US20050189074A1

US20050189074A1 - Gas processing apparatus and method and computer storage medium storing program for controlling same

Info

Publication number: US20050189074A1
Application number: US11/123,174
Authority: US
Inventors: Shigeru Kasai; Seiji Ishibashi; Kaoru Yamamoto; Sumi Tanaka; Kenichi Yanagitani
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2002-11-08
Filing date: 2005-05-06
Publication date: 2005-09-01

Abstract

A processing apparatus includes a processing vessel, a gas introduction unit, a processing gas supply unit, a nonreactive gas supply unit, a vacuum pumping unit, a pressure gauge and a control unit. The control unit controls a valve opening ratio of a pressure control valve based on a detection value of the pressure gauge while making a processing gas flow to a flow rate controller of the processing gas supply unit at a constant flow rate when performing a process in which a partial pressure of the processing gas is important. Meanwhile, when performing a process wherein the partial pressure of the processing gas is relatively unimportant, the control unit fixes the valve opening ratio of the pressure control valve at a predetermined value, and operating a flow rate controller of the nonreactive gas supply unit to control a flow rate based on the detection value.

Description

This application is a Continuation-In-Part of PCT International Application No. PCT/JP03/014266 filed on Nov. 10, 2003, which designated the United States.

FIELD OF THE INVENTION

The present invention relates to a processing apparatus and method for performing specific processes on, e.g., a semiconductor wafer and the like, and a computer readable storage medium storing therein a program for controlling same.

