Patent Publication Number: US-2019189403-A1

Title: Plasma processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Japanese Patent Application No. 2017-242308, filed Dec. 19, 2017. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The present invention relates to a plasma processing apparatus using plasma related to a semiconductor production. 
     Recently, high integration of devices has advanced, and a processing technique at an atomic layer level has been required. Complication of a device structure, miniaturization of the device structure, and increase in aspect ratio of the device structure have advanced every year. Thus, CD dimension control and depth control for a sparse part and a dense part of a high-aspect structure have become key techniques. 
     Conventionally, in order to control a sparse/dense difference, plasma has been generated inside an etching chamber to perform etching and adjustment of a deposited film. However, a problem that a covering property (Step Coverage) in a high-aspect pattern becomes worse has become apparent. For this problem, use of an Atomic Layer Deposition (ALD, hereinafter referred to as the ALD) that ensures film formation having a good covering property has been examined. 
     Although a precursor gas as a raw material differs depending on a membrane material as an object, a precursor gas in an atomic unit is periodically supplied to a film forming substrate surface together with a carrier gas to be physically adsorbed on the substrate surface, thus ensuring film formation of a film having one layer of atoms. The use of the ALD has been known as one of effective means that ensures uniform and highly accurate film thickness control even in the high-aspect structure. 
     As the precursor gas used in the ALD, for example, BDEAS is used. Since the BDEAS has a property close to that of ammonia, it is necessary to avoid being mixed with a supporting gas. In view of this, in a vacuum processing apparatus including an ALD mechanism that ensures uniform film formation, there is a need to include gas supply means having a hard interlock of a gas valve in accord with the safety. 
     For example, Japanese Unexamined Patent Application Publication No. 2016-145412 as a prior art regarding the atomic layer deposition (ALD) discloses a method for uniformly dosing a precursor for improving film uniformity in a vapor deposition cycle of an atomic layer depositing method (ALD). Regarding the interlock of the gas valve, WO2016/121075 discloses a vacuum processing apparatus that has gas supply means having a hard interlock for a pair of gas valves. Furthermore, Japanese Unexamined Patent Application Publication No. 2008-124190 discloses a vacuum processing apparatus capable of uniformly processing a specimen placed on a sample stand in a processing chamber. 
     In order to perform an atomic layer deposition (ALD) process, a configuration and a hard interlock of a gas supply system are required to safely supply a precursor gas having high reactivity and high inflammability into a vacuum container. 
     The atomic layer deposition (ALD) process supplies the precursor gas (adsorption species) into a vacuum processing apparatus to form a molecular layer with physical adsorption on a sample substrate and inside the vacuum processing apparatus. This molecular layer has one layer having strongest physical adsorption force (van der Waals force) that remains even when an exhaust process using an inert gas or the like is performed. In view of this, there is concern that the molecular layer adsorbed inside a vacuum processing chamber reacts at the time of processing after the atomic layer deposition (ALD) process to generate a particle. 
       FIG. 6  illustrates a method of supplying the precursor gas to a plasma processing apparatus. In this method of supplying the precursor gas to the plasma processing apparatus, the precursor gas is supplied into a processing chamber through a plate having a through-hole such as a shower plate. However, the passage through the through-hole of the shower plate causes concern about the generation of the particle in the through hole. There is concern that this particle drops on the sample substrate, which is an extension of the through-hole of the shower plate to generate a defect, and thus, a stable production by reducing a yield in an etching process of the sample substrate cannot be performed. 
     There is concern in the safety that, for example, the precursor gas mixes with a process gas inside a gas supply pipe to cause a product to be fixedly secured inside the gas pipe, and thus, the gas supply pipe gets stuck. Usually, an interlock function with software is implemented to avoid dangerous manipulation that is input incorrectly or purposely. However, in many cases, the soft interlock is considered insufficient as a foolproof function. Thus, in addition to an electrical interlock (soft interlock), yet another mechanism is required. 
     In view of this, it is necessary to implement a function that prevents the mixture by using a double hard interlock with respect to valves for a pair of gases that must not be simultaneously flowed. Accordingly, in opening/closing operation of the respective gas valves, it is required that, in accordance with a pressure signal or a preliminarily examined circuit using an electrical relay circuit or the like, the mutual opening/closing operations between different valves are controlled to prevent generation of abnormal reaction, leakage, contamination of a gas source (mixture with another gas), and the like of the gas. 
