the biasing force of the spring 30. A plurality of restricting members 31 for restricting are provided. The restricting member 31 is mainly composed of a plurality of bolts 31a that are disposed on the lower surface of the lid body 17 at appropriate intervals in the circumferential direction and project downward, and nuts 31b that are screwed to the tip portions of the bolts 31a. It is configured. A hole 32 that loosely penetrates the bolt 31 a is formed in the lid base portion 28, and an opening 33 for avoiding interference with the rotating mechanism 22 is formed. The spring 30 is interposed between the lid body 17 and the lid base portion 28 in a compressed state while being inserted through the bolts 31a. By adjusting the tightening of the nut 31b, the level of the lid 17 and the spring pressure of the spring 30 can be adjusted.

  The elevating mechanism 18 includes a vertically arranged screw shaft (ball screw) 34 and an elevating arm 35 that is moved up and down by forward and reverse rotation of the screw shaft 34, and the lid base portion 28 is provided on the elevating arm 35. Is installed. The elevating arm 35 is supported by a linear guide (not shown) so as to be movable up and down. The elevating mechanism 18 includes an electric motor M as its driving means, and the electric motor M is connected to one end of the screw shaft 34 via a reduction gear mechanism 36.

When the lid 17 is brought into contact with the furnace port flange portion 3f of the processing vessel 3 and closed at normal pressure in the processing vessel 3, the crushing amount (crushing allowance) of the O-ring 26 becomes 0.4 mm. The spring pressure (pressing force by the spring) is set so that a gap of 0.6 mm is generated between the upper surface of the peripheral portion of the steel plate and the lower surface of the furnace port flange portion 3f. By the way, because of the structure of the lid body 17, the pressure difference between the inside and outside (for example, 1400 kg / cm ² ) is applied to the lid body 17 in addition to the urging force (pressing force) of the spring 30 when the processing container 3 is depressurized. The O-ring 26 is excessively crushed due to an increase in the pressing force of the lid body 17, and therefore, the pressure difference between the internal and external pressures due to the reduced pressure is reduced when the pressure in the processing container 3 is reduced. A pressing force reducing means 37 for reducing the pressure is provided.

  In the present embodiment, the pressing force reducing means 37 includes, for example, a stepping motor 38 that drives the elevating mechanism 18, a closing position sensor 40 that detects that the lid body 17 is closed, and the lid body 17 by the closing position sensor 40. Is detected, the stepping motor 38 is moved at a predetermined angle (predetermined) in order to lower the lid 17 in the opening direction in order to reduce the pressing force of the pressure difference between the inside and outside due to the decompression when the processing container 3 is decompressed. And a control unit 41 that reversely rotates the rotation angle).

  The action or heat treatment method of the heat treatment apparatus 1 having the above configuration will be described. First, after the wafer w is transferred to the boat 3 in the loading area 23, the lid 17 is lifted by the elevating mechanism 18 to carry the boat 20 into the processing container 3, and the lid 17 is moved to the furnace port peripheral portion 3f. The contact is made through the O-ring 26. At this time, the lid base portion 28 is closed from the position where the O-ring 26 comes into contact with the bottom surface of the furnace port peripheral edge (flange) 3f (position A) [see FIG. 2 (a)]. The position is raised to the position (B position) [see FIG. 2 (b)]. In this case, the O-ring 26 reaches the initial collapse amount e by the spring pressure (biasing force) of the spring 30.

  Next, when the inside of the processing container 3 is depressurized (evacuated), a pressure difference between the inside and outside acts in addition to the biasing force (pressing force) of the spring 30, and the O-ring 26 is increased by increasing the pressing force of the lid 17. Is excessively crushed (the amount of crushed f by vacuuming), and the lid 17 is in direct contact with the peripheral edge 3f of the furnace port [see FIG. 2 (c)]. That is, the lid base portion 28 is at the same lid closing position (position B) as described above, but since the lid body 17 is movable in the vertical direction, the lid base portion 28 is pressed against the furnace port peripheral portion 3f by the internal and external pressure difference. End up. Therefore, in order to prevent this from happening, the lid body 17 is configured so that the O-ring 26 has a predetermined design collapse amount by reversely rotating the stepping motor 38 by a predetermined rotation angle at the start of pressure reduction. That is, the lid base portion 28 is pulled down in the opening direction (downward direction) to a position (C position) where the internal / external pressure difference is canceled (crushing amount g after the lid position correction) [see FIG. 2 (d)].

