Conveyor pad

Abstract

To provide a carrier pad that can stably transport a fragile wafer by preventing a problem due to wafer sagging or wafer breakage.SOLUTION: A carrier pad (40, 70) that sucks and holds the top surface (92) of a fragile wafer (90) and transports it to a chuck table (14) includes a central suction portion (44) that suctions and holds the central portion of the wafer, a ring-shaped peripheral suction portion (45, 71) that sucks and holds the outer circumference of the wafer, a plate (41) on which the central suction portion and the peripheral suction portion are arranged, and an atmosphere opening area (50, 72) that exposes the upper surface of the wafer that is not sucked by the central suction portion and the peripheral suction portion to the atmosphere.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a transfer pad.

Background Art

[0002] A grinding apparatus for grinding a wafer held on a chuck table with a grindstone includes a transfer mechanism that sucks and holds the upper surface of the wafer with a transfer pad and transfers it to the chuck table.

[0003] The wafer processed by the grinding apparatus may be warped. The holding surface of the chuck table of the grinding apparatus has a conical shape that becomes higher from the outer peripheral side toward the center. In the state where the wafer is warped, it cannot be reliably held on the chuck table.

[0004] [[ID=I9]] To solve this problem, in the invention described in Patent Document 1, a transfer mechanism is used that combines a transfer pad that sucks and holds only the central portion of the wafer and an annular pressing member that presses the outer peripheral portion of the wafer. In this transfer mechanism, the wafer is transferred to the chuck table while sucking and holding the central portion of the wafer with the transfer pad, and the wafer is held on the chuck table while pressing the outer peripheral portion of the wafer with the pressing member to correct the warp.

[0005] There is a method of processing a wafer in which a condensing point of a laser beam is positioned inside the surface side of the wafer, a modified layer is formed inside along a street (division planned line), and then the back surface side of the wafer is ground (for example, Patent Document 2).

[0006] Also, there is a method of processing a wafer in which a cutting groove that does not penetrate from the surface side to the back surface of the wafer is formed using a cutting blade, and then the back surface side of the wafer is ground to expose the cutting groove and the wafer is diced into a plurality of devices (for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-098073 [Patent Document 2] Japanese Patent Publication No. 2006-012902 [Patent Document 3] Japanese Patent Publication No. 2003-007653 [Overview of the project] [Problems that the invention aims to solve]

[0008] Wafers with modified layers or cutting grooves formed as described above are fragile wafers that are easily fractured along the modified layers or cutting grooves, and require care during transportation.

[0009] For example, a wafer with a modified layer formed on it tends to have a curved shape where one side is concave (concave towards the center) and the other side is convex (convex towards the center). The transport pad of Patent Document 1, which has a configuration that holds only the central part by suction, can hold wafers with such a curved shape.

[0010] However, wafers with a modified layer are prone to cleavage along the modified layer. Therefore, when the wafer is being transported by suction holding only the central part, vibrations and gravity can apply force, potentially causing the wafer to cleave along the modified layer. If cleavage occurs in an area not held by the transport pad (outside the central part), the outer edge of the wafer will sag, making it impossible to properly transfer the wafer to the chuck table and hold it by suction.

[0011] Furthermore, to prevent the outer edge of the wafer from sagging, it is conceivable to use a transport pad that uses a suction surface to hold the entire top surface of the wafer. However, when the entire top surface of the wafer is held by suction, the curved wafer becomes flat, but at that time, the force that flattens the wafer may cause it to break along the modified layer. If this occurs, debris will be generated when the wafer breaks, and this debris will adhere to the suction surface of the transport pad, and when the next wafer is sucked up, the debris will come into contact with the chip on the wafer, causing chipping at the corners of the chip.

[0012] This invention has been made in view of the above, and aims to provide a transport pad that can stably transport fragile wafers by preventing defects such as wafer sagging and wafer breakage. [Means for solving the problem]

[0013] One aspect of the present invention is a transport pad for suction-holding the upper surface of a fragile wafer and transporting it to a chuck table, comprising: a central suction section for suction-holding the central portion of the wafer; a ring-shaped outer suction section for suction-holding the outer periphery of the wafer; a plate on which the central suction section and the outer suction section are arranged; and an atmospheric release area for releasing the upper surface of the wafer that is not being suctioned by the central suction section and the outer suction section to the atmosphere.

[0014] The outer peripheral suction portion protrudes downward from the lower surface of the plate and extends in a circular arc in the circumferential direction, and comprises multiple circular arc annular portions arranged in the circumferential direction, an outer peripheral suction port that opens inside the circular arc annular portion to the lower surface of the plate and can communicate with a suction source, and an outer peripheral suction passage that connects the outer peripheral suction port to a suction source.

