Patent Publication Number: US-2002006323-A1

Title: Semiconductor processing system and transfer apparatus for the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-211875, filed Jul. 12, 2000, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates to a semiconductor processing system, and a transfer apparatus for transferring a target substrate, such as a semiconductor wafer, in a semiconductor processing system. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.  
       [0003] In a process of manufacturing a semiconductor device, a transfer apparatus is used to transfer a target substrate, such as a semiconductor wafer, between different chambers such as a cassette chamber, a process chamber, and a transfer chamber. As a transfer apparatus of this kind, there is known a structure having only one support portion for supporting a wafer, and a structure having a plurality of, e.g., two, support portions, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-163077, and Jpn. Pat. Appln. KOKAI Publication No. 11-284044. In recent years, a transfer apparatus having a plurality of support portions is becoming popular, because of a high transfer efficiency. For example, where a transfer apparatus has two support portions, the two support portions are constituted to have substantially the same structure, shape, and function, as each other. The two support portions are used appropriately, e.g., alternately, so as to increase the throughput of a process.  
       [0004] A support portion of a transfer apparatus of this kind for placing a wafer thereon is provided with a plurality of receiving members attached thereto. The receiving members are made of a material having a high friction coefficient, such as a silicone-based rubber, e.g., Kalrez(™). The receiving members are intended to prevent the wafer from sliding off the support portion during transfer. As the support portion is used for transferring wafers many times, dust sticks to the surface of the receiving members and can reduce the friction coefficient of the surface of the receiving members (which are made of silicone-based rubber). If the friction coefficient of the surface of the receiving members decreases, a wafer may laterally slide and cause a positional shift during transfer.  
       [0005] Where the positional shift is caused on the upstream side from a positioning mechanism for positioning wafers, this is not serious. On the other hand, where the positional shift is caused on the downstream side from the positioning mechanism, a wafer may be transferred into a process chamber in an undesirably shifted state. In addition, the positional shift tends to be accumulated upon each transfer, and thus, where a wafer is sequentially processed over a plurality of process chambers, the processes respectively performed in the process chambers are affected more by the positional shift on the downstream side.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006] An object of the present invention is to provide a semiconductor processing system and a transfer apparatus for the same, which suppresses the generation or accumulation of the positional shift of a target substrate during transfer of the substrate.  
       [0007] According to a first aspect of the present invention, there is provided a transfer apparatus for transferring a target substrate in a semiconductor processing system, comprising:  
       [0008] a common base;  
       [0009] an intermediate section disposed on the common base and configured to be pivotable and extensible/contractible; and  
       [0010] a pickup section connected to the intermediate section and having first and second support portions each configured to support the target substrate, the first and second support portions having functions different from each other.  
       [0011] According to a second aspect of the present invention, there is provided a semiconductor processing system comprising:  
       [0012] a transfer chamber;  
       [0013] a cassette chamber connected to the transfer chamber and configured to accommodate a cassette configured to hold a plurality of target substrates;  
       [0014] a vacuum processing section connected to the transfer chamber and configured to subject a target substrate to a process in a vacuum atmosphere;  
       [0015] a positioning mechanism disposed in or connected to the transfer chamber and configured to subject the target substrate to a positioning operation;  
       [0016] a transfer apparatus disposed in the transfer chamber and configured to transfer the target substrate between the cassette chamber, the vacuum processing section, and the positioning mechanism, the transfer apparatus comprising a common base, an intermediate section disposed on the common base and configured to be pivotable and extensible/contractible, and a pickup section connected to the intermediate section and having first and second support portions each configured to support the target substrate, the first and second support portions having functions different from each other; and  
       [0017] a control section configured to control the transfer apparatus.  
