Patent Publication Number: US-2016233118-A1

Title: Workpiece transport device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a division of U.S. patent application Ser. No. 13/952,000 filed on Jul. 26, 2013, which claims priority to Japanese Patent Application No. 2012-166701 filed on Jul. 27, 2012, and Japanese Patent Application No. 2013-43948 filed on Mar. 6, 2013, each of which is hereby incorporated by reference in its entirety herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a mechanism for holding and transporting a workpiece in an apparatus for processing a workpiece such as a semiconductor wafer. 
     BACKGROUND ART 
     In semiconductor device manufacturing processes, various devices are ordinarily used for transport of workpieces such as semiconductor wafers (see, for example, International Publication No. WO2007/099976). In some cases, semiconductor wafer is bonded on a glass substrate, the semiconductor wafer is transported together with the glass substrate and a treatment such polishing is performed on the semiconductor wafer. In such cases, when the semiconductor wafer is transported, it is desirable to perform transport by holding only the glass substrate so that the transport mechanism does not contact the semiconductor portion to be treated. 
     In some case of manufacture of a semiconductor device, transport of semiconductor wafers differing in size is required. Since the semiconductor wafer transport mechanism is designed and adjusted according to a size of wafer to be treated, failure to suitably transport wafers may occur if the wafers are not uniform in size. For example, in a case where the size of a semiconductor wafer is smaller than the size for which the transport mechanism is adjusted, the holding force is reduced and a gap at a position at which the wafer is held may become so excessively large so that the wafer positioning accuracy is reduced. Also, in a case where the size of a semiconductor wafer is larger than the size for which the transport mechanism is adjusted, the holding force is excessively large, an excessive stress may be caused in the wafer and failure to suitably hold the wafer may occur. 
     International Publication No. WO2007/099976 discloses a linear transporter in a chemical mechanical polishing (CMP) apparatus that transports a substrate between a polishing unit that polishes the substrate and a cleaning unit that cleans the substrate after polishing. This linear transporter has a plurality of pins projecting upward from a stage capable of moving linearly and reciprocatingly. Each pin has such a shape as to become smaller in outside diameter toward its upper portion or end. A slant surface slanted with respect to a horizontal direction is formed with such a shape. The linear transporter transports a substrate by moving the transport stage while maintaining the substrate in a state of being placed on the slant surfaces in the region inside the plurality of pins. 
     It is desirable to design the wafer holding mechanism in the transport mechanism so that, in transporting a semiconductor wafer bonded to an upper surface of a glass substrate, the wafer holding mechanism contacts only the glass substrate and does not contact the semiconductor wafer. However, there is an error in positioning the semiconductor wafer in bonding the semiconductor wafer to the glass substrate, and bonding at the desired position cannot always be performed correctly. If the bonded position of the semiconductor wafer on the glass substrate deviates from the ideal position, there is a possibility of the transport mechanism contacting and damaging the semiconductor wafer when holding the glass substrate. It is, therefore, desirable that the holding mechanism in the transport mechanism be prevented from contacting the semiconductor wafer even when the bonded position of the semiconductor wafer on the glass substrate deviates from the ideal position. 
     In some case of transport of semiconductor wafers differing in size, the range of movement of a holding mechanism including arms for holding a wafer is changed. However, changing the range of movement of the holding mechanism requires temporarily stopping the manufacturing process and is, therefore, time-consuming. It is, therefore, desirable for transport of semiconductor wafers of a variety of sizes to be enabled in advance. 
     In the above-described linear transporter, the substrate including a wafer is only placed on the slant surfaces of the pins and is not firmly fixed on the pins. Therefore, there is a possibility of the placed position of the substrate being shifted due to acceleration (including negative acceleration) during transport of the substrate, for example, by an impact when the substrate is stopped. When a large shift is caused thereby, that is, one end of the placed substrate is largely shifted upward along the slant surfaces, the other end of the placed substrate is shifted downward. This may result in a fall of the substrate from the transport device. If the substrate falls, the recovery time for again placing the substrate is required and the manufacturing efficiency is reduced. There is also a risk of the substrate being damaged by the fall. This is a common problem with substrate transport devices of the type characterized by transporting a substrate in a placed-on state, not limited to the above-described linear transporter. Under the above-described circumstances, there is a need to reduce the occurrence of falls of substrates in substrate transport devices. Transport of a substrate at a low speed, as a prevention against the occurrence of large acceleration, is conceivable as a measure to reduce the occurrence of falls of substrates. Such a measure increases the time required for transport, resulting in a reduction in manufacturing efficiency. 
     SUMMARY OF INVENTION 
     The present invention solves at least part of the above-described problem. 
     According to a first aspect of the present invention, there is provided a workpiece transport device for transporting a workpiece having a substrate layer and a layer to be processed, such as polishing, on a portion of the substrate layer. This workpiece transport device has a workpiece holding mechanism arranged to operate so as to hold and release the workpiece. The workpiece holding mechanism has at least one slanted workpiece holding surface on which the substrate layer of the workpiece is held in a state where the layer to be processed is positioned below the substrate layer. The slanted workpiece holding surface is formed so that a clearance equal to or larger than a predetermined distance R exists between the workpiece holding surface and the layer to be processed of the workpiece when the workpiece is held by the workpiece holding mechanism. 
     According to a second aspect of the present invention, in the first aspect, the slope angle θb of the slanted workpiece holding surface satisfies θ 3 ≦θb≦90° and θ 3 =θ 1 +θ 2 . A straight line tangent to the substrate layer and the layer to be processed is assumed to be L 1 ; the angle between the straight line L 1  and the substrate layer is assumed to be θ 1 ; when a circle with a radius R centered at the point at which the straight line L 1  is tangent to the layer to be processed is drawn, a straight line tangent to the circle with radius R and the substrate layer is assumed to be L 2 ; the angle between the straight line L 1  and the straight line L 2  is assumed to be θ 2 ; and the angle formed by the straight line L 2  and a straight line parallel to a surface of the layer to be processed is assumed to be θ 3 . 
     According to a third aspect of the present invention, in the first or second aspect, the workpiece holding surface has a first surface for holding a workpiece of a first size and a second surface for holding a workpiece of a second size. 
     According to a fourth aspect of the present invention, a workpiece holding surface has a first surface for holding a workpiece of a first size and a second surface for holding a workpiece of a second size. 
     According to a fifth aspect of the present invention, there is provided a workpiece polishing apparatus including the workpiece transport device according to the first or fourth aspect of the present invention. 
     According to a sixth aspect of the present invention, there is provided a substrate transport device for transporting a substrate. This substrate transport device includes a transport stage arranged to be movable in a horizontal direction, and three or more substrate placement parts provided so as to project upward from the transport stage along a vertical direction. Each of the substrate placement parts includes a first slant surface slanted with respect to the horizontal direction, facing upward and provided for placement of the substrate inside the three or more substrate placement parts, and a second slant surface slanted with respect to the horizontal direction, facing downward, and formed above the first slant surface. 