[0015] The central suction section is, The plate comprises a central suction port opening on its lower surface and communicating with a suction source, an annular portion disposed on the lower surface of the plate surrounding the central suction port and in contact with the upper surface of the wafer to apply suction force to the center of the wafer, and a contact portion disposed on the lower surface of the plate inside the annular portion and in contact with the upper surface of the wafer, wherein the contact portion suppresses deformation of the center of the wafer. ru. [Effects of the Invention]

[0016] According to the transfer pad of the present invention, by sucking and holding the upper surface of the wafer by the central suction portion and the outer peripheral suction portion, it is possible to prevent the sagging of the outer peripheral portion and the central portion of the wafer. Further, since the portions other than the central suction portion and the outer peripheral suction portion of the transfer pad are made into an air release area, it is possible to suppress the cutting of the wafer, and even if the wafer is cut within the range of the air release area, chips are hardly attached to the transfer pad. Therefore, it is possible to obtain a transfer pad that can stably transfer a fragile wafer by preventing problems caused by the sagging of the wafer and the cutting of the wafer.

Brief Description of Drawings

[0017] [Figure 1] It is a perspective view showing a grinding device. [Figure 2] It is a perspective view of the transfer pad of the first embodiment as seen from above. [Figure 3] It is a perspective view of the transfer pad of the first embodiment as seen from below. [Figure 4] It is a cross-sectional view of the transfer pad of the first embodiment. [Figure 5] It is a cross-sectional view showing a state where a wafer is placed on a temporary table. [Figure 6] It is a cross-sectional view showing a state where a transfer pad is pressed against a wafer on a temporary table. [Figure 7] It is a cross-sectional view showing a state where a wafer sucked and held by a transfer pad is being transferred. [Figure 8] It is a cross-sectional view showing a state where a wafer is transferred from a transfer pad to a chuck table. [Figure 9] It is a perspective view of the transfer pad of the second embodiment as seen from above. [Figure 10] It is a perspective view of the transfer pad of the second embodiment as seen from below. [Figure 11] It is a cross-sectional view showing a process of forming a modified layer on a wafer. [Figure 12] It is a cross-sectional view showing a state where a modified layer is formed on a wafer. [Figure 13] It is a perspective view of a wafer on which a modified layer is formed. [Modes for carrying out the invention]

[0018] The transport pad according to this embodiment will be described below with reference to the attached drawings. Figure 1 shows a grinding apparatus that transports wafers using a transport pad. Figures 2 to 4 show the configuration of the transport pad according to the first embodiment. Figures 5 to 8 show the operation of transporting a wafer to a chuck table using the transport pad according to the first embodiment. Figures 9 and 10 show the configuration of the transport pad according to the second embodiment. Figures 11 to 13 show the process of forming a modified layer on a wafer and the wafer with the modified layer formed on it.

[0019] The grinding apparatus 1 shown in Figure 1 is an example of a processing apparatus equipped with a transport pad. The grinding apparatus 1 performs grinding on a fragile wafer 90 that is prone to cracking due to external force. First, the fragile wafer 90 will be described with reference to Figures 11 to 13.

[0020] The wafer 90 is a semiconductor wafer made of, for example, silicon, and has a front surface 91 and a back surface 92. On the front surface 91 side of the wafer 90, an electronic device chip 94 is formed in multiple regions demarcated by a grid of multiple division lines 93 (see Figure 13). A protective tape 95 is attached to cover the entire front surface 91 of the wafer 90.

[0021] A modified layer 96 is formed on the wafer 90 by the laser processing apparatus 80. As shown in Figure 11, the laser processing apparatus 80 includes a chuck table 81 for holding the wafer 90 by suction, and a laser irradiation unit 82 for irradiating the wafer 90 on the chuck table 81 with a laser beam L. The chuck table 81 is capable of horizontal movement and rotation around an axis that faces vertically. The laser irradiation unit 82 is equipped with a focuser 83 for focusing and irradiating the wafer 90 with a laser beam L emitted from a laser light source (not shown). The laser beam L is a pulsed laser beam that is penetrating to the material of the wafer 90.

[0022] In the modified layer formation process performed by the laser processing apparatus 80, the wafer 90 is held with the protective tape 95 (front surface 91) side resting on the holding surface of the chuck table 81 (see Figure 11). In other words, the wafer 90 is held with its back surface 92 facing upwards. A suction source (not shown) communicating with a suction hole on the holding surface of the chuck table 81 is activated to hold the wafer 90 in place by suction to the holding surface of the chuck table 81. An imaging device or the like is used to detect the division line 93 formed on the wafer 90, and the laser beam irradiation position is aligned so that the laser beam L can be irradiated along the division line 93.

