JP4640891B2 - Heat treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment apparatus.
[0002]
[Prior art]
For example, as an apparatus for processing a semiconductor wafer, there are an oxidation processing apparatus for performing an oxidation processing process and a CVD apparatus for performing a CVD (Chemical Vapor Deposition) processing process. Conventionally, an oxidation processing apparatus is provided with a normal pressure and reduced pressure exhaust system mainly composed of Teflon piping, and a CVD apparatus is provided with a reduced pressure exhaust system mainly composed of stainless steel piping.
[0003]
[Problems to be solved by the invention]
In recent years, there has been a demand to continuously perform oxidation treatment and CVD treatment with the same apparatus. However, when trying to perform CVD processing with an oxidation processing system that uses Teflon piping for the exhaust system, the diameter of the piping is limited due to cost and other factors, resulting in insufficient exhaust conductance or gas permeability. Therefore, there is a problem that it cannot be applied as it is because the evacuation becomes inappropriate.
Further, when an attempt was made to oxidize with a CVD apparatus using a stainless steel pipe for the exhaust system, there was a problem of corrosion of the pipe inner surface by the processing gas. In particular, in the continuous treatment of oxidation treatment and CVD treatment, etc., a strong corrosive environment is caused by chlorine-based corrosive gas and moisture. It was rare.
[0004]
In these heat treatment equipment, although the processing furnace itself is made of quartz, metal is used for the furnace lids and manifolds that are difficult to process, thus preventing metal contamination of the wafer (metal contamination). In order to prevent the metal parts from coming into contact with the gas in the furnace, such parts may be covered with a quartz cover, and then an inert gas may be supplied locally. However, in that case, the configuration is complicated and the cost is increased by providing a quartz cover or supplying an inert gas.
[0005]
The present invention has been made in consideration of the above circumstances, and there is no concern about corrosion even in a severe corrosive environment, and it is possible to suppress adhesion of by-products, and there is a problem of metal contamination. It is an object of the present invention to provide a heat treatment apparatus that can eliminate the problem and can perform a stable process at any time.
[0006]
[Means for Solving the Problems]
Among the present inventions, the invention according to claim 1 is an apparatus that accommodates an object to be processed in a processing furnace, supplies a processing gas, and performs heat treatment at a predetermined processing temperature. A normal pressure exhaust system for exhausting, a decompression exhaust system for exhausting the inside of the processing furnace at a lower exhaust pressure than the normal pressure exhaust system, and opening / closing and pressure regulation provided in each of the normal pressure exhaust system and the decompression exhaust system. control and the combination valve capable, a pressure sensor for differential pressure or absolute pressure type gas contact surfaces to detect the exhaust pressure is formed by corrosion-resistant materials non-metallic, each combination valve based on the detected pressure of the pressure sensor In accordance with a pre-input heat treatment method program recipe, normal pressure or slightly reduced pressure oxidation treatment using an atmospheric pressure exhaust system, and supply of inert gas while evacuating the inside of the processing furnace. And a control device that continuously performs a cycle purge that performs rapid pressure reduction and replacement in the processing furnace by alternately repeating stop and stop, a diffusion process using a vacuum exhaust system, or a low pressure CVD process, and the furnace of the processing furnace A gas contact surface of a metal member exposed to the environment is coated with a chromium oxide film for suppressing corrosion of the metal member and metal contamination of the object to be processed from the metal member.
[0007]
The invention according to claim 2, in the heat treatment apparatus according to claim 1, corrosion and byproducts of the metal member to the gas-contact surface of said atmospheric exhaust system and evacuation system of a metal member including at least a pipe and valve It is characterized in that it is coated with a fluororesin film for suppressing adhesion of water.
[0008]
According to a third aspect of the present invention, in the heat treatment apparatus according to the first aspect, a coating for suppressing adhesion of by-products is applied to the inner surface of the exhaust pipe portion communicating with the normal pressure exhaust system and the reduced pressure exhaust system. Features.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a first embodiment in which the present invention is applied to an oxidation processing apparatus that mainly performs an oxidation processing step.
[0010]
The oxidation treatment apparatus (heat treatment apparatus) of the present embodiment is configured as a type capable of normal pressure treatment and decompression treatment. In FIG. 1, reference numeral 1 denotes a vertical batch type processing furnace that accommodates a semiconductor wafer (object to be processed) W, supplies water vapor as a processing gas, and performs heat treatment at a high temperature of about 850 ° C., for example. Includes a reaction tube (processing vessel) 2 made of, for example, quartz having heat resistance in a vertically long cylindrical shape with the upper end closed and the lower end opened.