     In consideration of the above-described problems, the present invention provides a plasma processing apparatus that ensures a stable supply of a process gas and a precursor gas to a processing chamber. 
     SUMMARY 
     The present invention is a plasma processing apparatus that includes a processing chamber where plasma processing is performed on a sample, a radio frequency power supply that supplies radio frequency power to generate plasma, a sample stage on which the sample is placed, and a gas supply unit that supplies a gas to the processing chamber. 
     The gas supply unit includes a first pipe that supplies a first gas as a gas for etching process to the processing chamber, a second pipe that supplies a second gas as a gas for etching process to the processing chamber, and a third pipe through which a third gas as a gas for deposition process flows. The third pipe is coupled to the second pipe. A fourth valve is arranged on the second pipe. The fourth valve prevents the third gas from flowing in a direction toward a supply source of the second gas. 
     The present invention ensures the stable supply of the process gas and the precursor gas to the processing chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a plasma processing apparatus according to the present invention; 
         FIG. 2  is a schematic diagram of an air circuit of air for air-driven according to the present invention; 
         FIG. 3A-3D  are diagrams illustrating a flow of an ALD process; 
         FIG. 4A-4D  are diagrams illustrating operation of a gas supply unit according to the present invention at the time of the ALD process; 
         FIG. 5A-5D  are diagrams illustrating operation of a gas supply unit according to the present invention at the time of the ALD process; 
         FIG. 6  is a schematic diagram illustrating a gas supply mechanism; 
         FIG. 7  is a schematic diagram illustrating a gas supply mechanism; 
         FIG. 8  is a schematic diagram of an air circuit of air for air-driven; and 
         FIG. 9  is a schematic diagram of an air circuit of air for air-driven. 
     
    
    
     DETAILED DESCRIPTION 
     A plasma processing apparatus according to the embodiment excites particles such as atoms or molecules of a gas for processing to turn them into plasma. The gas for processing is supplied into a processing chamber arranged in a vacuum container using a microwave electric field as an electric field supplied into the processing chamber to generate the plasma inside the processing chamber. Then, the plasma processing apparatus etches a film structure containing a mask and a film layer as a process target that are preliminarily formed on a sample top surface having a substrate shape such as a semiconductor wafer arranged inside the processing chamber. 
     Especially, the plasma processing apparatus according to the embodiment is what is called a microwave ECR type plasma etching apparatus that forms a magnetic field inside the processing chamber together with the electric field, and causes the electric field to interact with the magnetic field with Electron Cyclotron Resonance (ECR) as a specific resonance between these electric field and magnetic field to generate the plasma. 
     A description will be given of a configuration of a plasma processing apparatus illustrated in  FIG. 1 . This plasma processing apparatus includes a vacuum container  105 , a first gas supply unit  106 , a second gas supply unit  107 , and a stage  109 . The vacuum container  105  can be decompressed and has a vacuum processing chamber  113  as an inside processing chamber where plasma processing is performed on a semiconductor wafer  108 . The first gas supply unit  106  is coupled to the vacuum container  105  and supplies a first gas to generate the plasma inside the vacuum container  105 . The second gas supply unit  107  supplies a second gas into the vacuum container  105 . The stage  109  is a sample stage on which the semiconductor wafer  108  as a sample is placed. 
     Further, this plasma processing apparatus includes an electromagnetic-wave supply unit  101  and a radio frequency power supply  112 . The electromagnetic-wave supply unit  101  supplies electromagnetic wave to generate the plasma. The radio frequency power supply  112  is coupled to the stage  109  and supplies radio frequency power via a matching box  111  to adjust ion energy that enters the wafer  108 . The electromagnetic-wave supply unit  101  includes a radio frequency power supply  118  that supplies the radio frequency power to the vacuum processing chamber  113 . The plasma processing apparatus includes a vacuum exhaust air unit  110  that exhausts air inside the vacuum processing chamber  113  of the vacuum container  105  to decompress the vacuum container  105 . 