     In this substrate transport device, even if one end of the substrate is shifted upward along the first slant surface of one of the substrate placement parts when the substrate is transported by being placed on the substrate placement parts, this one end is brought into abutment against the second slant surface, so that this one end does not further move upward. As a result, the other end of the substrate does not fall from the first slant surfaces of the other substrate placement parts. That is, the occurrence of falls of substrates can be reduced. 
     According to a seventh aspect of the present invention, in the sixth aspect, the second slant surface may be formed in such a position as to continue to the first slant surface. According to this aspect, the range of upward shifting of the substrate can be limited in comparison with a case where a surface extending along a direction perpendicular to the horizontal direction exists between the first slant surface and the second slant surface. As a result, the occurrence of falls of substrates can be further reduced. 
     According to an eighth aspect of the present invention, in the sixth or seventh aspect, the lower end of the first slant surface may be positioned on the side on which the substrate is placed relative to the upper end of the second slant surface along the direction of a straight line passing through centers of arbitrary two of the three or more substrate placement parts. According to this aspect, the substrate can be placed on the first slant surface from above while being held in a state of being parallel to the horizontal direction without interfering with the upper end of the second slant surface. That is, there is no need to incline the substrate with respect to the horizontal direction. As a result, the operability relating to transport of the substrate is improved. 
     According to a ninth aspect of the present invention, in any one of the sixth to eighth aspects, the first slant surface may include a third slant surface having a first slope angle with respect to the horizontal direction, and a fourth slant surface formed higher than the third slant surface and having a second slope angle larger than the first slope angle. According to this aspect, a substrate differing in size can be placed on any one of the third slant surface and the fourth slant surface. That is, one substrate transport device can handle a plurality of substrates differing in size, and the device is thus improved in versatility. 
     According to a tenth aspect of the present invention, there is provided a substrate polishing apparatus including the substrate transport device according to any one of the sixth to ninth aspects. This substrate polishing apparatus has the same advantage as that in the sixth to ninth aspects. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view showing the entire construction of an illustrative example of a polishing apparatus; 
         FIG. 2  is a perspective view showing an outline of the polishing apparatus shown in  FIG. 1 ; 
         FIG. 3  is a perspective view showing an illustrative example of a swing transporter; 
         FIG. 4 a    is a top view showing holding parts of the swing transporter shown in  FIG. 3 ; 
         FIG. 4 b    is a side view showing the holding parts of the swing transporter shown in  FIG. 3 ; 
         FIG. 4 c    is an enlarged side view of a contact piece of the holding parts of the swing transporter shown in  FIG. 3 ; 
         FIG. 5  is a front view of an illustrative example of a linear transport; 
         FIG. 6  is a plan view of the linear transporter shown in  FIG. 5 ; 
         FIG. 7 a    is a top view of a transport stage of the linear transporter shown in  FIG. 5 ; 
         FIG. 7 b    is a side view of the transport stage of the linear transporter shown in  FIG. 5 ; 
         FIG. 7 c    is an enlarged side view of a pin according to one embodiment of the transport stage of the linear transporter shown in  FIG. 5 ; 
         FIG. 7 d    is a diagram showing the construction of a pin (substrate placement part) according to another embodiment usable for the transport stage of the linear transporter shown in  FIG. 5 ; 
         FIG. 7 e    is a diagram showing a state where the occurrence of falls of substrates is reduced; 
         FIG. 7 f    is a diagram showing a state where a substrate falls from a substrate transport device as a comparative example; 
         FIG. 8  is a perspective view showing an illustrative example of an inverter; 
         FIG. 9  is a plan view of the inverter shown in  FIG. 8 ; 
         FIG. 10  is a side view of the inverter shown in  FIG. 8 ; 
         FIG. 11  is a longitudinal sectional view showing an opening/closing mechanism of the inverter shown in  FIG. 8 ; 
         FIG. 12  is a longitudinal sectional view showing the opening/closing mechanism of the inverter shown in  FIG. 8 , and showing a state where a wafer is released; 
         FIG. 13 a    is a side view of a chuck of the inverter shown in  FIG. 8 , showing a state before a wafer is inverted; 
         FIG. 13 b    is a side view of the chuck of the inverter shown in  FIG. 8 , showing a state after the wafer is inverted; 
         FIG. 14  is a diagram for explaining a method of determining a slope angle θb of the slant surface of the chuck of the inverter shown in  FIG. 8 ; 
         FIG. 15  is a longitudinal sectional view of an illustrative example of a lifter; 
         FIG. 16 a    is a top view showing a stage of the lifter shown in  FIG. 15 ; 
         FIG. 16 b    is a side view showing the stage of the lifter shown in  FIG. 15 ; 
         FIG. 16 c    is an enlarged partial side view showing a claw of the stage of the lifter shown in  FIG. 15 ; 
         FIG. 17  is a perspective view showing an illustrative example of a transport unit in a cleaning section  4 ; 
         FIG. 18 a    is a perspective view showing a chuck contact piece in a single state of the transport unit shown in  FIG. 17 ; 
         FIG. 18 b    is top view of the chuck contact piece shown in  FIG. 18 ; and 
         FIG. 18 c    is a sectional view of the chuck contact piece shown in  FIG. 18 , taken along line B-B. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the accompanying drawings. A semiconductor wafer polishing apparatus similar to the one disclosed in International Publication No. WO2007/099976 is taken as an example. Components identical or corresponding to each other are indicated by the same reference characters in the accompanying drawings, and redundancy of descriptions of them is avoided. In the polishing apparatus described below, a well-known arrangement or an arrangement disclosed in International Publication No. WO2007/099976 can be adopted for a component of the polishing apparatus described below other than the structure of wafer holding mechanisms in wafer transport devices. Therefore, detailed descriptions for it will not be made. 
       FIG. 1  is a plan view showing the entire construction of an illustrative example of the polishing apparatus.  FIG. 2  is a perspective view showing an outline of the polishing apparatus shown in  FIG. 1 . As shown in  FIG. 1 , the polishing apparatus is provided with a generally rectangular housing  1 . The interior of the housing  1  is partitioned into a loading/unloading section  2 , polishing sections  3  ( 3   a ,  3   b ) and a cleaning section  4  by partition walls  1   a ,  1   b , and  1   c . Each of the loading/unloading section  2 , the polishing sections  3   a  and  3   b  and the cleaning section  4  is independently assembled and is independently exhausted. 
     The loading/unloading section  2  has two or more (four in the present embodiment) front loading portions  20  on which wafer cassettes in which a multiplicity of semiconductor wafers are stocked are placed, and which are arranged adjacent to each other along the width direction of the polishing apparatus (a direction perpendicular to the lengthwise direction). On each front loading portion  20 , an open cassette, a Standard Manufacturing Interface (SMIF) pod, or a Front Opening Unified Pod (FOUP) can be mounted. Each of the SMIF and the FOUP is a hermetically sealed container in which a wafer cassette is housed and covered with a partition wall to be maintained in an environment independent of the external space. 