[0011]
The reaction tube 2 is configured such that the lower end opening opened as a furnace port is hermetically closed by the lid 3, thereby forming a highly airtight processing furnace 1. On the lid 3, for example, a wafer boat 4 made of quartz, for example, which is a substrate support for supporting a plurality of, for example, about 150 semiconductor wafers W in a horizontal state with multiple intervals in the vertical direction, holds the heat insulating cylinder 6. Is placed through.
[0012]
The lid 3 is configured to load (unload) and unload (unload) the wafer boat 4 into and into the processing furnace 1 and to open and close the furnace port by an elevating mechanism (not shown). Further, around the reaction tube 2, a heater 8 made of a resistance heating element capable of heating and controlling the inside of the furnace at a predetermined temperature, for example, 300 to 1000 ° C. is provided. The periphery of the heater 8 is covered with a cooling jacket 9.
[0013]
An appropriate number of gas introduction pipe portions 10 are provided on the lower side of the reaction tube 2, and one of them is hydrogen gas H ₂ and oxygen gas O ₂ as processing gas supply means (water vapor supply means). A combustion device (external combustion device) 11 that generates and supplies water vapor by a combustion reaction is connected. A gas supply source for supplying other processing gas such as nitrogen monoxide gas NO, dinitrogen monoxide gas N ₂ O, hydrogen chloride HCl or inert gas such as N ₂ is connected to the other gas introduction pipe section. (Not shown).
[0014]
Further, an exhaust pipe portion 13 for exhausting the inside of the reaction tube 2 is integrally provided on the lower wall of the quartz reaction tube 2, and the exhaust pipe portion 13 constitutes a vacuum exhaust system 14. An exhaust pipe 15 is connected. The lid 3 is made of metal (mainly made of stainless steel), but is exposed to a high-temperature furnace environment and processing gas. The coating for suppressing the metal contamination of the to-be-processed object from the manufacturing member is given. Here, a chromium oxide film which is a kind of ceramic is coated. In addition, the inner surface of the exhaust pipe portion 13 is provided with a coating for suppressing adhesion of by-products in the furnace when cooled. Here, a chromium oxide film or a fluororesin film having high heat resistance is coated.
[0015]
The exhaust pipe 15 is composed of a pipe having a large diameter, for example, an inner diameter of about 3 inches, which can be evacuated under high vacuum. Further, the exhaust pipe 15 is made of a corrosion-resistant pipe. For example, the inner peripheral surface of a pipe made of metal, preferably stainless steel, is coated with a coating of a fluororesin that is a corrosion-resistant resin. The downstream end of the exhaust pipe 15 is connected to a decompression pump (vacuum pump) 16 capable of decompressing the inside of the processing furnace 1 to, for example, about -1 Pa at maximum, and an abatement device 17 is connected downstream of the decompression pump 16. Yes. The inner surface of the pipe to the abatement device 17 is also coated with a fluororesin coating. As the decompression pump 16, for example, a dry pump is preferable.
[0016]
In the middle of the exhaust pipe 15, a normal pressure exhaust pipe 19 constituting a normal pressure exhaust system 18 leading to an exhaust duct of a factory exhaust system equipped with an abatement apparatus and an exhaust blower (not shown) is branched and connected. Processing with slight negative pressure is possible. Similarly to the exhaust pipe 15, the normal pressure exhaust pipe 19 is formed by coating a fluororesin film, which is a corrosion-resistant resin, on the inner peripheral surface of a pipe made of metal, preferably stainless steel. It is preferable that heating means, for example, a resistance heating element for heating to exhaust (evaporate) moisture in the pipe that causes corrosion is provided on the outer periphery of the exhaust pipe 15 and the normal pressure exhaust pipe 19.
[0017]
The normal pressure exhaust system 18 and the reduced pressure exhaust system 14 are respectively provided with combination valves 20 and 21 that can be opened and closed and pressure-adjusted. In the reduced pressure exhaust system 14, a combination valve 21 is attached at a position downstream of the branch connection portion of the normal pressure exhaust pipe 19 in the exhaust pipe 15. These combination valves 20 and 21 perform, for example, an electrical signal converted into air pressure to control the position of the valve body, and have an O-ring at the seating portion of the valve body to enable shut-off. ing. These combination valves 20 and 21 are formed of a corrosion-resistant material such as a fluororesin, or the metal contact surface in contact with the exhaust is coated with a fluororesin coating when the parts in contact with the exhaust are made of a corrosion-resistant material such as fluororesin. Has been.