     Here, the first gas for plasma generation, which is supplied to the vacuum processing chamber  113 , is supplied via a shower plate  104  from the first gas supply unit  106  via a gas supply line G 1 . An arrow  115  in  FIG. 1  indicates a gas flow of the first gas. The use of the shower plate  104  improves in-plane uniformities of a distribution of the plasma and a flow rate distribution, thus uniformizing etching rates and deposition rates of the center and the outermost periphery in a processed sample. 
     Similarly, the second gas for plasma generation, which is supplied to the vacuum processing chamber  113 , is supplied from the second gas supply unit  107  via a gas supply line G 3 . An arrow  116  in  FIG. 1  indicates a gas flow of the second gas. Types and compositions of the first and second gases differ depending on a type and an objective processed shape of the processed material formed on the wafer  108 . 
     A pressure inside the vacuum processing chamber  113  is adjusted by the vacuum exhaust air unit  110 . For the vacuum exhaust air unit  110 , for example, a configuration where a pressure control valve is coupled to a dry pump or a turbo molecular pump is used. The pressure inside the vacuum processing chamber  113  can be controlled at a desired pressure value appropriate for the plasma such that a degree of opening of the pressure control valve is controlled. In order to cause the ion to enter the wafer  108  with improving anisotropy, a pressure of about 0.1 to 100 Pa is generally used in an etching process. 
     The electromagnetic wave to generate the plasma is supplied from the electromagnetic-wave supply unit  101  to the vacuum processing chamber  113  via a dielectric window  103  formed of a material through which the electromagnetic wave is transmitted. For example, the electromagnetic wave is microwave having a frequency of 2.45 GHz, and the dielectric window  103  is formed of a material through which the microwave is transmitted, such as quartz. Additionally, an electromagnetic coil  102  forms the magnetic field required for the electron cyclotron resonance inside the vacuum processing chamber  113 . For example, a magnetic-flux density required for the electron cyclotron resonance in the microwave of 2.45 GHz is 875 G. Here, a magnetic field forming mechanism is considered to include the magnetic field coil  102 . 
     The microwave efficiently accelerates electron to obtain the electron having a high energy at the proximity of this magnetic field required for the electron cyclotron resonance. Then, this high-energy electron efficiently ionizes molecules of an etching gas, thus efficiently generating the plasma. Charged particles generated by the plasma are transported with being restrained by a magnetic line of the magnetic field formed by the electromagnetic coil  102 . Accordingly, for example, controlling the magnetic field formed by the electromagnetic coil  102  ensures control of an ionic flux distribution onto the wafer  108 . 
     The following describes a gas supply line and a valve configuration and control system in the gas supply unit of the plasma processing apparatus using  FIG. 1 . 
     A process-gas supply system  201  has the gas supply lines G 1  and G 3 . The gas supplied from the gas supply line G 1  is supplied to the vacuum container  105  via through-holes  114  of the shower plate  104 . The gas supplied from the gas supply line G 3  is supplied to the vacuum container  105  from a position without passing through the through-hole  114  of the shower plate  104 . The gas supply line G 1  has a valve V 1 . The gas supply line G 3  has a valve V 3  and a valve V 4 . 
     These valves V 1  and V 3  are normally closed type air-driven valves. The valve V 4  is a normally open type air-driven valve. The valve V 3  is arranged on a position far from the vacuum container  105  with respect to the valve V 4 . In this embodiment, the normally open type air-driven valve is used for the valve V 4 . However, if the normally closed type air-driven valve is used for the valve V 4 , there will be concern that the process gas mixes with the precursor gas. In view of this, in order to decrease the potential that the process gas mixes with the precursor gas, it is required to use the normally open type air-driven valve for the valve V 4 . 
     Next, a precursor-gas supply system  202  has a gas supply line G 2 . This gas supply line G 2  has a valve V 2 . This valve V 2  is a normally closed type air-driven valve. This gas supply line G 2  is coupled to the gas supply line G 3  to be coupled to a pipe between the valve V 4  and the second gas supply unit  107 . The “gas supply unit” of the plasma processing apparatus according to the present invention includes the process-gas supply system  201  and the precursor-gas supply system  202 . The following describes a hard interlock between the above-described respective valves using  FIG. 2 . 
