Patent Publication Number: US-2011076117-A1

Title: Process module, substrate processing apparatus, and substrate transferring method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based on Japanese Priority Application No. 2009-220775 filed Sep. 25, 2009, the entire contents of which are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a process module where a substrate such as a semiconductor wafer is processed, a substrate processing apparatus including the process module, and a substrate transferring method performed in the process module and the substrate processing apparatus. 
     2. Description of the Related Art 
     In a fabrication process of semiconductor integrated circuits (ICs), a so-called cluster tool has been used that includes plural process chambers coupled with one another via one transfer chamber (for example, Patent Documents 1, 2). With this, because a substrate can be transferred from one process chamber to another through the transfer chamber where a vacuum environment (or clean environment) is realized, the substrate can be kept in a clean environment when the substrate is transferred, which may improve a production yield by reducing contamination of the substrate. In addition, the plural process chambers are coupled adjacent to one another to the transfer chamber, so that a transfer route along which the substrate is transferred from one process chamber to another can be reduced to minimum. Therefore, throughput can be increased in a reduced period of time of transferring the substrate. 
     Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2008-258192. 
     Patent Document 2: Japanese Patent Application Laid-Open Publication No. H07-142551. 
     With further higher integration of ICs and further reduction of dimensions that enable the higher integration, a thin film deposited on a substrate becomes thinner, and a deposition time becomes shorter accordingly. Therefore, a time required to transfer the substrate into/out from a process chamber becomes longer relative to the deposition time, and thus is likely to limit the throughput even in the cluster tool. 
     The present invention has been made in view of the above, and provides a process module that can reduce substrate transfer time, thereby contributing to increased throughput, a substrate processing apparatus including the process module, and a substrate transferring method performed in the process module and the substrate processing apparatus. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention provides a process module including a substrate receiving part on which a substrate is placed and a process is carried out with respect to the substrate on the substrate receiving part; and a substrate transfer mechanism including plural substrate holding members, each of which can be positioned in a first position where the substrate is transferred to/from a substrate transfer apparatus provided outside the process module and a second position above the substrate receiving part, wherein each of the substrate holding members can hold the substrate. 
     A second aspect of the present invention provides a substrate processing apparatus including a process module according to the first aspect; and a substrate transfer apparatus that can transfer the substrate to/from one of the plural substrate holding members that is positioned in the first position. 
     A third aspect of the present invention provides a substrate transfer method of transferring a substrate between a substrate transfer apparatus and a substrate receiving part on which the substrate is placed and a process is carried out with respect to the substrate on the substrate receiving part. The substrate transfer method includes steps of transferring a first substrate using the substrate transfer apparatus to and maintaining the first substrate in a first position; transferring the first substrate maintained in the first position by the substrate transfer apparatus to a first one of plural substrate holding members, each of which can be positioned in the first position and a second position above the substrate receiving part and hold a substrate; moving the first substrate holding member holding the first substrate to the second position; and transferring a second substrate from a second one of the plural substrate holding members to the substrate transfer apparatus that has stayed in the first position. 
     A fourth aspect of the present invention provides a substrate transfer method of transferring a substrate between a substrate transfer apparatus and a substrate receiving part on which the substrate is placed and a process is carried out with respect to the substrate on the substrate receiving part. The substrate transfer method includes steps of transferring a first substrate held by a first one of plural substrate holding members, each of which can be positioned in a first position and a second position, the second position being above the substrate receiving part, and hold a substrate, to the second position; transferring a second substrate using the substrate transfer apparatus to and maintaining the second substrate in the first position; transferring the second substrate from the substrate transfer apparatus to a second one of the plural substrate holding members in the first position; moving the first substrate holding member holding the first substrate from the second position to the first position; and transferring the first substrate from the first substrate holding member to the substrate transfer apparatus in the first position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a substrate processing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a perspective view schematically illustrating a main substrate transfer mechanism provided in the substrate processing apparatus of  FIG. 1 ; 
         FIG. 3  is a perspective view schematically illustrating a process module provided in the substrate processing apparatus of  FIG. 1  and the main substrate transfer mechanism of  FIG. 2 ; 
         FIG. 4  provides a plan view (a) and a side view (b) schematically illustrating the process module of  FIG. 3 ; 
         FIG. 5  provides another plan view (a) and another side view (b) schematically illustrating the process module of  FIG. 3 ; 
         FIG. 6  provides perspective views for explaining a substrate transfer method according to an embodiment of the present invention; 
         FIG. 7  provides perspective views for explaining the substrate transfer method according to the embodiment of the present invention, following  FIG. 6 ; 
         FIG. 8  provides perspective views for explaining a substrate transfer method according to another embodiment of the present invention; 
         FIG. 9  provides perspective views for explaining the substrate transfer method according to the embodiment of the present invention, following  FIG. 8 ; 
         FIG. 10  provides perspective views for explaining the substrate transfer method according to the embodiment of the present invention, following  FIG. 9 ; 
         FIG. 11  provides perspective views for explaining the substrate transfer method according to the embodiment of the present invention, following  FIG. 10 ; 
         FIG. 12  provides perspective views for explaining the substrate transfer method according to the embodiment of the present invention, following  FIG. 11 ; 
         FIG. 13  provides perspective views for explaining a substrate transfer method according to yet another embodiment of the present invention; 
         FIG. 14  provides perspective views for explaining the substrate transfer method according to the embodiment of the present invention, following  FIG. 13 ; 
         FIG. 15  provides a plan view (a) and a side view (b) schematically illustrating a modified example of the process module illustrated in  FIGS. 3 through 6 ; and 
         FIG. 16  provides another plan view (a) and another side view (b) of the modified example of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Non-limiting, exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings, the same or corresponding reference symbols are given to the same or corresponding members or components. It is to be noted that the drawings are illustrative of the invention, and there is no intention to indicate scale or relative proportions among the members or components. Therefore, the specific thickness or size should be determined by a person having ordinary skill in the art in view of the following non-limiting embodiments. 
     First Embodiment 
     A substrate processing apparatus according to a first embodiment of the present invention is explained with reference to  FIGS. 1 through 5 . 
