Abstract:
A plasma processing device according to one embodiment comprises a processing vessel, a gas supply unit, a lower electrode and an upper electrode. The processing vessel defines a processing space. The gas supply unit supplies processing gas into the processing space. The lower electrode is provided below the processing space. The upper electrode is provided above the processing space, and a covering layer having plasma-resistant properties is formed on this upper electrode. The surface of this covering layer is polished.

Description:
TECHNICAL FIELD 
       [0001]    An aspect of the present disclosure relates to a plasma processing device. 
       BACKGROUND ART 
       [0002]    As a plasma processing device, Patent Document 1 or Patent Document 2 discloses a parallel plate type plasma processing device. The plasma processing device disclosed in Patent Document 1 or Patent Document 2 includes a processing vessel, a gas supply unit, a lower electrode and an upper electrode. In the plasma processing device, a processing gas is supplied into a processing space by the gas supply unit to provide a high-frequency electric field between the lower electrode and the upper electrode. This generates plasma of the processing gas so that a substrate to be processed is processed by, for example, radicals of elements included in the processing gas. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0003]    Patent Document 1: Japanese Patent Laid-open Publication No. 2008-198843 
         [0004]    Patent Document 2: Japanese Patent Laid-open Publication No. 2008-112751 
       SUMMARY OF THE INVENTION 
     Problems to be Solved 
       [0005]    In the above described plasma processing device, immediately after manufacturing of the device, or after replacement of a component such as an upper electrode, a seasoning process is performed. A time required for the seasoning is relatively long. 
         [0006]    Accordingly, what is requested in the technical field is a plasma processing device capable of shortening a time for seasoning. 
       Means for Solving the Problems 
       [0007]    A plasma processing device according to an aspect of the present disclosure is provided with a processing vessel, a gas supply unit, a lower electrode, and an upper electrode. The processing vessel defines a processing space. The gas supply unit is configured to supply a processing gas into the processing space. The lower electrode is provided at a lower side of the processing space. The upper electrode is provided at an upper side of the processing space, and formed with a covering layer having plasma resistance. A surface of the covering layer is polished. In an exemplary embodiment, the covering layer may be a Y 2 O 3  layer. 
         [0008]    When plasma etching is performed by a processing gas in the plasma processing device provided with an upper electrode having a covering layer immediately after forming, the etching speed has a tendency to be reduced as compared to the etching speed in the case where an upper electrode having a covering layer subjected to predetermined seasoning is used. It is assumed that this is due to the fact that the amount of radicals consumed to be bound to an element constituting the covering layer is increased. Also, the predetermined seasoning refers to, for example, seasoning that is performed under a condition set to stably obtain a required etching speed. It is assumed that in a case where the covering layer is formed through thermal-spraying of Y 2 O 3 , when plasma etching is performed using a gas including carbon and fluorine (CF-based gas) immediately after thermal-spraying, the amount of fluorine atom radicals consumed to be bound to Y of the Y 2 O 3  layer is increased, thereby lowering the etching speed. 
         [0009]    In the plasma processing device according to an aspect of the present disclosure, the surface of the covering layer of the upper electrode is polished. Accordingly, the surface area of the covering layer is smaller than the surface of the covering layer immediately after forming That is, the surface area of the covering layer to be in contact with radicals is reduced such that the amount of radicals to be consumed to be bound to a constituent element of the covering layer is reduced. As a result, it is possible to obtain an upper electrode capable of providing an etching speed close to a required etching speed. Therefore, a time required for seasoning may be shortened. 
         [0010]    In an aspect of the present disclosure, the surface area of the covering layer may be 30,000 μm 2  or less. Also, the surface area of the covering layer may be 20,000 μm 2  or more. By the upper electrode having a covering layer with such a surface area, it is possible to obtain an etching speed closer to a required etching speed. 
       Effect of the Invention 
