Conveying device

Abstract

To provide a conveying device that can convey a wafer while holding an outer periphery part thereof, while preventing a center part of the wafer from hanging down.SOLUTION: In a conveying device 70, which conveys a wafer W from a first position to a second position by making a conveying pad 71 suction and hold the wafer, ring-shaped suction parts (an annular convex part 71A and a suction groove 71a formed on the convex part) which suction an outer periphery part on an upper surface of the wafer W, a circular concave part 71B inside the suction parts and a pressure adjustment port 82 opening to the circular concave part 71B are formed on a lower surface of the conveying pad 71, and also a pressure gauge 85 and a pressure adjustment valve V are arranged in a communication path (piping 83) through which the pressure adjustment port 82 is communicated with a suction source 86. The conveying device is provided with a control part 110 that when conveying the wafer W by making the suction parts suction and hold the wafer W, controls the pressure adjustment valve V so that a pressure of the circular concave part 71B blocked by the wafer W is set to a value at which downward force and upward force acting on the wafer W become equal to each other.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a transfer device that holds and transfers a wafer by suction. [Background technology]

[0002] In the manufacturing process of semiconductor devices such as ICs and LSIs used in various electronic devices, the back surface of the wafer is ground by a grinding device to thin the wafer to a predetermined thickness in order to reduce the size and weight of the semiconductor device. The thin wafer ground by the grinding device is then transported to, for example, a cleaning device while the top surface of the wafer is suction-held by a transport pad of a transport device.

[0003] Among the transport devices that transport a wafer by suction holding the wafer with a transport pad, there is one that transports the wafer by suction holding the central portion of the upper surface of the wafer with the suction surface of the transport pad (see, for example, Patent Document 1). When a wafer is transported by such a transport device, contact marks may remain on the upper surface of the wafer because the transport pad is in contact with the upper surface of the wafer, and these contact marks cause a decrease in the flexural strength of the wafer.

[0004] Therefore, an edge clamping method has been adopted in which the wafer is transported by clamping its outer periphery (edge) (see, for example, Patent Document 2). However, when the wafer is clamped and transported by this edge clamping method, the thinned central portion of the wafer is deflected and deformed, which may cause cracks at the boundary between the central portion and the outer periphery.

[0005] As another method for transporting a wafer by suction holding, Patent Document 3 proposes a method in which a first annular wall and a second annular wall are formed concentrically on the holding surface of a transport pad, suction holes are formed between these first and second annular walls, and the wafer is held by suction using suction force acting between the first and second annular walls through the suction holes. According to this method, the wafer is held by the arcuate surfaces of the first and second annular walls, so that the contact area between the wafer and the first and second annular walls can be minimized, but there is a problem in that the first and second annular walls come into contact with the wafer, leaving contact marks on the wafer.

[0006] As another method, Patent Document 4 proposes a method in which the holding surface of a transfer pad faces the upper side of the held surface (back surface) of a wafer with a specified gap provided, a layer of water is placed in the gap between the transfer pad and the held surface of the wafer, and the wafer is held on the holding surface of the holding pad by the surface tension of the water. With this method, the wafer can be held by the transfer pad without contact, so there is no problem of leaving contact marks on the held surface of the wafer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2014-086485 A [Patent Document 2] JP 2014-004658 A [Patent Document 3] JP 2007-294588 A [Patent Document 4] JP 2009-252877 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method proposed in Patent Document 4 requires water to be stored in a circular recess formed in the center of the supporting surface of the transport pad, which causes the surface tension of the water to cause the center of the wafer held on the supporting surface of the transport pad to sag under its own weight and the weight of the water.

[0009] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a transport device that can transport a wafer by holding its outer periphery while preventing the central portion of the wafer from sagging. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the present invention provides a transport device that holds a wafer under suction with a transport pad and transports it from a first position to a second position, the underside of the transport pad being formed with a ring-shaped suction section that sucks in the outer periphery of the upper surface of the wafer, a circular recess inside the suction section, and a pressure adjustment port that opens into the circular recess, the underside of the transport pad being formed with a pressure gauge and a pressure adjustment valve in a communication passage that connects the pressure adjustment port to a suction source, and the device being characterized in that it further comprises a control section that, when a wafer is held under suction by the suction section and transported, controls the pressure adjustment valve to set the pressure in the circular recess blocked by the wafer to a value such that the downward force and upward force acting on the wafer are equal. Effect of the Invention

[0011] According to the present invention, when the wafer is transported by holding its outer periphery under suction using the suction part of the transport pad, the pressure regulating valve is controlled to set the pressure in the circular recess of the transport pad blocked by the wafer to a value such that the downward force and upward force acting on the wafer are equal. As a result, the central part of the wafer, whose outer periphery is held under suction by the suction part of the transport pad, does not sag, and the wafer can be transported while held horizontally. [Brief description of the drawings]