       FIG. 1  is a schematic view illustrating the substrate processing apparatus according to the first embodiment. As shown, a substrate processing apparatus  10  is provided with cassette stages  11  on which a wafer cassette CS such as a Front-Opening Unified Pod is placed, a transfer chamber  12  that is coupled in physical communication with the cassette stages  11  through openings  11   a  and in which a wafer W may be transferred in an atmospheric environment, load lock chambers  13  whose insides can be maintained at an atmospheric pressure or a reduced pressure and that are coupled to the transfer chamber  12 , a transport chamber that is coupled to the load lock chambers  13  and where the wafer W may be transferred in a reduced pressure environment, and process modules  15  that are coupled to the transport chamber  14  and where the wafer W is processed. 
     A transfer robot R is provided inside the transfer chamber  12 . The transfer robot R takes the wafer W out from the wafer cassette CS placed on the cassette stage  11  through the opening  11   a  to transfer the wafer W to the load lock chamber  13 , and takes the wafer W out from the load lock chamber  13  to transfer the wafer W to the wafer cassette CS. In addition, an alignment chamber  12   b  where the wafer W is aligned is coupled to the transfer chamber  12 . 
     The load lock chambers  13  are provided with susceptors  13 S on one of which is placed the wafer W transferred from the transfer chamber  12  or the transport chamber  14  into the corresponding load lock chamber  13 . In addition, gate valves  12   a  are provided between the load lock chambers  13  and the transfer chamber  12 , and gate valves  13   a  are provided between the load lock chambers  13  and the transport chamber  14 . When the gate valve  12   a  and the gate valve  13   a  are closed, the load lock chamber  13  is kept airtight, and the inside of the load lock chamber  13  can be maintained at atmospheric pressure or at a reduced pressure by an evacuation apparatus and an inert gas (including nitrogen gas) supplying apparatus (not shown) coupled to the load lock chamber  13 . When the inside of the load lock chamber  13  is at atmospheric pressure, the gate valve  12   a  is opened, so that the wafer W is transferred between the load lock chamber  13  and the transfer chamber  12 . When the inside of the load lock chamber  13  is at a reduced pressure, the gate valve  13   a  is opened, so that the wafer W is transferred between the load lock chamber  13  and the transport chamber  14  whose inside has been evacuated to a reduced pressure. 
     The transport chamber  14  has a hexagonal top-view shape in this embodiment. The load lock chambers  13  are coupled to two faces of the six faces, and the four process modules  15  are coupled to the other four faces. Gate valves GV 1  are provided between the transport chamber  14  and the process modules  15 . A main transfer apparatus  16  is provided in substantially the center of the transport chamber  14 . The main transfer apparatus  16  transfers the wafer W into/out from the load lock chambers  13  or the process modules  15 . 
     Referring to  FIG. 2 , the main transfer apparatus  16  includes a transfer arm  16   a  that has at both end portions wafer holding areas capable of holding the wafers W and can rotate around a rotation axis C 1  at substantially the center of the substrate processing apparatus  10 ; a first supporting arm  16   b  that rotatably supports the transfer arm  16   a  at one end and can rotate around a rotation axis C 2  at the other end; a second supporting arm  16   c  that rotatably supports the first supporting arm  16   b  at one end and can rotate around a rotation axis C 3  at the other end; and a base part  16   d  that rotatably supports the second supporting arm  16   c  and is arranged in a bottom portion of the transport chamber  14  ( FIG. 1 ). Three suction holes  16 H are provided in the wafer holding areas, and thus the wafer W placed on the wafer holding area is held by suction through the suction holes  16 H. The transfer arm  16   a , the first supporting arm  16   b , and the second supporting arm  16   c  of the main transfer chamber  16  arbitrarily rotate around the corresponding rotation axes C 1 , C 2 , and C 3 , thereby transferring the wafer held by a distal end (wafer holding area) of the transfer arm  16   a  into a predetermined process module  15  or the load lock chamber  13 . 
     Referring to  FIG. 3 , the process module  15  includes a buffer chamber  15   a  and a process chamber  15   b  that are configured so that the insides thereof can be evacuated to and maintained at a reduced pressure, and a gate valve GV 2  provided between the buffer chamber  15   a  and the process chamber  15   b  in order to allow the buffer chamber  15   a  and the process chamber  15   b  to be or not to be in pressure communication with each other. 
     The buffer chamber  15   a  is provided in the inside of the process chamber  15  with a substrate transfer mechanism  150  that includes plural substrate holding members  15 U,  15 M,  15 D and a pivot shaft  15 L that can independently pivot the plural substrate holding members  15 U,  15 M,  15 D. 
     In addition, the process chamber  15   b  is provided in its inside with a susceptor  15 S on which the wafer W is placed. In the process chamber  15   b , a predetermined process is performed with respect to the wafer W placed on the susceptor  15 S. The process may be deposition of an insulation film or an electrically conductive film, etching, thermal processing, or the like. In addition, the process may be a smoothing process performed to improve a line width roughness (LWR) of a patterned resist film, a film thickness measurement, a particle counting process, or the like. The process chamber  15   b  may be arbitrarily provided with a gas supplying line, a gas supplying nozzle (or showerhead), a wafer chuck, a wafer heating mechanism, electrodes for generating plasma, an optical system, or the like, depending on the process performed in the process chamber  15   b.    
     Next, the process module  15  is further explained with reference to  FIGS. 4 and 5 . A subsection (a) of  FIG. 4  is a plan view schematically illustrating the process module  15 , and a subsection (b) of  FIG. 4  is a side view schematically illustrating the process module  15  seen from a direction indicated by an arrow A 4  in the subsection (a) of  FIG. 4 . In these drawings, the transfer arm  16   a  (simply referred to as transfer arm  16  hereinafter) that has proceeded into the buffer chamber  15   a  of the process module  15  from the transport chamber  14  is also shown. 