BACKGROUND OF THE INVENTION

Generally, for fabricating a semiconductor integrated circuit, various processes, such as a film forming process, an etching process, a thermal oxidation process, a diffusion process, a reforming process, a crystallization process and the like, are performed repeatedly on an object to be processed such as a semiconductor wafer to form a desired integrated circuit. Further, in order to remove unnecessary films or particles deposited to a processing vessel and the like, a cleaning process for removing the above-mentioned unnecessary films and the like by flowing with an etching gas is also performed suitably.
However, in some cases, a single processing apparatus is used in performing different kinds of processes as described above or plural processes that are of the same kind but differ in processing conditions. Conventionally, a pumping system installed in the processing apparatus is designed by taking a pressure range applied during a process wherein this processing apparatus is used into consideration; a diameter of an exhaust line is set to optimize a pumping conductance in the employed pressure range; and a type of the vacuum pump is also determined to be suitable for the employed pressure range.
Moreover, in case a single processing apparatus is to be used for different kinds of processes or plural processes which are of the same kind but differ in processing conditions as described above and there are included processes performed under a relatively low processing pressure and performed under a relatively high processing pressure, it is required to control an inner pressure of the processing vessel stably within each pressure range. For this, when employing a conventional processing apparatus, an inner pressure of a processing vessel is detected to control a pressure control valve of a pumping system based on the detected pressure value or a ballast gas is introduced to a pumping system while a flow rate thereof is controlled as shown in reference 1 [Japanese Patent Laid-open Application No. H10-11152 (Pages 2 to 4, and FIGS. 1 to 5)].
Further, another conventional apparatus wherein a bypass line is installed in a pumping system to be used alternatively depending on the employed pressure range has been also known. An example of this conventional apparatus will now be described with reference to FIG. 8. FIG. 8 is a schematic diagram illustrating an exemplary conventional processing apparatus.
As is shown, a processing apparatus 2 includes a barrel-shaped processing vessel 4 made of, e.g., aluminum, wherein the processing vessel 4 is designed to be vacuum-exhausted. In the processing vessel 4, there is installed a mounting table 8 having a heating unit 6, e.g., a heater and the like, wherein the mounting table 8 is configured to mount a semiconductor wafer W to be fixed thereon. Further, in a ceiling portion of the processing vessel 4, there is installed as a gas introduction unit, e.g., a shower head unit 10, for introducing various processing gases towards the mounting table 8 inside the processing vessel 4. Gases are injected downward from multiple gas injection holes 10A installed on a lower surface of the shower head unit 10.
Further, to the shower head unit 10, there are connected a nonreactive gas supply unit 12 for providing nonreactive gases such as Ar, He, N₂and the like; and plural, i.e., three in this example, processing gas supply units 14, 16 and 18. For example, a first processing gas supply unit 14 provides a WF₆gas as a processing gas for a film formation; a second processing gas supply unit 16 provides a H₂gas as a processing gas for a film formation; and a third processing gas supply unit 18 provides a ClF₃gas as a processing gas (cleaning gas) for a cleaning process. Further, for controlling flow rates of gases flowing through the nonreactive gas supply unit 12 and the processing gas supply units 14, 16 and 18, flow rate controllers 12A, 14A, 16A and 18A formed of, e.g., mass flow controller and the like, are installed, respectively. Moreover, in upstream sides and downstream sides of the respective flow rate controllers 12A to 18A, there are installed opening/ closing valves 22, 24, 26 and 28, respectively, and they are configured to be opened or closed if necessary.
Meanwhile, a gas exhaust port 30 is installed on a bottom portion of the processing vessel 4 and a vacuum pumping unit 32 is connected to the exhaust port 30. The vacuum pumping unit 32 contains a main exhaust line 34 having a large inner diameter and thus having a high pumping conductance. In the main exhaust line 34, there are installed a first pressure control valve 36 such as a throttle valve capable of controlling a valve opening ratio, and a vacuum pump 38 in this order from the upstream side to the downstream side thereof. Also, the first pressure control valve 36 is disposed between opening/closing valves 40.
Further, a bypass exhaust line 42 having a smaller inner diameter than that of the main exhaust line 34 and thus having a lower pumping conductance is connected such that it bypasses the first pressure control valve 36 and the respective opening/closing valves 40. In the bypass exhaust line 42, there is installed a second pressure control valve 44 such as a throttle valve capable of controlling a valve opening ratio. Also, the second pressure control valve 44 is disposed between opening/closing valves 46.
Still further, a pressure gauge 48 is installed in the processing vessel 4 for detecting an inner pressure thereof, and a control unit 50 comprising, e.g., a microcomputer and the like, is configured to control the first and the second pressure control valve 36 and 44, the vacuum pump 38 and opening/closing operations of the respective opening/ closing valves 40 and 46, based on a detection value of the pressure gauge 48. The control unit 50 also controls the whole operation of the processing apparatus 2, and control operations are performed based on plural processing programs (also referred to as recipes) inputted therein in advance.
For example, when performing a film forming process on a tungsten film by applying a low pressure process at a low processing pressure, only a WF₆gas and a H₂gas are provided while flow rates thereof are controlled to have specific values, respectively (a nonreactive gas may be provided, if necessary), and at the same time, the opening/closing valves 46 of the bypass exhaust line 42 are closed to prevent the gases from flowing through the bypass exhaust line 42. Further, the opening/closing valves 40 of the main exhaust line 34 are opened, and a valve opening ratio of the first pressure control valve 36 is controlled to keep an inner pressure of the processing vessel 4 constant.
Contrary to this, when performing, e.g., a cleaning process as a high pressure process under a high processing pressure, only a ClF₆is provided while a flow rate thereof is controlled to have a specified value (a nonreactive gas may be provided, if necessary), and at the same time, the opening/closing valves 40 of the main exhaust line 34 are closed to prevent the gas from flowing through the first pressure control valve 36. Further, the opening/closing valves 46 of the bypass exhaust line 42 are opened to flow the gas through the bypass exhaust line 42, and a valve opening ratio of the second pressure control valve 44 is controlled to keep an inner pressure of the processing vessel 4 constant.
As described above, by alternatively using the main exhaust line 34 and the bypass exhaust line 42 in cases of the high processing pressure and the low processing pressure, it is possible to deal with many kinds of processes wherein there are big differences in the employed pressure ranges. Meanwhile, as for examples of high processing pressure processes, there are an oxidation processing, a diffusion processing and the like in addition to the cleaning process.
Further, as a technology related to the present invention, there has been known a processing apparatus described in reference 2 [Japanese Patent Laid-open Application No. H8-290050 ( Pages 4 and 5 and FIG. 1)] wherein a bypass exhaust line is installed to cope with a difference in an operation pressure range in case where a multiplicity of vacuum pumps are installed.
However, in the conventional apparatus of the aforementioned reference 1 [Japanese Patent Laid-open Application No. H10-11152 (Pages 2 to 4 and FIGS. 1 to 5)], the ballast gas whose flow rate is controlled is to be introduced to the pumping system, so that it cannot properly cope with a case where there is a big change in the processing pressure. Further, a large amount of unnecessary nonreactive gas is employed, resulting in an operation cost increase for the apparatus.
Moreover, in the conventional apparatus shown in FIG. 8, the bypass exhaust line 42 in which the second pressure control valve 44 is installed needs to be installed, resulting in a further cost increase of the apparatus itself. In addition, since many components are employed and it takes much time for maintenance thereof, the maintenance becomes problematic.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention to provide a processing apparatus and method and a computer readable storage medium storing therein a program for controlling same, wherein a pressure control can be properly performed in each processing without using a bypass line or multiple pressure control valves, even in case when many kinds of processes of big differences in processing pressure ranges are carried out.
Further, it is another object of the present invention to provide a processing apparatus and method and a computer readable storage medium storing therein a program for controlling same, wherein a pressure control can be properly performed in each processing without using multiple pressure control valves.
In accordance with one aspect of the present invention, there is provided a processing apparatus including: a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a processing gas towards the mounting table inside the processing vessel; a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a processing gas; a nonreactive gas supply unit, connected to the gas introduction unit and provided a flow rate controller, for supplying a nonreactive gas; a vacuum pumping unit connected to the processing vessel and provided with a pressure control valve having a variable valve opening ratio and a vacuum pump; a pressure gauge installed at the processing vessel; and a control unit for controlling the valve opening ratio of the pressure control valve based on a detection value of the pressure gauge while making the processing gas flow to the flow rate controller of the processing gas supply unit at a constant flow rate when performing a process wherein a partial pressure of the processing gas is important and for fixing the valve opening ratio of the pressure control valve at a predetermined value, and at the same time, operating the flow rate controller of the nonreactive gas supply unit to control a flow rate based on the detection value of the pressure gauge when performing a process wherein the partial pressure of the processing gas is relatively unimportant.
As described above, in case when performing a process wherein a processing pressure is low and the partial pressure of the processing gas is important, the valve opening ratio of the pressure control valve is adjusted to control an inner pressure of the processing vessel while making the processing gas at a constant flow rate, or in case when performing a process wherein the processing pressure is high and the partial pressure of the processing gas is relatively unimportant, the flow rate of the nonreactive gas is adjusted to control the inner pressure of the processing vessel while fixing the valve opening ratio of the pressure control valve at a predetermined value. Therefore, a pressure control can be properly performed in each process without using a bypass line or multiple pressure control valves, even in case when many kinds of processes of big differences in a processing pressure ranges are carried out.
In accordance with another aspect of the present invention, there are provided a processing method and a computer readable storage medium storing therein a program for controlling same, the processing method being used for performing a process on an object by using a processing apparatus, which contains a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a processing gas towards the mounting table inside the processing vessel; a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined processing gas; a nonreactive gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a nonreactive gas; a vacuum pumping unit connected to the processing vessel and provided with a pressure control valve having a variable valve opening ratio and a vacuum pump; and a pressure gauge installed at the processing vessel, wherein the valve opening ratio of the pressure control valve is controlled based on a detection value of the pressure gauge while a flow rate of a processing gas flowing to the processing gas supply unit is maintained constant when performing a first process in which a partial pressure of the processing gas is important; and wherein the valve opening ratio of the pressure control valve is fixed at a predetermined value, and at the same time, a flow rate of a nonreactive gas flowing to the nonreactive gas supply unit is controlled based on the detection value of the pressure gauge when performing a second process in which the partial pressure of the processing gas is relatively unimportant.