[0012] [Figure 1]1 is a perspective view of a grinding apparatus including a conveying device according to the present invention; [Diagram 2] 1 is a cutaway side view of a transfer device and a chuck table according to a first embodiment of the present invention. [Diagram 3] 1A and 1B are perspective views of a transport pad of a transport device according to a first embodiment of the present invention, in which FIG. 1A is a view of the transport pad seen from diagonally above, and FIG. 1B is a view of the transport pad seen from diagonally below. [Figure 4] FIG. 4 is an enlarged plan view of a portion X in FIG. [Diagram 5] 1 is a cutaway side view of the transport device and the chuck table, illustrating a state in which a wafer on the chuck table is being sucked by a transport pad of the transport device according to a first embodiment of the present invention. FIG. [Figure 6] 1 is a cutaway side view of the transfer device and the chuck table illustrating a state in which a wafer is suction-held by a transfer pad of the transfer device according to a first embodiment of the present invention and is being separated from the chuck table. [Figure 7] 3 is a side cross-sectional view showing the relationship of forces acting on a wafer held by suction by a transport pad of the transport device according to the first embodiment of the present invention. FIG. [Figure 8] 11A and 11B are perspective views of a transport pad of a transport device according to a second embodiment of the present invention, in which (a) is a view of the transport pad seen obliquely from above, and (b) is a view of the transport pad seen obliquely from below. [Figure 9] 11 is a cutaway side view of a transport device and a chuck table, illustrating a state in which a wafer on the chuck table is being sucked by a transport pad of the transport device according to a second embodiment of the present invention. FIG. [Figure 10] 11 is a cutaway side view of a transfer device and a chuck table illustrating a state in which a wafer is suction-held by a transfer pad of a transfer device according to a second embodiment of the present invention and is being separated from the chuck table. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0014] [Grinding equipment configuration] First, the basic configuration of a grinding device equipped with a conveying device according to the present invention will be described below with reference to Fig. 1. In the following description, the directions of the arrows shown in Fig. 1 will be the X-axis (left-right direction), the Y-axis (front-back direction), and the Z-axis (up-down direction), respectively.

[0015] The grinding apparatus 1 shown in FIG. 1 grinds the back surface (the upper surface in FIG. 1) of a thin, disk-shaped wafer W, which is a workpiece, and includes the following components.

[0016] That is, the grinding apparatus 1 mainly comprises a chuck table 10 that holds the wafer W, a grinding unit 20 that grinds the back surface (top surface in FIG. 1) of the wafer W held on the holding surface of the chuck table 10, a spinner cleaning device 40 that cleans the wafer W, a robot 50 that transports the wafer W into and out of the cassette 2, a first transport device 60 that holds the wafer W aligned on the alignment table 3 and transfers it to the chuck table 10, a second transport device 70 that holds the wafer W after grinding and transports it from the chuck table 10 to the spinner cleaning device 40, and a control unit 110 that controls the various components.

[0017] Here, the wafer W is made of a single crystal silicon base material, and a plurality of devices (not shown) are formed on the surface facing downward in the state shown in Fig. 1, and these devices are protected by a protective tape affixed to the surface of the wafer W. The wafer W has its front surface (the lower surface in Fig. 1) sucked and held on the holding surface of the chuck table 10, and its back surface (the upper surface in Fig. 1) is ground by a grinding unit 20 as described below.

[0018] Next, the configurations of the main components of the grinding apparatus 1, that is, the chuck table 10, the grinding unit 20, the spinner cleaning device 40, the robot 50, the first transfer device 60, the second transfer device 70, and the control unit 110 will be described.

[0019] (Chuck table) The chuck table 10 is a disk-shaped member, and a disk-shaped porous member 10A made of porous ceramic or the like is mounted in the center thereof. Here, the upper surface of the porous member 10A constitutes a holding surface that suction-holds the disk-shaped wafer W, and the holding surface is selectively connected to a suction source 11, an air supply source 12, or a water supply source 13, as shown in FIG.

[0020] That is, as shown in Fig. 2, a communication passage 15 is formed vertically at the axial center of the chuck table 10 and the rotating shaft 14 that rotatably supports the chuck table 10, and this communication passage 15 opens into the lower surface of the porous member 10A. The communication passage 15 is also connected to a plurality of communication passages 16 (only two are shown in Fig. 2) that extend horizontally radially outward from the communication passage 15 inside the chuck table 10, and the outer end of each communication passage 16 stands vertically upward and opens into the lower surface of the porous member 10A.