     The substrate holding member  15 U positioned at a home position is illustrated in the subsection (a) of  FIG. 4 . The substrate holding member  15 U is large enough to support the wafer W subject to the process performed in the process chamber  15   b , and may be made of metal such as aluminum or stainless steel. As shown, the substrate holding member  15 U has a cutout portion  15   c  having a width wider than the width of the transfer arm  16 . With this, when the transfer arm  16  proceeds into the buffer chamber  15   a , the transfer arm  16  can relatively pass through the cutout portion  15   c  in a vertical direction, which allows the transfer arm  16  to move upward or downward. With such an upward/downward movement of the transfer arm  16 , the wafer W can be transferred from the transfer arm  16  to the substrate holding member  15 U and from the substrate holding member  15 U to the transfer arm  16 . In addition, a length (depth) of the cutout portion  15   c  is determined so that the transfer arm  16  that has proceeded into the cutout portion  15   c  can certainly transfer the wafer W to the substrate holding member  15 U. As stated, the substrate holding member  15 U has the cutout portion  15   c  that allows the transfer arm  16  (wafer holding area) to relatively pass therethrough when the substrate holding member  15 U moves in the vertical direction in order to transfer the wafer W to or from the transfer arm  16 . 
     Referring to the subsection (b) of  FIG. 4 , an elevation driving part  15 Aa is provided below the pivot shaft  15 L of the substrate holding member  15 U. The elevation driving part  15 Aa pivots the substrate holding member  15 U and moves the substrate holding member  15 U (the entire substrate transfer mechanism  150 ) upward or downward. A bellows  15 Ba is provided between the pivot shaft  15 L and (a chassis of) the buffer chamber  15   a . The bellows  15 Ba allows the pivot shaft  15 L to move upward or downward while maintaining airtightness of the buffer chamber  15   a.    
     The susceptor  15 S arranged inside the process chamber  15   b  is provided with plural (three in the illustrated example) lift pins  15 P that can go through the susceptor  15 S in the vertical direction. The lift pins  15 P are moved upward or downward by an elevation driving part  15 Ab. With this, the lift pins  15 P can place the wafer W onto the susceptor  15 S and bring the wafer W upward from the susceptor  15 S. In addition, a bellows  15 Bb is provided between a rod that moves the lift pins  15 P upward or downward and the (chassis of) the process chamber  15   b . The bellows  15 Bb allows the rod to move upward or downward while maintaining airtightness of the process chamber  15   b.    
     Next, referring to subsections (a) and (b) of  FIG. 5 , the substrate holding member  15 U is pivoted by the pivot shaft  15 L and proceeds into the process chamber  15   b  through the gate valve GV 2  to be positioned substantially above the susceptor  15 S. In this embodiment, the substrate holding member  15 U is pivoted by about 80° until reaching the position above the susceptor  15 S from the home position. While a pivoting angle may be determined in accordance with a size of the wafer W to be processed in the substrate processing apparatus  10  (process module  15 ), the pivoting angle is preferably 90° or less, from a viewpoint of reduced dimension (footprint) of the process module  15 . Incidentally, the subsection (a) of  FIG. 5  is another plan view schematically illustrating the process module  15 , and a subsection (b) of  FIG. 4  is a side view schematically illustrating the process module  15  seen from a direction indicated by an arrow A 5  in the subsection (a) of  FIG. 5 . As shown in the subsection (a) of  FIG. 5 , three slits  15   t  are formed in the substrate holding member  15 U, which correspond to the lift pins  15 P. When the substrate holding member  15 U is positioned substantially above the susceptor  15 S and then the lift pins  15 P are raised, distal ends of the lift pins  15 P go through the slits  15   t  to be projected above the substrate holding member  15 U. In addition, the slits  15   t  have a curved shape. Therefore, the substrate holding member  15 U can be pivoted back to the buffer chamber  15   a  by the pivot shaft  15 L, even when the lift pins  15 P are projected above the substrate holding member  15 U, because the curved slits  15   t  allow the lift pins  15   t  to move along and through the curve. Namely, the substrate holding member  15 U has the slits  15   t  of curved shapes that are formed corresponding to the lift pins  15 P and allow the lift pins  15   t  to relatively pass therethrough when the substrate holding member  15 U is pivoted by the pivot shaft  15 L, even when the susceptor  15 S is provided with plural lift pins  15  capable of moving upward or downward from the susceptor  15 S. 
     Referring again to the subsection (b) of  FIG. 4 , substrate holding members  15 M,  15 D are arranged one above the other below the substrate holding member  15 U. The substrate holding members  15 M,  15 D have the same configuration as the substrate holding member  15 U, and can be independently pivoted in the same manner as the substrate holding member  15 U. The substrate holding members  15 U,  15 M,  15 D can be pivoted, for example, by motors provided corresponding to the substrate holding members  15 U,  15 M,  15 D within the elevation driving part  15 Aa and a ternary coaxial shaft having an outer tube, a middle tube arranged inside the outer tube, and an inner rod that couple the motors with the corresponding substrate holding members  15 U,  15 M,  15 D. 
     Referring again to  FIG. 1 , the substrate processing apparatus  10  is provided with a control part that controls constituent components or members of the substrate processing apparatus  10 , in order to execute various processes in the substrate processing apparatus  10 . The control part  17  includes a central processing unit, and operates in accordance with a program that includes a group of instructions that make the substrate processing apparatus  10  execute a substrate transfer method described later. The program is stored in a computer readable storage medium  17   a , and loaded into a memory device  17   b  through an input/output (I/O) device (not shown) corresponding to the computer readable storage medium  17   a . The computer readable storage medium  17   a  may be a flexible disk, a solid state memory, or a hard disk, for example. In addition, the program may be downloaded into the memory device  17   b  from a predetermined communication line rather than the computer readable storage medium  17   a.    
     Advantages or effects of the process module  15  and the substrate processing apparatus  10  including the process module  15  are easily understood from the following explanation about a substrate transfer method according to an embodiment of the present invention. 
     Second Embodiment 
     A substrate transfer method according to a second embodiment of the present invention is explained with reference to  FIGS. 6 and 7 . In the following explanation, the substrate transfer method is carried out in the substrate processing apparatus  10 . In  FIGS. 6 and 7 , the gate valves GV 1 , GV 2 , (the chassis of) the buffer chamber  15   a , and (the chassis of) the process chamber  15   b  that are shown in  FIG. 3  are omitted for the sake of explanatory convenience, but a positional relationship of the substrate holding members  15 U,  15 M,  15 D, (the distal end of) the transfer arm  16 , and the susceptor is mainly illustrated. 
