Patent Publication Number: US-2022220606-A1

Title: Method and device for substrate processing

Description:
TECHNICAL FIELD 
     The present disclosure relates to a method and device for substrate processing. 
     BACKGROUND 
     A processing apparatus for a substrate such as a semiconductor substrate or the like, e.g., a film forming apparatus, performs processing that requires an extremely low temperature. For example, a technique for forming a magnetic film in an ultra-high vacuum and ultra-low temperature environment is required to obtain a magnetoresistive element having a high magnetoresistive ratio. 
     As a technique for uniformly cooling a substrate at an extremely low temperature in an ultra-high vacuum environment, there is known one in which a stage on which a substrate is placed is rotatably provided, and a frozen heat transfer body is disposed at a center of a back surface of a stage with a gap interposed therebetween (see, e.g., Patent Document 1). Such technique uniformly cools the substrate to an extremely low temperature by supplying cold heat of a chiller to the stage via the frozen heat transfer body while supplying a cooling gas to the gap between the rotating stage and the frozen heat transfer body. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Patent Application Publication No. 2019-016771 
       
    
     SUMMARY 
     Problems to Be Resolved by the Invention 
     The present disclosure provides a method and device for processing a substrate, capable of shortening a time required until a temperature of a substrate reaches a steady cooling temperature in the case of rotating and processing the substrate in a state where the substrate is cooled to an extremely low temperature. 
     Means of Solving the Problems 
     A method according to an aspect of the present disclosure is a method for processing a substrate, and comprises: preparing a substrate processing device including a rotatable stage on which a substrate is placed, a frozen heat transfer body fixed on a backside of the stage with a gap interposed therebetween and cooled to an extremely low temperature, a gas supply mechanism configured to supply to the gap a cooling gas for transferring a cold heat of the frozen heat transfer body to the stage, a rotation mechanism configured to rotate the stage, and a processing mechanism configured to process the substrate; preheating the stage such that a temperature of the stage reaches a steady cooling temperature within a fixed range; and after preheating, continuously processing a plurality of substrates by the processing mechanism while rotating the stage that has reached the steady cooling temperature in a state where a substrate having a specific temperature higher than or equal to room temperature is placed on the stage. 
     Effect of the Invention 
     In accordance with the present disclosure, there are provided a method and device for processing a substrate, capable of shortening a time required until a temperature of a substrate reaches a steady cooling temperature in the case of rotating and processing the substrate in a state where the substrate is cooled to an extremely low temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view showing an example of a substrate processing device capable of performing a substrate processing method according to an embodiment. 
         FIG. 2  is a cross-sectional view schematically showing a state in which a stage temperature is measured by a temperature measuring mechanism in the substrate processing device of  FIG. 1 . 
         FIG. 3  schematically shows another example of a shape of a comb teeth portion in a stage device of the substrate processing device of  FIG. 1 . 
         FIG. 4  shows a change in a stage temperature depending on the number of processed wafers in the case of processing a wafer that is a substrate by a conventional method in the substrate processing device of  FIG. 1 . 
         FIG. 5  is a flowchart showing a substrate processing method according to an embodiment. 
         FIG. 6  explains an example of a preheating step of the substrate processing method according to the embodiment. 
         FIG. 7  shows changes in a stage temperature depending on the number of processed wafers in the case of processing a wafer that is a substrate by the substrate processing method according to an embodiment and the conventional method in the substrate processing device of  FIG. 1 . 
         FIG. 8  explains another example of the preheating step. 
         FIG. 9  explains still another example of the preheating step. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. 
     &lt;Processing Device&gt; 
     First, an example of a substrate processing device capable of performing a substrate processing method according to an embodiment will be described.  FIG. 1  is a schematic cross-sectional view showing an example of the substrate processing device. 
     As shown in  FIG. 1 , a substrate processing device  1  includes a processing chamber  10  that can be maintained in a vacuum state, a target  30 , a stage device  50 , and a controller  100 . The substrate processing device  1  is configured as a film forming device capable of performing sputtering film formation of a magnetic film on a semiconductor wafer (hereinafter, simply referred to as “wafer”) W that is a substrate in an ultra-high vacuum and ultra-low temperature environment in the processing chamber  10 . The magnetic film is used for, e.g., a tunneling magneto resistance (TMR) element. 