[0021] A pipe 4 is connected to the communication passage 15, and three branch pipes 4a, 4b, and 4c are branched from the pipe 4. The branch pipe 4a is connected to a suction source 11 via a flow rate control valve 5 and an on-off valve V1, and the branch pipe 4b is connected to an air supply source 12 via a flow rate control valve 6 and an on-off valve V2. The branch pipe 4c is connected to a water supply source 13 via a flow rate control valve 7 and an on-off valve V3.

[0022] The chuck table 10 is rotated at a predetermined speed around the axis by a rotation mechanism (not shown) provided at the lower end of the rotation shaft 14, and can be moved back and forth along the Y-axis direction (front-back direction) between the processing area R1 and the transfer area R2 shown in Fig. 1 by a horizontal movement mechanism (not shown) provided below. Note that the horizontal movement mechanism (not shown) is composed of a known ball screw mechanism or the like, and therefore illustration and description thereof will be omitted.

[0023] A thickness measuring device 8 is disposed near the chuck table 10 located in the processing region R1 on the base 1A of the grinding apparatus 1. This thickness measuring device 8 is a height gauge, and includes a first probe 8a that contacts the top surface of the wafer W held on the chuck table 10, and a second probe 8b that contacts the outer peripheral top surface of the chuck table 10. Therefore, by subtracting the top surface height of the chuck table 10 measured by the second probe 8b from the top surface height of the wafer W measured by the first probe 8a, the thickness of the wafer W during grinding can be measured in real time.

[0024] (Grinding unit) 1, the grinding unit 20 includes a holder 21 that is open at the top, a spindle motor 22 that is a rotational drive source that is fixed to the holder 21 in an upright position, a spindle 23 that is rotationally driven by the spindle motor 22, a disk-shaped mount 24 that is attached to the lower end of the spindle 23, and a grinding wheel 25 that is detachably attached to the lower surface of the mount 24. Here, a plurality of grinding stones 25a in the shape of a rectangular block that is a processing tool are attached in an annular shape to the grinding wheel 25.

[0025] The grinding unit 20 can be raised and lowered in a direction (Z-axis direction) perpendicular to the holding surface of the chuck table 10 by a vertical movement mechanism 30, and this vertical movement mechanism 30 is disposed on the -Y-axis direction end face (front face) of a rectangular box-shaped column 31 vertically erected on the +Y-axis direction end face (rear end face) of the upper surface of the base 1A, as shown in Fig. 1. This vertical movement mechanism 30 raises and lowers a rectangular plate-shaped lift plate 32 attached to the back face of the holder 21 in the Z-axis direction along a pair of left and right guide rails 33 together with the holder 21 and the spindle motor 22 and grinding wheel 25 held by the holder 21. Here, the pair of left and right guide rails 33 are disposed perpendicular to the front face of the column 31 and parallel to each other.

[0026] A rotatable ball screw 34 is vertically installed along the Z-axis direction (up-down direction) between the pair of left and right guide rails 33, and the upper end of the ball screw 34 is connected to a reversible electric motor 35, which serves as a drive source. The electric motor 35 is attached in a vertical position to the column 31 via a rectangular plate-shaped bracket 36 attached to the upper surface of the column 31. The lower end of the ball screw 34 is rotatably supported by the column 31, and a nut member (not shown) that is horizontally protrudes rearward (in the +Y-axis direction) from the back surface of the lifting plate 32 is screwed into the ball screw 34.

[0027] Therefore, when the electric motor 35 is driven to rotate the ball screw 34 forward or backward, the lift plate 32, to which a nut member (not shown) that screws onto the ball screw 34 is attached, moves up and down in the Z-axis direction along the guide rail 33 together with the grinding unit 20.

[0028] (Spinner cleaning device) The spinner cleaning device 40 cleans the back surface (surface to be ground) of the wafer W after grinding (the upper surface in FIG. 1), and includes a spinner table 41 that holds and rotates the wafer W after grinding, a cleaning water nozzle 42 that sprays cleaning water toward the back surface of the wafer W, and a polygonal cylindrical cover 43 that can be raised and lowered and covers the periphery of the spinner table 41 and the cleaning water nozzle 42. Pure water is preferably used as the cleaning water.

[0029] (robot) The robot 50 is an articulated robot, and a plate-shaped robot hand 53 is attached to the tip of a rectangular box-shaped mounting part 51 via a holder 52. The robot 50 is provided with a horizontal movement mechanism 54 for moving the mounting part 51 and the robot hand 53 in the horizontal direction, and a lifting mechanism 55 for raising and lowering the mounting part 51 and the robot hand 53.

