JP2006040990A - Reduced pressure heat treatment apparatus and method of restoration to normal pressure of the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduced-pressure heat treatment apparatus which can restore a processing container to normal pressure stably and rapidly without making the inside of the processing container into a pressurized state and can shorten a TAT, and to provide a method of restoration to normal pressure. <P>SOLUTION: The reduced-pressure heat treatment apparatus 1 is so structured that, after a workpiece is stored in the processing container 2 and then heat-treated in a prescribed low pressure atmosphere, an inert gas is introduced into the processing container 2 by means of a flow controller 9 to restore the inside of the processing container 2 to normal pressure. The apparatus 1 includes a pressure sensor 18 for detecting pressure inside the processing container 2; and a controlling unit 19 which controls the flow controller 19 so that the inert gas may be introduced in such a flow rate as to keep the inside of the processing container 2 from becoming a pressurized state, when restoring the inside of the processing container 2 to normal pressure by introducing the inert gas into the container 2 after heat treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reduced pressure heat treatment apparatus and a method for returning to normal pressure.

In the manufacture of a semiconductor device, there are processes for subjecting an object to be processed, such as a semiconductor wafer, to various heat treatments such as oxidation, diffusion, CVD, annealing, etc., and for performing these processes in a predetermined reduced pressure (vacuum) atmosphere. A vacuum heat treatment apparatus is used as the apparatus. The reduced pressure heat treatment apparatus includes a processing container for accommodating a wafer and heat-treating in a predetermined reduced pressure atmosphere. The processing container includes an exhaust system capable of evacuating the processing container to a predetermined reduced pressure, and a processing container. A gas introduction system for introducing processing gas and inert gas is connected. In such a reduced-pressure heat treatment apparatus (for example, a CVD apparatus), after the heat treatment (after completion of the process), in order to unload the wafer from the treatment container to the normal pressure (atmospheric pressure) side, An inert gas such as nitrogen gas (N ₂ ) is introduced into the processing vessel through a flow controller while evacuating at normal pressure or slightly reduced pressure, and the inside of the processing vessel is replaced with inert gas from high vacuum to normal pressure ( (For example, refer to JP-A-7-227534 and JP-A-2001-146975).

JP-A-7-227534 JP 2001-146975 A

  By the way, an attempt has been made to introduce an inert gas at a normal temperature into a processing vessel at a large flow rate in order to shorten the time required for the return to normal pressure to shorten TAT (Turn Around Time). However, since the processing container not only has a large heat capacity and is difficult to cool, but is often kept at a high temperature in preparation for the next processing, if a normal temperature inert gas flows into the processing container at a large flow rate, the gas rapidly Due to the thermal expansion, the inside of the processing container is in a pressurized state, which may cause a problem such as leakage from the sealing surface.

  The present invention has been made in view of the above circumstances, and a reduced pressure heat treatment apparatus that can return to normal pressure stably and quickly without bringing the inside of the processing vessel into a pressurized state, and can reduce TAT. An object of the present invention is to provide a method for restoring the normal pressure.

  Among the present inventions, the invention according to claim 1 is a process in which an object to be processed is accommodated in a processing container and heat-treated in a predetermined reduced-pressure atmosphere, and then an inert gas is introduced into the processing container by a flow controller. A normal pressure recovery method of a reduced pressure heat treatment apparatus for returning the inside of a container to normal pressure, wherein the pressure in the processing container is detected, and a flow rate controller introduces an inert gas flow rate so that the pressure does not become a pressurized state. It is characterized by controlling.

  In the invention according to claim 2, after the object to be processed is accommodated in the processing container and heat-treated in a predetermined reduced pressure atmosphere, an inert gas is introduced into the processing container by a flow rate controller, and the inside of the processing container is kept at normal pressure. And a pressure sensor for detecting the pressure in the processing container, and for introducing an inert gas into the processing container after the heat treatment to return the processing container to normal pressure. And a control unit that controls the flow rate controller so that the pressure in the processing vessel becomes an introduction flow rate of an inert gas that does not enter a pressurized state.

  The invention according to claim 3 is the reduced pressure heat treatment apparatus according to claim 2, wherein the control unit compares the target pressure value with the detected pressure value, and when the detected pressure value reaches the target pressure value, the current control is performed. The flow rate value is used as it is as a control flow rate value, and when the detected pressure value does not reach the target pressure value, an auto-tuning function that outputs a value calculated from the pressure difference as the control flow rate value is provided.