     The processing chamber  10  processes the wafer W that is a substrate to be processed. An exhaust device (not shown) such as a vacuum pump capable of decreasing a pressure to an ultra-high vacuum level is connected to the processing chamber  10 , so that the inside of the processing chamber  10  can be depressurized to an ultra-high vacuum state (e.g., 10 −5  Pa or less). A gas supply line (not shown) from the outside is connected to the processing chamber  10  to supply a sputtering gas (e.g., noble gas such as argon (Ar) gas, krypton (Kr) gas, neon (Ne) gas, or nitrogen gas) required for sputtering film formation. Further, a loading/unloading port (not shown) for the wafer W is formed on a sidewall of the processing chamber  10 , and can be opened and closed by a gate valve (not shown). 
     At an inner upper portion of the processing chamber  10 , the target  30  is disposed above the wafer W held by the stage device  50  to face the wafer W. An AC voltage or a DC voltage is applied from a plasma generation power source (not shown) to the target  30 . When an AC voltage or a DC voltage is applied from the plasma generation power source to the target  30  in a state where the sputtering gas is introduced into the processing chamber  10 , plasma of the sputtering gas is produced in the processing chamber  10 , and the target  30  is sputtered by ions in the plasma. Atoms or molecules of the sputtered target material are deposited on the surface of the wafer W held by the stage device  50 . Although the number of targets  30  is not particularly limited, from the viewpoint that different films made of different materials can be formed by one substrate processing device  100 , it is preferable that a plurality of targets are present. For example, in the case of depositing a magnetic film (film containing a ferromagnetic material such as Ni, Fe, Co, or the like), CoFe, FeNi, and NiFeCo can be used as the material of the target  30 . Further, those materials containing another element can also be used as the material of the target  30 . 
     As will be described later, the stage device  50  holds the wafer W on the stage  56 , and cools the wafer W to an extremely low temperature via the stage  56  while rotating the stage  56  together with the wafer W. Further, as will be described later, the stage device  50  has an elevating mechanism  74  for raising and lowering the stage  56  and a temperature measuring mechanism  90  for measuring a temperature of the stage. 
     The controller  100  is a computer, and includes a main controller including a central processing unit (CPU) for controlling individual components of the substrate processing device, an input device, an output device, a display device, and a storage device. The main controller controls a voltage applied to the target  30  during sputtering, introduction of a sputtering gas, raising/lowering and rotation of the stage  56  to be described later, loading/unloading of the wafer W, introduction of a cooling gas to be described later, an operation of a chiller  52  to be described later, or the like. Further, the main controller executes an operation set in the substrate processing device  1  based on a processing recipe called from the storage medium of the storage device. 
     Next, the stage device  50  will be described in detail. 
     As shown in  FIG. 1 , the stage device  50  includes the stage  56 , the elevating mechanism  74 , and the temperature measuring mechanism  90 . The stage device  50  further includes the chiller  52 , a frozen heat transfer body  54 , a stage support  58 , a seal rotation mechanism  62 , and a driving mechanism  68 . 
     The elevating mechanism  74  is configured to move the wafer W among a transfer position for transferring the wafer W to the stage  56 , a processing position for forming a film on the wafer W placed on the stage  56 , and a temperature measurement position for measuring a temperature of the stage using a substrate transfer device. The transfer position is set to be lower than the processing position and the temperature measurement position, and the temperature measurement position is set to be lower than the processing position. Further, the elevating mechanism  74  can control the distance between the target  30  and the wafer W. 
     The temperature measuring mechanism  90  includes a temperature detection contact portion  91  disposed at a portion of the stage  56  that does not interfere with the placement of the wafer W, and a temperature detector  92  attached to a bottom portion of the processing chamber  10  under the stage  56 . The temperature detector  92  has a temperature sensor and is separated from the temperature detection contact portion except during temperature measurement. When the temperature detector  92  is in contact with the temperature detection contact portion  91 , the temperature of the stage  56  can be measured. The temperature detection contact portion  91  can be brought into contact with and separated from the temperature detector  92  by raising and lowering the stage  56  using the elevating mechanism  74 . As shown in  FIG. 2 , the positions of the temperature detection contact portion  91  and the temperature detector  92  are made to correspond to each other by rotating the stage  56 , and the temperature of the stage  56  is measured by bringing the temperature detection contact portion  91  into contact with the temperature detector  92  by lowering the stage  56  to the temperature measurement position. Such temperature measurement is performed without rotating the stage  56  immediately before the wafer W is processed while rotating the stage  56 , for example. 