     The polishing section  3  is a region where polishing is performed on semiconductor wafers. The polishing section  3  includes a first polishing section  3   a  having a first polishing unit  30 A and a second polishing unit  30 B provided therein, and a second polishing section  3   b  having a third polishing unit  30 C and a fourth polishing unit  30 D provided therein. The first polishing unit  30 A, the second polishing unit  30 B, the third polishing unit  30 C and the fourth polishing unit  30 D are arranged along the lengthwise direction of the apparatus, as shown in  FIG. 1 . 
     As shown in  FIG. 1 , the first polishing unit  30 A is provided with a polishing table  300 A having a polishing surface, a top ring  301 A for polishing a semiconductor wafer while holding the semiconductor wafer and pressing the semiconductor wafer against the polishing table  300 A, a polishing liquid supply nozzle  302 A for supplying a polishing liquid and a dressing liquid (e.g., water) to the polishing table  300 A, a dresser  303 A for dressing the polishing table  300 A, and an atomizer  304 A for atomizing a mixture fluid formed of a liquid (e.g., pure water) and a gas (e.g., nitrogen) or a liquid (e.g., pure water) and jetting the atomized fluid or liquid from one or a plurality of nozzles to the polishing surface. Similarly, the second polishing unit  30 B is provided with a polishing table  300 B, a top ring  301 B, a polishing liquid supply nozzle  302 B, a dresser  303 B, and an atomizer  304 B. The third polishing unit  30 C includes a polishing table  300 C, a top ring  301 C, a polishing liquid supply nozzle  302 C, a dresser  303 C, and an atomizer  304 C. The fourth polishing unit  30 D includes a polishing table  300 D, a top ring  301 D, a polishing liquid supply nozzle  302 D, a dresser  303 D, and an atomizer  304 D. 
     Between the first polishing unit  30 A and the second polishing unit  30 B in the first polishing section  3   a  and the cleaning section  4 , a first linear transporter  5  is disposed that transports a wafer between four transport positions (assumed to be a first transport position TP 1 , a second transport position TP 2 , a third transport position TP 3  and a fourth transport position TP 4  in order from the loading/unloading section  2  side) along the lengthwise direction. Above the first transport position TP 1  of the first linear transporter  5 , an inverter  31  that inverts a wafer received from a transfer robot  22  in the loading/unloading section  2  is disposed. Below the first transport position TP 1 , a lifter  32  capable of moving upward and downward is disposed. Below the second transport position TP 2 , a pusher  33  capable of moving upward and downward is disposed. Below the third transport position TP 3 , a pusher  34  capable of moving upward and downward is disposed. A shutter  12  is provided between the third transport position TP 3  and the fourth transport position TP 4 . 
     In the second polishing section  3   b , a second linear transporter  6  that transports a wafer between three transport positions (assumed to be a fifth transport position TP 5 , a sixth transport position TP 6  and seventh transport position TP 7  in order from the loading/unloading section  2  side) along the lengthwise direction is disposed adjacent to the first linear transporter  5 . A pusher  37  is disposed below the sixth transport position TP 6  of the second linear transporter  6 . A pusher  38  is disposed below the seventh transport position TP 7 . A shutter  13  is provided between the fifth transport position TP 5  and the sixth transport position TP 6 . 
     The cleaning section  4  is a region where a polished semiconductor wafer is cleaned. The cleaning section  4  is provided with an inverter  41  that inverts a wafer, four cleaners  42  to  45  that clean a polished semiconductor wafer, and a transport unit  46  that transports a wafer between the inverter  41  and the cleaners  42  to  45 . The inverter  41  and the cleaners  42  to  45  are arranged in a straight row along the lengthwise direction. A filter fan unit with a clean air filter (not illustrated) is provided above the cleaners  42  to  45 . Clean air produced by the filter fan unit removing particles is blown downward at all times. The interior of the cleaning section  4  is always maintained at a pressure higher than the pressure in the polishing section  3  in order to prevent particles from flowing thereinto from the polishing section  3 . 
     As shown in  FIG. 1 , a swing transporter (wafer transport mechanism)  7  that transports a wafer between the first linear transporter  5 , the second linear transporter  6  and the inverter  41  in the cleaning section  4  is disposed between the first linear transporter  5  and the second linear transporter  6 . The swing transporter  7  can transport a wafer from the fourth transport position TP 4  of the first linear transporter  5  to the fifth transport position TP 5  of the second linear transporter  6 , transport a wafer from the fifth transport position TP 5  of the second linear transporter  6  to the inverter  41  and transport a wafer from the fourth transport position TP 4  of the first linear transporter  5  to the inverter  41 . 
     Each transport mechanism will be described below. 
     Swing Transporter 
     The swing transporter  7  will be described.  FIG. 3  is a perspective view showing the swing transporter  7  together with the inverter  41  in the cleaning section  4 . As shown in  FIG. 3 , the swing transporter  7  in the present embodiment is mounted on a frame  102  of a box-like member in the first polishing section  3   a , and is provided with a robot cylinder  104  disposed in the frame  102  extending vertically and generally U-shaped in section, a base bracket  106  that moves upward and downward on the robot cylinder  104 , a motor  107  that causes the robot cylinder  104  to move upward and downward, a motor cover  108  attached to the base bracket  106 , a turnable arm  110  attached to a rotating shaft of a motor housed in the motor cover  108 , and a wafer holding mechanism  112  attached to a distal end of the turnable arm  110 . 
     The wafer holding mechanism  112  is provided with a pair of holding parts  114  that hold peripheral edges of wafer W from opposite sides and an opening/closing mechanism  116  that opens or closes rods  114   a  of the holding parts along a diametric direction (the direction of arrow A) of wafer W. The pair of holding parts  114  are disposed so as to face each other from positions on opposite sides of a center of wafer W, and two pairs of contact pieces (chuck mechanism)  118  that contact outer peripheral portions of wafer W in a point contact manner are respectively provided on opposite ends of the holding parts  114 . The contact pieces  118  are provided so as to project downward from the opposite ends of the holding parts  114 . 
     The opening/closing mechanism  116  is constituted by an air cylinder, for example. The opening/closing mechanism  116  moves the holding parts  114  in such directions that the holding parts  114  are brought closer to each other, thereby holding wafer W. The opening/closing mechanism  116  moves the holding parts  114  in such directions that the holding parts  114  move away from each other, thereby releasing wafer W.  FIG. 4  comprises diagrams showing the holding parts  114 .  FIG. 4( a )  is a top view of the holding parts  114 ;  FIG. 4( b )  is a side view of the holding parts  114 ; and  FIG. 4( c )  is an enlarged side view of the contact piece  118 . In  FIG. 4 , illustration of structures other than the holding parts is omitted for clarification of illustration and description. As shown in  FIG. 4( c ) , tapered portions  120   a  and  120   b  differing in slope angle from each other are formed in the contact piece  118 , and each of workpieces differing in size (for example, wafers W 1 , W 2  shown in  FIGS. 7 c  and 7 d   ; and a glass substrate G having a semiconductor wafer W shown in  FIGS. 13 and 14 ) can be supported on the corresponding one of the tapered portions  120   a  and  120   b . Therefore the swing transporter  7  in the thus-arranged embodiment can transport wafers differing in size. In the description of the present embodiment, an example of the provision of two contact pieces  118  on each of the holding parts  114  has been described. However, the present invention is not limited to this. Three or more contact pieces  118  may be provided on each of the holding parts  114 . 