     Referring to a subsection (a) of  FIG. 6 , the buffer chamber  15   a  (see  FIG. 3 ) is provided in its inside with the substrate transfer mechanism  150  having the substrate holding members  15 U,  15 M,  15 D, which are positioned in their home positions. In addition, the two substrate holding members  15 U,  15 M from above hold corresponding wafers WP 1 , WP 2  that have been processed in the process chamber  15   b  (see  FIG. 3 ), (referred to as processed wafers WP 1 , WP 2 ), and the lowermost substrate holding member  15 D holds no wafer. Moreover, there is no wafer on the susceptor  15 S in the process chamber  15   b  (see  FIG. 3 ), and the transfer arm  16  in the transport chamber  14  (see  FIG. 3 ) holds at one end a wafer WU 1  that is to be processed in the process chamber  15   b  (referred to as an unprocessed wafer WU 1 ). 
     First, the substrate transfer mechanism  150  is moved upward or downward in order to adjust a vertical position of the substrate transfer mechanism  150  so that the transfer arm  16  can proceed into a space between the substrate holding members  15 M and  15 D. Second, when the gate valve GV 1  (see  FIG. 3 ) between the buffer chamber  15   a  and the transport chamber  14  is opened, the transfer arm  16  proceeds into the buffer chamber  15   a  and holds the unprocessed wafer WU 1  between the substrate holding members  15 M and  15 D, as shown in a subsection (b) of  FIG. 6 . Next, when the substrate transfer mechanism  150  is moved upward, the transfer arm  16  relatively passes through the cutout part  15   c  of the substrate holding member  15 D from above to below, and thus the unprocessed wafer WU 1  is received by the substrate holding member  15 D, as shown in a subsection (c) of  FIG. 6 . After the unprocessed wafer WU 1  is received by the substrate holding member  15 D, the transfer arm  16  does not return to the transport chamber  14  but stays in the same position in the buffer chamber  15   a.    
     Next, when the gate valve GV 2  between the buffer chamber  15   a  and the process chamber  15   b  (see  FIG. 3 ) is opened, the substrate holding member  15 D holding the unprocessed wafer WU 1  is pivoted into the process chamber  15   b  by the pivot shaft  15 L, and holds the unprocessed wafer WU 1  above the susceptor  15 S in the process chamber  15   b , as shown in a subsection (a) of  FIG. 7 . While the pivot angle of the substrate holding member  15 D is about 80°, the pivot angle may be determined in accordance with the size of the unprocessed wafer WU 1  (processed wafers WP 1 , WP 2 ), as explained in the first embodiment. The same is true for the substrate holding members  15 U,  15 M. When the substrate holding member  15 D is being pivoted or after the substrate holding member  15 D is pivoted, the pivot shaft  15 L is moved downward, the transfer arm  16  relatively passes through the cutout part  15   c  of the substrate holding member  15 M from below to above, and thus the processed wafer WP 2  is received by the transfer arm  16 , as shown in a subsection (b) of  FIG. 7 . Then, the transfer arm  16  transfers the processed wafer WP 2  out from the buffer chamber  15   a  to the transport chamber  14 , and the substrate holding member  15 D is returned to the home position while holding the unprocessed wafer WU 1 . After a series of the above procedures, the substrate holding member  15 U holds the processed wafer WP 1 ; the substrate holding member  15 M holds no wafer; and the substrate holding member  15 D holds the unprocessed wafer WU 1 , inside the buffer chamber  15   a  (see  FIG. 3 ), as shown in a subsection (c) of  FIG. 7 . 
     Next, when the transfer arm  16  is rotated by 180° around the rotation axis C 1  (see  FIG. 2 ), another unprocessed wafer (called an unprocessed wafer WU 2 , for the sake of explanatory convenience, although not shown) is moved by the other end of the transfer arm  16  to a position in front of the buffer chamber  15   a . Then, the substrate transfer is continued in the following manner. Namely, the transfer arm  16  proceeds into the buffer chamber  15   a , and holds the unprocessed wafer WU 2  between the substrate holding members  15 U and  15 M. Next, when the substrate transfer mechanism  150  is moved upward, the unprocessed wafer WU 2  is transferred from the transfer arm  16  to the substrate holding member  15 M. After the unprocessed wafer WU 2  is received by the substrate holding member  15 M, the transfer arm  16  does not return to the transport chamber  14  but stays in the same position in the buffer chamber  15   a.    
     Then, when the substrate holding member  15 M holding the unprocessed wafer WU 2  is pivoted by the pivot shaft  15 L of the substrate transfer mechanism  150 , and holds the unprocessed wafer WU 2  above the susceptor  15 S in the process chamber  15   b . When the substrate holding member  15 M is being pivoted or after the substrate holding member  15 M is pivoted, the substrate transfer mechanism  150  is moved downward, the processed wafer WP 1  held by the substrate holding member  15 U is received by the transfer arm  16 . Next, the transfer arm  16  transfers the processed wafer WP 1  out from the buffer chamber  15   a , and the substrate holding member  15 M holding the unprocessed wafer WU 2  is returned to the home position. After this series of the above procedures, the substrate holding member  15 U holds no wafer; the substrate holding member  15 M holds the unprocessed wafer WU 2 ; and the substrate holding member  15 D holds the unprocessed wafer WU 1 , inside the buffer chamber  15   a  (see  FIG. 3 ). 
     Subsequently, the unprocessed wafers WU 1 , WU 2  are transferred from the buffer chamber  15   a  to the process chamber  15   b  in turn, and each of the unprocessed wafers WU 1 , WU 2  goes through a predetermined process in the process chamber  15   b . Specifically, the substrate holding member  15 M is pivoted by the pivot shaft  15 L and holds the unprocessed wafer WU 2  above the susceptor  15 S in the process chamber  15   b . Next, the lift pins  15 P of the susceptor  15 S are moved upward and go through the corresponding slits  15   t  to move the unprocessed wafer WU 2  upward. Namely, the unprocessed wafer WU 2  is received by the lift pins  15 P. Then, the substrate holding member  15 M is pivoted back to the home position. The lift pins  15 P are moved downward, and thus the unprocessed wafer WU 2  is placed on the susceptor  15 S. After the gate valve GV 2  is closed, so that the process chamber  15   b  is hermetically sealed, the predetermined process is performed with respect to the unprocessed wafer WU 2  on the susceptor  15 S. In the following, the wafer WU 2  that has gone through the predetermined process is called a processed wafer WP 3 , for the sake of explanatory convenience, although not shown. 