[0018]
A pressure sensor 22 for detecting the exhaust pressure during normal pressure processing and a pressure for detecting the exhaust pressure during pressure reduction processing (during pressure reduction exhaust) are located upstream of the pressure reducing combination valve 21 in the exhaust pipe 15. A sensor 23 is provided via pneumatic control valves 24 and 25. The pressure sensors 22 and 23 have a gas contact surface in contact with exhaust gas made of a fluororesin so that the pressure sensors 22 and 23 can be used in a severe corrosive environment where moisture H ₂ O and a corrosive gas such as HCl are present. .
[0019]
The combination valves 20 and 21 provided in the normal pressure exhaust system 18 and the decompression exhaust system 14 are controlled by a common control unit (controller) 32 based on the pressure detected by the pressure sensors 22 and 23. ing. That is, the control unit 32 switches to the combination valve 20 of the normal pressure exhaust system 18 at the time of normal pressure processing and controls this based on the detected pressure of the pressure sensor 22 for normal pressure processing, and at the time of the pressure reduction processing, the pressure reduction exhaust system. It is possible to perform two systems of control such as switching to 14 combination valves 21 and controlling this based on the pressure detected by the pressure sensor 23 for pressure reduction processing.
[0020]
The oxidation processing apparatus configured as described above has a leak tight, highly airtight structure capable of high-pressure exhaust, such as providing an O-ring as a sealing means at each connection part of the exhaust system of the processing furnace 1. In addition, the oxidation treatment apparatus controls the combustion apparatus 11, the heater 8, the control unit 32 of the combination valves 20, 21 and the like by a control apparatus (not shown) to which a program recipe for a desired heat treatment method has been input in advance, thereby performing a desired heat treatment. The method is configured to be performed automatically.
[0021]
As a method for coating the chromium oxide film, for example, a method for forming a chromium oxide film described in JP-A-63-317680 can be used. In this method, a slurry prepared by adding SiO ₂ and Al ₂ O ₃ powder to an anhydrous oxidation aqueous solution is applied to a metal surface, and then heated to form a porous film, on which ammonium chromate or heavy chromium is formed. Impregnation with an aqueous chromic anhydride solution to which 10% by weight or less of acid ammonium has been added is carried out and heat-treated. By repeating this chromic acid impregnation and heat treatment, a chromium oxide film rich in heat resistance and corrosion resistance can be obtained.
[0022]
Examples of the fluororesin coated on the exhaust pipes 15 and 19 and the valves 20 and 21 include PTFE = polytetrafluoroethylene (tetrafluoroethylene resin), PFA = tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroethylene). Fluoroalkoxy resin), ETFE = tetrafluoroethylene-ethylene copolymer (tetrafluoroethylene-ethylene copolymer resin), and the like can be used. Examples of the fluororesin coating method for the gas contact surface of the exhaust system include spraying, dripping, brushing, and lining. By coating with the fluororesin, it becomes possible to prevent corrosion of the exhaust system and to prevent adhesion of reaction by-products due to its surface smoothness.
[0023]
Next, the operation of the oxidation treatment apparatus and the heat treatment method will be described. First, the inside of the processing furnace 1 is open to the atmosphere and is preliminarily heated to a predetermined temperature, for example, 300 ° C. by a heater 8. In this state, the wafer boat 4 holding a large number of semiconductor wafers W is processed. After loading into the furnace 1, the furnace port of the processing furnace 1 is sealed with the lid 3, and the inside of the processing furnace 1 is decompressed by evacuation by the decompression exhaust system 14. This decompression or evacuation preferably includes a cycle purge. At the time of the load and cycle purge, an inert gas such as N ₂ is supplied into the processing furnace so that a natural oxide film is not formed on the surface of the semiconductor wafer W, and N ₂ is 100%. Since the surface of the semiconductor wafer W is nitrided and the surface of the semiconductor wafer W is not easily oxidized in the subsequent oxidation step, a small amount of O _2, for example, about 1% is supplied to prevent this.