       [0011]    As described above, according to an aspect of the present disclosure, a plasma processing device capable of shortening a time for seasoning is provided. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a view schematically illustrating a plasma processing device according to an exemplary embodiment. 
           [0013]      FIG. 2  is a cross-sectional view illustrating an upper electrode of the plasma processing device illustrated in  FIG. 1 . 
           [0014]      FIG. 3  is a view illustrating an example of a polishing device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Hereinafter, various exemplary embodiments will be described in detail with reference to drawings. In the respective drawings like parts are denoted by like reference numerals. 
         [0016]      FIG. 1  is a view schematically illustrating a plasma processing device according to an exemplary embodiment.  FIG. 1  illustrates a cross section of the plasma processing device according to an exemplary embodiment. A plasma processing device  10  illustrated in  FIG. 1  is a parallel plate type plasma processing device. 
         [0017]    The plasma processing device  10  is provided with a processing vessel  12 . The processing vessel  12  has a substantially cylindrical shape, and defines a processing space S as its inner space. The plasma processing device  10  is provided with a base  14  in a substantially disk shape within the processing vessel  12 . The base  14  is provided at the lower side of the processing space S. The base  14  is made of, for example, aluminum, and constitutes a lower electrode. 
         [0018]    In an exemplary embodiment, the plasma processing device  10  is further provided with a cylindrical holding unit  16  and a cylindrical supporting unit  17 . The cylindrical holding unit  16  holds the base  14  by being in contact with the lateral surface and the bottom surface periphery of the base  14 . The cylindrical supporting unit  17  extends vertically from the bottom of the processing vessel  12 , and supports the base  14  through the cylindrical holding unit  16 . The plasma processing device  10  is further provided with a focus ring  18  placed on the top surface of the cylindrical holding unit  16 . The focus ring  18  may be made of, for example, silicon or quartz. 
         [0019]    In an exemplary embodiment, an exhaust path  20  is formed between the lateral wall of the processing vessel  12 , and the cylindrical supporting unit  17 . A baffle plate  22  is mounted at the inlet or in the middle of the exhaust path  20 . Also, an exhaust hole  24  is provided at the bottom of the exhaust path  20 . The exhaust hole  24  is defined by an exhaust tube  28  fitted to the bottom of the processing vessel  12 . An exhaust device  26  is connected to the exhaust tube  28 . The exhaust device  26  includes a vacuum pump, and thus may decompress the processing space S within the processing vessel  12  to a predetermined degree of vacuum. A gate valve  30  configured to open/close a carrying-in/out port of a substrate to be processed W is mounted at the lateral wall of the processing vessel  12 . 
         [0020]    A high frequency power source  32  configured to generate a high frequency power for ion attraction is electrically connected to the base  14  via a matching unit  34 . The high frequency power source  32  applies a high frequency power of a predetermined high frequency (e.g., 400 KHz to 27 MHz) to the lower electrode, that is, the base  14 . 
         [0021]    The plasma processing device  10  is further provided with a shower head  38  within the processing vessel  12 . The shower head  38  is provided at the upper side of the processing space S. The shower head  38  includes an electrode plate  40  and an electrode support  42 . 
         [0022]    The electrode plate  40  is a conductive plate having a substantially disk shape, and constitutes an upper electrode. A high frequency power source  35  for plasma generation is electrically connected to the electrode plate  40  via a matching unit  36 . The high frequency power source  35  applies a high frequency power of a predetermined high frequency (e.g., 27 MHz or more) to the electrode plate  40 . When the high frequency power is applied to the base  14  and the electrode plate  40  by the high frequency power source  32  and the high frequency power source  35 , respectively, a high-frequency electric field is formed in the space between the base  14  and the electrode plate  40 , that is, in the processing space S. 