       [0018] Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
     [0019] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
     [0020]FIG. 1 is a schematic diagram showing a semiconductor processing system, which includes a transfer apparatus according to an embodiment of the present invention;  
     [0021]FIG. 2 is a perspective view showing the transfer apparatus in the system shown in FIG. 1;  
     [0022]FIG. 3 is a plan view showing a first support portion in the transfer apparatus shown in FIG. 2;  
     [0023]FIG. 4 is a side view of the first support portion shown in FIG. 3;  
     [0024]FIG. 5 is a plan view showing a second support portion in the transfer apparatus shown in FIG. 2;  
     [0025]FIG. 6 is a side view of the second support portion shown in FIG. 5;  
     [0026]FIG. 7 is a perspective view showing an edge receiving member in the second support portion shown in FIG. 5;  
     [0027]FIG. 8 is a schematic diagram showing a semiconductor processing system of a cluster-tool type, which includes a transfer apparatus according to another embodiment of the present invention;  
     [0028]FIG. 9 is a perspective view showing the transfer apparatus in the system shown in FIG. 8;  
     [0029]FIG. 10 is a plan view showing a second support portion in the transfer apparatus shown in FIG. 9;  
     [0030]FIG. 11 is a side view of the second support portion shown in FIG. 10; and  
     [0031]FIG. 12 is a side view for explaining functions of the second support portion shown in FIG. 10. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0032] Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. In the following description, the constituent elements having substantially the same function and arrangement are denoted by the same reference numerals, and a repetitive description will be made only when necessary.  
     [0033]FIG. 1 is a schematic diagram showing a semiconductor processing system, which includes a transfer apparatus according to an embodiment of the present invention. As shown in FIG. 1, the semiconductor processing system  2  includes a transfer chamber  4  formed of a rectangular box of, e.g., stainless steel. A guide rail  7  is disposed in the transfer chamber  4  and extends along the longitudinal direction of the chamber  4 , and a transfer apparatus  6  is slidably supported on the rail  7 .  
     [0034] Three cassette chambers  8 A,  8 B, and  8 C are connected to one side of the transfer chamber  4  through gate valves G 1 , G 2 , and G 3 , respectively. Each of the cassette chambers  8 A to  8 C is arranged to accommodate a cassette C, which can hold a plurality of, e.g., 25, target substrates, such as semiconductor wafers, in a stacked state at predetermined intervals. Cassette doors DR 1 , DR 2 , and DR 3  are respectively arranged on the sides of the cassette chambers  8 A to  8 C, opposite to the transfer chamber  4  sides, for transferring cassettes C between the system and the outside. The transfer chamber  4  and the cassette chambers  8 A to  8 C are kept at atmospheric pressure (generally in the atmosphere of a clean room).  
     [0035] Two load-lock chambers  10 A and  10 B are connected to the side of the transfer chamber  4 , opposite to the cassette chambers  8 A to  8 C side, through gate valves G 4  and G 5 , respectively. Vacuum process chambers  12 A and  12 B are connected to the sides of the load-lock chambers  10 A and  10 B, opposite to the transfer chamber  4  sides, through gate valves G 6  and G 7 , respectively. In each of the vacuum process chambers  12 A and  12 B, a wafer W is subjected to a semiconductor process, such as oxidation, diffusion, film formation, etching, or annealing, under a vacuum atmosphere.  
     [0036] Each of the load-lock chambers  10 A and  10 B is provided therein with a worktable (not shown) for placing a wafer W, and a transfer arm (not shown) for transferring the wafer between the load-lock chamber  10 A or  10 B and the process chamber  12 A or  12 B. The load-lock chambers  10 A and  10 B are capable of being vacuum-exhausted and being N 2 -purged.  
     [0037] A positioning chamber  14  is connected to one side of the transfer chamber  4  in the longitudinal direction, and is opened to the transfer chamber  4 . The positioning chamber  14  is provided therein with a positioning mechanism  20  for detecting the positional shift of a wafer W and positioning the wafer W. The positioning mechanism  20  is mainly constituted of a worktable  16  rotatable along with the wafer W and an optical system  18  for detecting the edge of the wafer W.  
     [0038] In the semiconductor processing system  2 , the operations of the transfer apparatus  6 , the cassette chambers  8 A to  8 C, the load-lock chambers  10 A and  10 B, and the positioning mechanism  20  are controlled in accordance with a program stored in a CPU  5 , which works as a control section.  
     [0039]FIG. 2 is a perspective view showing the transfer apparatus  6 . The transfer apparatus  6  includes a traveling base  22 , an intermediate section disposed on the traveling base  22  and arranged to be pivotable and extensible/contractible, and a pickup section connected to the intermediate section and arranged to engage with a wafer W. The intermediate section of the transfer apparatus  6  has a single rotational table  24  disposed on the traveling base  22  and arranged to be rotatable and elevatable, and first and second extensible/contractible arms  26 A and  26 B disposed on the rotation table  24  and arranged to be extensible/contractible independently of each other by, e.g., multi-joint mechanisms. The pickup section has first and second pick arms  27 A and  27 B connected to the first and second extensible/contractible arms  26 A and  26 B, respectively, and made of, e.g., a ceramic. The first and second pick arms  27 A and  27 B are provided with first and second support portions  28 A and  28 B, respectively, each for supporting the wafer W. The first and second support portions  28 A and  28 B have structures and functions different from each other.  