     The chiller  52  holds the frozen heat transfer body  54  and cools an upper surface of the frozen heat transfer body  54  to an extremely low temperature. The chiller  52  has a cold head portion  52   a  at an upper portion thereof, and cold heat is transferred from the cold head portion  52   a  to the frozen heat transfer body  54 . The chiller  52  preferably uses a Gifford-McMahon (GM) cycle in view of cooling performance. In the case of forming a magnetic film used for a TMR element, a cooling temperature of the frozen transfer body  54  by the chiller  52  is within a range of, e.g., 250K to 50K (−23° C. to −223° C.) 
     The frozen heat transfer body  54  is fixed on the chiller  52 , and is formed in a substantially cylindrical shape and made of a material having high thermal conductivity such as pure copper (Cu) or the like. An upper portion of the frozen heat transfer body  54  is disposed in the processing chamber  10 . 
     The frozen heat transfer body  54  is disposed below the stage  56  such that the center thereof coincides with a central axis C of the stage  56 . A first cooling gas supply line  54   a  through which a first cooling gas can flow is formed along the central axis C inside the frozen heat transfer body  54 , and a gas supply mechanism  59  is connected to the first cooling gas supply line  54   a . The first cooling gas is supplied from the gas supply mechanism  59  to the first cooling gas supply line  54   a . It is preferable to use helium (He) gas having high thermal conductivity as the first cooling gas. 
     The stage  56  is separated from the upper surface of the frozen heat transfer body  54  by a gap G (e.g., 2 mm or less). The stage  56  is made of a material having high thermal conductivity such as pure copper (Cu) or the like. The gap G communicates with the first cooling gas supply line  54   a  formed inside the frozen heat transfer body  54 . Therefore, the extremely low temperature first cooling gas cooled by the frozen heat transfer body  54  is supplied from the gas supply mechanism  59  to the gap G through the first cooling gas supply line  54   a . Accordingly, the cold heat of the chiller  52  is transferred to the stage  56  via the first cooling gas supplied to the frozen heat transfer body  54  and the gap G, thereby cooling the stage  56  to an extremely low temperature. The gas supply mechanism  59  can perform the removal of the first cooling gas from the gap G as well as the supply of the first cooling gas to the gap G. 
     The stage  56  includes an electrostatic chuck  56   a . The electrostatic chuck  56   a  is formed of a dielectric film, and a chuck electrode  56   b  is embedded therein. A predetermined DC voltage is applied to the chuck electrode  56   b  through a wiring L. Accordingly, the wafer W can be attracted and fixed by an electrostatic attractive force. 
     The stage  56  has a first heat transfer portion  56   c  under the electrostatic chuck  56   a , and convex portions  56   d  protruding toward the frozen heat transfer body  54  are formed on a bottom surface of the first heat transfer portion  56   c . In the illustrated example, the convex portions  56   d  are formed as two annular portions surrounding the central axis C of the stage  56 . The height of each convex portion  56   d  may be, e.g., 40 mm to 50 mm. The width of each convex portion  56   d  may be, e.g., 6 mm to 7 mm. Although the shape and number of the convex portions  56   d  are not particularly limited, it is preferable to set the shape and number thereof such that a sufficient heat exchangeable surface area can be obtained in order to increase the heat transfer efficiency with the frozen heat transfer body  54 . 
     The frozen heat transfer body  54  has a second heat transfer portion  54   b  on an upper surface of the main body, i.e., on the surface facing the first heat transfer portion  56   c . The second heat transfer portion  54   b  has concave portions  54   c  to be fitted into the convex portions  56   d  with the gap G interposed therebetween. In the illustrated example, the concave portions  54   c  are formed as two annular portions surrounding the central axis C of the stage  56 . The height of each concave portion  54   c  may be the same as the height of each convex portion  56   d , and may be, e.g., 40 mm to 50 mm. The width of each concave portion  54   c  may be slightly greater than the width of each convex portion  56   d , and is preferably, e.g., 7 mm to 9 mm. The shape and number of the concave portions  54   c  are determined to correspond to those of the convex portions  56   d.    