[0024]
The cycle purge is performed by alternately supplying and stopping an inert gas such as N 2 while evacuating the inside of the processing furnace 1. In this case, the exhaust system is switched to the reduced pressure exhaust system 14 by the combination valve 21, and the pressure inside the processing furnace 1 is controlled to a predetermined pressure, for example, −1 Pa by controlling the combination valve 21 while detecting the pressure by the pressure sensor 23 in the operating state of the pressure reducing pump 16. Exhaust under reduced pressure. In this depressurized exhaust state, an inert gas controlled to a predetermined flow rate, for example, N ₂ is intermittently supplied by repeatedly opening and closing the inert gas supply valve, whereby a cycle purge is performed and the inside of the processing furnace 1 is quickly performed. It can be fully replaced with an inert gas under reduced pressure. In other words, rapid depressurization (reduction of vacuum arrival time) and replacement can be performed by this cycle purge.
[0025]
Next, the processing furnace 1 is heated to a predetermined processing temperature, for example, 850 ° C. by controlling the heater 8 in the reduced pressure exhaust state, and the exhaust system is switched to the normal pressure exhaust system 18 by the combination valve 20. The inside is controlled to normal pressure or slightly reduced pressure, and after recovery (stabilization of the temperature of the semiconductor wafer) is performed in this state, a desired heat treatment such as HCl oxidation is performed. This heat treatment is performed by supplying oxygen gas O ₂ and hydrogen gas H ₂ to the combustion device 11 for combustion, and supplying the generated water vapor into the processing furnace 1 together with the hydrogen chloride gas HCl and an inert gas such as N 2. Performed under reduced pressure.
[0026]
When the heat treatment process is completed, the exhaust system is switched to the vacuum exhaust system 14 and the inside of the processing furnace 1 is again evacuated by evacuation, and then the temperature in the processing furnace 1 is controlled to a predetermined temperature, for example, 300 ° C. by controlling the heater 8. In parallel with this, the processing furnace 1 is returned to normal pressure, the wafer boat 4 is unloaded from the processing furnace 1, and cooling (cooling to a temperature at which the semiconductor wafer can be transferred) is performed. Good. The decompression or evacuation after completion of the heat treatment step preferably includes a cycle purge.
[0027]
In this way, the semiconductor wafer W is accommodated in the processing furnace 1 heated in advance to a predetermined temperature, the temperature in the processing furnace 1 is increased to a predetermined processing temperature, and water vapor as a processing gas is supplied to supply the semiconductor wafer W. When the heat treatment is performed, the temperature raising step is performed under reduced pressure, so that the semiconductor wafer W can be heated to a predetermined processing temperature in a state where the oxidizing species are excluded, and a natural oxide film in the temperature raising step can be obtained. Therefore, it is possible to form an ultrathin oxide film with excellent quality. Moreover, since the inside of the processing furnace 1 is depressurized by evacuation not only before the desired heat treatment step but also after the step, natural oxidation is performed by sufficiently eliminating unnecessary oxidizing species in portions other than the desired heat treatment step. The formation of the film can be sufficiently suppressed, and an ultrathin oxide film having a uniform film quality and film thickness and excellent quality can be formed. Incidentally, it is possible to form a SiO ₂ film having a thickness of about 2 nm.
[0028]
Since the process of decompressing or evacuating the processing furnace 1 includes a so-called cycle purge, rapid depressurization and replacement are possible, and throughput can be improved. Further, in the oxidation processing apparatus, a combustion apparatus 11 which is a steam supply means for supplying water vapor into the processing furnace 1 and a normal pressure exhaust system 18 which exhausts the inside of the processing furnace 1 at normal pressure or slight pressure reduction in the heat treatment process. And a reduced pressure exhaust system 14 capable of evacuating the inside of the processing furnace 1 before and after the heat treatment step, and switching between the normal pressure exhaust system 18 and the reduced pressure exhaust system 14 is performed by the combination valves 20 and 21. The heat treatment method described above can be carried out reliably and easily.
[0029]
Thus, according to the oxidation treatment apparatus (heat treatment apparatus) capable of performing the decompression process, in the apparatus for accommodating the semiconductor wafer W in the treatment furnace 1 and supplying the treatment gas to perform the heat treatment at a predetermined treatment temperature, the treatment furnace 1 A normal pressure exhaust system 18 for exhausting the interior at a predetermined exhaust pressure, a decompression exhaust system 14 for exhausting the inside of the processing furnace 1 at a pressure lower than that of the normal pressure exhaust system 18, a normal pressure exhaust system 18 and a decompression exhaust system. 14, combination valves 20, 21 capable of opening / closing and pressure adjustment, absolute pressure type pressure sensors 22, 23 for detecting the exhaust pressure, and the pressure detected by the pressure sensors 22, 23 And a control unit 32 for controlling the combination valves 20 and 21, so that normal pressure or slightly reduced pressure oxidation using the normal pressure exhaust system 18 and cycle purge using the reduced pressure exhaust system 14 are provided. Continuous processing such as decompression CVD processing is possible. The atmospheric pressure exhaust system 18 enables stable control without requiring introduction of air or inert gas, simplifies the structure of the exhaust system, and eliminates the running cost of inert gas such as N _2. This can reduce the cost.