     [0040]FIGS. 3 and 4 are a plan view and a side view, respectively, showing the first support portion  28 A. The first support portion  28 A has a support plate  30  with a distal end divided into two portions. The support plate  30  is provided with three or more backside receiving members  32  located within the plan-view contour of the wafer at the normal position. In this embodiment, four backside receiving members  32  are uniformly disposed at the corners of a rectangle. The backside receiving members  32  are made of an elastic material having a high friction coefficient, such as silicone-based rubber. The diameter and the height H 1  of the backside receiving members  32  are set at about 7.6 mm, and at about 0.2 mm, respectively. The backside receiving members  32  respectively have horizontal surfaces  32 A at the top ends. The horizontal surfaces  32 A come into contact with the backside of the wafer W, so that they support the weight of the wafer W.  
     [0041] Around the backside receiving members  32 , there are three or more, in this embodiment, four, stoppers  34  having a height H 2  larger than that of the backside receiving members  32 . The stoppers  34  are made of an elastic material, such as silicone-based rubber. The height of the stoppers  34  is set at, e.g., about 0.8 mm in light of the thickness of the wafer W. Even if the wafer W laterally slides on the backside receiving members  32 , the edge of the wafer W comes into contact with the stoppers  34 , so that the wafer W is prevented from further sliding, and thus from falling off.  
     [0042] The first support portion  28 A has a larger tolerance for the positional shift of the wafer W, and a smaller thickness, than the second support portion  28 B does. The positional shift tolerance of the first support portion  28 A is set to fall in a range of from 2 to 3 mm. In this embodiment, the distance D 1  between the edge of the wafer at the normal position and the stoppers  34 , i.e., the positional shift tolerance, is set at, e.g., about 2.5 mm. Even when the wafer W has some positional shift, the first support portion  28 A can reliably receive the wafer W with the positional shift, so long as the positional shift falls in the tolerance range.  
     [0043]FIGS. 5 and 6 are a plan view and a side view, respectively, showing the second support portion  28 B. The second support portion  28 B has a support plate  40  with a distal end divided into two portions. The support plate  40  is provided with three or more edge receiving members  42  located across the plan-view contour of the wafer at the normal position. In this embodiment, four edge receiving members  42  are uniformly disposed at the corners of a rectangle. The edge receiving members  42  are made of an elastic material having a high friction coefficient, such as silicone-based rubber. The diameter D 2  of the edge receiving members  42  are set at about 4 mm. The edge receiving members  42  respectively have slant surfaces  42 A inclined downward toward the wafer center. The slant surfaces  42 A come into contact with the edge of the wafer W, so that they support the weight of the wafer W.  
     [0044] In the case of the first support portion  28 A, the wafer W may laterally slide to generate a positional shift during transfer of the wafer W, after the backside receiving members  32  are degraded. However, in the case of the second support portion  28 B, since the wafer edge is supported on the slant surfaces  42 A, the wafer W is prevented from laterally sliding to generate a positional shift during transfer of the wafer W, even after the edge receiving members  42  are degraded. In other words, the second support portion  28 B works as a support portion with a function of preventing the positional shift.  
     [0045] The height H 4  of the edge receiving members  42  is set at, e.g., about 1.0 mm in light of the thickness of the wafer W. The tilting angle θ 1  of the slant surfaces  42 A is set at, e.g., about 30° in light of the friction between the slant surfaces  42   a  and the wafer W, and such that the edge receiving members  42  are not too high. The length D 4  (see FIG. 5) of the slant surfaces  42 A in the direction toward the wafer center is set at about 1.6 mm, in light of the maximum tolerance for the positional shift of the wafer W.  
     [0046] In other words, the second support portion  28 B has a smaller tolerance for the positional shift of the wafer W than the first support portion  28 A. The second support portion  28 B may be formed of a structure in which the distance D 1  between the wafer edge and the stoppers  34  in FIG. 3, i.e., the positional shift tolerance, is set to fall in a range of from about 0.1 to 0.3 mm, and at, e.g., about 0.2 mm, in place of the structure shown in FIGS. 5 and 6.  