     The convex portions  56   d  of the first heat transfer portion  56   c  and the concave portions  54   c  of the second heat transfer portion  54   b  are fitted to each other via the gap G, thereby forming a comb teeth portion. Due to the presence of the comb teeth portion, the gap G is saw-toothed, so that the heat transfer efficiency of the first cooling gas between the first heat transfer portion  56   c  of the stage  56  and the second heat transfer portion  54   b  of the frozen heat transfer body  54  can be increased. 
     As shown in  FIG. 3 , the convex portions  56   d  and the concave portions  54   c  may have corresponding wave shapes. Further, it is preferable that the surfaces of the convex portions  56   d  and the concave portions  54   c  are subjected to uneven processing by blasting or the like. Accordingly, the surface area for heat transfer can be increased to further improve the heat transfer efficiency. 
     Alternatively, the concave portions may be formed at the first heat transfer portion  56   c , and the convex portions corresponding to the concave portions may be formed at the second heat transfer portion  54   b.    
     The electrostatic chuck  56   a  and the first heat transfer portion  56   c  in the stage  56  may be integrally formed, or may be separately formed and joined. Further, the main body of the frozen heat transfer body  54  and the second heat transfer portion  54   b  may be integrally formed, or may be separately formed and joined. 
     The stage  56  has a through-hole  56   e  penetrating therethrough vertically. A second cooling gas supply line  57  is connected to the through-hole  56   e , and a second cooling gas for heat transfer is supplied from the second cooling gas supply line  57  to the backside of the wafer W through the through-hole  56   e . Similarly to the first cooling gas, He gas having high thermal conductivity is preferably used as the second cooling gas. By supplying the second cooling gas to the backside of the wafer W, i.e., to the gap between the wafer W and the electrostatic chuck  56   a , the cold heat of the stage  56  can be efficiently transferred to the wafer W via the second cooling gas. Although one through-hole  56   e  may be formed, it is preferable to form a plurality of through-holes  56   e  in order to particularly efficiently transfer the cold heat of the frozen heat transfer body  54  to the wafer W. 
     By separating the flow path of the second cooling gas supplied to the backside of the wafer W from the flow path of the first cooling gas supplied to the gap G, the cooling gas can be supplied at a desired pressure and a desired flow rate to the backside of the wafer W regardless of the supply of the first cooling gas. At the same time, the cooling gas in a high pressure and extremely low temperature state can be continuously supplied to the gap G without being limited by the pressure, the flow rate, and the supply timing of the gas supplied to the backside. 
     Further, the stage  56  may have a through-hole connected from the gap G, so that a part of the first cooling gas may be supplied as the cooling gas to the backside of the wafer W. 
     The stage support  58  is disposed at an outer side of the frozen heat transfer body  54  and rotatably supports the stage  56 . The stage support  58  has a substantially cylindrical main body  58   a  and a flange portion  58   b  extending outward on a bottom surface of the main body  58   a . The main body  58   a  is disposed to cover the gap G and an upper outer peripheral surface of the frozen heat transfer body  54 . Accordingly, the stage support  58  also has a function of shielding the gap G that is a connection portion between the frozen heat transfer body  54  and the stage  56 . 
     The seal rotation mechanism  62  is disposed below a heat insulating member  60 . The seal rotation mechanism  62  has a rotating portion  62   a , an inner fixing portion  62   b , an outer fixing portion  62   c , and a heating device  62   d.    
     The rotating portion  62   a  has a substantially cylindrical shape extending downward coaxially with the heat insulating member  60 , and is rotated by the driving device  68  while being hermetically sealed with a magnetic fluid with respect to the inner fixing portion  62   b  and the outer fixing portion  62   c . Since the rotating portion  62   a  is connected to the stage support  58  via the heat insulating member  60 , the transfer of the cold heat from the stage support  58  to the rotating portion  62   a  is blocked by the heat insulating member  60 . Therefore, it is possible to suppress deterioration of the sealing performance or occurrence of condensation caused by a decrease in the temperature of the magnetic fluid of the seal rotation mechanism  62 . 