[0030] (First and second conveying devices) The first transport device 60 suction-holds the wafer W aligned on the alignment table 3 and transports it to the chuck table 10, and the second transport device 70 receives the wafer W after grinding from the chuck table 10, suction-holds the received wafer W, and transports it to the spinner cleaning device 40. Since the basic configurations of the first transport device 60 and the second transport device 70 are the same, only the configuration of the second transport device 70 will be described below, and illustrations and descriptions of the configuration of the first transport device 60 will be omitted.

[0031] First Embodiment 2, the second transfer device 70 includes a disk-shaped transfer pad 71 for suction-holding the wafer W, a rotation mechanism 90 for rotating the transfer pad 71 in a horizontal plane, and a lifting mechanism 100 for raising and lowering the transfer pad 71. The rotation mechanism 90 includes a vertical rotation shaft 92 rotatably inserted into a cylindrical vertical sleeve 91, and an electric motor 93 as a rotary drive source for rotating the rotation shaft 92. One end of a horizontal arm 72 is attached to the upper end of the rotation shaft 92. The transfer pad 71 is supported horizontally at the tip of the arm 72. The electric motor 93 is electrically connected to a control unit 110, and its drive is controlled by the control unit 110.

[0032] 2, the lifting mechanism 100 includes a vertical guide rail 102 attached to an end surface of a column 101 that stands vertically in the base 1A, a vertical ball screw 103 housed in the column 101, and a reversible electric motor 104 that rotates the ball screw 103. The electric motor 104 is equipped with an encoder 105 that detects the rotation direction and number of rotations of the electric motor 104, and a detection signal detected by the encoder 105 is transmitted to a control unit 110, and the drive of the electric motor 104 is controlled by the control unit 110 based on this detection signal.

[0033] A sleeve 91, through which a rotating shaft 92 is inserted and supported, is supported on the guide rail 102 via a pair of upper and lower sliders 106 so as to be able to rise and fall, and a ball screw 103 is threadedly inserted into a nut member 107 that protrudes horizontally from the sleeve 91. Therefore, when the electric motor 104 is started to rotate the ball screw 103 forward and backward, the sleeve 91, to which the nut member 107 that threads onto the ball screw 103 is attached, moves up and down together with the rotating shaft 92 and the electric motor 93, so that the arm 72 attached to the upper end of the rotating shaft 92 and the transport pad 71 supported at the tip of the arm 72 rise and fall.

[0034] 2 and 3(a), the transport pad 71 is supported horizontally by three pins 74 on an annular retaining ring 73 attached to the tip of a horizontal arm 72, and is constantly urged downward by coil springs 75 compressed between the transport pad 71 and the arms 72 on the outer periphery of each pin 74. The transport pad 71 is made of a highly hydrophilic material such as titanium oxide, glass, or aluminum.

[0035] As shown in FIG. 3(b), an annular protrusion 71A is provided on the outer periphery of the lower surface of the transport pad 71, and a circular recess 71B is formed on the radially inner side of the annular protrusion 71A on the bottom surface of the transport pad 71. A ring-shaped suction groove 71a is formed on the annular protrusion 71A of the transport pad 71, and a plurality of circular hole-shaped suction ports 76 (only a portion of which is shown in FIG. 4) are opened in the suction groove 71a, as shown in FIG. 4. The suction groove 71a shown in FIG. 4 is connected to a plurality of horizontal suction paths 77 (only two of which are shown in FIG. 2) formed radially inside the transport pad 71, as shown in FIG. 2. The suction paths 77 are connected to a suction hole 78 formed vertically near the center of the transport pad 71, and one end of a pipe 79 is connected to the suction hole 78. The other end of the pipe 79 is connected to a suction source 80 via an electromagnetic on-off valve V4. The on-off valve V4 is electrically connected to the control unit 110, and its opening and closing operation is controlled by the control unit 110. The suction groove 71a formed in the annular convex portion 71A of the transport pad 71 and the multiple suction ports 76 opening into the suction groove 71a constitute a suction portion of the transport pad 71.

[0036] 2, a communication hole 81 is formed vertically in the center of the conveying pad 71, and one end (lower end) of the communication hole 81 opens as a circular pressure adjustment port 82 in the center of the circular recess 71B of the conveying pad 71 as shown in FIG. 3(b). One end of a pipe 83 is connected to the other end (upper end) of the communication hole 81, and two branch pipes 83a and 83b branch off from the other end of the pipe 83. Here, one branch pipe 83a is connected to an air supply source 84 via an electromagnetic on-off valve V5, and the other branch pipe 83b is connected to a suction source 86 via a pressure gauge 85, an electromagnetic pressure adjustment valve V, and an electromagnetic on-off valve V6. The on-off valves V4 to V6 and the pressure adjustment valve V are electrically connected to the control unit 110, and their opening and closing operations are controlled by the control unit 110. The pressure gauge 85 is also electrically connected to the control unit 110 , and the detection signal thereof is input to the control unit 110 .