     The wafer holding mechanism  112  of the swing transporter  7  in the present embodiment holds and releases wafer W by oppositely moving the pair of holding parts  114  along one direction and can therefore hold wafer W with reliability. 
     A ball screw and a slide guide are provided in the robot cylinder  104 , and the base bracket  106  on the robot cylinder  104  is moved upward or downward by driving with the motor  107  (arrow B). The wafer holding mechanism  112  is thereby moved upward and downward with the base bracket  106 . Thus, the robot cylinder  104  and the base bracket  106  constitute an upward/downward movement mechanism for moving the wafer holding mechanism  112  along the frame  102 . 
     The turnable arm  110  is swung on the rotating shaft of the motor in the motor cover  108  by driving with the motor (arrow C). The wafer holding mechanism  112  is thereby moved between the first linear transporter  5 , the second linear transporter  6  and the inverter  41  in the cleaning section  4 . A turn mechanism for turning the wafer holding mechanism  112  on the rotating shaft of the motor  108  adjacent to the frame  102  is constituted by the motor in the motor cover  108  and the turnable arm  110 . In the description of the present embodiment, an example of turning the wafer holding mechanism  112  on the rotating shaft of the motor in the motor cover  108  adjacent to the frame  102  has been described. However, the present invention is not limited to this. The wafer holding mechanism  112  may be turned on the frame  102 . 
     To hold wafer W, the base bracket  106  is moved downward until the contact pieces  118  of the holding parts  114  are positioned below wafer W, while the holding parts  114  is in an open state. The opening/closing mechanism  116  is then driven to move the holding parts  114  in such directions that the holding parts  114  are brought closer to each other, thereby positioning innermost peripheral portions of the contact pieces  118  inside the outermost peripheral end of wafer W. In this state, the base bracket  106  is moved upward to lift wafer W in the state of being held on the contact pieces  118  of the holding parts  114 . In the present embodiment, the contact pieces  118  and wafer W are brought into point contact with each other and the area of contact of wafer W can be minimized, so that dust attached to the surface of wafer W when the wafer is held can be reduced. 
     Linear Transporter 
     Next, the first linear transporter  5  in the first polishing section  3   a  will be described.  FIG. 5  is a front view of the first linear transporter  5 , and  FIG. 6  is a plan view of  FIG. 5 . As shown in  FIGS. 5 and 6 , the first linear transporter  5  is provided with four transport stages TS 1 , TS 2 , TS 3 , and TS 4  capable of moving linearly and reciprocatingly, and these stages are constructed in two upper and lower strata. That is, the first transport stage TS 1 , the second transport stage TS 2  and the third transport stage TS 3  are disposed in the lower stratum, and the fourth transport stage TS 4  is disposed in the upper stratum. 
     The transport stages TS 1 , TS 2 , and TS 3  in the lower stratum and the transport stage TS 4  in the upper stratum move on the same axis as viewed in the plan view of  FIG. 6 . However, because of the disposition at different heights, the transport stages TS 1 , TS 2 , and TS 3  in the lower stratum and the transport stage TS 4  in the upper stratum can move freely without interfering with each other. The first transport stage TS 1  transports a wafer between the first transport position TP 1 , at which the inverter  31  and the lifter  32  are disposed, and the second transport position TP 2 , at which the pusher  33  is disposed (which is a wafer delivery position); the second transport stage TS 2  transports a wafer between the second transport position TP 2  and the third transport position TP 3 , at which the pusher  34  is disposed (which is a wafer delivery position); and the third transport stage TS 3  transports a wafer between the third transport position TP 3  and the fourth transport position TP 4 . The fourth transport stage TS 4  delivers a wafer between the first transport position TP 1  and the fourth transport position TP 4 . 
     As shown in  FIG. 6 , each of the transport stages TS 1 , TS 2 , TS 3 , and TS 4  has, as four substrate mount portions, pins  50   a  to  50   d  are fixed on its upper surface. A wafer is supported on the transport stage by being placed on slant surfaces (described later in detail) formed on the pins  50   a  to  50   d , with the outer peripheral edges of the wafer guided and positioned thereby. The number of pins is not limited to four. Any number of pins not smaller than three may be provided. These pins  50   a  to  50   d  are formed of a resin such as polypropylene (PP), polychlorofluoroethylene (PCTFE) or polyetheretherketone (PEEK). A sensor (not shown) that detects the presence/absence of a wafer by means of a transmission-type sensor is arranged on each transport stage to enable detection of whether or not a wafer exists on the transport stage. 
     Placement of a wafer on the pins  50   a  to  50   d  is performed by the lifter  32 . First, the lifter  32  disposed lower than the transport stages TS 1  to TS 4  passes through the internal space of one of the transport stages TS 1  to TS 4  (assumed here to be the first transport stage TS 1 ) (the configuration of which is described later) and moves upward to a position immediately below a wafer held in a clamping manner by the inverter  31  (see  FIG. 1 ) disposed above. Next, the inverter  31  opens the clamp to place the wafer on the lifter  32 . The lifter  32  moves downward and passes through the internal space of the first transport stage TS 1  with the wafer placed thereon. By this passing operation, the wafer placed on the lifter  32  is removed from the lifter  32  and placed on the pins  50   a  to  50   d  disposed outside the lifter  32 . The pusher  33 , whose operation not described in detail, delivers to the top ring  301 A a wafer placed on the first transport stage TS 1  by using the same principle as that used by the lifter  32 , which operation will not be described in detail. The pusher  33  also delivers to the second transport stage TS 2  a wafer polished by the first polishing unit  30 A. Similarly, the pusher  34  delivers to the top ring  301 B a wafer placed on the second transport stage TS 2 , and delivers to the third transport stage TS 3  a wafer polished by the second polishing unit  30 B. 
     The transport stages TS 1  to TS 4  are respectively supported by supporting portions  51 ,  52 ,  53 , and  54 . As shown in  FIG. 5 , a connecting member  56  connected to a rod  55   a  of an air cylinder (drive mechanism)  55  is attached to a lower portion of the supporting portion  52  for the second transport stage TS 2  (driving-side transport stage). A shaft  57  and a shaft  58  are passed through the supporting portion  52  for the second transport stage TS 2 . One end of the shaft  57  is connected to the supporting portion  51  for the first transport stage TS 1  (driven-side transport stage), and a stopper  571  is provided on the other end of the shaft  57 . One end of the shaft  58  is connected to the supporting portion  53  for the third transport stage TS 3  (driven-side transport stage), and a stopper  581  is provided on the other end of the shaft  57 . A spring  572  is provided on the shaft  57  and stretched between the supporting portion  51  for the first transport stage TS 1  and the supporting portion  52  for the second transport stage TS 2 . Similarly, a spring  582  is provided on the shaft  58  and stretched between the supporting portion  52  for the second transport stage TS 2  and the supporting portion  53  for the third transport stage TS 3 . Mechanical stoppers  501  and  502  that respectively abut against the supporting portion  51  for the first transport stage TS 1  and the supporting portion  53  for the third transport stage TS 3  are provided on opposite end portions of the first linear transporter  5 . 