[0023] One end of a predetermined division line 93 from among multiple division lines 93 is positioned directly below the focuser 83 of the laser irradiation unit 82 (see Figure 11). Then, the focal point P of the laser beam L irradiated from the focuser 83 is aligned to a predetermined position inside the thickness of the wafer 90.

[0024] Next, while irradiating the focal point P in the wafer 90 with a laser beam L from the focuser 83 of the laser irradiation unit 82, the chuck table 81 is moved in the feed direction M at a predetermined feed speed. As shown in Figure 12, when the irradiation position from the focuser 83 of the laser irradiation unit 82 reaches the other end of the division line 93, the irradiation of the laser beam L from the laser irradiation unit 82 is stopped, and the movement of the chuck table 81 in the feed direction M is stopped.

[0025] As a result, a modified layer 96 is formed inside the wafer 90 along the planned division line 93. Modification means that the density, refractive index, mechanical strength, and other physical properties inside the wafer 90 become different from the surrounding area due to irradiation with the laser beam L. As a result of modification, the modified layer 96 becomes a region with lower strength than the surrounding area.

[0026] Once a modified layer 96 is formed along one planned division line 93, the relative positions of the chuck table 81 and the laser irradiation unit 82 are changed so that one end of the next planned division line 93 is positioned directly below the concentrator 83 of the laser irradiation unit 82. Then, a modified layer 96 is formed along the next planned division line 93. In this way, by forming a modified layer 96 along all the grid-like planned division lines 93, the wafer 90 shown in Figure 13 is obtained. When a predetermined external force is applied to the wafer 90 in this state, it is fractured along the planned division lines 93 whose strength has been reduced by the modified layer 96, and fragmented into sections containing individual chips 94. In other words, the wafer 90 becomes fragile and easily fractured.

[0027] The modified layer 96 is formed inside the wafer 90 near the surface 91 on which devices such as the chip 94 are formed. Therefore, the vulnerable wafer 90 has a convex shape on the surface 91 side (convex in the center) and a concave shape on the back surface 92 side (concave in the center) (see Figure 5).

[0028] It should be noted that the formation of a fragile wafer is not limited to the processing methods described above. For example, in addition to forming the modified layer 96 by irradiation with a laser beam L, a half-cut process may be performed using a cutting blade to form cutting grooves on the surface side of the wafer that do not penetrate to the back side. By forming cutting grooves along all planned division lines 93 using the half-cut process, a fragile wafer that is easily fractured along the planned division lines 93 is obtained.

[0029] The fragile wafer 90, which has undergone the modified layer formation process in the laser processing apparatus 80, is transported to the grinding apparatus 1 shown in Figure 1, where its back surface 92 is ground until it reaches a predetermined thickness. The grinding apparatus 1 is configured to perform a series of operations on the wafer 90, which is the workpiece, in a fully automated manner, consisting of loading, grinding, cleaning, and unloading. The wafer 90 is loaded into the grinding apparatus 1 while contained in cassette C.

[0030] In the grinding device 1, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other. The X-axis and Y-axis directions are approximately horizontal, while the Z-axis direction is vertical. Of the two arrows indicating the X-axis direction, the side with the letter X is considered the front, and the side without the letter X is considered the rear. Of the two arrows indicating the Y-axis direction, the side with the letter Y is considered the left, and the side without the letter Y is considered the right. Of the two arrows indicating the Z-axis direction, the side with the letter Z is considered the top, and the side without the letter Z is considered the bottom.

[0031] A cassette C capable of accommodating multiple wafers 90 is placed on the front side of the base 10 of the grinding apparatus 1. Behind the cassette C is a robot hand 11 for loading and unloading wafers 90 into and out of the cassette C. To the left and right and diagonally behind the robot hand 11 are a temporary storage table 12 for placing wafers 90 before processing and a spin cleaning mechanism 13 for cleaning processed wafers 90 (ground wafers 90).

[0032] The robot hand 11 is configured with a hand section 112 at the tip of an arm section 111 consisting of a multi-bar link. The robot hand 11 transports the wafers 90 before processing from the cassette C to the temporary storage table 12, and also transports the processed wafers 90 from the spin cleaning mechanism 13 back to the cassette C.

[0033] The wafer 90, transported to the temporary storage table 12 by the robot hand 11, is positioned so that its center aligns with the center of the temporary storage table 12.

[0034] The spin cleaning mechanism 13 is equipped with nozzles 132 that spray cleaning water and drying air toward the spinner table 131. In the spin cleaning mechanism 13, cleaning water is sprayed from the nozzles 132 toward the wafer 90 held on the spinner table 131 to clean the wafer 90, and after cleaning, drying air is blown from the nozzles 132 to dry the wafer 90.