  According to the first aspect of the present invention, the object to be processed is accommodated in the processing container and heat-treated in a predetermined reduced-pressure atmosphere, and then an inert gas is introduced into the processing container by the flow rate controller. A method for returning to normal pressure by a reduced-pressure heat treatment apparatus that returns to normal pressure, wherein the pressure in the processing vessel is detected, and the flow rate of the inert gas is controlled by a flow rate controller so that the pressure does not become a pressurized state. Therefore, it is possible to return to normal pressure stably and quickly without bringing the inside of the processing container into a pressurized state, and TAT can be shortened.

  According to the invention of claim 2, after the object to be processed is accommodated in the processing container and heat-treated in a predetermined reduced pressure atmosphere, an inert gas is introduced into the processing container by the flow rate controller, and the inside of the processing container is filled. A reduced-pressure heat treatment apparatus configured to return to normal pressure, a pressure sensor that detects the pressure in the processing container, and an inert gas introduced into the processing container after the heat treatment to return the processing container to normal pressure Since there is a controller that controls the flow rate controller so that the pressure inside the processing vessel is an inert gas introduction flow rate that does not become a pressurized state, the processing vessel is stable without being pressurized. Thus, normal pressure can be quickly restored, and TAT can be shortened.

  According to the invention of claim 3, the control unit compares the target pressure value with the detected pressure value, and when the detected pressure value has reached the target pressure value, the current control flow value is used as it is as the control flow value, When the detected pressure value does not reach the target pressure value, it has an auto-tuning function that outputs the value calculated from the pressure difference as the control flow rate value, so the volume of the processing vessel and the inert gas from the primary side The optimum value can be obtained in a short time according to the inflow amount, and the inside of the processing container can be quickly returned to normal pressure.

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 diagram schematically illustrating a reduced pressure heat treatment apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram illustrating a flow rate control system, and FIG. 3 is a flowchart diagram illustrating flow rate control when normal pressure is restored. In these drawings, reference numeral 1 denotes a vertical heat treatment apparatus exemplified as a reduced pressure heat treatment apparatus. This vertical heat treatment apparatus 1 includes a heat treatment furnace for accommodating an object to be processed, for example, a semiconductor wafer, and performing heat treatment in a predetermined reduced pressure atmosphere. A processing vessel (also referred to as a reaction tube) 2 made of, for example, quartz is provided. For example, the processing container 2 is formed in a vertically long cylindrical shape having a lower end opened as a furnace port. Around the processing container 2, a heater 3 is provided as a heating means for heating the wafer to a predetermined temperature, for example, about 800 to 1200 ° C.

  Below the processing container 2, a lid body 4 that closes the furnace port, which is the open end of the processing container 2, is provided so that it can be opened and closed by an elevator mechanism (not shown). An upper part of the lid 4 is provided with, for example, a quartz boat (not shown) that holds a large number of wafers in multiple stages at predetermined intervals in the vertical direction. By the elevating mechanism, the boat is carried in (loaded) and carried out (unloaded) from the processing container 2 and the lid 4 is opened and closed.

  The vertical heat treatment apparatus 1 includes a casing (not shown) whose inside is a clean atmosphere, and the processing container 2 is installed above the rear part in the casing. Below the processing container 2 in the housing is a loading area (working area). In this loading area, wafers are transferred (transferred) between the boat unloaded from the processing container 2 and the cassette as the transport container. ) Is provided.

The processing container 2 includes a gas introduction pipe 5 as a gas introduction system for introducing a processing gas and an inert gas (for example, N ₂ ) into the processing container 2, and an exhaust system (mainly capable of evacuating the processing container 2 under reduced pressure). A main exhaust pipe 6 as an exhaust system) is connected. In the illustrated example, a gas introduction port 7 for connecting the gas introduction pipe 5 is provided at the lower side (for example, flange portion) of the processing container 2, and an exhaust port 8 for connecting the main exhaust pipe 6 is provided at the top of the processing container 2. It has been. The processing vessel 2 is closed at the upper end, and a cylindrical manifold having a gas introduction port for connecting the gas introduction pipe and an exhaust port for connecting the main exhaust pipe is connected to the opening end of the lower end. It may be.

The number of the gas introduction ports 7 and the gas introduction pipes 5 is provided in a number corresponding to, for example, the gas type. The gas introduction pipe 5 is provided with a flow rate controller (Mass Flow Controller, also referred to as MFC for short) 9 for adjusting the gas flow rate, and an on-off valve 10 is provided upstream of the flow rate controller 9. It has been. A vacuum pump 11 capable of evacuating the inside of the processing vessel 2 to about 1 × 10 ⁻⁵ Torr, for example, is provided downstream of the main exhaust pipe 6.