     The inner fixing portion  62   b  has a substantially cylindrical shape having an inner diameter greater than an outer diameter of the frozen heat transfer body  54  and having an outer diameter is smaller than the inner diameter of the rotating portion  62   a . The inner fixing portion  62   b  is disposed between the frozen heat transfer body  54  and the rotating portion  62   a  via a magnetic fluid. 
     The outer fixing portion  62   c  has a substantially cylindrical shape having an inner diameter greater than an outer diameter of the rotating portion  62   a , and is disposed at an outer side of the rotating portion  62   a  via a magnetic fluid. 
     The heating device  62   d  is embedded in the inner fixing portion  62   b  and heats the entire seal rotation mechanism  62 . Accordingly, it is possible to suppress the deterioration of the sealing performance or the occurrence of condensation caused by a decrease in the temperature of the magnetic fluid of the seal rotation mechanism  62 . 
     With such a configuration, the seal rotation mechanism  62  can rotate the stage support  58  in a state where a region communicating with the processing chamber  10  is hermetically sealed with a magnetic fluid and held in a vacuum state. 
     A bellows  64  is disposed between an upper surface of the outer fixing portion  62   c  and a bottom surface of the processing chamber  10 . The bellows  64  is a metal bellows structure that can be extended and contracted vertically. The bellows  64  surrounds the frozen heat transfer body  54 , the stage support  58 , and the heat insulating member  60 , and separates the space in the processing chamber  10  and the space communicating therewith and held in a vacuum state from a space in an atmospheric atmosphere. 
     A slip ring  66  is disposed below the seal rotation mechanism  62 . The slip ring  66  has a rotating body  66   a  including a metal ring, and a fixed body  66   b  including a brush. The rotating body  66   a  is fixed to a bottom surface of the rotating portion  62   a  of the seal rotating mechanism  62 , and has a substantially cylindrical shape extending downward coaxially with the rotating portion  62   a . The fixed body  66   b  has a substantially cylindrical shape having an inner diameter slightly greater than an outer diameter of the rotating body  66   a.    
     The slip ring  66  is electrically connected to a DC power supply (not shown), and a voltage supplied from the DC power supply is transmitted to the wiring L via the brush of the fixed body  66   b  and the metal ring of the rotating body  66   a . Accordingly, a voltage can be applied from the DC power supply to the chuck electrode without causing torsion or the like in the wiring L. The rotating body  66   a  of the slip ring  66  is configured to rotate via the driving mechanism  68 . 
     The driving mechanism  68  is a direct drive motor having a rotor  68   a  and a stator  68   b . The rotor  68   a  has a substantially cylindrical shape extending coaxially with the rotating body  66   a  of the slip ring  66 , and is fixed to the rotating body  66   a . The stator  68   b  is formed in a substantially cylindrical shape having an inner diameter greater than an outer diameter of the rotor  68   a . When the driving mechanism  68  is driven, the rotor  68   a  rotates, and the rotation of the rotor  68   a  is transmitted to the stage  56  via the rotating body  66   a , the rotating portion  62   a , and the stage support  58 . Then, the stage  56  and the wafer W thereon are rotated with respect to the frozen heat transfer body  54 . In  FIG. 1 , for convenience, the rotating members are hatched with dots. 
     Although the direct drive motor is illustrated as an example of the driving mechanism  68 , the driving mechanism  68  may be driven via a belt or the like. 
     A first insulation structure  70  that is a vacuum insulation structure (vacuum double tube structure) formed in a cylindrical shape of a double tube structure and having an inner space maintained in a vacuum state is disposed to cover the cold head portion  52   a  of the chiller  52  and the lower portion of the frozen heat transfer body  54 . The first heat insulation structure  70  can suppress the deterioration of the cooling performance caused by heat input from the outside such as the driving mechanism  68  or the like into the cold head portion  52   a  and the lower portion of the frozen heat transfer body  54  that are important for cooling the stage  56  and the wafer W. 