  As described above, according to the heat treatment apparatus 1 or the heat treatment method, the pressing force of the pressure difference between the inside and the outside due to the reduced pressure acting on the lid body 17 when the pressure in the processing container 3 is reduced is reduced. 26 can be prevented from being excessively crushed, the durability of the O-ring 26 can be improved, the damage to the furnace port peripheral part 3f caused by the direct contact between the cover and the furnace peripheral part 3f, and the cover 17 Generation | occurrence | production of the rubbing of the furnace port peripheral part 3f can be prevented. Therefore, it is possible to improve the durability of the peripheral edge 3f of the furnace port and the lid 17 of the processing vessel 3, and to prevent generation of particles and metal contamination of the wafer due to the rubbing. Further, the lid 17 is connected to the lifting mechanism 18 via the lid base 28, and a spring 30 for biasing the lid 17 in the closing direction between the lid 17 and the lid base 28, Since a regulating member 31 that regulates the gap between the lid 17 and the lid base portion 28 at a predetermined interval against the biasing force of the spring 30 is interposed, the lid 17 is closed when the lid 17 is closed. Can be pressed uniformly against the peripheral edge 3f of the furnace port and sealed. In the above-described embodiment, the closed position of the lid body 17 is detected by the closed position sensor 40, but may be detected by the rotation angle of the stepping motor 38. Further, pressure control, temperature control, and the like in the processing container 3 are performed by a control device (not shown) of the heat treatment apparatus 1. For example, when the processing container 3 is depressurized, a decompression start signal may be input to the control unit 41 from the control device. It has become.

  FIG. 3 is a cross-sectional view schematically showing an example in which the movement of the lid body is restricted by a stopper with respect to the fixed portion, and FIG. 4 is a cross-sectional view showing a modified example of the stopper. In this embodiment, the same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the pressing force reducing means 37 is provided on the lid body 17 for fixing the furnace port peripheral edge portion 3f of the processing vessel 3 and abuts against the fixing portion 42. The stopper 17 is configured to prevent the lid 17 from further moving in the closing direction from the closed position (see FIG. 2B) when the processing container 3 is depressurized. . A plurality of stoppers 43 are preferably provided on the outer peripheral portion of the lid body 17 at appropriate intervals. As the fixing portion 42, for example, the support frame 12 of the flange support member 11 is suitable. According to the present embodiment, even when the lid 17 is pressed in the closing direction due to a pressure difference between the inside and the outside when the processing container 3 is depressurized, the stopper 43 abuts on the fixing portion 42 and the lid 17 is moved in the closing direction. Since the movement is prevented, the O-ring 26 is not crushed excessively, a predetermined amount of crushing can be ensured, and the durability of the O-ring 26 can be improved and the airtightness of the lid 17 can be maintained. As shown in FIG. 4, a plurality of stoppers 43 may be provided at appropriate intervals in the circumferential direction on the lower surface of the support frame 12, for example, the fixing portion 42, and corresponding to these stoppers 43, A receiving portion 44 against which the stopper 43 abuts may be provided on the outer peripheral portion.

  FIG. 5 is a cross-sectional view schematically showing an example in which the movement of the lid body with the fixing portion is suppressed by an air cylinder. In this embodiment, the same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the pressing force reducing means 37 includes, as shown in FIGS. 5 (a) to 5 (b), a fixing portion 42 for fixing the furnace port peripheral portion 3f of the processing vessel 3, and the fixing portion 42 and At least one of the lid bodies 17 is provided on the lid body 17, for example, and air that separates the lid body 17 from the furnace port 3 a when the inside of the processing container 3 is decompressed by taking a reaction force against the fixing portion 42. A cylinder (fluid pressure expansion / contraction mechanism) 45 is provided. An air cylinder 45 is fixed to the outer periphery of the lid body 17 at appropriate intervals in the circumferential direction with the push rod 45a facing upward. As shown in FIG. 5 (b), the push rod 45a of the air cylinder 45 is projected to depress the pressing portion 42, for example, the lower surface of the support frame 12 of the flange support member 11, so that the O-ring 26 is not crushed excessively. Secure the amount of crushing. As a result, the same effect as in the above embodiment can be obtained. Note that a plurality of air cylinders 45 may be provided at appropriate intervals in the circumferential direction on the lower surface of the support frame 12 that is a fixed part, and the air cylinder 45 is provided on the outer peripheral part of the lid 17 corresponding to these air cylinders 45. A receiving portion (not shown) for abutting the 45 push rods 45a may be provided.

  FIG. 6 is a cross-sectional view schematically showing an example in which the positional relationship between the lid and the lid base member is fixed by a chuck mechanism. In this embodiment, the same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the pressing force reducing means 37 is provided between the lid 17 and the lid base 28 as shown in FIGS. 6A and 6B, and the inside of the processing container 3 is decompressed. In this case, a gap fixing mechanism 46 is provided to fix the gap between the lid body 17 and the lid base portion 28 to the gap immediately before the lid body is closed. The interval fixing mechanism 46 includes, for example, a convex portion 47 provided on the upper portion of the lid base portion 28 and a chuck provided on the lower portion of the lid body 17 for chucking (gripping) the convex portion 47 when the processing container 3 is decompressed. The mechanism 48 is mainly configured. The convex portion 47 may be provided on the lid body side, and the chuck mechanism 48 may be provided on the lid base portion side. According to the present embodiment, the lid 17 is raised and brought into contact with the lower surface of the furnace port flange portion 3 f of the processing vessel 3 via the O-ring 26, and the O-ring 26 is made to have a predetermined collapse amount by the urging force of the spring 30. When the lid 17 is closed, the chuck mechanism 48 is operated to depress the convex portion 47 when the inside of the processing container 3 is depressurized, whereby the gap between the lid 17 and the lid base portion 28 is obtained. Therefore, the lid 17 is prevented from being pressed against the upper furnace port flange portion 3f by the pressure difference between the inside and outside during decompression, and an appropriate crushing amount of the O-ring 26 can be secured. The same effect as the form can be obtained.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention is not limited to the above-described embodiments, and various design changes and the like can be made without departing from the gist of the present invention. is there. For example, the object to be processed may be a glass substrate, an LCD substrate, or the like. In the present invention, a metallic (stainless steel) cylindrical manifold (furnace port forming member) is connected to the lower opening end of a quartz processing vessel, and the lower opening end of the manifold is connected to the lid through an O-ring. The present invention can also be applied to a heat treatment apparatus (vacuum CVD apparatus) designed to be closed. In this case, an appropriate crushing amount of the O-ring can be ensured, and the same effect as in the above embodiment can be obtained. Rubbing due to direct contact between the body metals and a difference in thermal expansion can be prevented in advance, and deterioration of durability due to rubbing and occurrence of metal contamination of the wafer can be prevented.