[0030]
In particular, since the pressure sensors 22 and 23 of the absolute pressure type are used as the pressure sensor of the normal pressure exhaust system 18 and the pressure sensor of the decompression exhaust system 14, for example, the pressure sensor is not affected by fluctuations in atmospheric pressure such as low atmospheric pressure. Stable absolute pressure control near atmospheric pressure and stable absolute pressure control under reduced pressure are possible, so that an oxide film having a uniform film thickness can be formed at any time and a thin film can be formed.
[0031]
Further, the gas contact surface of the metal lid 3 is coated with a chromium oxide film for suppressing the corrosion of the lid 3 and the metal contamination of the wafer w from the lid 3. It is not necessary to take costly measures such as covering the metal part exposed to the environment with a quartz cover or supplying the inert gas locally to prevent the gas in the furnace from contacting the metal part. It is possible to improve corrosion resistance and prevent metal contamination.
[0032]
In addition, since the fluororesin coating is coated on the inner surface of the exhaust pipe section 13 that is the outlet of the reaction furnace 2 and the gas contact surfaces of the exhaust pipes 15 and 19 and the combination valves 20 and 21, adhesion of by-products in the furnace is prevented. While being able to suppress, stable corrosion resistance can be ensured. Therefore, the maintenance load can be reduced.
[0033]
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 scope of the present invention. is there. For example, although the vertical furnace is exemplified as the processing furnace in the above-described embodiment, it may be a horizontal furnace or a batch type, but may be a single wafer type. The object to be processed may be, for example, an LCD substrate or a glass substrate in addition to the semiconductor wafer. The steam supply means is not limited to the combustion type, and may be, for example, a vaporizer type, a catalytic type, a boiling type, or the like.
[0034]
Moreover, although the case where this invention is applied to an oxidation treatment apparatus is shown in the said embodiment, this invention is not only an oxidation treatment apparatus, for example, a diffusion treatment apparatus, a CVD treatment apparatus, an annealing treatment apparatus, etc. Alternatively, it can also be applied to these composite devices.
[0035]
FIG. 2 is a diagram showing an embodiment when applied to a CVD processing apparatus. In the processing furnace 51 of this CVD processing apparatus, a metal manifold 53 is provided below a reaction tube 52 composed of an inner tube 52A and an outer tube 52B, and a gas introduction tube portion 54 and an exhaust tube portion are provided in the manifold 53. 55 is provided. The processing gas is supplied from the lower side of the inner pipe 52A, rises, turns back at the upper end, descends the gap between the inner pipe 52A and the outer pipe 52B, and is then exhausted from the exhaust pipe portion 55 to the reduced pressure exhaust system 14. .
[0036]
In this processing furnace 51, the lid 3 and the inner surface (gas contact surface) of the manifold 53, the receiving member 56 of the inner pipe 52A and the heat retaining cylinder 57 are used as the gas contact surface of the metal member exposed to the high temperature furnace gas. The surface of the base 58 to be received and the gas contact surfaces of the gas introduction pipe portion 54 and the exhaust pipe portion 55 are coated with a chromium oxide film. In addition, the inner surface of the stainless steel exhaust pipe 15 constituting the vacuum exhaust system 14 and the gas contact surface of the metal part of the combination valve 21 are coated with a fluororesin coating. As a result, it is possible to prevent corrosion of metal members (such as the lid 3 and the manifold 53) exposed to the in-furnace gas, and it is possible to prevent metal contamination by these metal members. In addition, since the exhaust pipe portion 55 is coated with a chromium oxide film, and the metal gas contact surface of the vacuum exhaust system 14 is coated with a fluororesin film, it is possible to prevent corrosion and to produce by-product due to gas cooling. The adhesion of objects can be suppressed, and the maintenance load can be reduced. Note that parts having substantially the same functions as those in the apparatus of FIG.
[0037]
【The invention's effect】
In short, according to the present invention, the following effects can be obtained.