In accordance with further aspect the present invention, there is provided a processing apparatus including: a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a processing gas towards the mounting table inside the processing vessel; a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined processing gas; a nonreactive gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a nonreactive gas; a vacuum pumping unit connected to the processing vessel and provided with a pressure control valve having a variable valve opening ratio and a first vacuum pump; a pressure gauge installed at the processing vessel; and a control unit for fixing the valve opening ratio of the pressure control valve at a predetermined value, and at the same time, performing a first control for controlling a flow rate by using the flow rate controller of the nonreactive gas supply unit based on a detection value of the pressure gauge.
In accordance with further aspect of the present invention, there are provided a processing method and a computer readable storage medium storing therein a program for controlling same, the processing method being used for performing a process on an object by using a processing apparatus, which contains a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a processing gas towards the mounting table inside the processing vessel; a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined processing gas; a nonreactive gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a nonreactive gas; a vacuum pumping unit connected to the processing vessel and a pressure control valve having a variable valve opening ratio and a first vacuum pump; and a pressure gauge installed at the processing vessel, wherein the valve opening ratio of the pressure control valve is fixed at a predetermined value; and wherein a first control for controlling a flow rate is performed by using the flow rate controller of the nonreactive gas supply unit based on a detection value of the pressure gauge.
In accordance with further aspect of the present invention, there is provided a processing apparatus containing a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a processing gas towards the mounting table inside the processing vessel; a gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined gas; a vacuum pumping unit connected to the processing vessel and provided with a first vacuum pump, a second vacuum pump and a pressure control valve having a variable valve opening ratio; and a pressure gauge for detecting a pressure of the processing vessel, the processing apparatus including: a bypass exhaust path installed to bypass the pressure control valve and the second vacuum pump; a soft start valve mechanism installed in the bypass exhaust path, the soft start valve mechanism having a function of buffering an impact of a vacuum exhaust when exhausting an inside of the processing vessel from an atmospheric pressure to vacuum; and a control unit installed to control an inner pressure of the processing vessel by adjusting the valve opening ratio of the pressure control valve based on a detection value of the pressure gauge during a relatively low processing pressure process and to stop an exhaust toward the pressure control valve, and at the same time, to flow an exhaust gas to the bypass exhaust path while maintaining the soft start valve mechanism at a low pumping conductance state during a relatively high processing pressure process.
As described above, the bypass exhaust path is installed in the vacuum pumping unit, and at the same time, the soft start valve mechanism is installed in the bypass exhaust path. Moreover, the valve opening ratio of the pressure control valve is adjusted to control the inner pressure of the processing vessel during the relatively low processing pressure process; and the exhaust toward the pressure control valve is stopped, and at the same time, the exhaust gas flows to the bypass exhaust path to set the inner pressure of the processing vessel while the soft start valve mechanism is maintained at a low pumping conductance state during the relatively high processing pressure process. Therefore, it is unnecessary to install expensive and large scaled multiple pressure control valves, and it is possible to make small a structure of the pumping unit and to simplify it.
In accordance with further aspect of the present invention, there are provided a processing method and a computer readable storage medium storing therein a program for controlling same, the processing method being used for performing a process on an object by using a processing apparatus, which contains a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a processing gas towards the mounting table inside the processing vessel; a gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined gas; a vacuum pumping unit connected to the processing vessel and provided with a first vacuum pump, a second vacuum pump and a pressure control valve having a variable valve opening ratio; and a pressure gauge for detecting a pressure of the processing vessel, wherein a bypass exhaust path bypassing the pressure control valve and the second vacuum pump is installed; wherein a soft start valve mechanism in the bypass exhaust path is installed, the soft start valve mechanism having a function of buffering an impact of a vacuum exhaust when exhausting an inside of the processing vessel from an atmospheric pressure to vacuum; and wherein an inner pressure of the processing vessel is controlled by adjusting the valve opening ratio of the pressure control valve based on a detection value of the pressure gauge during a relatively low processing pressure process and an exhaust toward the pressure control valve is stopped, and at the same time, an exhaust gas flows to the bypass exhaust path while the valve mechanism is maintained at a low pumping conductance state during a relatively high processing pressure process.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
FIG. 1 describes a schematic diagram showing a first embodiment of a processing apparatus in accordance with the present invention;
FIG. 2 provides a flowchart showing an embodiment of process in accordance with a first processing method;
FIG. 3 offers a flowchart showing an embodiment of process in accordance with a second processing method;
FIG. 4 illustrates a schematic cross sectional view showing an embodiment of mounting table used for a pre-cleaning process in which a third processing method is applied;
FIG. 5 is a flowchart showing an embodiment of process in accordance with the third processing method;
FIG. 6 sets forth to a schematic diagram showing a second embodiment of a processing apparatus in accordance with the present invention;
FIG. 7 provides a schematic diagram showing a third embodiment of a processing apparatus in accordance with the present invention; and
FIG. 8 is a schematic diagram of an exemplary conventional processing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a schematic diagram showing a first embodiment of a processing apparatus in accordance with the present invention; FIG. 2 is a flowchart showing an embodiment of process in accordance with a first processing method; FIG. 3 is a flowchart showing an embodiment of process in accordance with a second processing method; FIG. 4 is a cross sectional view showing an embodiment of mounting table in case when a pre-cleaning process is carried out; and FIG. 5 is a flowchart showing an embodiment of process in accordance with a third processing method. Identical reference numerals will be assigned and explained for corresponding parts having substantially the same functions and configurations with those in FIG. 8. Further, the term “a process wherein a partial pressure of a processing gas is relatively important” to be explained below means a low processing pressure process (low pressure process), and the term “a process wherein a partial pressure of a processing gas is relatively unimportant” to be explained below means a high processing pressure process (high pressure process), generally.
As is shown, a processing apparatus 52 includes a barrel-shaped processing vessel 4 made of, e.g., aluminum, wherein the processing vessel 4 is designed to be vacuum-exhausted. In the processing vessel 4, there is installed a mounting table 8 having a heating unit 6, e.g., a heater and the like, wherein the mounting table 8 is configured to mount a semiconductor wafer W to be fixed thereon. Further, in a ceiling portion of the processing vessel 4, there is installed as a gas introduction unit, e.g., a shower head unit 10, for introducing various processing gases towards the mounting table 8 inside the processing vessel 4. Gases are injected downward from multiple gas injection holes 10A installed on a lower surface of the shower head unit 10.
Further, to the shower head unit 10, there are connected a nonreactive gas supply unit 12 for supplying nonreactive gases such as Ar, He, N₂and the like; and plural, i.e., three in this example, processing gas supply units 14, 16 and 18. For example, a first processing gas supply unit 14 supplies a WF₆gas as a processing gas for a film formation; a second processing gas supply unit 16 supplies a H₂gas as a processing gas for a film formation; and a third processing gas supply unit 18 provides a ClF₃gas as a processing gas (cleaning gas) for a cleaning process. Here, the WF₆gas and the H₂gas are supplied during a film formation of a tungsten film, and a nonreactive gas may be supplied during the film formation, if necessary.
Still further, for controlling flow rates of gases flowing through the nonreactive gas supply unit 12 and the first, the second and the third processing gas supply units 14, 16 and 18, flow rate controllers 12A, 14A, 16A and 18A formed of, e.g., mass flow controller and the like, are installed, respectively. Moreover, in upstream sides and downstream sides of the respective flow rate controllers 12A to 18A, there are installed opening/ closing valves 22, 24, 26 and 28, respectively, and they are configured to be opened or closed if necessary.
Meanwhile, a gas exhaust port 30 is installed on a bottom portion of the processing vessel 4 and a vacuum pumping unit 32 is connected to the exhaust port 30. The vacuum pumping unit 32 contains an exhaust line 34 having a large inner diameter and thus having a high pumping conductance. The inner diameter of the exhaust line 34 is in the range from about 100 to 150 mm, for example. In the exhaust line 34, there are installed a pressure control valve 36 such as a throttle valve capable of controlling a valve opening ratio and a vacuum pump 38 in this order from the upstream side to the downstream side thereof. Also, the pressure control valve 36 is disposed between opening/closing valves 40. Here, the inner diameter of the line or capacities of the pressure control valve 36 and the vacuum pump 38 are set such that an optimum pumping conductance required for the process in which a partial pressure of a processing gas needs to be controlled with high accuracy, i.e., the film forming process of the tungsten film, can be realized in the vacuum pumping unit 32. Thus, in the present embodiment, the bypass exhaust line 42 and the second pressure control valve 44 used in the conventional apparatus (see FIG. 8) are not installed.
Further, a pressure gauge 48 is installed in the processing vessel 4 for detecting an inner pressure thereof based on a detection value of the pressure gauge 48; and a control unit 54 including, e.g., a microcomputer and the like, controls the flow rate controllers 12A to 18A, the pressure control valve 36, the vacuum pump 38 and opening/closing operations of the respective opening/closing valves 22 to 28 and 40. The control unit 54 also controls the whole operation of the processing apparatus 52. Various control operations of the control unit 54 are performed under the control or based on corresponding processing programs (recipes). A conventional personal computer may also be employed as the control unit 54. Processing programs are prestored in a storage unit (or computer storage medium) 55, such as a hard disc, ROM and the like, of the control unit 54. The processing programs may be programmed directly on the control unit 54 or can be made outside the control unit 54 and then transferred thereto via network or by using a CD or DVD for example.