It is a longitudinal cross-sectional view which shows roughly the heat processing apparatus which is embodiment of this invention. It is explanatory drawing which illustrates schematically the method to control the height position of a cover body and to reduce the surface pressure which a cover body presses against a furnace port. It is sectional drawing which shows roughly the example which controls the movement of a cover body with a stopper by a stopper. It is sectional drawing which shows the modification of a stopper. It is sectional drawing which shows roughly the example which suppresses a movement of a cover body between fixed parts with an air cylinder. It is sectional drawing which shows roughly the example which fixes the positional relationship of a cover body and a cover body base member with a latch mechanism.

Explanation of symbols

1 Heat treatment equipment w Semiconductor wafer (object to be processed)
3a Furnace port 3f Furnace port peripheral part 3 Processing container 17 Lid 18 Lifting mechanism 20 Boat (holding tool)
26 O-ring (airtight member)
28 Lid base part 30 Spring 31 Restriction member 37 Pushing force reduction means 40 Blocking position sensor 41 Control part 42 Fixing part 43 Stopper (movement prevention member)
44 Receiving part 45 Air cylinder (fluid pressure expansion and contraction mechanism)
46 Spacing fixing mechanism

Claims (7)

  The object to be processed is mounted in multiple stages on a holder placed on the top of the lid that opens and closes the furnace port at the bottom of the processing vessel, and the lid is raised by an elevating mechanism to carry the holder into the heat treatment furnace. In addition, in the heat treatment method in which the furnace port is closed with a lid through an airtight member and the object to be treated is heat treated under a predetermined reduced pressure, the pressure difference between the inside and outside due to the reduced pressure acting on the lid when the inside of the processing container is decompressed. A heat treatment method characterized by reducing the pressing force of the material.   A processing chamber having a furnace port at the bottom, capable of accommodating the object to be processed and capable of performing a predetermined heat treatment under reduced pressure, and a lid for placing a holder on which the object to be processed is mounted in multiple stages and opening and closing the furnace port And an elevating mechanism for carrying in and out the holder into the processing container and opening and closing the lid, and an annular airtight member that is provided on the lid and seals between the periphery of the furnace port of the processing container In the heat treatment apparatus, the heat treatment apparatus is provided with a pressing force reducing means for reducing the pressing force of the pressure difference between the inside and outside due to the reduced pressure acting on the lid when the inside of the processing container is decompressed. .   The lid body is connected to the elevating mechanism via the lid body base portion, a spring for biasing the lid body in the closing direction between the lid body and the lid body base portion, and against the biasing force of the spring 3. A heat treatment apparatus according to claim 2, wherein a regulating member for regulating the gap between the lid body and the lid body base portion at a predetermined interval is interposed.   The pressing force reducing means includes a stepping motor that drives the elevating mechanism, a closing position sensor that detects that the lid is closed, and after detecting that the lid is closed by the closing position sensor, 3. A heat treatment apparatus according to claim 2, further comprising a controller that reversely rotates the stepping motor by a predetermined angle so as to urge the lid in the opening direction when the pressure is reduced.   The pressing force reducing means is provided in at least one of the fixing part for fixing the peripheral edge of the furnace port of the processing container, and the fixing part and the lid body, and comes into contact with the other to thereby fix the inside of the processing container. The heat treatment apparatus according to claim 2, further comprising a movement preventing member that prevents the lid body from moving further in the closing direction from the closed position during decompression.   The pressing force reducing means is provided in at least one of the fixing portion for fixing the peripheral edge of the furnace port of the processing vessel, and the fixing portion and the lid body, and takes a reaction force against the other, thereby processing vessel The heat treatment apparatus according to claim 2, further comprising a fluid pressure expansion / contraction mechanism that separates the lid from the furnace port when the pressure is reduced.   The pressing force reducing means is provided between the lid and the lid base, and when the inside of the processing container is depressurized, an interval between the lid and the lid base is set to an interval when the lid is closed. The heat treatment apparatus according to claim 2, further comprising an interval fixing mechanism for fixing.

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