[0038]
(1) According to the first aspect of the present invention, in an apparatus for accommodating a target object in a processing furnace, supplying a processing gas, and performing a heat treatment at a predetermined processing temperature, the processing furnace is heated at a predetermined exhaust pressure. A normal pressure exhaust system for exhausting, a decompression exhaust system for exhausting the inside of the processing furnace at a lower exhaust pressure than the normal pressure exhaust system, and opening / closing and pressure regulation provided in each of the normal pressure exhaust system and the decompression exhaust system. control and the combination valve capable, a pressure sensor for differential pressure or absolute pressure type gas contact surfaces to detect the exhaust pressure is formed by corrosion-resistant materials non-metallic, each combination valve based on the detected pressure of the pressure sensor A normal pressure or slightly reduced pressure oxidation process using an atmospheric pressure exhaust system in accordance with a pre-input heat treatment method program recipe, and supply of inert gas while evacuating the inside of the processing furnace under reduced pressure A cycle purge that performs rapid depressurization and replacement in the processing furnace by alternately repeating the stop, a control device that continuously performs diffusion processing using a vacuum exhaust system or low-pressure CVD processing, and the in-furnace environment of the processing furnace The gas contact surface of a metal member exposed to metal is coated with a chromium oxide coating to prevent corrosion of the metal member and metal contamination of the workpiece from the metal member, so that the metal exposed to the furnace environment While being able to improve the corrosion resistance of a manufacturing member, the metal contamination of the to-be-processed object from these metal members can be prevented.
[0039]
(2) According to the invention of claim 2, piping and suppress the adhesion of the corrosion and byproducts of the metal member to the gas-contact surface of at least including the normal pressure exhaust system and evacuation system of the metal member to the valve since coated with fluororesin coating to, the it is possible to improve the corrosion resistance of the normal pressure exhaust system and evacuation system, the attachment of by-products can be suppressed, to reduce the cleaning load of maintenance be able to.
[0040]
(3) According to the invention of claim 3, since the coating for suppressing the adhesion of by-products is applied to the inner surface of the exhaust pipe portion leading to the normal pressure exhaust system and the reduced pressure exhaust system, the exhaust pipe of the processing furnace By-product adhesion on the inner surface of the part can be suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment in which the present invention is applied to an oxidation treatment apparatus.
FIG. 2 is a diagram showing a configuration of an embodiment in which the present invention is applied to a CVD processing apparatus.
[Explanation of symbols]
W Semiconductor wafer (object to be processed)
1 Processing furnace 3 Lid (metal member)
13 Exhaust pipe portion 14 Depressurized exhaust system 15 Exhaust pipe 18 Normal pressure exhaust system 19 Exhaust pipes 20, 21 Combination valve 51 Processing furnace 53 Manifold (metal member)
55 Exhaust pipe (metal member)

Claims (3)

In an apparatus that accommodates an object to be processed in a processing furnace, supplies a processing gas, and performs heat treatment at a predetermined processing temperature, an atmospheric pressure exhaust system that exhausts the inside of the processing furnace at a predetermined exhaust pressure, and the inside of the processing furnace a vacuum exhaust system to evacuate at a low exhaust pressure than atmospheric pressure exhaust system, and the possible combination valve opens and pressure regulation is provided to each of the normally pressure exhaust system and evacuation system, the gas contacting surfaces nonmetal A differential pressure type or absolute pressure type pressure sensor formed of a corrosion resistant material for detecting the exhaust pressure, a control unit for controlling each combination valve based on the pressure detected by the pressure sensor, and a heat treatment method program input in advance According to the recipe, normal pressure or slightly reduced pressure oxidation using an atmospheric pressure exhaust system, while supplying and stopping the inert gas alternately and repeatedly evacuating the inside of the processing furnace, A gas purging surface of a metal member that is exposed to the in-furnace environment of the processing furnace, comprising a cycle purging that performs rapid pressure reduction and replacement, a control device that continuously performs diffusion processing using a vacuum exhaust system or pressure reduction CVD processing Further, a heat treatment apparatus coated with a chromium oxide film for suppressing corrosion of a metal member and metal contamination of an object to be processed from the metal member.   The gas contact surface of the metal member of the normal pressure exhaust system and the vacuum exhaust system including at least piping and valves is coated with a fluororesin film for suppressing corrosion of the metal member and adhesion of by-products. The heat treatment apparatus according to claim 1.   2. The heat treatment apparatus according to claim 1, wherein a coating for suppressing adhesion of by-products is applied to an inner surface of an exhaust pipe portion communicating with the normal pressure exhaust system and the reduced pressure exhaust system.

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