     [0047] On the inner side of the edge receiving members  42 , there are three or more, in this embodiment, four, auxiliary receiving members  44  having a height smaller than that of the edge receiving members  42 . The auxiliary receiving members  44  are made of an elastic material having a high friction coefficient, such as silicone-based rubber. The height H 5  (see FIG. 6) of the auxiliary receiving members  44  is set at, e.g., about 0.2 mm, so that it is lower than the substantial portion of the slant surfaces  42 A. The auxiliary receiving members  44  respectively have horizontal surfaces at the top ends. Even if the wafer W positionally shifts more than the maximum tolerance, the horizontal surfaces of the auxiliary receiving members  44  come into direct contact with the backside of the wafer W, so that they support the weight of the wafer W.  
     [0048] An explanation will be given of a manner of transferring a wafer W in the semiconductor processing system shown in FIG. 1. The operations described below of the transfer apparatus  6  and so forth for transferring the wafer W in the semiconductor processing system shown in FIG. 1 are controlled in accordance with a program stored in the CPU  5 .  
     [0049] A plurality of new wafers are held in a cassette accommodated in any one of the cassette chambers  8 A to  8 C. One of the wafers W is taken out and placed on the worktable  16  of the positioning mechanism  20  by the transfer apparatus  6 . While the worktable  16  is rotated, the edge of the wafer W is observed by the optical system  18 , so that the wafer W is subjected to a positioning operation.  
     [0050] The wafer W treated in the positioning mechanism  20  is supported by the transfer apparatus  6  at a position without any positional shift, and is transferred into either one of the load lock chambers, e.g., the load lock chamber  10 A. Then, the wafer W is transferred from the load lock chamber  10 A into the process chamber  12 A by the transfer arm (not shown) arranged in the load lock chamber  10 A.  
     [0051] After the wafer W is subjected to a predetermined process in the process chamber  12 A, the wafer W is transferred from the process chamber  12 A into the load lock chamber  10 A by the transfer arm (not shown) arranged in the load lock chamber  10 A. Then, the wafer W is supported by the transfer apparatus  6 , and is transferred into a cassette for holding processed wafers W.  
     [0052] When the new wafer W is transferred from the cassette chambers  8 A to  8 C to the positioning mechanism  20 , the first support portion  28 A having a larger positional shift tolerance shown in FIGS. 3 and 4 is used. On the other hand, when the wafer W is transferred from the positioning mechanism  20  to the process chambers  12 A and  12 B, i.e., to the load lock chambers  10 A and  10 B, the second support portion  28 B having a function of preventing the positional shift shown in FIGS. 5 and 6 is used.  
     [0053] In this respect, specifically, wafers W may have positional shifts in various directions within a cassette C, so long as the positional shift tolerance given by the hardware allows. The positional shifts are caused by, e.g., the wafers W laterally sliding in the cassette C when the cassette C is carried automatically or manually.  
     [0054] For this reason, when a wafer W is transferred from the cassette C, the first support portion  28 A shown in FIGS. 3 and 4 is used. The wafer W is transferred to the positioning mechanism  20  by the first support portion  28 A, while the backside of the wafer W is supported by the horizontal surfaces  32 A of the backside receiving members  32 . Accordingly, even when the wafer W has a positional shift in the cassette C, it is reliably received by the first support portion  28 A.  
     [0055] As the first support portion  28 A is repeatedly used, the backside receiving members  32  are degraded, and the friction coefficient of the horizontal surfaces  32 A decreases. In this case, the wafer W may laterally slide when the wafer W is transferred. Even when the wafer W laterally slides, the edge of the wafer W comes into contact with the stoppers  34 , so that the wafer W is stopped. As a result, the wafer W is prevented from falling off the first support portion  28 A.  
     [0056] The height H 2  of the stoppers  34  is set at a value with which the stoppers  34  do not interfere with a wafer above the wafer W to be transferred in the cassette C, when the first support portion  28 A enters the cassette C to take out the wafer W. Although the wafer W cannot be prevented from falling off, such a structure may be employed that the four stoppers  34  are omitted from the first support portion  28 A.  