[0037] <Second embodiment> Next, the configuration of the second conveying device 70A according to the second embodiment will be described below with reference to Figures 8 to 10. In Figures 8 to 10, the same elements as those shown in Figures 2 to 6 are denoted by the same reference numerals, and further description thereof will be omitted below.

[0038] In the second transport device 70A according to this embodiment, as shown in FIG. 8(b), a plurality of (four in the illustrated example) arc-shaped protrusions 71C are integrally formed in a ring shape on the outer periphery of the lower surface of the transport pad 71, and an arc-shaped suction port 76 is formed in each of the arc-shaped protrusions 71C. Note that a minute gap δ is formed between each of the adjacent arc-shaped protrusions. Note that, although the number of the arc-shaped protrusions 71C is four in this embodiment, the number of the arc-shaped protrusions 71C may be any number as long as it is more than one.

[0039] Also in this embodiment, as shown in FIG. 8(b), a circular recess 71B is formed in the central portion surrounded by the arc-shaped protrusion 71C on the underside of the transport pad 71, and a circular hole-shaped pressure adjustment port 82 opens in the center of this circular recess 71B.

[0040] 9 and 10, in the second transfer device 70A according to the present embodiment, another branch pipe 83c branches off from the piping 83, and this branch pipe 83c is connected to a water supply source 87 via an electromagnetic on-off valve V7. The on-off valve V7 is electrically connected to the control unit 110, and its opening and closing operation is controlled by the control unit 110.

[0041] (Control unit) The control unit 110 controls each of the components constituting the grinding apparatus 1, and includes a CPU (Central Processing Unit) that performs arithmetic processing according to a control program, and memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory). In particular, in this embodiment, as described later, the opening and closing of the pressure regulating valve V is controlled so that the pressure in the circular recess 71B of the transfer pad 71 detected by the pressure gauge 85 (the pressure in the space sealed by the wafer W in the circular recess 71B) becomes a predetermined value, and details of this will be described later.

[0042] [Function of grinding equipment] Next, the operation of the grinding device 1 configured as above will be described.

[0043] 1, the wafer W before grinding is taken out of the cassette 2. The wafer W taken out of the cassette 2 is aligned on the alignment table 3, and then sucked and held by the first transfer device 60 and transferred to the chuck table 10 waiting in the transfer area R2.

[0044] In the chuck table 10, the wafer W is placed with the protective tape T facing down on the holding surface of the chuck table 10. Then, the porous member 10A is evacuated by the suction source 11 shown in Fig. 5, generating a negative pressure in the porous member 10A, and the wafer W placed on the holding surface of the porous member 10A is sucked and held on the holding surface of the chuck table 10 by the negative pressure.

[0045] From the above state, the horizontal movement mechanism (not shown) is driven to move the chuck table 10 in the +Y-axis direction to the processing region R1 shown in Fig. 1, and the wafer W sucked and held on the chuck table 10 is positioned below the grinding wheel 25 of the grinding unit 20. Then, the rotation mechanism (not shown) is driven to rotate the chuck table 10 at a predetermined speed. At the same time, the spindle motor 22 of the grinding unit 20 is started to rotate the grinding wheel 25 at a predetermined speed.

[0046] As described above, while the wafer W and the grinding wheel 25 are rotating, the vertical movement mechanism 30 is started to lower the grinding wheel 25 in the -Z-axis direction. That is, when the electric motor 35 is started to rotate the ball screw 34, the lift plate 32 provided with a nut member (not shown) screwed to the ball screw 34 is lowered in the -Z-axis direction together with the holder 21, the grinding wheel 25, etc. Then, the lower surface (processing surface) of the grinding wheel 25a of the grinding wheel 25 comes into contact with the upper surface (back surface) of the wafer W. When the grinding wheel 25 is further lowered in the -Z-axis direction by a predetermined amount (grinding allowance) from the state in which the lower surface of the grinding wheel 25a comes into contact with the upper surface of the wafer W, the upper surface (back surface) of the wafer W is ground by the predetermined amount by the grinding wheel 25a. During the grinding process, a grinding fluid (pure water) is supplied from a grinding fluid supply source (not shown) to a contact portion (processing portion) between the grinding wheel 25a and the wafer W. The thickness of the wafer W during the grinding process is measured by a thickness gauge 8.

[0047] When the above-mentioned grinding process for the wafer W is completed, the vacuum pumping of the porous member 10A of the chuck table 10 is stopped, and air is supplied to the porous member 10A from the air supply source 12 shown in Fig. 2 in order to separate the wafer W from the chuck table 10. Then, the wafer W is separated from the chuck table 10, and the grinding fluid containing the grinding debris is sprayed out from the holding surface of the porous member 10A.