As will be explained below, when a process, wherein a partial pressure of a processing gas is important as in, e.g., a film forming process of a tungsten film, is performed as a low pressure process under a low processing pressure, only a WF₆gas and a H₂gas are provided while flow rates thereof are controlled to be set at specified values respectively (a nonreactive gas may be provided, if necessary), and at the same time, a valve opening ratio of the pressure control valve 36 is controlled to keep an inner pressure of the processing vessel 4 constant. It is preferable that the pressure control valve 36 is the one selected to have operational characteristics offering a highest operational accuracy within an operational pressure range of the processing vessel 4.
Contrary to this, when a process, wherein a partial pressure of a processing gas is relatively unimportant as in the case of, e.g., a cleaning process, is performed as a high pressure process under a high processing pressure, a ClF₆is provided while a flow rate thereof is controlled to be set at a specified value, and at the same time, a nonreactive gas is provided. Simultaneously, a flow rate of the nonreactive gas is controlled to keep an inner pressure of the processing vessel 4 substantially constant while a valve opening ratio of the pressure control valve 36 is maintained at a predetermined valve opening ratio. Meanwhile, as a high pressure process performed under a high processing pressure, e.g., an oxidation process, a diffusion process and the like may be included, for example.
Next, a processing method to be performed by using the processing apparatus as configured above will be discussed.
In the processing apparatus 52, there are performed various processes such as a process wherein a partial pressure of a processing gas is important, e.g., a film forming process of a tungsten film; and a process wherein a partial pressure of a processing gas is relatively unimportant, e.g., a cleaning process. The respective cases will now be explained. The term “process” used herein includes a process performed in a case when a semiconductor wafer W is present in the processing vessel 4 as well as a process such as a cleaning process performed in a case when there is no semiconductor wafer W present.
<A Process Wherein a Partial Pressure of a Processing Gas is Important: a Film Forming Process of a Tungsten Film>
First, a process wherein a partial pressure of a processing gas is important will now be discussed.
Here, the term “a process wherein a partial pressure of a processing gas is important” refers to a film forming process for depositing a tungsten film by using, e.g., a WF₆gas and a H₂gas. For depositing the tungsten film of good electrical characteristics with an appropriate film forming rate while maintaining a high in-surface uniformity in a film thickness in an in-surface of a wafer, flow rates of both gases, a flow rate ratio, a processing pressure, a processing temperature and the like must be kept with a high accuracy. Such a process is performed by following steps as illustrated in, e.g., a flowchart described in FIG. 2.
First, if an unprocessed semiconductor wafer W is mounted on the mounting table 8 of the processing vessel 4, the vacuum pump 38 of the vacuum pumping unit 32 is operated to exhaust an inside of the processing vessel 4 to vacuum, and the vacuum pump 38 is maintained at the specified number of revolutions for the film forming process (S1). The number of revolutions may be different from that when performing a cleaning process. At the same time, the wafer W is heated to be kept at a predetermined temperature (S2). Then, a film forming process is started to deposit a tungsten film by setting the WF₆gas and the H₂gas at specified flow rates, respectively, and flowing them (S3). During the film forming process, an inner pressure of the processing vessel 4 is detected all the time by the pressure gauge 48 (S4). A pressure detection value is compared with a set value preset in the control unit 54, and an opening ratio of the pressure control valve 36 installed in the exhaust line 34 is properly adjusted such that the detection value becomes equal to the set value (NO of S5 and S6). The film forming process is carried out for a predetermined time (YES of S5 and NO of S7). After the film forming process is carried out for the predetermined time (YES of S7), the process is terminated. The time required in adjusting the pressure control valve 36 (about several seconds) is much shorter than the time required for the film forming process, and thus negligibly offsets the film thickness produced during the film forming process.
<A Process Wherein a Partial Pressure of a Processing Gas is Relatively Unimportant: a Cleaning Process>
Next, a process wherein a partial pressure of a processing gas is relatively unimportant will now be discussed.
Here, the term “a process wherein a partial pressure of a processing gas is relatively unimportant” refers to a cleaning process for removing residual deposition films and the like inside the processing vessel by using, e.g., a cleaning gas. For keeping a specified etching rate, a flow rate of the cleaning gas and a processing pressure need to be maintained at preset values, respectively. At this time, the processing pressure is set at a much higher value than that for the case when performing the prior film forming process. Such a processing is carried out as illustrated in, e.g., a flowchart shown in FIG. 3.
First, the wafer W is unloaded from the processing vessel 4 to make an inside of the processing vessel 4 an airtight state, and the vacuum pump 38 is set and maintained at the preset specific number of revolutions for the cleaning (S11). Subsequently, a cleaning process is started by flowing a nonreactive gas, e.g., Ar or the like, and at the same time, flowing as a processing gas a cleaning gas, e.g., ClF₃gas, at a preset flow rate (S12). Simultaneously, the pressure control valve 36 is set at a preset specific valve opening ratio, and this state is maintained continuously (S13). The valve opening ratio has been experimentally obtained in advance such that the pumping conductance of the vacuum pumping unit 32 during the cleaning process is optimized.
Further, during the cleaning process, an inner pressure of the processing vessel 4 is detected all the time by the pressure gauge 48 (S14). A pressure detection value is compared with a set value preset in the control unit 54, and the flow rate controller 12A installed in the nonreactive gas supply unit 12 is properly adjusted such that the detection value becomes equal to the set value (NO of S15 and S16). During this time, a flow rate of the ClF₃gas is maintained at a constant value all the time. The cleaning process is carried out for a predetermined time (YES of S15 and NO of S17). After the cleaning process is carried out for the predetermined time (YES of S17), the process is terminated.
As described above, even in case when many kinds of processes having big differences in the employed pressure ranges, such as the film forming process of the tungsten film or the cleaning process for removing unnecessary depositions inside the processing vessel 4, are performed, the pressure control in each process can be properly carried out without using a bypass line or multiple pressure control valves.
Further, the number of components to be used becomes small, so that maintenance and repair can be carried out rapidly, thereby improving the efficiency in the maintenance and repair.
Generally, since a response operation of the flow rate controller 12A is much faster than that of the pressure control valve 36, the processing pressure can be obtained faster by the pressure control of the flow rate controller 12A; and, in accordance with the present invention, the pressure controls are conducted by using the flow rate controller having a rapid response operation in some processes, in contrast with the conventional apparatus in which the pressure controls are conducted by the pressure control valve in all processes. As a result, the processing time can be reduced in the present invention and thus throughput can be improved.
Next, in case of using many kinds of processing gases contrary to the respective processes as mentioned above, if corresponding process can be performed within a specific partial pressure range without deteriorating quality of the processing result, the valve opening ratio (open angle) of the pressure control valve 36 may be set large, e.g., 100%, during such a process and an inner pressure of the processing vessel 4 is controlled by adjusting flow rates of the respective processing gases while keeping constant the flow rate ratio between the processing gases. Thus, a predetermined process may be carried out by only adjusting the flow rate.
Typical examples of such a process can be a PVD (Physical Vapor Deposition) process, a plasma pre-cleaning process, a dry etching process and the like, which can be performed in processing apparatus using a mounting table having an electrostatic chuck.
FIG. 4 shows a cross sectional view of a mounting table in case of performing a pre-cleaning process of one embodiment.
A mounting table 101 has an electrostatic chuck 107 on a mounting table main body 103, and a DC electrode 102 is embedded in the electrostatic chuck 107. A wafer is configured to be adsorbed or separated by ON/OFF of currents flowing towards the DC electrode 102. The electrostatic chuck 107 is made of a dielectric insulation member, and the wafer W is mounted on the electrostatic chuck 107. Meanwhile, in the mounting table main body 103, there is formed a heat exchange medium path 109 for cooling the electrode, and a cooling fluid, e.g., a water or a fluorine-based fluid (galden etc.), is supplied and circulated through a medium supply path 106 and a medium collection path 108. Further, the mounting table 103 is cooled by the cooling fluid and thus the wafer W is cooled. In the electrostatic chuck 107, there is installed a gas introduction path 117 supplying between the wafer W and the mounting table 101 a backside gas, e.g., a He and the like, having a high thermal conductivity. The backside gas is supplied through a gas supply path 105 and flows between the wafer W and the dielectric insulation member, to thereby make the heat transfer from a plasma processed wafer W to the electrode easier and to facilitate a cooling effect resulting in improvement of etching efficiency. Further, the backside gas is discharged from the backside gas introduction path 117 and passes through between the wafer W and the dielectric insulation member, and thus it leaks from an outer periphery of the wafer W to an inside of the processing vessel, as indicated by an arrow R.
In case when a process is carried out by using such a mounting table 101, the wafer temperature to be controlled for each plasma process is changed, so that a supply amount of the backside gas is minutely changed, or a supply amount of the backside gas must be adjusted in accordance with this. Accordingly, the inner pressure of the chamber is changed for each wafer process, but it cannot be controlled by the pressure control valve 36 since the pressure change inside the chamber is very small.
For preventing such a pressure change inside the chamber by finely adjusting the supply of the nonreactive gas, a pre-cleaning process is performed in accordance with a flowchart described in FIG. 5.
First, the vacuum pump 38 of the vacuum pumping unit 32 is operated to exhaust the inside of the processing vessel 4 to vacuum, and is maintained at the predetermined number of revolutions (S21). Subsequently, the wafer W is chucked (S22). Then, the backside gas formed of Ar is provided between the wafer W and the mounting table 101 (S23). Subsequently, the nonreactive gas is supplied into the chamber, and the processing gas is set at a specified flow rate (S24). Simultaneously, the pressure control valve 36 is set at a specified valve opening ratio (S25). Further, an inner pressure of the processing vessel is detected by the pressure gauge 48 (S26). A pressure detection value is compared with a set value preset in the control unit 54 (S27). If the detection value is different from the set value, the flow rate controller 12A installed in the nonreactive gas supply unit 12 is properly adjusted by the control unit 54 such that the detection value becomes equal to the set value (S28). Further, if the detection value comes to be equal to the set value, plasma ignition is conducted by the control unit 54 (S29). Then, it is determined whether or not a predetermined processing time is elapsed (S30), and the process is terminated after the predetermined time has elapsed.
As described above, in such a control, a minor pressure change of the chamber caused by the backside gas leakage can be prevented by adjusting the supply amount of the nonreactive gas with high accuracy. In this case, the processing pressure can be controlled by using only a control operation of the flow rate controller having a rapid response speed without adjusting the valve opening ratio of the pressure control valve 36, so that controllability is enhanced, thereby resulting in improvement of throughput.