         [0023]    A plurality of gas vent holes  40   h  are formed in the electrode plate  40 . The electrode plate  40  is detachably supported by the electrode support  42 . A buffer chamber  42   a  is provided within the electrode support  42 . The plasma processing device  10  is further provided with a gas supply unit  44 , and the gas supply unit  44  is connected to a gas inlet  25  of the buffer chamber  42   a  through a gas supply conduit  46 . The gas supply unit  44  supplies a processing gas to the processing space S. The gas supply unit  44  may supply, for example, a CF-based etching gas. The electrode support  42  is formed with a plurality of holes continued from the plurality of the gas vent holes  40   h,  respectively, and the plurality of holes are communicated with the buffer chamber  42   a.  Accordingly, the gas supplied from the gas supply unit  44  is supplied to the processing space S via the buffer chamber  42   a  and the gas vent holes  40   h.    
         [0024]    In an exemplary embodiment, a magnetic field forming mechanism  48  which extends annularly or concentrically is provided in the ceiling portion of the processing vessel  12 . The magnetic field forming mechanism  48  serves to facilitate initiation of high frequency discharge (plasma ignition) within the processing space S so as to stably maintain the discharge. 
         [0025]    In an exemplary embodiment, an electrostatic chuck  50  is provided on the top surface of the base  14 . The electrostatic chuck  50  includes an electrode  52  and a pair of insulating films  54   a  and  54   b.  The electrode  52  is a conductive film, and is provided between the insulating film  54   a  and the insulating film  54   b.  A DC power source  56  is connected to the electrode  52  via a switch SW. When a DC voltage is applied to the electrode  52  from the DC power source  56 , a Coulomb force is generated. By the Coulomb force, the substrate to be processed W is attracted and held on the electrostatic chuck  50 . 
         [0026]    In an exemplary embodiment, the plasma processing device  10  is further provided with gas supply lines  58  and  60  and heat transfer gas supply units  62  and  64 . The heat transfer gas supply unit  62  is connected to the gas supply line  58 . The gas supply line  58  extends to the top surface of the electrostatic chuck  50  and annularly extends at the central portion of the top surface. The heat transfer gas supply unit  62  supplies a heat transfer gas such as, for example, a He gas between the top surface of the electrostatic chuck  50  and the substrate to be processed W. Also, the heat transfer gas supply unit  64  is connected to the gas supply line  60 . The gas supply line  60  extends to the top surface of the electrostatic chuck  50  and annularly extends to surround the gas supply line  58  on the top surface. The heat transfer gas supply unit  64  supplies a heat transfer gas such as, for example, a He gas between the top surface of the electrostatic chuck  50  and the substrate to be processed W. 
         [0027]    In an exemplary embodiment, the plasma processing device  10  is further provided with a control unit  66 . The control unit  66  is connected to the exhaust device  26 , the switch SW, the high frequency power source  32 , the matching unit  34 , the high frequency power source  35 , the matching unit  36 , the gas supply unit  44 , and the heat transfer gas supply units  62  and  64 . The control unit  66  sends control signals to the exhaust device  26 , the switch SW, the high frequency power source  32 , the matching unit  34 , the high frequency power source  35 , the matching unit  36 , the gas supply unit  44 , and the heat transfer gas supply units  62  and  64 , respectively. By the control signals from the control unit  66 , exhaust by the exhaust device  26 , opening/closing of the switch SW, power supply from the high frequency power source  32 , impedance adjustment of the matching unit  34 , power supply from the high frequency power source  35 , impedance adjustment of the matching unit  36 , supply of the processing gas by the gas supply unit  44 , supply of the heat transfer gas by each of the heat transfer gas supply units  62  and  64  are controlled. 
         [0028]    In the plasma processing device  10 , the processing gas is supplied from the gas supply unit  44  to the processing space S. Also, the high-frequency electric field is formed between the electrode plate  40  and the base  14 , that is, in the processing space S. Accordingly, plasma is generated in the processing space S, and the substrate to be processed W is etched by, for example, radicals of elements included in the processing gas. 