     Further, a second insulation structure  71  that is a cylindrical vacuum double tube structure having an inner space maintained in a vacuum state is disposed to cover substantially the entire frozen heat transfer body  54  and to overlap the inner side of the first heat insulation structure  70 . The second insulation structure  71  can suppress the deterioration of the cooling performance caused by heat input from the outside such as the magnetic fluid seal, the first cooling gas leaking to the space S, or the like into the frozen heat transfer body  54 . Since the first heat insulation structure  70  and the second heat insulation structure  71  overlap at the lower portion of the frozen heat transfer body  54 , a non-insulated portion of the frozen heat transfer body  54  can be eliminated, and the insulation at the cold head portion  52   a  and its vicinity can be enhanced. 
     Further, the first heat insulation structure  70  and the second heat insulation structure  71  can suppress the transfer of cold heat of the chiller  52  and the frozen heat transfer body  54  to the outside. 
     A sealing member  81  is disposed between the main body  58   a  of the stage support  58  and the second heat insulation structure  71 . A space S sealed with a sealing member  81  is formed by the main body  58   a  of the stage support  58 , the second heat transfer portion  54   b  of the frozen heat transfer body  54 , and the upper portion of and the second heat insulation structure  71 . The first cooling gas leaking from the gap G flows into the space S. A gas flow path  72  is connected to the space S while penetrating through the sealing member  81 . The gas flow path  72  extends downward from the space S. A space between an upper surface of the second heat insulation structure  71  and the second heat transfer portion  54   b  of the frozen heat transfer body  54  is sealed with a sealing member  82 . The sealing member  82  suppresses the supply of the first cooling gas leaking into the space S to the main body of the frozen heat transfer body  54 . 
     The gas flow path  72  may allow the gas in the space S to be discharged, or may allow the cooling gas to be supplied to the space S. In both cases where the gas is discharged through the gas flow path  72  and where the cooling gas is supplied through the gas flow path  73 , it is possible to prevent deterioration of the sealing performance caused by a decrease in the temperature of the magnetic fluid due to the inflow of the first cooling gas from into the seal rotation mechanism  62 . When the gas flow path  72  has the cooling gas supply function, the third cooling gas is supplied to function as a counterflow to the first cooling gas leaking from the gap G. It is preferable that a supply pressure of the third cooling gas is substantially the same as or slightly higher than a supply pressure of the first cooling gas in order to enhance the function as the counterflow. The condensation can be prevented by using a gas having thermal conductivity lower than that of the first cooling gas, such as argon (Ar) gas or neon (Ne) gas, as the third cooling gas. 
     &lt;Substrate Processing Method&gt; 
     Next, a substrate processing method performed in the substrate processing device  1  will be described. 
     In the case of processing the wafer W in a normal state, the processing chamber  10  is evacuated, and the chiller  52  of the stage device  50  operates. At the same time, the first cooling gas is supplied to the gap G through the first cooling gas flow path  54   a . Accordingly, the cold heat transferred from the chiller  52  maintained at an extremely low temperature to the frozen heat transfer body is transferred to the stage  56  via the first cooling gas supplied to the gap G, and the rotatable stage  56  is maintained at a steady cooling temperature within a fixed range. 
     Then, the elevating mechanism  74  moves (lowers) the stage device  50  such that the stage  56  is located at the transfer position. Thus, the wafer maintained at a specific temperature (e.g., 75° C.) higher than room temperature is transferred from a vacuum transfer chamber (not shown) into the processing chamber  10  and placed on the stage  56  by a substrate transfer device (not shown). Next, a pressure in the processing chamber  10  is adjusted to an ultra-high vacuum (e.g., 10 −5  Pa or less) that is a processing pressure, and a DC voltage is applied to the chuck electrode  56   b  to electrostatically attract the wafer W on the electrostatic chuck  56   a . The second cooling gas is supplied to the backside of the wafer W, and the wafer W is maintained at the same temperature as that of the stage  56 . In that case, since the stage  56  is separated from the fixed frozen heat transfer body  54 , the wafer W can be rotated by the driving mechanism  68  via the stage support  58  while cooling the stage  56  and the wafer W. 
     In a state where the wafer W is rotated, a sputtering gas is introduced into the processing chamber  10 , and a voltage is applied from a plasma generation power source (not shown) to the target  30 . Accordingly, plasma of the sputtering gas is generated, and the target  30  is sputtered by ions in the plasma. Atoms or molecules of the sputtered target material are deposited on the surface of the wafer W held in an extremely low temperature state by the stage device  50 , thereby forming a desired film, e.g., a magnetic film for use in a TMR element having a high magnetoresistance ratio. The temperature of the stage  56  can be monitored by the temperature measuring mechanism  90  when the stage  56  is not rotating. 