Second Embodiment

In the aforementioned embodiment, such a case has been explained by using an example where an integrated exhaust line 34 is installed and one vacuum pump 38 is installed therein, as shown in FIG. 1. However, in case when pumping capacity is insufficient with one vacuum pump 38, a configuration of a second embodiment shown in FIG. 6 may be adopted. Namely, in this case, a second vacuum pump 60 formed of, e.g., a turbo molecular pump, is installed in series with the pressure control valve 36, and a bypass exhaust path 62 is connected to the exhaust line 34 such that it bypasses the pressure control valve 36 and the second vacuum pump 60. Further, a converting opening/closing valve 64 is installed in the bypass exhaust path 62. An inner diameter of the bypass exhaust path 62 is about in the range from 25 to 40 mm.
In this embodiment, the opening/closing valves 40 of the exhaust line 34 are first closed in case when vacuum-exhausting the inside of the processing vessel 4; instead, the converting opening/closing valve 64 of the bypass exhaust path 62 is opened to communicate with the bypass exhaust path 62; and the vacuum pump 38 is rotationally operated to roughly exhaust the processing vessel 4. After somewhat roughly exhausting it, if the inner pressure of the processing vessel 4 is reduced to a specified vacuum level, the opening/closing valves 40 of the exhaust line 34 are opened to rotationally drive the second vacuum pump 60. And, the converting opening/closing valve 64 of the bypass exhaust path 62 is closed. In this way, the vacuum exhaust operation is continuously carried out by two vacuum pumps of the prior vacuum pump 38 and the second vacuum pump 60. Further, in case when a relatively high processing pressure process, e.g., a cleaning process, is carried out, the cleaning process may be performed while the vacuum exhaust operation is performed by closing the opening/closing valves 40 of the exhaust line 34 and only by using the bypass exhaust path 62. In this embodiment, plural processes having big differences in the processing pressure ranges are performed in the same manner with reference to FIGS. 1 to 5.