     [0057] On the other hand, when the positioned wafer W is transferred from the positioning mechanism  20  to the process chambers  12 A and  12 B, the second support portion  28 B having a function of preventing the positional shift is used. The direction and amount of positional shift of the wafer W are specified by the positioning mechanism  20 , and the second support portion  28 B is positionally controlled in the horizontal coordinate system to cancel the positional shift when it receives the wafer W.  
     [0058] On the second support portion  28 B, the slant surfaces  42 A of the edge receiving members  42  come into direct contact with edge of the wafer W, so that they support the weight of the wafer W by means of four-point supporting. Consequently, the wafer W is supported by the second support portion  28 B without any positional shift, while it is transferred to the load lock chambers  10 A and  10 B (i.e., to the process chambers) by the second support portion  28 B.  
     [0059] As the second support portion  28 B is repeatedly used, the edge receiving members  42  are degraded, and the friction coefficient of the slant surfaces  42 A decreases. However, unlike the first support portion  28 A, the second support portion  28 B supports the wafer W, while the wafer edge is caught by the slant surfaces  42 A. Consequently, the wafer W hardly positionally shifts on the second support portion  28 B.  
     [0060] Even when the wafer edge slides on the slant surfaces  42  during transfer, the wafer backside is supported by the auxiliary receiving members  44  having a lower height H 5 . Accordingly, the wafer W is prevented from positionally shifting beyond the tolerance, and the wafer edge is prevented from hitting the support plate  40  of the second support portion  28 B.  
     [0061] When the processed wafer W is transferred from the process chambers  12 A and  12 B (i.e., from the load lock chambers  10 A and  10 B, respectively) to the cassette C, either one of the first and second support portions  28 A and  28 B can be used in the semiconductor processing system  2  shown in FIG. 1. Although the semiconductor processing system  2  shown in FIG. 1 has the two process chambers  12 A and  12 B, the present invention may be applied to a system having only one process chamber.  
     [0062]FIG. 8 is a schematic diagram showing a semiconductor processing system of a cluster-tool type, which includes a transfer apparatus according to another embodiment of the present invention. As shown in FIG. 8, this semiconductor processing system includes a transfer chamber  50  having a substantially hexagonal shape. The cassette chambers  8 A and  8 B respectively having cassette doors DR 1  and DR 2  are connected to two sides of the transfer chamber  50  through gate valves G 1  and G 2 , respectively. Vacuum process chambers  12 C to  12 F are connected to the other four sides of the transfer chamber  50  through gate valves G 11  to G 14 , respectively. The transfer chamber  50  is provided therein with a positioning mechanism  20  for a semiconductor wafer, which has a worktable  16  and an optical system  18 , and a transfer apparatus  52  for transferring the wafer.  
     [0063]FIG. 9 is a perspective view showing the transfer apparatus  52 . The transfer apparatus  52  includes a base  53  fixed at the center of the transfer chamber  50 , an intermediate section disposed on the base  53  and arranged to be pivotable and extensible/contractible, and a pickup section connected to the intermediate section and arranged to engage with a wafer W. The intermediate section of the transfer apparatus  52  has a single common intermediate arm  54  disposed on the base  53  and arranged to be pivotable and extensible/contractible, by, e.g., a multi-joint mechanism. The pickup section has a common pick arm  55  connected to the common intermediate arm  54 . The both ends of the common pick arm  55  are provided with first and second support portions  56 A and  56 B, respectively, facing in opposite directions and each for supporting the wafer W. The first and second support portions  56 A and  56 B have structures and functions different from each other.  
     [0064] The first support portion  56 A is completely the same as the first support portion  28 A of the transfer apparatus  6  described with reference to FIGS. 3 and 4, and thus no explanation will be given of the first support portion  56 A.  
     [0065]FIGS. 10 and 11 are a plan view and a side view, respectively, showing the second support portion  56 B. The second support portion  56 B has a support plate  63  with a distal end divided into two portions. The thickness H 6  of the second support portion  56 B is larger than that of the first support portion  56 A, and is set at, e.g., about 4 mm. The second support portion  56 B is provide with a receiving recess  58  having a circular contour, which is slightly larger than the plan-view contour of the wafer. The receiving recess  58  is arranged such that the wafer W falls into the receiving recess  58  and the positional shift of the wafer W is thereby corrected, when the wafer W is supported by the second support portion  56 B. More specifically, the distance D 5  (see FIG. 11) between the wall defining the recess  58  and the edge of the wafer at the normal position is set to be very small, such that it is, e.g., about 0.2 mm. Accordingly, the second support portion  56 B can position the wafer W with a high precision.  