     After the process is completed, the lift pins  15 P are moved upward to bring the wafer WP 3  from the susceptor  15 S. Then, when the gate valve GV 2  is opened, the substrate holding member  15 M is pivoted by the pivot shaft  15 L and positioned between the wafer WP 3  and the susceptor  15 S while allowing the lift pins  15 P to relatively pass through the corresponding silts  15   t  of the substrate holding member  15 M. Next, when the lift pins  15 P are moved downward, the wafer WP 3  is received by the substrate holding member  15 M. Subsequently, the substrate holding member  15 M holding the wafer WP 3  is returned to the home position and at the same time the substrate holding member  15 D holding the wafer WU 1  is pivoted and positioned above the susceptor  15 S, thereby holding the wafer WU 1  above the susceptor  15 S. When the lift pins  15 P are moved upward, the wafer WU 1  is transferred from the substrate holding member  15 D to the lift pins  15 P. Then, when the substrate holding member  15 D is returned to the home position and the lift pins  15 P are moved downward, the wafer WU 1  is placed on the susceptor  15 S. Next, the gate valve GV 2  is closed, the wafer WU 1  goes through the process. The wafer WU 1  that has gone through the process is called as a wafer WP 4 , for the sake of explanatory convenience, although not shown. 
     After the process is completed, the wafer WP 4  is moved upward by the lift pins  15 P, and the height of the substrate transfer mechanism  150  is adjusted so that the substrate holding member  15 U, which holds no wafer, can be positioned between the wafer WP 4  and the susceptor  15 S. Then, the gate valve GV 2  is opened, and the substrate holding member  15 U is pivoted and positioned between the wafer WP 4  and the susceptor  15 S. When the lift pins  15 P are moved downward, the wafer WP 4  is transferred from the lift pins  15 P to the substrate holding member  15 U. Finally, the substrate holding member  15 U holding the wafer WP 4  is returned to the home position, and the gate valve GV 2  is closed. The situation at this time is illustrated in the subsection (a) of  FIG. 6 . Subsequently, the same procedures are repeated until all the wafers to be processed go through the process. 
     As stated above, the unprocessed wafer WU 1  is transferred from the transfer arm  16  to the substrate holding member  15 D, when the substrate holding members  15 U,  15 M,  15 D are positioned at their home positions. While the wafer WU 1  is moved to the position above the susceptor  15 S by the substrate holding member  15 D, the transfer arm  16  stays in the home positions of the substrate holding members  15 U,  15 M,  15 D, receives the processed wafer WP 2  from the substrate holding member  15 M, and then leaves the home positions (the buffer chamber  15   a ) to the transport chamber  14 . Therefore, the transfer arm  16  can transfer the unprocessed wafer WU 1  into the buffer chamber  15   a , and transfer the processed wafer WP 2  out from the buffer chamber  15   a  while the transfer arm  16  reciprocates only once between the buffer chamber  15   a  and the transport chamber  14 . Namely, the transfer arm  16  is not required to reciprocate twice between the buffer chamber  15   a  and the transport chamber  14 . Accordingly, the time required to transfer a wafer into and out from the buffer chamber  15   a  may be reduced. 
     Such an advantage is easily understood when compared to a conventional case where a wafer transfer arm has to reciprocate twice between a first process chamber and a transport chamber. Namely, in a conventional manner, the wafer transfer arm proceeds into a first process chamber to take a processed wafer out from the first process chamber (first reciprocating movement), transfers the processed wafer to a second process chamber, takes an unprocessed wafer from a load lock chamber, transfers an unprocessed wafer into the first wafer and then goes back to the transport chamber (second reciprocating movement). 
     Moreover, transferring the processed wafer WP 3  out from and transferring the unprocessed wafer WU 1  into the process chamber  15   b  are carried out at the same time by pivoting the substrate holding member  15 M holding the wafer WP 3  moving from the process chamber  15   b  to the buffer chamber  15   a  and the substrate holding member  15 D holding the wafer WU 1  moving from the buffer chamber  15   a  to the process chamber  15   b  at the same time. Therefore, the wafer transfer time can be reduced. 
     In addition, because the main transfer apparatus  16  (transfer arm  16 ), which is relatively large, and the substrate transfer mechanism  150 , which is relatively small and can turn in a relatively small radius, move in concert with each other, the wafer W can be transferred in a quick and efficient manner. 
     Third Embodiment 
     Next, a substrate transfer method according to a third embodiment of the present invention is explained with reference to  FIGS. 8 through 12 . In the following explanation, the substrate transfer method is carried out in the substrate processing apparatus  10 . Even in  FIGS. 8 through 12 , the gate valves GV 1 , GV 2 , (the chassis of) the buffer chamber  15   a , and (the chassis of) the process chamber  15   b  that are shown in  FIG. 3  are omitted for the sake of explanatory convenience, but a positional relationship of the substrate holding members  15 U,  15 M,  15 D, (the distal end of) the transfer arm  16 , and the susceptor is mainly illustrated. 
     Referring to a subsection (a) of  FIG. 8 , the buffer chamber  15   a  (see  FIG. 3 ) is provided in its inside with the substrate transfer mechanism  150  having the substrate holding members  15 U,  15 M,  15 D, which are positioned in their home positions. In addition, the two substrate holding members  15 M,  15 D hold corresponding wafers WP 1 , WP 2  that have been processed in the process chamber  15   b  (see  FIG. 3 ), (referred to as processed wafers WP 1 , WP 2 ), and the uppermost substrate holding member  15 U holds no wafer. Moreover, there is no wafer on the susceptor  15 S in the process chamber  15   b  (see  FIG. 3 ), and the transfer arm  16  in the transport chamber  14  (see  FIG. 3 ) holds at one end a wafer WU 1  that is to be processed in the process chamber  15   b  (referred to as an unprocessed wafer WU 1 ). 
     First, the substrate transfer mechanism  150  is moved upward or downward in order to adjust a vertical position of the substrate transfer mechanism  150  so that the transfer arm  16  can proceed into a position above the substrate holding member  15 U. Second, the middle substrate holding member  15 M is pivoted by the pivot shaft  15 L, thereby temporarily holding the processed wafer WP 1  above the susceptor  15 S, as shown in a subsection (b) of  FIG. 8 . While the pivot angle of the substrate holding member  15 M is about 80°, the pivot angle may be determined in accordance with the size of the unprocessed wafer WP 1 , as explained in the first embodiment. The same is true for the substrate holding members  15 U,  15 D. 