Third Embodiment

Next, a third embodiment of the present invention will be explained.
FIG. 7 is a schematic diagram showing a third embodiment of a processing apparatus in accordance with the present invention. Identical reference numerals will be assigned and explained for corresponding parts having substantially the same functions and configurations with those in FIGS. 1, 6 and 8. Further, the term “a relatively low processing pressure process” explained herein means a process wherein a partial pressure of a processing gas is important as was explained before, and the term “a relatively high processing pressure process” means a process wherein a partial pressure of a processing gas is unimportant.
As shown in FIG. 7, in the main exhaust line 34, there are installed the pressure control valve 36, the second vacuum pump 60 formed of, e.g., a turbo molecular pump and the first vacuum pump 38 formed of, e.g., a dry pump, in this order from the upstream side to the downstream side thereof. Also, the pressure control valve 36 and the second vacuum pump 60 are disposed between opening/closing valves 40.
Further, the bypass exhaust path 62 is connected to the main exhaust line 34 such that it bypasses the pressure control valve 36, the second vacuum pump 60 and both of the opening/closing valves 40. As mentioned above, the inner diameter of the main exhaust line 34 is large, e.g., in the range from about 100 to 150 mm, and that of the bypass exhaust path 62 is small, e.g., in the range from about 25 to 40 mm.
Still further, in the bypass exhaust path 62, there is installed a soft start valve mechanism 70 having a function of buffering an impact of the vacuum exhaust when exhausting the inside of the processing vessel 4 from an atmospheric pressure to vacuum. Accordingly, the control unit 54 controls the inner pressure of the processing vessel 4 by adjusting the valve opening ratio of the pressure control valve 36 based on a detection value obtained from the pressure gauge 48 installed in the processing vessel 4, in case when performing a relatively low processing pressure process (e.g., film forming process etc.). In case when performing a relatively high processing pressure process (e.g., cleaning process, oxidation process, diffusion process etc.), the exhaust operation through the pressure control valve 36 is stopped, and at the same time, it is controlled such that the soft start valve mechanism 70 is maintained at a low pumping conductance state to flow the exhaust gas through the bypass exhaust path 62.
Specifically, the soft start valve mechanism 70 is formed of a first bypass opening/closing valve 72 installed in the bypass exhaust path 62; an auxiliary bypass exhaust line 74 of a small inner diameter, which is connected to the bypass exhaust path 62 such that it bypasses the first bypass opening/closing valve 72; and an orifice mechanism 76 and a second bypass opening/closing valve 78 that are installed in the auxiliary bypass exhaust line 74 in order.
Here, as is generally known, the orifice mechanism 76 has an orifice (not shown) for narrowing a flow path area, and the soft start valve mechanism 70 can be maintained at a low pumping conductance state by closing the first bypass opening/closing valve 72 and opening the second bypass opening/closing valve 78. Herein, each of the inner diameters of the bypass exhaust path 62 and the auxiliary bypass exhaust line 74, and the flow path area of the orifice hole in the orifice mechanism 76 are preset and the pumping conductance thereof is fixed, enabling a pressure substantially identical to a required processing pressure to be obtained when a relatively high processing pressure process is carried out.
In other words, there are many cases where the processing pressure need not be controlled with high accuracy in a relatively high processing pressure process. In these cases, it is configured such that the pressure control of the processing vessel 4 is conducted by a preset fixed pumping conductance, and operations such as the adjustment of the valve opening ratio and the like are not conducted actively.
Next, an operation of the embodiment as configured above will be explained.
<A Case of Exhausting an Atmospheric State to Vacuum>
In case when the inside of the processing vessel 4 is in the atmospheric state and is exhausted to vacuum, both opening/closing valves 40 of the main exhaust line 34 are first closed to isolate the second vacuum pump 60 comprising a turbo molecular pump, which cannot be used until the inner pressure of the processing vessel 4 reaches to a specified vacuum level. At the same time, the soft start valve mechanism 70 is kept at a low pumping conductance state by closing the first bypass opening/closing valve 72 installed in the bypass exhaust path 62 and by opening the second bypass opening/closing valve 78 installed in the auxiliary bypass exhaust line 74. Under the condition, the first vacuum pump 38 is operated to start the vacuum exhaust. In this case, since an atmosphere of the processing vessel 4 is exhausted only through the auxiliary bypass exhaust line 74 having therein the orifice hole of the orifice mechanism 76, the pumping conductance becomes very low as mentioned above. As a result, the impact of the vacuum exhaust caused in the processing vessel 4 is eased to thereby become very small, and structures or particles inside the processing vessel 4 can be prevented from being scattered in a moment. Further, an unnecessary film attached to an inner wall surface of the processing vessel 4 or a surface of the inner structure may not be peeled off to fall down, so that the generation of the particles can be prevented.
As a result of the vacuum exhaust, if a specific vacuum level (e.g., about 1330 Pa) is reached, the first bypass opening/closing valve 72 is turned to be opened to vacuum exhaust the whole bypass exhaust path 62. At this time, the second bypass opening/closing valve 78 may remain to be either opened or closed.
If a predetermined vacuum level, e.g., about 133 Pa, corresponding to an upper limit of the pressure value in the turbo molecular pump, is reached by further vacuum exhausting it, both of the opening/closing valves 40 installed in the main exhaust line 34 are turned open, and at the same time, the second vacuum pump 60 begins to be operated. At this time, the first pressure control valve 36 becomes fully opened. Simultaneously, the first and the second bypass opening/closing valve 72 and 78 are turned to be closed. By doing this, the inside of the processing vessel 4 can be vacuum exhausted to a low pressure atmosphere.
<A Low Processing Pressure Process: e.g., Film Forming Process>
Next, the pressure control of the processing vessel 4 during a low processing pressure process is substantially same as the case where the partial pressure of the processing gas is important as was explained in the first embodiment.
Namely, the first and the second bypass opening/closing valve 72 and 78 of the soft start valve mechanism 70 are converted into the closed state; both opening/closing valves 40 of the main exhaust line 34 are maintained at the opened state; and the inner pressure of the processing vessel 4 is controlled by adjusting the valve opening ratio of the pressure control valve 36 based on a detection value of the pressure gauge 48. At this time, the flow rate of each gas is maintained at a constant value as determined in a recipe. The processing pressure of a low processing pressure process is in the range from about tens of Pa to hundreds of Pa, for example.
<A High Processing Pressure Process: e.g., Cleaning Process or Oxidation Process>
Next, the pressure control of the processing vessel 4 during a high processing pressure process will be discussed.
In this case, the low pumping conductance state is kept same as in the case where the inside of the processing vessel 4 begins to be exhausted from the atmospheric pressure to vacuum. Namely, contrary to the above-described film forming process, both of the opening/closing valves 40 installed in the main exhaust line 34 are maintained at the closed state to isolate the second vacuum pump 60. In the soft start valve mechanism 70, the first bypass opening/closing valves 72 is maintained at the closed state, and at the same time, the second bypass opening/closing valves 78 is maintained at the opened state, so that the exhaust gas is vacuum exhausted only through the auxiliary bypass exhaust line 74 via the orifice mechanism 76. At this time, the pumping conductance of the soft start valve mechanism 70 is substantially same as that of the pressure control valve 36 in which a minimum gas is formed even in case of the fully closed state.
Accordingly, the process can be performed while the processing pressure inside the processing vessel 4 is kept high. The processing pressure of the process whose processing pressure is high as mentioned above is in the range from about thousands of Pa to 20000 Pa, for example.
In the high processing pressure process, the inner pressure of the processing vessel 4 could not be controlled actively, but it may not be limited thereto. For example, it can be configured such that the inner pressure of the processing vessel 4 is detected by the pressure gauge 48 and the flow rate controller is controlled by the control unit 54 to maintain the detection value at a predetermined pressure, and thus a gas flow rate, e.g., a flow rate of a nonreactive gas or a cleaning gas, or a flow rate of an oxidation gas in case of performing an oxidation process, is controlled.
By doing this, the processing pressure can be controlled with high accuracy even in case of the high processing pressure process.
Further, the soft start valve mechanism 70 is explained for a case where it is formed of the auxiliary bypass exhaust line 74, the first and the second bypass opening/closing valve 72 and 78 and the orifice mechanism 76. However, as the soft start valve mechanism 70, a soft start valve of SMC company (registered trademark) may be used for example, which has three functions of: setting the inside of the bypass exhaust path 62 at a completely blocked state; setting the bypass exhaust path 62 at a low pumping conductance state; and setting the inside of the bypass exhaust path 62 at about middle pumping conductance state somewhat higher than the low pumping conductance.
Further, in the respective embodiments, a case of the film forming process of the tungsten film was explained as an example, but the present invention may be applied for the case of forming other film species.
Still further, a process wherein a partial pressure of the processing gas is important is not limited to the film forming process, and other processes may be used. In the same manner, a processing wherein a partial pressure of the processing gas is relatively unimportant is not limited to the cleaning process, and other processes, e.g., the oxidation process, the diffusion processing and the like as mentioned above, may be applied.
Still further, the supply type of each gas is nothing but an example. If the kinds of the processing gases increase or decrease, the number of gas supply units accordingly increases or decreases. Further, with respect to the configuration of the shower head unit 10, the present invention may adopt any of a pre-mix type or a post-mix type, wherein in the pre-mix type, the processing gas is mixed before being injected towards the mounting table 8 inside the processing vessel 4, and in the post-mix type, the processing gas is mixed after being injected from the shower head unit 10. Still further, a gas introduction unit not using the shower head unit 10 may be applied for the present invention.
Still further, a single wafer processing apparatus was explained as an example, but the present invention may be applied to a batch type processing apparatus in which plural objects are processed at a time.
Sill further, the control by the mass flow controller is mainly employed for the PVD process which is performed within a specific partial pressure range, and the pressure control valve is used for the CVD process. But, they can be applied for the case of performing both of the PVD and the CVD processes in the same apparatus.
Still further, in the aforementioned embodiments, the semiconductor wafer was explained as an object to be processed. However, it is not limited to this, and a glass substrate, an LCD substrate or the like, may be used as well.
Still further, in the aforementioned embodiments, either the temperature control unit or the pressure control valve was kept constant during the pressure control, but the pressure control may be conducted all the time by both operations thereof while the temperature control unit and the pressure control valve are not made constant.
While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