A main exhaust valve 12 for adjusting the exhaust pressure is provided upstream of the vacuum pump 11 in the main exhaust pipe 6, and has a small diameter and a small exhaust flow rate so as to communicate with the front and rear of the main exhaust valve 12. A bypass pipe 13 serving as a secondary exhaust system is provided with a secondary exhaust valve 14 for adjusting the exhaust pressure. In the main exhaust pressure reducing step by opening the main exhaust valve 12, the pressure can be reduced to about 1 × 10 ⁻⁵ Torr, and in the sub exhaust pressure reducing step by opening the sub exhaust valve 14, the pressure can be reduced to, for example, about 10 Torr. It is.

  Further, upstream of the main exhaust valve 12 in the main exhaust pipe 6, a normal pressure exhaust pipe 15 as a normal pressure exhaust system connected to a factory exhaust system in order to exhaust the inside of the processing vessel 2 at normal pressure or slightly reduced pressure. Is branched. The normal pressure exhaust pipe 15 is provided with a normal pressure exhaust valve (vent valve) 16 and a check valve 17 for preventing a back flow from the normal pressure exhaust pipe 15 side to the main exhaust pipe 6 side. In order to detect the pressure in the processing container 2, a pressure sensor 18 is provided in the main exhaust pipe 6, which is the same decompression region as in the processing container 2.

  The main exhaust valve 12, the sub exhaust valve 14, and the opening / closing valve 16 are controlled to be opened / closed by a control unit (controller) 19. When evacuating the inside of the processing container 2 to a predetermined pressure, first, the on-off valve 10, the main exhaust valve 12 and the normal pressure exhaust valve 16 are closed, and the auxiliary exhaust valve 14 is opened to perform preliminary evacuation by slow exhaust at a low flow rate. Next, the sub exhaust valve 12 is closed, the main exhaust valve 12 is opened, and the main vacuum is drawn until a predetermined degree of vacuum is reached, and a predetermined processing gas is supplied into the processing container at a predetermined flow rate while maintaining the degree of vacuum. A predetermined heat treatment, for example, a CVD process is performed by introducing into the above. When the heat treatment is finished, the main on-off valve 12 is closed.

After heat treatment (after completion of the process), when an inert gas such as N ₂ is introduced into the processing vessel 2 to return to normal pressure, the pressure detected by the pressure sensor 18 is in a pressurized state (for example, atmospheric pressure: 760 Torr). The flow rate controller 9 is controlled by a control unit (controller) 19 so that the flow rate of the inert gas is not increased. In this case, the normal pressure exhaust valve 16 or the sub exhaust valve 14 is opened, normal pressure exhaust or reduced pressure exhaust is performed, the processing gas remaining in the processing container 2 is scavenged, and the inside of the processing container 2 is inert gas, for example, Purge with N ₂ .

When the inert gas is introduced into the processing container 2, it is preferably introduced at a large flow rate, for example, 500 to 1000 liters / minute in order to shorten TAT. In addition, in order to obtain the optimum value in a short time according to the volume of the processing container 2 and the inflow amount of the inert gas such as N ₂ from the primary side, the control unit 19 compares a target pressure value (for example, atmospheric pressure: 760 Torr) that is a set value with a current pressure value that is a detected value, and when the current pressure value has reached the target pressure value, the current control flow value is directly controlled. It is preferable to have an auto-tuning function that outputs a value calculated from the pressure difference as a control flow value when the current pressure value does not reach the target pressure value. As this auto-tuning method, a so-called limit cycle method or PID method is used.

  In the pressure control method or pressure control system for controlling the pressure by introducing an inert gas such as N 2 into the processing vessel 2 which is the decompression region when returning from the decompressed state to the normal pressure (atmospheric pressure) state, As shown in FIG. 3, after the pressure control process is started (S1), the target pressure value is acquired (S2), the control flow value is acquired (S3), and the current pressure value is acquired (S4) in this order. Then, it is compared whether or not the current pressure value has reached the target pressure value (S5). If the current pressure value has been reached, the current control flow value is used as the control flow value as it is (S6). The value is set as a control flow rate value (S7), and an optimal control flow rate value is output (S8) to control the flow rate controller 9. Note that when the current pressure value reaches a target pressure value (for example, atmospheric pressure), the inside of the processing vessel 2 has returned to normal pressure, so the on-off valve 10, the normal pressure exhaust valve 16, and the sub exhaust valve 14 are turned on. The normal pressure return process is closed to close, and the lid 4 is lowered to carry out the boat.