     As illustrated in  FIG. 2 , the air for air-driven of the valve V 2  is controlled by a  3 -position spring return center exhaust type  5 -port solenoid valve  12  via a pilot valve P 2 . This solenoid valve has solenoid coil excitation elements S 2  and S 3 , and any one of the solenoid coil excitation element S 2  and the solenoid coil excitation element S 3  is excited. For example, V 2  is opened via the pilot valve P 2  when the solenoid coil excitation element S 2  is excited, and V 3  is opened when the solenoid coil excitation element S 3  is excited. In view of this, an air signal is formed in inevitably only the solenoid coil excitation element at an excited side, thus preventing both of the valve V 2  and the valve V 3  from simultaneously opening. 
     The pilot valve P 2 , which is a pilot valve for forming the air signal, is controlled with a signal transmitted by a pilot air signal line  21  formed by a pilot valve P 11 . The air for air-driven of V 3  is controlled by the 3-position spring return center exhaust type 5-port solenoid valve  12 . 
     The air for air-driven of the valve V 1  and the valve V 4  is controlled by  2 -position spring return type solenoid valves  11  and  13  respectively. For these solenoid valves, the respective valves are opened such that respective solenoid coil excitation elements are excited. In accordance with signals that excite solenoid coil excitation elements S 1  and S 4 , the airs for opening the respective valve V 1  and valve V 4  are generated. Further, the pilot valve P 11  is controlled by the  2 -position spring return type solenoid valve  13  that controls the air for air-driven of the valve V 4 . 
     This pilot valve P 11 , which is a pilot valve for forming the air signal, forms the pilot air signal line  21 . The air is taken in from an air source  32  with a signal transmitted through the pilot air signal line  21 , this taken air is supplied to the pilot valve P 2 , and then, the air is supplied to the valve V 2  from the pilot valve P 2 . The air supplied from the air source  32  is exhausted from an air exhaust line  31  after driving the respective valves. The following describes operation of the respective valves when the precursor gas or the process gas is supplied. 
     In the case where the precursor gas is supplied in an air circuit illustrated in  FIG. 2 , when the solenoid coil excitation element S 4  is excited, the pilot air signal line  21  is formed through the pilot valve P 11  at the same time as the valve V 4  is closed. In view of this, the pilot valve P 2  is driven to make an inside of the pilot valve passable. When the solenoid coil excitation element S 2  is excited, the valve V 2  is opened to supply the precursor gas. In this respect, an inert gas is supplied such that the solenoid coil excitation element S 1  is excited to open the valve V 1  in order to prevent the precursor gas to the shower plate. 
     Next, in the case where the process gas is supplied in the air circuit illustrated in  FIG. 2 , when the solenoid coil excitation elements S 1  and S 3  are excited, the valves V 1  and V 3  are opened to supply the process gas to the vacuum container  105 . Since the solenoid coil excitation element S 2  is not excited, the valve V 4  is opened. In this case, even if the 3-position spring return center exhaust type 5-port solenoid valve  12  malfunctions or breaks down to excite the solenoid coil excitation element S 2 , the valve V 2  is not opened since the pilot valve P 2  is not driven. Thus, the precursor gas does not mix with the process gas. The following describes a necessity of the valve V 4 . 
     A hard interlock in a case where there is no normally open type air-driven valve V 4  in  FIG. 1  will be described using  FIG. 8 . As illustrated in  FIG. 8 , the airs for air-driven of the valves V 2  and V 3  are controlled by the 3-position spring return center exhaust type 5-port solenoid valve  12 . The air for air-driven of the valve V 1  is controlled by the  2 -position spring return type solenoid valve  11 . In the case of an air circuit as illustrated in  FIG. 8 , the air signal is formed at inevitably only the excited side of the solenoid coil excitation elements S 2  and S 3  for the valves V 2  and V 3 . 
     In such air circuit, when the valve V 1  is opened to supply the process gas other than the inert gas, there is concern that the solenoid coil excitation element S 2  excited due to the malfunction or the breakdown opens the valve V 2  to supply the precursor gas, and this causes the process gas to mix with and react to the precursor gas inside the plasma processing apparatus to generate a particle, thus breaking the plasma processing apparatus. 
     In view of this, the normally open type air-driven valve V 4  is arranged on the gas supply line G 3 , and the hard interlock illustrated in  FIG. 2  is applied, thus ensuring formation of a double hard interlock to improve a safe performance. The following describes a necessity that the valve V 4  is the normally open type air-driven valve. 