1. A processing apparatus comprising:

a processing vessel having therein a mounting table for mounting an object to be processed;

a gas introduction unit for introducing a gas towards the mounting table inside the processing vessel;

a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a processing gas;

a nonreactive gas supply unit, connected to the gas introduction unit and provided a flow rate controller, for supplying a nonreactive gas;

a vacuum pumping unit connected to the processing vessel and provided with a pressure control valve having a variable valve opening ratio and a vacuum pump;

a pressure gauge installed at the processing vessel; and

a control unit for controlling the valve opening ratio of the pressure control valve based on a detection value of the pressure gauge while making the processing gas flow to the flow rate controller of the processing gas supply unit at a constant flow rate when performing a process wherein a partial pressure of the processing gas is important; and for fixing the valve opening ratio of the pressure control valve at a predetermined value, and at the same time, operating the flow rate controller of the nonreactive gas supply unit to control a flow rate based on the detection value of the pressure gauge when performing a process wherein the partial pressure of the processing gas is relatively unimportant.

2. The processing apparatus of claim 1, further comprising one or more additional processing gas supply units, wherein the control unit is configured to set the valve opening ratio of the pressure control valve at a fully opened state during a predetermined process; and in that state, to let the flow rate controller of each processing gas supply unit control each flow rate based on the detection value of the pressure gauge while maintaining a flow rate ratio at a substantially constant state.

3. The processing apparatus of claim 1, wherein the vacuum pumping unit is provided with an additional vacuum pump; and a bypass exhaust path bypassing the pressure control valve of the vacuum pumping unit and the second vacuum pump, wherein a converting opening/closing valve is installed in the bypass exhaust path.

4. A processing method for performing a process on an object by using a processing apparatus, which includes a processing vessel having therein a mounting table for mounting the object to be processed; a gas introduction unit for introducing a gas towards the mounting table inside the processing vessel; a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a processing gas; a nonreactive gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a nonreactive gas; a vacuum pumping unit connected to the processing vessel and provided with a pressure control valve having a variable valve opening ratio and a vacuum pump; and a pressure gauge installed at the processing vessel,

wherein the valve opening ratio of the pressure control valve is controlled based on a detection value of the pressure gauge while a flow rate of the processing gas flowing to the processing gas supply unit is maintained constant when performing a first process in which a partial pressure of the processing gas is important; and

wherein the valve opening ratio of the pressure control valve is fixed at a predetermined value, and at the same time, a flow rate of the nonreactive gas flowing to the nonreactive gas supply unit is controlled based on the detection value of the pressure gauge when performing a second process in which the partial pressure of the processing gas is relatively unimportant.