  As shown in FIG. 2, the control unit 19 has a central processing unit (CPU) 20 that performs a comparison operation. The central processing unit 20 inputs and outputs various set values such as a target pressure value and current values. For example, an MMI (Man Machine Interface) 21 which is a touch panel type input / output display device is connected. The central processing unit 20 captures (inputs) the current pressure value, which is the output value from the pressure sensor 18, and the current flow value, which is the output value from the flow rate controller 9, after A / D conversion. Thus, the control flow rate value calculated by the comparison calculation process is D / A converted and output to the flow rate controller 9.

  According to the normal pressure recovery method of the vertical heat treatment apparatus 1 having the above-described configuration, the wafer is accommodated in the processing vessel 2 and heat-treated in a predetermined reduced pressure atmosphere, and then the processing vessel 2 is inactivated by the flow rate controller 9. A method for restoring normal pressure of the reduced pressure heat treatment apparatus 1 for introducing a gas to restore the inside of the processing vessel 2 to normal pressure, wherein the pressure in the processing vessel 2 is detected and the flow rate is set so that the pressure does not become a pressurized state. Since the introduction flow rate of the inert gas is controlled by the controller 9, the process vessel 2 can be stably and quickly returned to normal pressure without being in a pressurized state, and TAT can be shortened.

  Further, according to the vertical heat treatment apparatus 1, a wafer is accommodated in the processing container 2 and heat-treated in a predetermined reduced pressure atmosphere, and then an inert gas is introduced into the processing container 2 by the flow rate controller 9. 2 is a reduced pressure heat treatment apparatus 1 for returning the inside to normal pressure, and a pressure sensor 28 for detecting the pressure in the processing vessel 2 and an inert gas introduced into the processing vessel 2 after the heat treatment. 2 is provided with a control unit 19 that controls the flow rate controller 9 so that the pressure in the processing vessel 2 becomes a pressurized flow rate of an inert gas that does not enter a pressurized state when the inside is returned to normal pressure. Without bringing the inside of the processing container 2 into a pressurized state, the normal pressure can be stably and promptly restored, and TAT can be shortened.

  Further, the control unit 19 compares the target pressure value with the detected pressure value, and when the detected pressure value has reached the target pressure value, the current control flow value is used as the control flow value, and the detected pressure value is the target pressure value. Since it has an auto-tuning function that outputs a value calculated from the pressure difference as a control flow rate value when the pressure does not reach, the flow rate is short depending on the volume of the processing vessel 2 and the inflow amount of the inert gas from the primary side. The optimum value can be obtained over time, and the inside of the processing container 2 can be quickly returned to normal pressure.

  As mentioned above, although embodiment thru | or example of this invention has been explained in full detail with drawing, this invention is not limited to the said embodiment thru | or example, Various in the range which does not deviate from the summary of this invention. Design changes can be made. The inert gas may be argon gas or helium gas. The vacuum heat treatment apparatus may be a horizontal heat treatment apparatus, and is not limited to a batch type, but may be a sheet type.

1 is a diagram schematically showing a reduced pressure heat treatment apparatus according to an embodiment of the present invention. It is a block diagram explaining a flow control system. It is a flowchart explaining the flow control in the case of returning to normal pressure.

Explanation of symbols

1 Vertical heat treatment equipment (reduced pressure heat treatment equipment)
2 Processing vessel 5 Gas introduction pipe (gas introduction system)
6 Main exhaust pipe (exhaust system)
9 Flow controller 18 Pressure sensor 19 Control unit

Claims (3)

  After the object to be processed is stored in the processing container and heat-treated in a predetermined reduced-pressure atmosphere, an inert gas is introduced into the processing container by a flow controller to return the processing container to normal pressure. The pressure recovery method is characterized in that the pressure in the processing vessel is detected, and the flow rate of the inert gas is controlled by a flow rate controller so that the pressure does not enter a pressurized state. Pressure recovery method.   Low-pressure heat treatment in which an object to be processed is stored in a processing container and heat-treated in a predetermined reduced-pressure atmosphere, and then an inert gas is introduced into the processing container by a flow controller so that the inside of the processing container is returned to normal pressure. A pressure sensor for detecting the pressure in the processing container, and the pressure in the processing container is increased when an inert gas is introduced into the processing container after the heat treatment to return the processing container to normal pressure. A reduced-pressure heat treatment apparatus comprising: a control unit that controls the flow rate controller so that the flow rate of the inert gas that does not enter a state is reached. The control unit compares the target pressure value with the detected pressure value, and when the detected pressure value has reached the target pressure value, the current control flow value is used as the flow control value as it is, and the detected pressure value reaches the target pressure value. 3. A reduced pressure heat treatment apparatus according to claim 2, further comprising an auto-tuning function for outputting a value calculated from the pressure difference as a control flow rate value when not.

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