         [0029]    Hereinafter, the configuration of the electrode plate  40  constituting the upper electrode will be described.  FIG. 2  is a cross-sectional view illustrating an upper electrode of the plasma processing device illustrated in  FIG. 1 . As illustrated in  FIG. 2 , the electrode plate  40  includes a main body portion  40   a  and a covering layer  40   b.  The main body portion  40   a  has a substantially disk shape, and is constituted by a substrate having a surface made of, for example, aluminum. The main body portion  40   a  has an inner surface that defines the gas vent holes  40   h.  The inner surface is subjected to alumite treatment. On a a surface  40   s  of the main body portion  40   a  at the processing space S side, the covering layer  40   b  is formed. The covering layer  40   b  has plasma resistance. The covering layer  40   b  may be formed by thermal-spraying of Y 2 O 3 . Also, the forming method and the constituent material of the covering layer  40   b  are not limited thereto. 
         [0030]    The covering layer  40   b  is polished after formed by, for example, thermal-spraying. That is, the covering layer  40   b  has a polished surface  40   d  as a surface at the processing space S side. The surface area of the polished surface  40   d  as described above is smaller than the surface area of the covering layer immediately after forming Accordingly, the amount of radicals to be bound to a constituent element of the covering layer  40   b  is reduced. As a result, even immediately after the electrode plate  40  is manufactured, an etching speed close to a required etching speed may be obtained. Thus, in the plasma processing device  10 , a time required for seasoning may be reduced. Also, on the surface of the covering layer  40   b,  an additional surface treatment may be performed after the surface is polished. The surface treatment may include, for example, blasting. Ceramic particles used for the blasting may be made of SiO 2 , Al 2 O 3 , Y 2 O 3 , or SiC. 
         [0031]    In an exemplary embodiment, the surface area of the polished surface  40   d  of the covering layer  40   b  may be 30,000 μm 2  or less. Also, the surface area of the surface  40   d  may be 20,000 μm 2  or more. In the covering layer  40   b  having such a surface area, the etching speed immediately after the electrode plate  40  is manufactured may be closer to a required etching speed. 
         [0032]    Hereinafter, reference will be made to  FIG. 3 .  FIG. 3  illustrates an example of a polishing device used to polish the surface of the covering layer  40   b.  As illustrated in  FIG. 3 , in a polishing device  100  as an example, a polishing pad  106  is placed on the top surface of a stage  102  supported by a rotation shaft  104 . A slurry (Sr) is supplied to the polishing pad  106  from a slurry supply mechanism  108 . As the slurry (Sr), a slurry containing diamond abrasive grains is exemplified. Also, above the polishing pad  106 , a holding unit  110  is provided. The holding unit  110  may hold the electrode plate  40  on the bottom surface thereof. The holding unit  110  is supported by a supporting unit  112 . The supporting unit  112  supports the holding unit  110  in a direction perpendicular to a rotation axis X 1  of the rotation shaft  104  (in the horizontal direction). Also, the supporting unit  112  supports the holding unit  110  such that the holding unit  110  may be rotated around an axis X 2  parallel to the rotation axis X 1 . The axis X 2  is located at a position shifted from the axis X 1  in the horizontal direction. When the electrode plate  40  is pressed against the polishing pad  106 , the electrode plate  40  and the holding unit  110  receive a force allowing themselves to rotate around the axis X 2 , from the polishing pad  106 . 
         [0033]    In the polishing device  100 , the slurry (Sr) is supplied to the polishing pad  106  and the polishing pad  106  is rotated. Then, the electrode plate  40  [the covering layer  40   b ] held by the holding unit  110  is pressed against the polishing pad  106 . Accordingly, the covering layer  40   b  of the electrode plate  40  may be polished. Also, the surface area of the covering layer  40   b  may be varied by adjusting the abrasive grain diameter of the slurry, the rotation speed of the rotation shaft  104 , and the polished amount of the covering layer  40   b  (polished thickness). 
       Examples 
       [0034]    Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the examples. 
         [0035]    In Examples 1 to 3, covering layers having different surface areas, as the covering layer  40   b,  were subjected to seasoning, and then an oxide film of a substrate to be processed W, that is, an SiO 2  film was etched to evaluate the etching speed. The surface  40   d  of each of Examples 1 and 2 was obtained by polishing a Y 2 O 3 layer formed through thermal-spraying by using the polishing device illustrated in  FIG. 3 . The surface  40   d  of Example 3 was obtained by polishing an electrode plate Y 2 O 3 layer formed through thermal-spraying by using the polishing device illustrated in  FIG. 3 , and performing blasting using ceramic particles (SiO 2 ). The surface areas of the surfaces  40   d  of Examples 1 to 3 were 22,785 μm 2 , 27,325 μm 2, and  25,421 μm 2 , respectively. Also, the surface areas of the surfaces  40   d  were measured by using a laser microscope OLS3100 manufactured Olympus Corporation and using a surface area measurement mode of the laser microscope. 