5. The processing method of claim 4, wherein the processing apparatus includes one or more additional processing gas supply units; and

wherein the valve opening ratio of the pressure control valve is set at a fully opened state during a predetermined process; and in that state, each flow rate is controlled based on the detection value of the pressure gauge while a flow rate ratio of the processing gas flowing through each processing gas supply unit is maintained at a substantially constant state.

6. The processing method of claim 4, wherein the number of revolutions in the process wherein the partial pressure of the processing gas is important is controlled by the vacuum pump to be different from that in the process in which the partial pressure of the processing gas is unimportant.

7. The processing method of claim 4, wherein the process in which the partial pressure of the processing gas is important is a film forming process, and the process in which the partial pressure of the processing gas is relatively unimportant is a cleaning process.

8. The processing method of claim 4, wherein the processing vessel is pumped during the first and the second process by the vacuum pumping unit.

9. A processing apparatus comprising:

a nonreactive gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a nonreactive gas;

a vacuum pumping unit connected to the processing vessel and provided with a pressure control valve having a variable valve opening ratio and a first vacuum pump;

a pressure gauge installed at the processing vessel; and

a control unit for fixing the valve opening ratio of the pressure control valve at a predetermined value, and at the same time, performing a first control for controlling a flow rate by using the flow rate controller of the nonreactive gas supply unit based on a detection value of the pressure gauge.

10. The processing apparatus of claim 9, wherein the control unit performs a second control for controlling the valve opening ratio of the pressure control valve based on the detection value of the pressure gauge while making the processing gas flow to the flow rate controller of the processing gas supply unit at a constant flow rate, and

wherein the second control is used for a process wherein a partial pressure of the processing gas is important.

11. The processing apparatus of claim 9, wherein the first control is used for a process in which a partial pressure of the processing gas is relatively unimportant.

12. The processing apparatus of claim 9, wherein the first control is used for a case when a process is performed at a low pressure where a passing flow rate is not substantially changed even though the valve opening ratio of the pressure control valve is changed.

13. A processing method for performing a process on an object by using a processing apparatus, which includes a processing vessel having therein a mounting table for mounting the object to be processed; a gas introduction unit for introducing a gas towards the mounting table inside the processing vessel; a processing gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a processing gas; a nonreactive gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a nonreactive gas; a vacuum pumping unit connected to the processing vessel and a pressure control valve having a variable valve opening ratio and a first vacuum pump; and a pressure gauge installed at the processing vessel,

wherein the valve opening ratio of the pressure control valve is fixed at a predetermined value; and

wherein a first control for controlling a flow rate is performed by using the flow rate controller of the nonreactive gas supply unit based on a detection value of the pressure gauge.

14. The processing method of claim 13, wherein a second control for controlling the valve opening ratio of the pressure control valve is further performed based on the detection value of the pressure gauge while making the processing gas flow to the flow rate controller of the processing gas supply unit at a constant flow rate, the second control being used for a process in which a partial pressure of the processing gas is important.

15. The processing method of claim 13, wherein the first control is used for a process in which a partial pressure of the processing gas is relatively unimportant.

16. The processing method of claim 15, wherein the process in which the partial pressure of the processing gas is relatively unimportant is a cleaning process.

17. The processing method of claim 13, wherein the first control is used for a case when a process is performed at a low pressure where a passing flow rate is not substantially changed even though the valve opening ratio of the pressure control valve is changed.

18. The processing method of claim 17, wherein the low pressure process where the passing flow rate is not substantially changed even though the valve opening ratio of the pressure control valve is changed is a plasma etching process.

19. The processing method of claim 14, wherein the process in which the partial pressure of the processing gas is important is a film forming process.

20. A processing apparatus including a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a gas towards the mounting table inside the processing vessel; a gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined gas; a vacuum pumping unit connected to the processing vessel and provided with a first vacuum pump, a second vacuum pump and a pressure control valve having a variable valve opening ratio; and a pressure gauge for detecting a pressure of the processing vessel, the processing apparatus comprising:

a bypass exhaust path installed to bypass the pressure control valve and the second vacuum pump;

a soft start valve mechanism installed in the bypass exhaust path, the soft start valve mechanism having a function of buffering an impact of a vacuum exhaust when exhausting an inside of the processing vessel from an atmospheric pressure to vacuum; and

a control unit installed to control an inner pressure of the processing vessel by adjusting the valve opening ratio of the pressure control valve based on a detection value of the pressure gauge during a relatively low processing pressure process; and to stop an exhaust toward the pressure control valve, and at the same time, to flow an exhaust gas to the bypass exhaust path while maintaining the soft start valve mechanism at a low pumping conductance state during a relatively high processing pressure process.

21. The processing apparatus of claim 20, wherein the control unit adjusts a flow rate by using the flow rate controller based on the detection value of the pressure gauge during the relatively high processing pressure process, to thereby control the inner pressure of the processing vessel.

22. The processing apparatus of claim 20, wherein the soft start valve mechanism includes:

a first bypass opening/closing valve installed in a bypass exhaust line of the bypass exhaust path;

an auxiliary bypass exhaust line installed to bypass the first bypass opening/closing valve;

a second bypass opening/closing valve installed in the auxiliary bypass exhaust line; and

an orifice mechanism installed in the auxiliary bypass exhaust line.

23. The processing apparatus of claim 22, wherein the control unit turns the first bypass opening/closing valve into a closed state and turns the second bypass opening/closing valve into an opened state, in order to realize the low pumping conductance state.

24. The processing apparatus of claim 20, wherein the soft start valve mechanism is formed of a soft start valve.

25. A processing method for performing a process on an object by using a processing apparatus, which includes a processing vessel having therein a mounting table for mounting an object to be processed; a gas introduction unit for introducing a gas towards the mounting table inside the processing vessel; a gas supply unit, connected to the gas introduction unit and provided with a flow rate controller, for supplying a predetermined gas; a vacuum pumping unit connected to the processing vessel and provided with a first vacuum pump, a second vacuum pump and a pressure control valve having a variable valve opening ratio; and a pressure gauge for detecting a pressure of the processing vessel,

wherein a bypass exhaust path bypassing the pressure control valve and the second vacuum pump is installed; wherein a soft start valve mechanism in the bypass exhaust path is installed, the soft start valve mechanism having a function of buffering an impact of a vacuum exhaust when exhausting an inside of the processing vessel from an atmospheric pressure to vacuum; and

wherein an inner pressure of the processing vessel is controlled by adjusting the valve opening ratio of the pressure control valve based on a detection value of the pressure gauge during a relatively low processing pressure process; and an exhaust toward the pressure control valve is stopped, and at the same time, an exhaust gas flows to the bypass exhaust path while the soft start valve mechanism is maintained at a low pumping conductance state during a relatively high processing pressure process.

26. A computer readable storage medium storing therein a program for controlling the processing method of claim 4, 13 or 25.