[0048] Here, the operation of the second conveying device 70 according to the first embodiment will be described below with reference to FIGS.

[0049] <Function of the second conveying device according to the first embodiment> As described above, when grinding of the wafer W held on the holding surface of the chuck table 10 is completed, the transport pad 71 is horizontally rotated by the rotating mechanism 90 of the second transport device 70 and positioned above the wafer W, as shown in Fig. 5, and then the transport pad 71 is lowered by the lifting mechanism 100, and the lower surface of the circular recess 71B protruding from the outer periphery of the lower surface of the transport pad 71 is pressed against the upper surface of the wafer W. Then, from this state, the on-off valve V4 is opened and the suction source 80 evacuates the multiple suction ports 76 of the transport pad 71. That is, since the air in the suction holes 78 and the suction path 77 of the transport pad 71 is sucked by the suction source 80 through the piping 79, a negative pressure is generated in the multiple suction ports 76 opening on the lower surface of the annular protrusion 71A of the transport pad 71, and the outer periphery of the upper surface of the wafer W is sucked and held by the transport pad 71 together with the protective tape T by the negative pressure. At this time, since the on-off valve V5 is closed, air is not supplied from the air supply source 84 to the circular recess 71B of the transport pad 71.

[0050] As described above, when the wafer W is held by suction at the outer periphery of its upper surface by the transport pad 71, the lifting mechanism 100 is driven to raise the transport pad 71, and the wafer W together with the transport pad 71 is moved away from the holding surface of the chuck table 10 and positioned above the holding surface as shown in Figure 6. In order to prevent the central portion of the wafer W from sagging due to its own weight, when the wafer W is held on the holding surface of the chuck table 10 as shown in Figure 5, the on-off valve V6 is opened, and a predetermined amount of air is sucked in from within the circular recess 71B of the transport pad 71, and the pressure in the circular recess 71B of the transport pad 71 is set to a predetermined value (negative pressure).

[0051] Here, as shown in FIG. 7, if the pressure (absolute pressure) inside the circular recess 71B of the transport pad 71 is p1, the atmospheric pressure is p0, and the weight of the wafer W (including the protective tape T) is G, then the downward force F1 acting on the wafer W and the upward force F2 acting on the wafer W are respectively expressed by the following equations. F1 = p1 · A + G … (1) F2 = p0 A …(2) Therefore, as shown in FIG. 6, when the wafer W held by the transport pad 71 is separated upward from the holding surface of the chuck table 10, in order to prevent the wafer W from sagging due to its own weight G, if we consider the wafer W to be a film with its outer periphery fixed, the absolute values ​​of the downward force F1 and upward force F2 acting on this film need to be equal (F1=F2).

[0052] That is, when the above condition is expressed using equations (1) and (2), it is expressed by the following equation. p1·A+G=p0·A …(3) Therefore, the pressure p1 (absolute pressure) in the circular recess 71B of the transport pad 71 can be calculated from equation (3) as follows: p1 = p0 - (G / A) … (4) As is clear from the above formula (4), if the pressure p1 (gauge pressure) in the circular recess 71B of the transport pad 71 is kept at a negative pressure of -(W / A), it is possible to prevent the central portion of the wafer W from sagging when the wafer W held by the transport pad 71 is separated from the holding surface of the chuck table 10 as shown in Fig. 6, and the wafer W can be held horizontally and transported. The control unit 110 controls the opening and closing of the pressure regulating valve V so that the pressure (gauge pressure) detected by the pressure gauge 85 becomes -(W / A), and adjusts the pressure p1 (absolute pressure) in the circular recess 71B of the transport pad 71 to the value calculated by formula (4).

[0053] When the wafer W is held by suction and transported by the transport pad 71, the on-off valve V6 is closed and the pressure p1 in the circular recess 71B of the transport pad 71 is maintained at the value p1 (absolute pressure) calculated by equation (4) as shown in Fig. 6. When the wafer W is transported to the spinner cleaning device 40 while maintaining this state and the wafer W is transferred to the spinner table 41, the on-off valve V5 is opened to supply air from the air supply source 84 into the circular recess 71B of the transport pad 71, as shown in Fig. 6, to release the suction of the wafer W by the transport pad 71 and make it easier for the wafer W to separate from the transport pad 71.

[0054] As described above, according to the second transport device 70 of the first embodiment, when the outer periphery of the upper surface of the wafer W is held by suction by the transport pad 71, the pressure p1 inside the circular recess 71B of the transport pad 71 (the sealed pressure created by the wafer W in the circular recess 71B) is set to a value calculated by equation (4) such that the absolute values ​​of the downward force F1 and upward force F2 acting on the wafer W are equal. This prevents the central portion of the wafer W from sagging, and enables the wafer W to be transported while being held horizontally.