     Such a series of processes are continuously performed on a plurality of wafers W. However, it was found that in the process of continuously processing the wafers W at the time of starting processing, the stage temperature is gradually increased and saturated at a steady cooling temperature within a fixed range. 
     This may be because indirect cooling in which a cooling gas is supplied to a space between the frozen heat transfer body  54  and the rotating stage  56  to rotate and cool the wafer W to an extremely low temperature is employed and also because the temperature measuring mechanism  90  cannot monitor a temperature during the rotation of the stage  56 . In other words, in the case of performing indirect cooling using a cooling gas, if the wafers W maintained at room temperature or higher are continuously processed at the time of starting processing, the phenomenon that the temperature of the stage  56  is gradually increased due to heat received from the wafers W occurs. During the rotation of the stage  56 , the temperature cannot be monitored and, thus, the temperature cannot be controlled. Accordingly, it is difficult to correct such phenomenon. The temperature of the stage  56  is saturated at a steady cooling temperature within a fixed range because the heat received from the substrate and the cold heat supplied to the stage  56  via the cooling gas are balanced. In this case, the temperature continues to increase to the steady cooling temperature until several to several tens of wafers W are processed after the start of processing, which makes the temperature management of the wafer W difficult. Such phenomenon is remarkable particularly when the cooling temperature of the wafer W is about 120 K (−153° C.) or less. Specifically, as shown in  FIG. 4 , for example, the stage temperature is managed by the frozen heat transfer body  54  within a range of the center temperature ±1K and reaches the steady cooling temperature. However, the stage temperature is lower than the steady cooling temperature by about 3° C. to 4° C. at the time of starting processing, and is saturated at the steady cooling temperature when about ten wafers W are processed.  FIG. 4  plots the average value of the stage (electrostatic chuck) temperature during processing that is measured by a thermocouple when the control temperature of the frozen heat transfer body  54  is 95K (−178° C.) and the wafer temperature is 75° C. 
     Conventionally, there is a problem that about ten wafers W whose temperatures are not controlled are processed from the start of processing. Therefore, a processing method capable of shortening a time required until the temperature reaches the steady cooling temperature (steady cooling temperature arrival time) is required. 
     Therefore, in one embodiment, as shown in  FIG. 5 , before the processing of the wafer W that is a substrate is started, first, preheating is performed to increase the temperature of the stage  56  to the steady cooling temperature (step  1 ) and, then, multiple wafers W are continuously processed on the stage  56  that has reached the steady cooling temperature (step  2 ). 
     Such a processing sequence is executed based on a processing recipe preset in the controller  100 . In other words, a preheating time required until the temperature reaches the steady cooling temperature or the like is obtained in advance, and the processing recipe is stored in the storage device of the controller  100  based on the preheating time or the like. Then, the processing is performed based on the processing recipe. 
     By performing the preheating process of step  1 , the temperature of the stage  56  can be rapidly increased to the steady cooling temperature. 
     In the preheating of step  1 , as shown in  FIG. 6 , the first cooling gas is removed from the gap G between the stage  56  and the frozen heat transfer body  54 , and a dummy wafer DW heated to the same temperature as that of an actual device wafer is placed on the stage  56  and processed. The dummy wafer DW can be transferred by the same substrate transfer mechanism as that used for the wafer W. 
     By removing the first cooling gas from the gap G, the cooling of the stage  56  is blocked, and the stage  56  is heated by heat received from the dummy wafer having the same temperature as that of the actual device wafer. By processing about one to three dummy wafers, the temperature of the stage  56  can be stabilized at the steady cooling temperature, which makes it possible to considerably shorten the time required until the temperature of the stage  56  reaches the steady cooling temperature compared to the conventional case. 
     When the stage temperature reaches the steady cooling temperature by performing preheating, the first cooling gas is introduced into the gap G to start cooling of the stage  56 , and the processing of the actual device wafer (wafer W) in step  2  is continuously performed on a plurality of wafers W. The processing performed in this case is the same as that described above. In the case of continuously processing the actual device wafers in a state where the stage temperature has reached the steady cooling temperature, the variation in the stage temperature can be maintained within a range of ±1K, for example, as described above. 