     When the air cylinder  55  is driven so that the rod  55   a  is extended, the connecting member  56  connected to the rod  55   a  is moved and the second transport stage TS 2  moves together with the connecting member  56 . At this time, since the supporting portion  51  for the first transport stage TS 1  is connected to the supporting portion  52  for the second transport stage TS 2  through the shaft  57  and the spring  572 , the first transport stage TS 1  moves with the second transport stage TS 2 . Also, since the supporting portion  53  for the third transport stage TS 3  is connected to the supporting portion  52  for the second transport stage TS 2  through the shaft  58  and the spring  582 , the third transport stage TS 3  also moves with the second transport stage TS 2 . Thus, by driving with the air cylinder  55 , the first transport stage TS 1 , the second transport stage TS 2  and the third transport stage TS 3  are linearly reciprocated simultaneously and integrally with each other. 
     When the first transport stage TS 1  is about to move in the direction opposite to the direction of the second transport position TP 2  by exceeding the first transport position TP 1 , the supporting portion  51  for the first transport stage TS 1  is stopped by the mechanical stopper  501  and a further movement is absorbed by the spring  572 , so that the first transport stage TS 1  cannot move beyond the first transport position TP 1 . Therefore, the first transport stage TS 1  is accurately positioned at the first transport position TP 1 . Similarly, when the third transport stage TS 3  is about to move in the direction opposite to the direction of the third transport position TP 3  by exceeding the fourth transport position TP 4 , the supporting portion  53  for the third transport stage TS 3  is stopped by the mechanical stopper  502  and a further movement is absorbed by the spring  582 , so that the third transport stage TS 3  cannot move beyond the fourth transport position TP 4 . Therefore, the third transport stage TS 3  is accurately positioned at the fourth transport position TP 4 . 
     The first linear transporter  5  is provided with an air cylinder  590  for linearly reciprocating the fourth transport stage TS 4  in the upper stratum. With the air cylinder  590 , the fourth transport stage TS 4  is controlled so as to move simultaneously with the transport stages TS 1 , TS 2 , and TS 3  in the lower stratum and in the direction opposite to the direction in which the transport stages TS 1 , TS 2 , and TS 3  move. In the present embodiment, the linear transporter  5  is driven with the air cylinders  55  and  590 . This drive is not performed exclusively by a particular method. For example, the linear transporter  5  may be motor-driven by using a ball screw. 
     The second linear transporter  6  is provided with three transport stages TS 5 , TS 6 , and TS 7  capable of moving linearly and reciprocatingly, and these stages are constructed in two upper and lower strata. That is, the fifth transport stage TS 5  and the sixth transport stage TS 6  are disposed in the upper stratum, and the seventh transport stage TS 7  is disposed in the lower stratum. As a result, the transport stages TS 5  and TS 6  in the upper stratum and the transport stage TS 7  in the lower stratum can move freely without interfering with each other, as can those in the linear transporter  5 . 
     The fifth transport stage TS 5  transports a wafer between the fifth transport position TP 5  and the sixth transport position TP 6 , at which the pusher  37  is disposed (which is a wafer delivery position); the sixth transport stage TS 6  transports a wafer between the sixth transport position TP 6  and the seventh transport position TP 7 , at which the pusher  38  is disposed (which is a wafer delivery position); and the seventh transport stage TS 7  transports a wafer between the fifth transport position TP 5  and the seventh transport position TP 7 . The second linear transporter  6 , whose operation not described in detail, moves the transport stages TS 5 , TS 6 , and TS 7  and supports a wafer with the same arrangement as that for the linear transporter  5 . 
     The transport stages TS 1  to TS 7  are identical in construction to each other. The first transport stage TS 1  will therefore be described below as a representative of the transport stages TS 1  to TS 7 .  FIG. 7  comprises diagrams showing the construction of the first transport stage TS 1 .  FIG. 7 a    is a top view of the first transport stage TS 1 , and  FIG. 7 b    is a side view of the first transport stage TS 1 . As shown in  FIG. 7 a   , the first transport stage TS 1  is generally U-shaped. The internal space of the generally U-shaped first transport stage TS 1  is formed for passage of the lifter  32  at the time of delivery of a wafer, as described above. The pins  50   a  and  50   b  are provided on one of portions opposed to each other in the generally U-shaped stage, and the pins  50   c  and  50   d  are provided on the other portion. The pins  50   a  to  50   d  are provided so as to project upward along a vertical direction from the first transport stage TS 1 . In the present embodiment, the pins  50   a  to  50   d  are identical in shape to each other. 
     In the present embodiment, the pins  50   b  and  50   c  are provided by being placed side by side along the direction of movement of the first transport stage TS 1 . Similarly, the pins  50   a  and  50   d  are provided by being placed side by side along the direction of movement of the first transport stage TS 1 . The pins  50   a  and  50   b  are provided by being placed side by side along a direction perpendicular to the direction of movement of the first transport stage TS 1 . Similarly, the pins  50   c  and  50   d  are provided by being placed side by side along a direction perpendicular to the direction of movement of the first transport stage TS 1 . As shown in  FIGS. 7 a  and 7 b   , wafer W is placed on the pins  50   a  to  50   d  inside the pins  50   a  to  50   d.    
       FIG. 7( c )  is an enlarged side view of the pin  50  of the transport stage TS according to one embodiment. As shown in  FIG. 7( c ) , tapered portions  50 A and  50 B of different slope angles, and each of wafers differing in size (W 1 , W 2 ) can be supported on the corresponding one of the tapered portions  50 A and  50 B. Therefore the linear transporter  5  in the thus-arranged embodiment can transport wafers differing in size. 
       FIG. 7 d    is an enlarged sectional view of the pin  50   c  of the first transport stage TS 1  according to another embodiment.  FIG. 7 d    shows a section of the pin  50   c  containing centers of the pin  50   c  and the pin  50   b  (center points on a horizontal plane). As shown in  FIG. 7 d   , the pin  50   c  is fixed on TS 1  with a bolt  59   c  inserted in a bolt hole formed in a central portion of the pin  50   c  along a vertical direction. This pin  50   c  has a first slant surface  51   c  and a second slant surface  52   c . The first slant surface  51   c  is slanted with respect to a horizontal direction (a direction perpendicular to the vertical direction) and faces upward. The second slant surface  52   c  is slanted with respect to the horizontal direction and faces downward. The second slant surface  52   c  is formed above the first slant surface  51   c . In the present embodiment, the second slant surface  52   c  is formed at such a position as to continue to the first slant surface  51   c . Also, in the present embodiment, the first slant surface  51   c  and the second slant surface  52   c  are formed through the entire circumference perpendicular to the vertical direction. That is, the portion of the pin  50   c  corresponding to the first slant surface  51   c  has such a shape that the pin  50   c  gradually becomes smaller in outside diameter in an upward direction. On the other hand, the portion of the pin  50   c  corresponding to the second slant surface  52   c  has such a shape that the pin  50   c  gradually becomes larger in outside diameter in the upward direction. 