[0055] <Function of the second conveying device according to the second embodiment> Next, the operation of the second transfer device 70A according to the second embodiment will be described.

[0056] As described above, when grinding of the wafer W held on the holding surface of the chuck table 10 is completed, as shown in Fig. 9, the transport pad 71 is horizontally rotated by the rotating mechanism 90 of the second transport device 70A to be positioned above the wafer W, and then the transport pad 71 is lowered by the lifting mechanism 100, and the lower surface of the arc-shaped convex portion 71C protruding from the outer periphery of the lower surface of the transport pad 71 is pressed against the upper surface of the wafer W. Then, from this state, the on-off valve V4 is opened to evacuate the multiple suction ports 76 of the transport pad 71 by the suction source 80, and the outer periphery of the wafer W is sucked and held by the transport pad 71, and at the same time, the on-off valve V7 is opened to supply water from the water supply source 87 to the circular recess 71B of the transport pad 71. Then, part of the water supplied into the circular recess 71B of the transport pad 71 leaks out from the minute gaps δ (see Fig. 8(b)) between the multiple arc-shaped convex portions 71C of the transport pad 71, as shown in Fig. 9. By continuing this process, the dirty water in the circular recess 71B of the transport pad 71 is replaced with clean water. Note that pure water is preferably used as the water.

[0057] As described above, when the water in the circular recess 71B of the transport pad 71 is replaced with clean water, the on-off valve V7 is closed to stop the supply of water into the circular recess 71B. Then, the circular recess 71B of the transport pad 71 is filled with water. That is, since minute gaps δ are formed between the multiple (four in this embodiment) arc-shaped protrusions 71C protruding from the outer periphery of the transport pad 71, the gaps δ are sealed by the surface tension of the water, and the outflow of water from the gaps δ is prevented.

[0058] As described above, when the outer periphery of the wafer W is suction-held by the transport pad 71 and the circular recess 71B of the transport pad 71 is filled with water, as shown in Fig. 10, the lifting mechanism 100 is driven to raise the transport pad 71, and the wafer W together with the transport pad 71 moves away from the holding surface of the chuck table 10 and is positioned above the holding surface. In this state, to prevent the wafer W from sagging due to its own weight and the weight of the water filled in the circular recess 71B of the transport pad 71, as shown in Fig. 9, while the wafer W is held on the holding surface of the chuck table 10, the on-off valve V6 is opened, and the water in the circular recess 71B of the transport pad 71 is sucked in by the suction source 86, and the pressure in the circular recess 71B of the transport pad 71 is set to a predetermined value (negative pressure).

[0059] Here, if the pressure (absolute pressure) inside the circular recess 71B of the transport pad 71 is p1, the atmospheric pressure is p0, the weight of the wafer W (including the protective tape T) is G, and the weight of the water inside the circular recess 71B is M, then the downward force F1 acting on the wafer W and the upward force F2 acting on the wafer W are respectively expressed by the following equations. F1=p1·A+G+M …(5) F2=p0·A …(6) Therefore, as shown in FIG. 10, when the wafer W held by the transport pad 71 is separated upward from the holding surface of the chuck table 10, in order to prevent the wafer W from sagging due to its own weight G and the weight M of the water, the absolute values ​​of the downward force F1 and the upward force F2 acting on the wafer W need to be equal (F1=F2).

[0060] That is, when the above condition is expressed using equations (5) and (6), it is expressed as follows. p1·A+G+M=p0·A …(7) Therefore, the pressure p1 (absolute pressure) in the circular recess 71B of the transport pad 71 can be calculated from equation (7) as follows: p1 = p0 - (G + M) / A … (8) It becomes.

[0061] As is clear from the above equation (8), by maintaining the pressure p1 (gauge pressure) within the circular recess 71B of the transport pad 71 at a negative pressure represented by -(G+M) / A, when the wafer W, whose outer periphery is held by suction by the transport pad 71, is separated from the holding surface of the chuck table 10, as shown in FIG. 10, it is possible to prevent the central portion of the wafer W from sagging, and the wafer W can be held and transported in a horizontal state.

[0062] Therefore, the second transport device 70A according to the second embodiment can achieve the same effects as the second transport device 70 according to the first embodiment, but in the second transport device 70A according to the second embodiment, the wafer W is transported with its upper surface (the surface to be ground) in contact with water, thereby preventing the upper surface from coming into contact with the air and drying out.