     Next, when the gate valve GV 1  between the buffer chamber  15   a  and the transport chamber  14  is opened, the transfer arm  16  proceeds into the buffer chamber  15   a  and holds an unprocessed wafer WU 1  above the substrate holding member  15 U, as shown in a subsection (c) of  FIG. 8 . When the substrate transfer mechanism  150  is moved upward  150 , the transfer arm  16  relatively passes through the cutout part  15   c  of the substrate holding member  15 U from above to below, and thus the unprocessed wafer WU 1  is transferred from the transfer arm  16  to the substrate holding member  15 U, as shown in a subsection (a) of  FIG. 9 . After the wafer WU 1  is received by the substrate holding member  15 U, the transfer arm  16  does not return to the transport chamber  14  but stays in the same position in the buffer chamber  15   a.    
     Next, the substrate holding member  15 M holding the processed wafer WP 1  above the susceptor  15 S is pivoted back to the home position by the pivot shaft  15 L, as shown in a subsection (b) of  FIG. 9 . At this time, the vertical position of the substrate transfer mechanism  150  is adjusted so that the substrate holding member  15 M can be positioned between the substrate holding member  15 U and the transport arm  16 . After the substrate holding member  15 M is returned to the home position, the pivot shaft  15 L (substrate transfer mechanism  150 ) is moved downward, which allows the transfer arm  16  to relatively pass through the cutout part  15   c  of the substrate holding member  15 M, and thus the processed wafer WP 1  is transferred from the substrate holding member  15 M to the transfer arm  16 , as shown in a subsection (c) of  FIG. 9 . Subsequently, the transfer arm  16  transfers the processed wafer WP 1  out from the buffer chamber  15   a  to the transport chamber  14 . After a series of the above procedures, the substrate holding member  15 U holds the unprocessed wafer WU 1 ; the substrate holding member  15 M holds no wafer; and the substrate holding member  15 D holds the unprocessed wafer WP 2 , inside the buffer chamber  15   a  (see  FIG. 3 ), as shown in a subsection (a) of  FIG. 10 . 
     Next, when the transfer arm  16  is rotated by 180° around the rotation axis C 1  (see  FIG. 2 ), another unprocessed wafer WU 2  is moved by the other end of the transfer arm  16  to a position in front of the buffer chamber  15   a . At this time, the lowermost substrate holding member  15 D is pivoted, thereby temporarily holding the processed wafer WP 2  above the susceptor  15 S, as shown in a subsection (b) of  FIG. 10 . 
     Next, the transfer arm  16  holding the unprocessed wafer WU 2  proceeds into a space between the substrate holding members  15 U and  15 M, and holds the wafer WU 2  between the substrate holding members  15 U and  15 M, as shown in a subsection (c) of  FIG. 10 . At this time, the vertical position of the substrate transfer mechanism  150  is adjusted so that the transfer arm  16  can proceed into the space between the substrate holding members  15 U and  15 M. Then, when the pivot shaft  15 L (substrate transfer mechanism  150 ) is moved upward, the unprocessed wafer WU 2  is transferred from the transfer arm  16  to the substrate holding member  15 M, as shown in a subsection (a) of  FIG. 11 . At this time, the vertical position of the pivot shaft  15 L (substrate transfer mechanism  150 ) is adjusted so that the substrate holding member  15 D holding the processed wafer WP 2  above the susceptor  15 S can be returned above the transfer arm  16 . Then, the substrate holding member  15 D is pivoted back to the home position by the pivot shaft  15 L, as shown in a subsection (b) of  FIG. 11 . Next, when the pivot shaft  15 L is moved downward, the processed wafer WP 2  is transferred from the substrate holding member  15 D to the transfer arm  16 , as shown in a subsection (c) of  FIG. 11 . Subsequently, the transfer arm  16  transfers the processed wafer WP 2  from the buffer chamber  15   a  to the transport chamber  14  (see  FIG. 3 ). After this series of the procedures so far, the substrate holding member  15 U holds the unprocessed wafer WU 1 ; the substrate holding member  15 M holds the unprocessed wafer WU 2 ; and the substrate holding member  15 D holds no wafer, inside the buffer chamber  15   a  (see  FIG. 3 ), as shown in  FIG. 12 . 
     Next, the unprocessed wafers WU 1 , WU 2  are transferred to the process chamber  15   b  (see  FIG. 3 ), and go through a predetermined process in the process chamber  15   b , in turn. Then, the same procedures are repeated until all the wafers to be processed are processed in the same manner. 
     According to this embodiment, the transfer arm  16  can transfer the unprocessed wafer WU 1  to the uppermost substrate holding member  15 U, receive the processed wafer WP 1  from the middle substrate holding member  15 M, and return to the transport chamber  14 . In addition, the transfer arm  16  can transfer the unprocessed wafer WU 2  to the middle substrate holding member  15 M, receive the processed wafer WP 2  from the lowermost substrate holding member  15 D, and return to the transport chamber  14 . Therefore, the transfer arm  16  can transport a wafer in and out without reciprocating twice between the transport chamber  14  and the buffer chamber  15   a , thereby reducing the wafer transfer time. 
     In addition, this embodiment can also provide the same advantage provided by the relatively large main transfer apparatus  16  (transfer arm  16 ) and the relatively small substrate transfer mechanism  150  moving in concert with each other. 
     Fourth Embodiment 
     A substrate transfer method according to a fourth embodiment of the present invention is explained with reference to  FIGS. 13 through 14 , which are plan views illustrating the buffer chamber  15   a  and the process chamber  15   b . In addition, the process module  15  used to carry out the substrate transfer method of this embodiment is provided with a substrate transfer mechanism having two substrate holding members  15 U,  15 D in the buffer chamber  15   a.    
     Referring to a subsection (a) of  FIG. 13 , the substrate holding member  15 U holds the processed wafer WP 1  that has been processed in the process chamber  15   b  in the buffer chamber  15   a . The substrate holding member  15 D arranged below the substrate holding member  15 U holds no wafer. In addition, there is no wafer on the susceptor  15 S in the process chamber  15   b , and the transfer arm  16  in the transport chamber  14  holds at one end a wafer WU 1  to be processed in the process chamber  15   b.    