     In the present embodiment, the first slant surface  51   c  includes a third slant surface  53   c  and a fourth slant surface  54   c . The fourth slant surface  54   c  is formed above and continuously with the third slant surface  53   c . The fourth slant surface  54   c  is formed so that its slope angle with respect to the horizontal direction is larger than that of the third slant surface  53   c . The first slant surface  51   c  may include three or more slant surfaces differing in slope angle. 
     A wafer can be placed on any of the third slant surface  53   c  and the fourth slant surface  54   c  of the pin  50   c .  FIG. 7 d    shows a state where wafer W 1  is placed on the third slant surface  53   c  and a state where wafer W 2  is placed on the fourth slant surface  54   c . Wafer W 2  is larger than wafer W 1 . When the wafer W 1  is placed on the third slant surface  53   c  of the pin  50   c , placement of wafer W 1  on the third slant surfaces  53   a ,  53   b , and  53   d  of the pins  50   a ,  50   b , and  50   d , not illustrated, is performed. That is, wafer W 1  is placed substantially horizontally. Wafer W 2  is placed in the same way on the fourth slant surfaces  54   c.    
     Although wafer W 1  is placed in the vicinity of an upper end point  57   c  of the third slant surface  53   c  in the case shown in  FIG. 7 d   , it can be placed at an arbitrary position on the third slant surface  53   c . However, it is desirable to secure as large a wafer W 1  deviation margin as possible in order to reduce the occurrence of falls of wafers W 1  from the pin  50   c . From this viewpoint, it is desirable to place wafer W 1  as high as possible. Placement of wafer W 1  at the upper end point  57   c  facilitates regulation of the position of wafer W 1 . It is desirable to set the positions of the pins  50   a  to  50   d  in such a way according to the size of wafer W 1 . In these respects, the same can be said about wafer W 2 . 
     Thus, the third slant surface  53   c  and the fourth slant surface  54   c  are provided in the first slant surface  51   c  to enable placement of two kinds of wafers W 1  and W 2  differing in size on the first transport stage TS 1 . That is, one first transport stage TS 1  can handle a plurality of wafers differing in size and the device is thus improved in versatility. 
     In the present embodiment, the upper end point  57   c  of the third slant surface  53   c  (the lower end point of the fourth slant surface  54   c ) is positioned on the wafer placement side relative to an upper end point  56   c  of the second slant surface  52   c  along the direction of a straight line passing through the centers of the pins  50   c  and the pin  50   b . This positional relationship between the upper end point  57   c  and the upper end point  56   c  is established along the direction of a straight line (hereafter referred to simply as “straight line direction”) passing through the centers of arbitrary two of the pins  50   a  to  50   d . With this arrangement, wafer W 1  can be placed on the third slant surface  53   c  from above while being held in a state of being parallel to the horizontal direction without interfering with the upper end point  56   c . As a result, the efficiency of processing relating to transport of wafers can be improved and the mechanism for placing wafers can be simplified. 
     It is desirable that the position of the upper end point  56   c  be remoter from the upper end point  57   c  on the side opposite from the side on which the wafer is placed (hereinafter referred to simply as “opposite side”). For example, it is desirable that the upper end point  56   c  be positioned on the opposite side relative to the position of a center of the fourth slant surface  54   c  along the straight line direction. It is more desirable that the upper end point  56   c  be positioned in a region of the fourth slant surface  54   c  on the opposite side that is one-third of the fourth slant surface  54   c  when the fourth slant surface  54   c  is equally divided into three regions along the straight line direction. With this arrangement, the same effect as that in the case of placement of wafer W 1  on the third slant surface  53   c  can also be expected in the case of placement of wafer W 2  on the fourth slant surface  54   c.    
       FIG. 7 e    shows a state where the occurrence of falls of wafers is reduced by the pins  50   a  to  50   d .  FIG. 7 e    shows sections of the pins  50   b  and  50   c  containing the centers of the pin  50   c  and the pin  50   b . In an initial state, the wafer is placed on the third slant surfaces  53   b  and  53   c , as shown as wafer W 3  in  FIG. 7 e   . In a case where the wafer is transported by moving the pins  50   b  and  50   c  in the direction of the arrow in the figure, i.e., in the direction from the pin  50   b  toward the pin  50   c , if one end of the wafer (pin  50   c  side) is shifted upward along the first slant surface  51   c  by an impact received during transport of the wafer, particularly at the time of stopping, the other end of the wafer (pin  50   b  side) moves downward along the third slant surface  53   b . However, as shown as wafer W 4  in  FIG. 7 e   , the one end of the wafer is brought into abutment against the second slant surface  52   c  formed so as to face downward, so that this end does not further move upward from the point of abutment beyond the second slant surface  52   c . Therefore, the other end of wafer W 4  is maintained in a state of being placed on the third slant surface  53   b . As a result, the occurrence of falls of wafers is reduced. Moreover, since a reduction in speed of transport of wafers for a reduction of the occurrence of falls of wafers is not required, the manufacturing efficiency is not reduced. 
       FIG. 7 f    shows the construction of pins  150   b  and  150   c  as a comparative example. The pins  150   b  and  150   c  have first slant surfaces  151   b  and  151   c , as do the pins  50   b  and  50   c  according to the embodiment. The first slant surfaces  151   b  and  151   c  respectively have third slant surfaces  153   b  and  153   c  and fourth slant surfaces  154   b  and  154   c  identical in shape to the third slant surfaces  53   b  and  53   c  and the fourth slant surfaces  54   b  and  54   c  according to the embodiment. Vertical surfaces  152   b  and  152   c  perpendicular to a horizontal direction are formed above the first slant surfaces  151   b  and  151   c . In a case where a wafer is transported by moving the thus-constructed pins  150   b  and  150   c  in the direction of the arrow in the figure, when wafer W 3  placed on the third slant surfaces  153   b  and  153   c  receives an impact during transport of the wafer, particularly at the time of stopping, one end of wafer W 3  can be limitlessly moved upward along the vertical surface  152   c  and, therefore, there is a possibility of the other end falling from the pin  150   b , as shown as wafer W. With the pins  50   a  to  50   d  according to the above-described embodiment, falls of wafers occurring in such a way can be reduced. 
     Modified Example 1 
     A vertical surface perpendicular to a horizontal direction may be formed between the first slant surface  51   c  and the second slant surface  52   c . Also in such a case, the same effect as that in the above-described embodiment can be obtained. From the viewpoint of further limiting the range of movement of a wafer, however, the construction according to the above-described embodiment is more desirable. 