     [0066] Slant surfaces  60  are disposed along the periphery of the recess  58  and are inclined downward toward the recess  58 . The slant surfaces  60  are made of a ceramic having a small friction coefficient, integrally with the support plate  63  of the second support portion  56 B. When the wafer W is received by the second support portion  56 B, part of the edge of the wafer W may be placed on the slant surfaces  60 , if the wafer W has a positional shift. Even in such a case, the wafer W immediately slides down on the slant surfaces  60  and falls into the recess  58 , and the positional shift of the wafer W is thereby corrected.  
     [0067] The tilting angle θ 2  of the slant surfaces  60  is set to fall in a range of, e.g., from about 60° to 70°, so that the wafer W easily slides. The width D 6  of the slant surfaces  60  in the horizontal direction is set at about 2 mm. The length of the slant surfaces  60  in the tilting direction is set to be large enough to cover the maximum tolerance for the positional shift of the wafer W. As a result, the second support portion  56 B has a large thickness H 6 , as described above. The second support portion  56 B is not used for accessing the cassette C, as described later, and thus the thickness H 6  can be set without reference to the intervals of the wafers stacked and held in the cassette C.  
     [0068] On the bottom of the recess  58 , there are three or more, in this embodiment, four, backside receiving members  62 . The backside receiving members  62  are made of an elastic material having a high friction coefficient, such as silicone-based rubber. The backside receiving members  62  respectively have horizontal surfaces at the top ends. The horizontal surfaces of the backside receiving members  62  come into direct contact with the backside of the wafer W, so that they support the weight of the wafer W.  
     [0069] An explanation will be given of a manner of transferring a wafer W in the semiconductor processing system shown in FIG. 8. The operations described below of the transfer apparatus  52  and so forth for transferring the wafer W in the semiconductor processing system shown in FIG. 8 are controlled in accordance with a program stored in a CPU  5 .  
     [0070] The wafer W is taken out from a cassette C by the transfer apparatus  52 , and is subjected to a positioning operation at the positioning mechanism  20 . Then, the wafer W is sequentially transferred to the process chambers, as needed. In the transfer operation, when the transfer apparatus  52  accesses the cassette C, i.e., when the new wafer W is taken out from the cassette C, and when the processed wafer W is transferred into the cassette C, the first support portion  56 A having a smaller thickness is used. At another instance, i.e., when the wafer W is transferred between the process chambers  12 C to  12 F, e.g., when the wafer W is sequentially transferred from the process chamber  12 C, to the process chamber  12 D, to the process chamber  12 E, and to the process chamber  12 F, and when the wafer W is transferred from the positioning mechanism  20  to a predetermined one of the process chambers, the second support portion  56 B having a function of correcting the positional shift is used.  
     [0071] The wafer W is transferred by the second support portion  56 B, while it is received in the recess  58 , as shown in FIGS. 10 and 11. Consequently, even when the wafer W laterally slides during transfer, the slide of the wafer W is blocked by the wall defining the recess  58 , so that the wafer W is prevented from greatly positionally shifting. Furthermore, as shown in FIG. 12, when the wafer W is received by the second support portion  56 B, part of the edge of the wafer W may be placed on the slant surfaces  60 , if the wafer W has a positional shift. Even in such a case, the wafer W immediately slides down on the slant surfaces  60 , as indicated by an arrow  70 , and falls into the recess  58 , as shown by one-dot chain lines, and the positional shift of the wafer W is thereby corrected. In other words, the second support portion  56 B works as a support portion with a function of correcting the positional shift.  
     [0072] Since the wafer W is transferred between the process chambers  12 C to  12 F by the second support portion  56 B, the positional shift of the wafer W is corrected every time even on a downstream side of the transfer route, and thus is not accumulated. As a result, the wafer is always positioned with a high precision in the process chambers  12   c  to  12 F.  
     [0073] The transfer apparatuses  6  and  52  of the systems shown in FIGS. 1 and 8 are inter-exchangeable. Specifically, the system shown in FIG. 1 may employ the transfer apparatus  52  shown in FIG. 9, and the system shown in FIG. 8 may employ the transfer apparatus  6  shown in FIG. 2. Furthermore, the present invention may be applied to a target substrate other than a semiconductor wafer, such as an LCD substrate, or a glass substrate.  
     [0074] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.