     First, a vertical position of the substrate transfer mechanism is adjusted by the pivot shaft  15 L so that the transfer arm  16  can proceed into a space between the substrate holding members  15 U,  15 D. Next, when the gate valve GV 1  is opened, the transfer arm  16  proceeds into the buffer chamber  15   a , as shown in a subsection (b) of  FIG. 13 , and holds the unprocessed wafer WU 1  between the substrate holding members  15 U and  15 D. 
     When the pivot shaft  15 L is moved upward, the substrate holding member  15 D receives the unprocessed wafer WU 1  from the transfer arm  16 . Then, when the gate valve GV 2  is opened, the substrate holding member  15 D is pivoted by the pivot shaft  15 L, as shown in a subsection (c) of  FIG. 13  and holds the unprocessed wafer WU 1  above the susceptor  15 S. The pivot angle of the substrate holding member  15 D is about 80°. Next, the lift pins  15 P in the susceptor  15 S are moved upward and pass through the corresponding slits  15   t  (see  FIG. 3 ) of the substrate holding member  15 D, thereby receiving the unprocessed wafer WU 1  from the substrate holding member  15 D. In addition, the processed wafer WP 1  held by the substrate holding member  15 U is transferred to the transfer arm  16  by moving the pivot shaft  15 L downward, as shown in a subsection (d) of  FIG. 13 . 
     Next, the substrate holding member  15 D is pivoted by the pivot shaft  15 L without holding any wafer, as shown in a subsection (a) of  FIG. 14 , and positioned at the home position. Then, the gate valve GV 2  is closed. In the process chamber  15   b , the lift pins  15 P are moved downward, and thus the unprocessed wafer WU 1  is placed on the susceptor  15 S. On the other hand, the processed wafer WP 1  is transferred out from the buffer chamber  15   a  to the transport chamber  14  by the transfer arm  16 , as shown in a subsection (b) of  FIG. 14 . Then, the processed wafer WP 1  is transferred to another process chamber or the load lock chamber  13 , and the unprocessed wafer WU 1  on the susceptor  15 S in the process chamber  15   b  goes through a predetermined process (a subsection (c) of  FIG. 14 ). 
     After the process is completed, the processed wafer WP (a subsection (d) of  FIG. 14 ), which is the wafer WU 1  after the process, is transferred out to the buffer chamber  15   a  by the lift pins  15 P and the substrate holding member  15 U, and held at the home position of the substrate holding member  15 U. On the other hand, the transfer arm  16  holds another unprocessed wafer, and stays in front of the buffer chamber  15   a . Namely, the situation at this time is illustrated in the subsection (a) of  FIG. 13 . Subsequently, the above procedures are repeated until all the wafers to be processed are processed. 
     According to the fourth embodiment of the present invention, the transfer arm  16  transfers the unprocessed wafer WU 1  to the substrate holding member  15 D, receives the processed wafer WP 1  from the substrate holding member  15 U, and returns to the transport chamber  14 . Therefore, the transfer arm  16  can transfer wafers into and out from the buffer chamber  15   a  without reciprocating twice between the transport chamber  14  and the buffer chamber  15   a , thereby reducing the wafer transfer time. 
     In addition, because the substrate holding member  15 D returns to the home position after placing the unprocessed wafer WU 1 , which the substrate holding member  15 D has received from the transfer arm  16 , on the susceptor  15 S, the substrate holding member  15 D does not have to reciprocate between the home position and the position above the susceptor  15 S while keeping the unprocessed wafer WU 1 . Therefore, the number of reciprocating movements of the substrate holding member  15 D can be reduced, thereby contributing to further reduction of the wafer transfer time. Moreover, the transfer arm  16  can transfer the processed wafer WP 1  received from the substrate holding member  15 U to another process module  15 , take another unprocessed wafer from, for example, the load lock chamber  13 , and hold the unprocessed wafer in front of the buffer chamber  15   a , during a period of time when the wafer WU 1  on the susceptor  15 S in the process chamber  15   b  goes through the predetermined process and is taken out from the process chamber  15   b  by the substrate holding member  15 D. Therefore, the transfer arm  16  does not have to stand still for a long time, thereby contributing further to the reduction of the wafer transfer time. In this case, the main transfer apparatus  16  may have only one wafer holding area. 
     Fifth Embodiment 
     A modified example of the process module  15  is explained as a fifth embodiment of the present invention with reference to  FIGS. 15 through 16 . 
     A subsection (a) of  FIG. 15  is a plan view of the process module according to the modified example, where a substrate holding member  15 TU is positioned in a home position. As shown, the substrate holding member  15 TU has the cutout part  15   c  having a width greater than the width of the transfer arm  16 , in the same manner as the substrate holding member  15 U shown in the subsection (a) of  FIG. 3  and the like. With the cutout part  15   c , the transfer arm  16  can be moved upward and downward in the buffer chamber  15   a . The substrate holding member  15 TU is provided with three slits  15   t . The slits  15   t  of the substrate holding member  15 TU have linear shapes because the substrate holding member  15 TU linearly reciprocates. 
     The substrate holding member  15 TU is supported from both sides thereof by two horizontal driving parts  15 R 1 , which include linear driving mechanisms  15 R 2  and linear driving mechanisms  15 R 3  that serve also as supporting parts that the support the substrate holding member  15 TU. When the linear driving mechanisms  15 R 2 ,  15 R 3  slide, the substrate holding member  15 TU can be linearly moved, thereby being positioned at the home position in the buffer chamber  15   a  and the position above the susceptor  15 S in the process chamber  15   b.    
     Referring to a subsection (b) of  FIG. 15 , which is a side view of the process module  15  seen from a direction of an arrow A 15  shown in the subsection (a) of  FIG. 15 , substrate holding members  15 TM,  15 TD are arranged below the substrate holding member  15 TU. The substrate holding members  15 TM,  15 TD have the same configuration, and are supported by corresponding horizontal driving parts  15 R 1 , thereby being positioned at the home position in the buffer chamber  15   a  and the position above the susceptor  15 S in the process chamber  15   b , in the same manner as the substrate holding member  15 TU. The three horizontal driving parts  15 R 1  corresponding to the substrate holding members  15 TU,  15 TM,  15 TD are supported by rods  15 L 2  whose bottom portions are coupled to elevation driving parts  15 Aa, thereby moving the substrate holding members  15 TU,  15 TM,  15 TD upward and downward. 