     Modified Example 2 
     The first slant surface  51   c  may be formed by only one slope angle. Also in such a case, the same effect of reducing the occurrence of falls of wafers as that in the above-described embodiment can be obtained. In such a case, the second slant surface  52   c  may be positioned on the side of the lower end point  55   c  of the first slant surface  51   c  (see  FIG. 7 d   ) opposite from the wafer placement side along the straight line direction, or may be positioned on the side of the position of a center of the first slant surface  51   c  opposite from the wafer placement side along the straight line direction. In this way, the facility with which a wafer is placed can be improved, as in the above-described embodiment. 
     Modified Example 3 
     It is not necessary to form the first slant surface  51   c  and the second slant surface  52   c  through the entire circumference of the pin  50   c . The first slant surface  51   c  and the second slant surface  52   c  may be formed at least through a region where a wafer is placed. 
     Inverter 
     Next, the inverter  31  in the first polishing section  3   a  will be described. The inverter  31  in the first polishing section  3   a  is disposed in such a position that the hand of the transport robot  22  in the loading/unloading section  2  can reach the inverter  31 . The inverter  31  receives a wafer before polishing from the transport robot  22 , turns the wafer upside down and delivers the wafer to the lifter  32 . 
       FIG. 8  is a perspective view showing the inverter  31 ,  FIG. 9  is a plan view of  FIG. 8 , and  FIG. 10  is a side view of  FIG. 8 . As shown in  FIGS. 8 to 10 , the inverter  31  is provided with a pair of circular-arc holding parts  310  that hold the peripheral edge of wafer W from opposite sides, shafts  314  attached to the holding parts  310 , and an opening/closing mechanism  312  that opens and closes the holding parts  310  by moving the shafts  314  in the axial directions of the shafts  314 . The pair of holding parts  310  are disposed so as to face each other, with the center of wafer W positioned therebetween. Two pairs of chuck parts  311  that contact outer peripheral portions of wafer W in a line contact manner are respectively provided on pairs of end portions of the holding parts  310 . In the description of the present embodiment, an example of the provision of two chuck parts  311  on each holding part  310  is described. However, the present invention is not limited to this. Three or more chuck parts  311  may be provided on each holding part  310 . 
       FIG. 11  is a longitudinal sectional view showing the opening/closing mechanism  312  of the inverter  31 . As shown in  FIG. 11 , the opening/closing mechanism  312  is provided with compression springs  315  that urge the shafts  314  and the holding parts  310  in closing directions, and slide-type air cylinders  313  respectively connected to the shafts  314 . This opening/closing mechanism  312  moves the holding parts  310  with compression springs  315  in such directions that the holding parts  310  are brought closer to each other, thereby holding wafer W. At this time, movable parts  313   a  of the air cylinders  313  are brought into abutment against mechanical stoppers  317 . Also, the opening/closing mechanism  312  moves the holding parts  310  by driving with the air cylinders  313  in such directions that the holding parts  310  move away from each other, thereby releasing wafer W.  FIG. 12  shows the state at the time of this movement. 
     That is, to hold wafer W, one of the air cylinders  313  is pressurized, while the other air cylinder  313  is closed only by the urging force of the compression spring  315 . At this time, only the movable part  313   a  of the pressurized air cylinders  313  is pressed against the mechanical stopper  317  and fixed at the corresponding position. At this time, the position of the holding part  310  connected to the other air cylinder  313  urged by the compression spring  315  is detected with a sensor  319 . In the case of absence of wafer W, the air cylinder  313  not pressurized is at the full stroke position and there is no response from the sensor  319 . This is a detection result indicating that no wafer W is held. 
     As described above, the compression springs  315  are used to hold wafer W and the air cylinders  313  are used to release wafer W, thus enabling preventing wafer W from being damaged by pneumatic pressure in the air cylinders  313 . 
     As shown in  FIGS. 8 to 10 , a rotary shaft  316  that rotates on an axis perpendicular to the center axis of wafer W is attached to the opening/closing mechanism  312 . The rotary shaft  316  is connected to an inverting mechanism  318  and is rotated by the inverting mechanism  318 . Accordingly, when the inverting mechanism  318  is driven, the opening/closing mechanism  312  and holding parts  310  are rotated to invert wafer held on the holding parts  310 . 
       FIG. 13  comprises side views of the chuck  311 .  FIG. 13( a )  shows a state before inversion of semiconductor wafer W adhered to glass substrate G, and  FIG. 13( b )  shows a state after inversion. As shown in  FIG. 13 , the chuck part  311  of the inverter  31  has a slant surface  311   a  (a lower projecting portion) that gradually becomes higher from the inside of wafer G, W along a diametric direction toward the outside, and a slant surface  311   b  that gradually becomes higher from the outside of wafer G, W along the diametric direction toward the inside. Wafer G, W is positioned between these slant surfaces  311   a  and  311   b . Referring to  FIG. 13 , wafer W is bonded on glass substrate G. In the state before inversion shown in  FIG. 13( a ) , wafer W is positioned on the upper side of glass substrate G. In the state after inversion shown in  FIG. 13( b ) , wafer W is positioned on the lower side of glass substrate G. It is desirable to prevent wafer W from contacting any one of the slant surfaces  311   a  and  311   b . Then the slant surfaces  311   a  and  311   b  of the chuck  311  are set as described below. 
       FIG. 14  is a diagram for explaining a method of determining the slope angle θb of slant surface  311   b  of the chuck  311 .  FIG. 14  shows a section of the workpiece in which wafer W is bonded on glass substrate G. A straight line tangent to glass substrate G and semiconductor wafer W in the section of wafer G, W is assumed to be L 1 . The angle between L 1  and the glass substrate is assumed to be θ 1 . A circle with a radius R centered at the point at which L 1  is tangent to wafer W is drawn. This radius R is a clearance between the slant surface  311   b  and wafer W, which is preferably secured as a design value. R is determined by considering an error in positioning when wafer W is bonded on glass substrate G. A straight line tangent to the circle with radius R and glass substrate G is assumed to be L 2 . The angle between L 1  and L 2  is assumed to be θ 2 . The angle formed by L 2  and a straight line parallel to the surface of wafer W is assumed to be θ 3 . Then the slope angle θb of the slant surface  311   b  is set equal to or larger than θ 3  and smaller than 90° (θ 3 ≦θb≦90°). If θb is set in this range, a clearance equal to or larger than the design value R is necessarily formed between the slant surface  311   b  and wafer W. Since R is determined by considering an error in positioning when wafer W is bonded on glass substrate G, the slant surface  311   b  does not contact wafer W even if a positioning error exists when wafer W is bonded on glass substrate G. Determination based on the same way of thinking as that for determination on the slant surface  311   b  can be made on the slant surface  311   a . If the slope angle θb exceeds 90°, wafer W falls from the inverter by not being supported by the slant surface  311   b  in the state shown in  FIG. 13( b ) . To prevent falling of wafer W from the inverter, therefore, θb is set smaller than 90°. 
     The same wafer holding structure as that of the inverter  31  in the polishing section  3  can be constructed for the inverter  41  in the cleaning section  4 . 