     A structure of a hard interlock when the normally closed type air-driven valve is used for the valve V 4  will be described using  FIG. 9 .  FIG. 9  illustrates a valve V 5  used as a substitute for the valve V 4 . As illustrated in  FIG. 9 , the air for air-driven of the valve V 1  is controlled by the 2-position spring return type solenoid valve  11  via a pilot valve P 1 . The pilot valve P 1  is controlled with the signal transmitted from the pilot air signal line  21  from a pilot valve P 3 . The valve V 2  is controlled by the 3-position spring return center exhaust type 5-port solenoid valve  12 . 
     The air for air-driven of the valve V 3  is controlled by the 3-position spring return center exhaust type 5-port solenoid valve  12  via the pilot valve P 3 . The air is supplied to the pilot valve P 3  from the air source  32  via the pilot valve  11 . The air for air-driven of the valve V 5 , which is the normally closed type air-driven valve, is controlled by the 2-position spring return type solenoid valve  13 . The pilot valve P 11  is controlled by the 2-position spring return type solenoid valve  13 . 
     In such air circuit illustrated in  FIG. 9 , when the valve V 1  is opened to supply the process gas other than the inert gas similarly to the case in  FIG. 8 , although the valve V 2  must not be opened to supply the precursor gas, there is concern that the solenoid coil excitation element S 2  excited due to the malfunction or the breakdown opens the valve V 2  to supply the precursor gas, and this causes the process gas to react to the precursor to break the plasma processing apparatus. 
     The following describes an outline of an ALD process using  FIGS. 3A to 3D .  FIG. 3A  is an adsorption species step of supplying a precursor (an adsorption species).  FIG. 3B  is a purge step of exhausting the precursor.  FIG. 3C  is a reaction step of supplying a reactive species to cause the adsorption species to react to the reactive species using the plasma.  FIG. 3D  is a purge step of exhausting the reactive species. The ALD process sequentially repeats the respective steps in  FIGS. 3A to 3D  until a desired film thickness is obtained. The following describes operation of the gas supply unit when such ALD process is performed using  FIGS. 4A to 4D . 
     As illustrated in  FIG. 4A , in the adsorption species step ( FIG. 3A ), in order to supply the precursor gas as a gas for deposition process from the precursor-gas supply system  202 , the valve V 2  is opened with air control, and simultaneously, the valve V 4  is closed with the air control. The valve V 3  is closed since the valve V 2  is opened. In order to prevent the precursor gas from flowing backward to the shower plate  104 , the valve V 1  is opened with the air control to supply an Ar gas from the gas supply system  201 . Here, the inert gas such as a He gas, a Kr gas, and a Xe gas may be used instead of the Ar gas. The precursor gas is, for example, a BTBAS {chemical name: Bis-Tertiary Butyl Amino Silane, chemical formula: SiH2[NHC(CH3)3]2} gas, a BDEAS {chemical name: Bis(DiEthylAmido)Silane, chemical formula: H2Si[N(C2H5)2]2}gas, and a SiCl 4  gas. 
     Next, as illustrated in  FIG. 4B , in the purge step ( FIG. 3B ), in order to exhaust the precursor gas from the vacuum container  105 , the valve V 1  is opened, the valve V 2  is opened, and the valve V 4  is closed to supply the Ar gas from the process-gas supply system  201  and the precursor-gas supply system  202 . The valve V 3  is closed since the valve V 2  is opened. Here, the inert gas such as the He gas, the Kr gas, and the Xe gas may be used instead of the Ar gas. 
     Subsequently, as illustrated in  FIG. 4C , in the reaction step ( FIG. 3C ), the valve V 2  is closed with the air control, and simultaneously, the valve V 4  is opened with the air control. The valve V 3  is opened since the valve V 2  is closed. The valve V 1  is opened to supply the reactive species from the process-gas supply system  201  to generate the plasma, thus causing the reactive species to react to the adsorption species. Here, when the reactive species is caused to react to the adsorption species to generate SiO 2  (a silicon oxide film), an O 2  gas is used as the reactive species. When the reactive species is caused to react to the adsorption species to generate Si 3 N 4  (a silicon nitride film), an N 2  gas is used as the reactive species. 