     The dummy wafer used for preheating preferably has the same temperature as that of the actual device wafer subjected to dummy processing under the same conditions as those applied to the actual device wafer. Further, it is preferable that the dummy processing of the dummy wafer in the substrate processing device  1  is performed under the same conditions as those applied to the actual device wafer. 
     In the case of performing preheating using the dummy wafer whose temperature is the same as that of the actual device wafer, the dummy wafer can be processed during the preheating under the same conditions as those of other actual processing except that the first cooling gas is removed from the gap G. Therefore, it is highly compatible with the actual processing. 
     Next, a result of monitoring a change in the stage temperature in the case of performing preheating and then continuously processing the actual device wafers will be described. Here, the preheating of the stage was performed by continuously processing two dummy wafers heated to 75° C. equal to the temperature of the actual device wafer in a state where the first cooling gas was removed from the gap G and, then, the first cooling gas was supplied to continuously process the actual device wafers.  FIG. 7  shows a relationship between the number of processed wafers and the stage temperature in that case.  FIG. 7  also shows, for comparison, a result of processing using a conventional method in which the dummy wafer shown in  FIG. 4  is not used. Similarly to  FIG. 4 ,  FIG. 7  plots the average value of the temperature of the stage (the electrostatic chuck) during processing that is measured by a thermocouple when the control temperature of the frozen heat transfer body  54  is 95 K (−178° C.) and the wafer temperature is 75° C. 
     As shown in  FIG. 7 , it was found that by processing two dummy wafers in a state where the first cooling gas is removed, the processing is performed within a management temperature range (steady cooling temperature) in subsequent processing of the actual device wafer. Since the processing time of one wafer is predetermined, the time required to reach the steady cooling temperature is considerably shortened compared to when the dummy wafer is not processed. Specifically, when the dummy wafer is not used, it is necessary to process about 10 wafers until the temperature reaches the steady cooling temperature. Therefore, the time required to reach the steady cooling temperature is shortened to about ¼ to ⅕ by the present method. 
     The preheating process of step  1  is not necessarily performed by the technique using the dummy wafer having the same temperature as that of the actual device wafer as long as the stage  56  can be preheated to the steady cooling temperature, and may be performed by various techniques. 
     For example, the dummy processing may be performed using a dummy wafer having a temperature higher than that of the actual device wafer. Further, the stage may be heated by a heater. Accordingly, the preheating can be performed with an enhanced heating effect. In such cases, the effect of shortening the steady cooling temperature arrival time can be obtained without removing the first cooling gas from the gap G. Also in such cases, the steady cooling temperature arrival time can be further shortened by removing the first cooling gas from the gap G. 
     As a technique for heating the stage  56  using a heater, there may be used a technique for performing heating by providing a lamp heater  120  at a movable shutter  110  for shielding sputtered particles from the target  30 , which is generally used in a sputtering device, as shown in  FIG. 8 . Further, as shown in  FIG. 9 , a technique for performing heating by providing a resistance heater  130  at the stage  56  may also be used. 
     &lt;Other Applications&gt; 
     While the embodiments of the present disclosure have been described, the embodiments of the present disclosure are illustrative in all respects and are not restrictive. The above-described embodiments may be omitted, replaced, or changed in various forms without departing from the scope of the appended claims and the gist thereof. 
     For example, in the above embodiment, sputtering film formation of a magnetic film for use in a TMR element has been described as an example of substrate processing. However, the present disclosure is not limited to the above embodiment as long as the substrate is rotated and processed while indirectly cooling the stage holding the substrate using a cooling gas. 
     Further, although an example in which a semiconductor wafer is used as a substrate has been described in the above embodiment, the substrate is not limited to the semiconductor wafer and may be another substrate such as a flat panel display (FPD) substrate, a ceramic substrate, or the like. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1 : substrate processing device 
               10 : processing chamber 
               30 : target 
               50 : stage device 
               52 : chiller 
               54 : frozen heat transfer body 
               54   a : first cooling gas supply line 
               56 : stage 
               74 : elevating mechanism 
               90 : temperature measuring mechanism 
               100 : controller 
               110 : shutter 
             G: gap 
             W: wafer (substrate)