     Lifter 
     The lifter  32  in the first polishing section  3   a  will be described. The lifter  32  in the first polishing section  3   a  is disposed in such a position that the transport robot  22  and the first linear transporter  5  can access the lifter  32 . The lifter  32  functions as a delivery mechanism for delivering a wafer therebetween. That is, the lifter  32  delivers a waver inverted by the inverter  31  to the first transport stage TS 1  or the fourth transport stage TS 4  of the first linear transporter  5 . 
       FIG. 15  is a longitudinal sectional view showing the lifter  32 .  FIG. 16( a )  is a top view of a stage  322  of the lifter  32 ,  FIG. 16( b )  is a side view of the stage  322 , and  FIG. 16( c )  is an enlarged partial side view of a claw  325  of the stage  322 . The lifter  32  is provided with the stage  322  on which a wafer is placed and a cylinder  323  for performing an operation to move the stage  322  upward or downward. The cylinder  323  and the stage  322  are connected by a slidable shaft  324 . As shown in  FIG. 16( a ) , the stage  322  is ramified into a plurality of claws  325 , which are disposed by being spaced apart from each other by such distances as to be capable of holding even a wafer with an orientation flat placed thereon in such a region that the transport is not influenced. The claws  325  are disposed in such orientations as to be out of phase with the chuck parts of the inverter  31 . That is, first wafer edge portions by which the chuck parts  311  hold the wafer and second wafer edge portions held by the claws  325  of the lifter  32  do not coincide with each other. Also, the claws  325  with which wafer delivery operations on the inverter  31  and the first linear transporter  5  are performed have surfaces on which a wafer is placed, and portions of the claws  325  projecting upward beyond these surfaces are tapered so as to absorb an error in transport positioning and to center a wafer when the wafer is placed. 
     As shown in  FIG. 16( c ) , the claws  325  are provided with wafer supporting members  326 . It is preferable that the wafer supporting members  326  be formed of an elastomer material having a hardness of durometer D scale 30 to 50, more preferably 40. 
     Transport Unit in Cleaning Section 
     The transport unit  46  in the cleaning section  4  will be described.  FIG. 17  is a perspective view showing the transport unit  46 . As shown in  FIG. 17 , the transport unit  46  is provided with four chucking units  461  to  464  as a wafer holding mechanism for detachably holding a wafer in the cleaner. The chucking units  461  to  464  are attached to a guide frame  466  extending in a horizontal direction from a main frame  465 . A ball screw (not shown) extending in a vertical direction is attached to the main frame  465 . The chucking units  461  to  464  are moved upward and downward by driving with a motor  468  connected to the ball screw. Thus, the motor  468  and the ball screw constitute an upward/downward movement mechanism for moving the chucking units  461  to  464  upward and downward. 
     A ball screw  469  extending parallel to the row of the cleaners  42  to  45  is also attached to the main frame  465 . The main frame  465  and the chucking units  461  to  464  are moved in a horizontal direction by driving with a motor  470  connected to the ball screw  469 . Thus, the motor  470  and the ball screw  469  constitute a moving mechanism for moving the chucking units  461  to  464  along the direction of arrangement of the cleaners  42  to  45  (the direction of arrangement of chucking units  461  to  464 ). 
     In the present embodiment, the number of chucking units corresponding to the number of cleaners  42  to  45  are used. The structure of the chucking units  461  and  462  and the structure of the chucking units  463  and  464  are basically the same and are symmetrical about the main frame  465 . Therefore, description will be made only of the chucking units  461  and  462  below. 
     The chucking unit  461  is provided with an openable/closable pair of arms  471   a  and  471   b  for holding wafer W, and the chucking unit  462  with a pair of arms  472   a  and  472   b . At least three (four in the present embodiment) chuck contact pieces  473  are provided on the arms in each chucking unit. Peripheral portions of wafer W are chucked and held by the chuck contact pieces  473 , thereby enabling the wafer to be transported to the next cleaner. The structure of the chuck contact piece  473  will be described with reference to the drawings.  FIG. 18  comprises diagrams showing the chuck contact piece  473 .  FIG. 18( a )  is a perspective view showing the chuck contact piece  473  in a single state before the chuck contact piece  473  is attached.  FIG. 18( b )  is a top view of the chuck contact piece  473 , and  FIG. 18( c )  is a sectional view taken along line B-B in  FIG. 18( b ) . As shown in  FIG. 18( c ) , slant surfaces  473   a  and  473   b  for supporting wafers differing in size are formed on the chuck contact piece  473 . Therefore, wafers W differing in size can be transported without adjusting the range of movement of the arms. 
     As shown in  FIG. 17 , an air cylinder  474  for opening/closing the arms  471   a  and  471   b  of the chucking unit  461  and the arms  472   a  and  472   b  of the chucking unit  462  in such directions that the pair of arms are brought closer to each other or moved away from each other is provided on the guide frame  466 . A link mechanism or the like for transmitting the motion of the air cylinder  474  to the arms  471   a ,  471   b ,  472   a , and  472   b , not be described in detail, is provided. Accordingly, the end surface of wafer W is chucked between the arms  471   a ,  471   b ,  472   a , and  472   b  by closing the arms  471   a ,  471   b ,  472   a , and  472   b  with the air cylinder  474 . Wafer W can be held in this way. Thus, the air cylinder  474  constitutes an opening/closing mechanism for opening/closing the arms of the chucking units  461  to  464  in such directions that the arms are brought closer to or moved away from each other. Each chucking unit is capable of detecting the presence/absence a wafer by sensing the stroke of the air cylinder. Holding of a wafer may be performed in a vacuum attraction manner. In such a case, wafer presence/absence detection may be performed by measuring the vacuum pressure. 
     The arms  471   a  and  471   b  of the chucking unit  461  and the arms  472   a  and  472   b  of the chucking unit  462  are attached to a rotary shaft  475  rotatably mounted on the guide frame  466 . Also, an air cylinder  476  for turning the arms  471   a ,  471   b ,  472   a , and  472   b  on the rotary shaft  475  is provided on the guide frame  466 . A link member  478  capable of turning on a pin  477  is provided on a distal end of a rod of the air cylinder  476 . The link member  478  is connected to the rotary shaft  475  by a rod  479 . Thus, the air cylinder  476 , the link member  478  and the rod  479  constitute a turning mechanism for turning the arms of the chucking units  461  to  464  on the rotary shaft  475 . 
     The embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments. For example, the embodiments of the wafer holding mechanisms in the above-described swing transporter, linear transporter, inverter, lifter, cleaning section transport unit, etc., are replaceable with each other if no conflict occurs between them. 
     For example, the method of determining the slope angle θb of the slant surface  311   b  of the inverter can be applied in the same way to determination of the slope angles of the tapered portions  120   a  and  120   b  of the contact pieces  118  of the swing transporter  7 , the slope angles of the tapered portions  50   a  and  50   b  of the pins  50  of the linear transporter  5  and the slope angles of the slant portions  473   a  and  473   b  of the chucking contact pieces  473  of the transport unit  46 . In the case where wafer W is bonded on a glass substrate, determination of the slope angles in the above-described way enables prevention of contact of the holding mechanism with wafer W in the same way as described with respect to the example with the inverter.