[0063] 6 or 10, the wafer W horizontally held by the conveying pad 71 is conveyed to the spinner cleaning device 40 shown in FIG. 1 and transferred to the spinner table 41 of the spinner cleaning device 40. In the spinner cleaning device 40, the spinner table 41 and the wafer W held by suction thereon rotate at a predetermined high speed, and cleaning water is sprayed from the cleaning water nozzle 42 toward the wafer W rotating at high speed, so that the upper surface (surface to be ground) of the wafer W is cleaned by the cleaning water, and foreign matter such as grinding chips attached to the upper surface of the wafer W is removed. The wafer W thus cleaned is held by suction by the robot hand 53 of the robot 50 shown in FIG. 1, conveyed to the cassette 2, and stored in the cassette 2, completing a series of grinding processes for the wafer W. Pure water is preferably used as the cleaning water.

[0064] Although the above describes an embodiment in which the present invention is applied to the second transport device 70 (70A) provided in the grinding device 1 for wafers W, the present invention can be similarly applied to a transport device provided in any processing device other than the grinding device 1, such as a polishing device or a cutting device.

[0065] In addition, the present invention is not limited to the application of the embodiments described above, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0066] 1: grinding device, 2: cassette, 3: alignment table, 4: piping, 4a to 4c: piping 5 to 7: flow rate control valve, 8: thickness measuring instrument, 8a: first probe, 8b: second probe, 10: chuck table, 10A: porous member, 11: suction source, 12: air supply source, 13: water supply source, 14: rotating shaft, 15, 16: piping, 20: grinding unit, 21: holder, 22: spindle motor, 23: spindle, 24: mount, 25: grinding wheel, 25a: grinding stone, 30: vertical movement mechanism, 31: column, 32: lift plate, 33: guide rail, 34: ball screw, 35: electric motor, 36: bracket, 40: spinner cleaning device, 41: spinner table, 42: cleaning water nozzle; 43: cover; 50: robot; 51: mounting part; 52: holder; 53: robot hand, 54: lifting mechanism, 60: first conveying device, 70, 70A: second conveying device, 71: conveying pad, 71A: annular convex portion, 71B: circular recess, 71C: arc-shaped protrusion, 71a: suction groove, 72: arm, 73: retaining ring, 74: pin, 75: coil spring, 76: suction port, 77: Suction path, 78: Suction hole, 79: Piping, 80: Suction source, 81: Communication hole, 82: pressure adjustment port, 83: piping, 83a to 83c: branch pipes, 84: air supply source, 85: pressure gauge, 86: suction source, 87: water supply source, 90: turning mechanism, 91: sleeve, 92: Rotating shaft, 93: Electric motor, 100: Lifting mechanism, 101: Column, 102: guide rail, 103: ball screw, 104: electric motor, 105: encoder; 106: slider; 107: nut member; 110: control unit; A: pressure-receiving area of ​​the wafer, G: weight of the wafer, M: weight of water, p1: pressure inside the circular recess of the transport pad, p2: atmospheric pressure R1: Processing area R2: Delivery area, T: Protective tape, V: Pressure adjustment valve, V1 to V7: On-off valve, W: Wafer

Claims

1. A transfer apparatus that transfers a wafer from a first position to a second position by suction holding the wafer with a transfer pad, A ring-shaped suction portion for sucking the outer periphery of the upper surface of the wafer, a circular recess on the inside of the suction portion, and a pressure adjustment port opening into the circular recess are formed on the lower surface of the transfer pad, a pressure gauge and a pressure regulating valve are provided in a communication passage that communicates between the pressure regulating port and a suction source; a control unit that controls the pressure regulating valve to set the pressure in the circular recess blocked by the wafer to a value such that the downward force and upward force acting on the wafer are equal when the wafer is held by the suction unit and transported.

2. a water supply source that supplies water to the circular recess, and an on-off valve that is disposed in a water supply passage that connects the water supply source to the pressure regulating port, 2. The transport device according to claim 1, wherein the control unit, when transporting the wafer by suction holding with the suction unit while opening the on-off valve to supply water to the circular recess, controls the pressure adjustment valve to set the pressure in the circular recess blocked by the wafer to a value such that the downward force and upward force acting on the wafer are equal.

3. 3. The conveying device according to claim 1, wherein the suction section is composed of a ring-shaped suction groove and a plurality of suction ports opening into the suction groove.

4. 4. The conveying device according to claim 3, wherein the suction ports are arranged in a ring shape at equal intervals in the circumferential direction.

5. 5. The transport device according to claim 4, wherein the control unit supplies water to the circular recess while holding the wafer by suction through the plurality of suction ports, causes the water to flow out from gaps between the suction ports adjacent in the circumferential direction, and then controls the pressure adjustment valve to set the pressure in the circular recess filled with water to a value such that the downward force and upward force acting on the wafer are equal.

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