     Next, as illustrated in  FIG. 4D , in the purge step ( FIG. 3D ), in order to exhaust the reactive species from the vacuum container  105 , the valves V 1  and V 2  are opened with the air control to supply the inert gas from the process-gas supply system  201  and the precursor-gas supply system  202 . At this time, the valve V 3  is closed since the valve V 2  is opened, and the valve V 4  is closed with the air control. 
     As described above, the ALD process according to the present invention sequentially repeats the respective steps in  FIGS. 4A to 4D  until the desired film thickness is obtained. The following describes operation when the ALD process is performed with a structure illustrated in  FIG. 7  as a comparative example. 
     In the adsorption species step ( FIG. 3A ), in order to supply the precursor gas from the precursor-gas supply system  202 , the valve V 2  is opened with the air control. In order to prevent the precursor gas from flowing backward to a shower plate  203 , the valve V 1  is opened with the air control to supply the inert gas from the gas supply system  201 . 
     Next, in the purge step ( FIG. 3B ), in order to exhaust the precursor gas from a vacuum container  204 , the valves V 1  and V 2  are opened with the air control to supply the inert gas from the process-gas supply system  201  and the precursor-gas supply system  202 . Then, in the reaction step ( FIG. 3C ), the valve V 2  is closed with the air control, and the valve V 1  is opened to supply the reactive species from the process-gas supply system  201 . Next, in the purge step ( FIG. 3D ), in order to exhaust the reactive species from the vacuum container  204 , the valves V 1  and V 2  are opened with the air control to supply the inert gas from the process-gas supply system  201  and the precursor-gas supply system  202 . 
     In the case of such ALD process with the structure illustrated in  FIG. 7 , in the reaction step ( FIG. 3C ), if there is no function that supplies the process gas to the precursor-gas supply system  202  when the reactive species is supplied from the process-gas supply system  201 , the reactive species cannot be supplied simultaneously with the process gas. The reason that the reactive species cannot be supplied is that there is concern that etchant that has turned into plasma flows backward to the gas supply line G 2  to break the precursor-gas supply system. 
     In this case, for preventing the inert gas from flowing backward, it is thought that the inert gas is supplied simultaneously with the reactive species. However, there is concern that, when the inert gas is supplied simultaneously with the reactive species, spatter of the inert gas cuts the generated film. Thus, the inert gas cannot be used for preventing the backflow. Further, although the structure in  FIG. 7  can include a function that supplies the reactive species to the precursor-gas supply system, it is necessary to add a mass flow controller (MFC) and a gas supply line. In view of this, it is necessary to include the mass flow controller and the like for each of all the used reactive species, thus causing a large disadvantage from the aspect of cost. 
     Meanwhile, the gas supply unit according to the present invention illustrated in  FIG. 1  can supply the reactive species from the gas supply line G 3  through which the gas is supplied to the vacuum container  105  without the through-hole  114  of the shower plate  104 . This can prevent the etchant that has turned into plasma from flowing backward to break the precursor-gas supply system  202 . 
     As described above, the gas supply unit of the present invention can include the double hard interlock with respect to the precursor gas, thus having a sufficient performance as a foolproof function. This ensures reliability and a safety of a vacuum processing apparatus. In other words, the process gas does not mix with the precursor gas since the hard interlock for a precursor gas supply valve is double even if any one function in the hard interlock malfunctions or breaks down. In view of this, it can be said to have a double hard interlock function having a sufficient performance as the foolproof function. 
     The following describes an embodiment different from the operation of the gas supply unit at the time of the ALD process illustrated in  FIGS. 4A to 4D , regarding the operation of the gas supply unit when the ALD process is performed, using  FIGS. 5A to 5D . In the following embodiment, the operation of the respective valves of the gas supply unit illustrated in  FIGS. 5A to 5D  is different from the operation of the respective valves of the gas supply unit illustrated in  FIGS. 4A to 4D  in that the valves V 1  and V 3  become an identical open/close state in conjunction. For example, in the gas supply unit illustrated in  FIGS. 5A to 5D , V 3  is opened when V 1  is opened, and V 3  is closed when V 1  is closed. 