         [0036]    Also, as a comparative example, for an electrode plate having a Y 2 O 3  layer formed through thermal-spraying, blasting was performed on the surface of the Y 2 O 3  layer using ceramic particles (SiO 2 ), the seasoning was performed in the same manner as that in Examples 1 to 3, and the SiO 2  film was etched to evaluate the etching speed. In the comparative example, the surface area of the surface of the Y 2 O 3 layer was 39,753 μm 2 . Also, in the comparative example, the surface of the Y 2 O 3  layer was not polished. 
         [0037]    Seasoning conditions in Examples 1 to 3 and the comparative example were as follows. 
         [0038]    Pressure of processing space S: 20 mT 
         [0039]    Power supplied to lower electrode: 0 W 
         [0040]    Power supplied to upper electrode: 2000 W 
         [0041]    Processing gas: C 4 F 6  at flow rate of 80 sccm, mixed gas of CO at a flow rate of 500 sccm 
         [0042]    Pressure of He gas from heat transfer gas supply unit 62: 15 T 
         [0043]    Pressure of He gas from heat transfer gas supply unit 64: 40 T 
         [0044]    Etching time: 120 sec 
         [0045]    Size of substrate to be processed W: 300 mmφ 
         [0046]    Also, etching conditions in Examples 1 to 3 and the comparative example were as follows. 
         [0047]    Pressure of processing space S: 20 mT 
         [0048]    Power supplied to lower electrode: 200 W 
         [0049]    Power supplied to upper electrode: 1,800 W 
         [0050]    Processing gas: CHF 3  at flow rate of 135 sccm, CO at flow rate of 465 sccm, mixed gas of O 2 at flow rate of 18 sccm 
         [0051]    Pressure of He gas from heat transfer gas supply unit 62: 15 T 
         [0052]    Pressure of He gas from heat transfer gas supply unit 64: 40 T 
         [0053]    Etching time: 30 sec 
         [0054]    Size of substrate to be processed W: 300 mmφ 
         [0055]    The etching speed was obtained by measuring the thickness of a substrate to be processed W before and after etching at the center of the substrate to be processed W, and at respective points ±30 mm, ±60 mm, ±90 mm, ±120 mm, ±130 mm, ±145 mm in the radial direction from the center, obtaining an average value of the obtained measurement values, converting the average value in terms of the etching speed per minute, and determining the conversion value as the etching speed. 
         [0056]    The etching speeds of Examples 1 to 3 were 129.6 nm/min, 131.2 mm/min, and 133.2 mm/min, respectively. Meanwhile, the etching speed of the comparative example was 127.4 mm/min It was found that in Examples 1 to 3, an etching speed closer to a required etching speed (132 nm/min) was obtained as compared to an etching speed in the comparative example. 
       DESCRIPTION OF REFERENCE NUMERALS 
       [0057]      
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 10: plasma processing device 
                 12: processing vessel 
               
               
                   
                 14: base 
                 18: focus ring 
               
               
                   
                 26: exhaust device 
                 28: exhaust tube 
               
               
                   
                 30: gate valve 
                 32: high frequency power source 
               
               
                   
                 34: matching unit 
                 35: high frequency power source 
               
               
                   
                 36: matching unit 
                 38: shower head 
               
               
                   
                 40: electrode plate 
                 38a: gas vent holes 
               
               
                   
                 40a: main body portion 
                 40b: covering layer 
               
               
                   
                 40d: surface (covering layer) 
                 42: electrode support 
               
               
                   
                 44: gas supply unit 
                 50: electrostatic chuck 
               
               
                   
                 58: gas supply line 
                 60: gas supply line 
               
               
                   
                 62: heat transfer gas supply unit 
                 64: heat transfer gas supply unit 
               
               
                   
                 66: control unit 
                 S: processing space 
               
               
                   
                 W: substrate to be processed