     A subsection (a) of  FIG. 16  is another plan view illustrating the process module  15  according to the modified example, and a subsection (b) of  FIG. 16  is another side view of the process module  15  according to the modified example, seen from a direction of an arrow A 16  shown in the subsection (a) of  FIG. 16 . In these drawings, the gate valve GV 2  is opened; and the substrate holding member  15 TU proceeds into the process chamber  15   b  and is positioned at a position above the susceptor  15 S. As shown, the linear driving mechanism  15 R 2  extends into the process chamber  15   b  and the linear driving mechanism  15 R 3  slides with respect to the linear driving mechanism  15 R 2 , so that the substrate holding member  15 TU is held above the susceptor  15 S. As shown in the subsection (a) of  FIG. 16 , the lift pins  15 P in the susceptor  15 S are arranged corresponding to the slits  15   t  of the substrate holding member  15 TU ( 15 TM,  15 TD) held above the susceptor  15 S. Therefore, distal ends of the lift pins  15 P can be projected above the substrate holding member  15 TU ( 15 TM,  15 TD) through the corresponding slits  15   t . In addition, the substrate holding member  15 TU can be horizontally moved by the linear driving mechanisms  15 R 2 ,  15 R 3  even when the lift pins  15 P are projected upward from the susceptor  15 S. Namely, with such a configuration, a wafer can be transferred between the substrate holding member  15 TU ( 15 TM,  15 TD) and the lift pins  15 P. In addition, the wafer is placed onto and brought upward from the susceptor  15 S by moving the lift pins  15 P downward and upward, respectively. 
     Even in the process module  15  according to the modified example (and the substrate processing apparatus including the process module  15 ), the substrate transfer method according to the second and the third embodiments can be carried out. Therefore, the same advantages and effects thereof can be provided through the process module  15  according to the modified example. 
     While the present invention has been described with reference to the foregoing embodiments, the present invention is not limited to the disclosed embodiments, but may be modified or altered within the scope of the accompanying claims. 
     For example, while the substrate transfer mechanism  150  having the three substrate holding members  15 U,  15 M,  15 D is explained with reference to  FIGS. 3 through 12 , the substrate transfer mechanism  150  may have four or more substrate holding members. 
     In addition, while the substrate transfer mechanism  150  is configured to be moved upward and downward by the elevation driving part  15 Aa and the wafer is transferred between the transfer arm  16  and the substrate holding members  15 U,  15 M,  15 D ( 15 TU,  15 TM,  15 TD) in the above embodiments, the transfer arm  16  may be configured to be moved upward and downward instead of the substrate transfer mechanism  150  so that the wafer is transferred between the transfer arm  16  and the substrate holding members  15 U,  15 M,  15 D ( 15 TU,  15 TM,  15 TD). 
     Moreover, the elevation driving part  15 Aa may be configured to independently move the substrate holding members  15 T,  15 M,  15 D ( 15 TU,  15 TM,  15 TD) instead of moving the entire substrate transfer mechanism  150 . 
     Furthermore, while the process module including the substrate transfer mechanism  150  that has two substrate holding members  15 U,  15 D is used to carry out the substrate transfer method according to the fourth embodiment, the substrate transfer method can be carried out using the process module including the substrate transfer mechanism  150  that has three or more substrate holding members. In addition, the transfer arm  16  transfers the processed wafer WP 1  out to the transport chamber  14  after the substrate holding member  15 D transfers the unprocessed wafer WU 1  into the process chamber  15   b  and returns to the home position without any wafer in the fourth embodiment. However, the transfer arm  16  may transfer the processed wafer WP 1  to the transport chamber  14 , during a period of time when the substrate holding member  15 D transfers the unprocessed wafer WU 1  into the process chamber  15   b  and returns to the home position without any wafer in the fourth embodiment. 
     Additionally, while the process module  15  has the buffer chamber  15   a  and the process chamber  15   b  with the gate valve GV 2  therebetween, the process module may have only one chamber in which the substrate transfer mechanism  150  and the susceptor  15 S are arranged, depending on a process carried out in the chamber. 
     While the substrate processing apparatus  10  includes the plural process modules  15  in the above explanation, the substrate processing apparatus  10  may include only one process module  15  in other embodiments. In addition, while the process chamber  15   b  of the process module  15  has only one susceptor  15 S on which one wafer is placed in the above explanation, the process chamber  15   b  may include a wafer plate (wafer tray) in which plural wafers can be accommodated. 
     While the substrate holding member  15 U and the like have the slits  15   t  having a curved shape and the substrate holding member  15 TU and the like have the slits  15   t  having a linear shape, the shape of the slits  15   t  may be arbitrarily determined as long as the substrate holding member can reciprocate between the home position and the position above the susceptor  15 S without being obstructed by the lift pins  15 P and certainly hold the wafer. Specifically, the shape of the slits  15   t  is preferably determined in accordance with a direction of the movement (or a route) of the substrate holding member  15 U ( 15 TU) and the like. 
     In addition, the shape of the cutout part  15   c  may be arbitrarily determined as long as the transfer arm  16  that has proceeded into the buffer chamber  15   a  can relatively move upward or downward relative to the substrate holding members  15 U ( 15 TU) and the like. 
     While the substrate holding member  15 U ( 15 TU) and the like have the same number of the slits  15   t  as the number of the lift pins  15 P in the susceptor  15 S, and the slits  15   t  allow the corresponding lift pins  15 P to pass therethrough horizontally and vertically in the above explanation, the substrate holding member  15 U ( 15 TU) and the like may be configured so that plural (e.g., two) lift pins  15 P can pass through one slit  15   t . For example, the substrate holding member  15 TU may have one long slit and one short slit in the fifth embodiment, and the three lift pins  15 P may be arranged accordingly so that two lift pins  15 P pass through the long slit and one lift pin  15 P pass through the short slit. 
     The substrate transfer methods according to the second through the fourth embodiments can be carried out not only independently but also in combination during one lot of wafers to be processed. Namely, the substrate transfer method according to the third embodiment can be changed to the substrate transfer method according to the fourth embodiment, as the situation demands, while a process is carried out with respect to one lot of wafers.