     As illustrated in  FIG. 5A , in the adsorption species step ( FIG. 3A ), in order to supply the precursor gas as the gas for deposition process from the precursor-gas supply system  202 , the valve V 2  is opened with the air control, and simultaneously, the valve V 4  is closed with the air control. In order to prevent the precursor gas from flowing backward to the shower plate  104 , the valve V 1  is opened with the air control to supply the Ar gas from the gas supply system  201 . Although the valve V 3  is opened since the valve V 1  is opened, the gas is not supplied from the process-gas supply system  201 . Here, the inert gas such as the He gas, the Kr gas, and the Xe gas may be used instead of the Ar gas. The precursor gas is, for example, the BTBAS {chemical name: Bis-Tertiary Butyl Amino Silane, chemical formula: SiH2[NHC(CH3)3]2} gas, the BDEAS {chemical name: Bis(DiEthylAmido)Silane, chemical formula: H2Si[N(C2H5)2]2} gas, and the SiCl 4  gas. 
     Next, as illustrated in  FIG. 5B , in the purge step ( FIG. 3B ), in order to exhaust the precursor gas from the vacuum container  105 , the valve V 1  is opened, the valve V 2  is opened, and the valve V 4  is closed to supply the Ar gas from the process-gas supply system  201  and the precursor-gas supply system  202 . Although the valve V 3  is opened since the valve V 1  is opened, the gas is not supplied from the process-gas supply system  201 . Here, the inert gas such as the He gas, the Kr gas, and the Xe gas may be used instead of the Ar gas. 
     Subsequently, as illustrated in  FIG. 5C , in the reaction step ( FIG. 3C ), the valve V 2  is closed with the air control, and simultaneously, the valve V 4  is opened with the air control. The valve V 1  is opened to supply the reactive species from the process-gas supply system  201  to generate the plasma, thus causing the reactive species to react to the adsorption species. The valve V 3  is opened since the valve V 1  is opened, thus supplying the reactive species from the process-gas supply system  201 . Here, when the reactive species is caused to react to the adsorption species to generate SiO 2  (the silicon oxide film), the O 2  gas is used as the reactive species. When the reactive species is caused to react to the adsorption species to generate Si 3 N 4  (the silicon nitride film), the N 2  gas is used as the reactive species. 
     Next, as illustrated in  FIG. 5D , in the purge step ( FIG. 3D ), in order to exhaust the reactive species from the vacuum container  105 , the valves V 1  and V 2  are opened with the air control to supply the inert gas from the process-gas supply system  201  and the precursor-gas supply system  202 . At this time, although the valve V 3  is opened since the valve V 1  is opened, the gas is not supplied from the process-gas supply system  201 . The valve V 4  is closed with the air control. 
     As described above, the ALD process according to the present invention sequentially repeats the respective steps in  FIGS. 5A to 5D  until the desired film thickness is obtained. The respective valves V 1  to V 4  illustrated in  FIGS. 5A to 5D  do not need to use the  3 -position spring return center exhaust type  5 -port solenoid valve. For example, the operation of the respective valves V 1  to V 4  illustrated in  FIGS. 5A to 5D  can be performed such that the  2 -position spring return type solenoid valve controls the airs for air-driven of all the valves V 1  to V 4 . 
     As described above, the gas supply unit illustrated in  FIGS. 5A to 5D  can include the hard interlock with respect to the precursor gas to ensure the reliability and the safety of the vacuum processing apparatus. 
     The operation of the respective valves V 1  to V 4  according to  FIGS. 4A to 4D  and  FIGS. 5A to 5D  is controlled by a control device  117 . Further, the control device  117  also performs control according to the plasma processing by the plasma processing apparatus according to the present invention such as the electromagnetic-wave supply unit  101 , the radio frequency power supply  118 , the electromagnetic coil  102 , and the vacuum exhaust air unit  110 . 
     In the above-described embodiment, the plasma processing apparatus having the microwave ECR plasma source has been described as one embodiment. However, also in a plasma processing apparatus in another plasma generation system such as a capacitive coupling type plasma source and an inductive coupling type plasma source, the effect similar to that of this embodiment can be obtained. 
     The present invention can inhibit reduction in yield of the sample substrate in accordance with particle generation on the shower plate with the precursor gas.