[0035] Between the temporary storage table 12 and the spin cleaning mechanism 13 in the Y-axis direction, there is a first transport mechanism 15 for transporting the wafer 90 before processing from the temporary storage table 12 to the chuck table 14, and a second transport mechanism 16 for transporting the processed wafer 90 from the chuck table 14 to the spin cleaning mechanism 13. The first transport mechanism 15 and the second transport mechanism 16 are each equipped with a transport pad 40 for suction and holding the wafer 90. The detailed configuration of the first transport mechanism 15 and the second transport mechanism 16, including the transport pad 40, will be described later.

[0036] A rectangular opening extending in the X-axis direction is formed on the upper surface of the base 10 at the rear of the grinding device 1. This opening is covered by a movable plate 17 that can move in the X-axis direction together with the chuck table 14 and a bellows-shaped waterproof cover 18. Below the waterproof cover 18 is a table moving mechanism (not shown) that moves the chuck table 14 in the X-axis direction. The table moving mechanism is equipped with a ball screw that extends in the X-axis direction, and when the ball screw is rotated, the movable plate 17 moves back and forth in the X-axis direction.

[0037] The chuck table 14 is connected to a table rotation mechanism (not shown), and can rotate about an axis facing the Z-axis direction by the drive of the table rotation mechanism. As shown in Figure 8, the chuck table 14 comprises a frame 141 and a disc-shaped porous plate 142 mounted in a recess on the upper side of the frame 141.

[0038] The porous plate 142 is made of a porous material such as ceramics, and fine pores are formed throughout its entire surface. When the porous plate 142 is fitted into the recess of the frame 141, the upper surface of the frame 141 and the upper surface of the porous plate 142 become flush. The upper surface of the porous plate 142 constitutes a holding surface 143 that holds the wafer 90 by suction. The holding surface 143 has a conical shape that becomes higher from the radial outer edge towards the center.

[0039] A flow path 144 is formed in the frame 141, which communicates with the porous plate 142. The flow path 144 is connected to the suction source 20, the air supply source 21, and the water supply source 22 via on / off valves 201, 211, and 221.

[0040] When the on / off valve 201 is opened and the suction source 20 is activated, air is drawn in from the porous plate 142 side via the flow path 144, and the wafer 90 can be held in place from below by the suction force acting on the holding surface 143.

[0041] When the on / off valve 211 is opened and the air supply source 21 is activated, air supplied via the flow path 144 is ejected from the holding surface 143. When the on / off valve 221 is opened and the water supply source 22 is activated, water supplied via the flow path 144 is ejected from the holding surface 143. It is also possible to activate the air supply source 21 and the water supply source 22 simultaneously to eject a mixed fluid of air and water from the holding surface 143.

[0042] A column 23 erected at the rear of the base 10 is provided with a lifting mechanism 25 that moves the grinding mechanism 24 closer to and further away from the chuck table 14 in the Z-axis direction.

[0043] The lifting mechanism 25 includes a pair of parallel guide rails 251 positioned on the front side of the column 23 and extending in the Z-axis direction, a lifting table 252 slidably mounted on the pair of guide rails 251 in the Z-axis direction, and a ball screw 253 extending in the Z-axis direction and screwed into a threaded portion (not shown) of the lifting table 252. The ball screw 253 is rotated by the driving force of a motor 254 connected to one end of the ball screw 253, causing the lifting table 252 to move in the Z-axis direction.

[0044] The grinding mechanism 24 is mounted to the front of the lifting table 252 via a housing 241 and is configured to rotate the grinding wheel 243 with a spindle unit 242. The spindle unit 242 is, for example, an air spindle, which rotatably supports the spindle shaft 244 inside the casing via high-pressure air. The spindle shaft 244 is a shaft body extending in the Z-axis direction.

[0045] A mount 245 is connected to the tip (lower end) of the spindle shaft 244, and a grinding wheel 243 is mounted on the mount 245. Multiple grinding wheels 246 are arranged in an annular pattern on the lower surface of the grinding wheel 243. The grinding mechanism 24 grinds the back surface 92 of the wafer 90, which is held by suction on the chuck table 14, using the grinding wheels 246.

[0046] The grinding apparatus 1 is equipped with a control unit 30 that centrally controls each part of the apparatus. The control unit 30 consists of a processor, memory, etc., which execute various processes. For example, the control unit 30 controls the grinding feed amount and grinding feed speed of the grinding mechanism 24 in the Z-axis direction, the rotation speed of the grinding wheel 243, etc., and performs grinding until the thickness of the wafer 90 reaches the finish thickness. The control unit 30 also controls the transport operation of the wafer 90 by the robot hand 11, the first transport mechanism 15, and the second transport mechanism 16, as well as the cleaning operation of the wafer 90 by the spin cleaning mechanism 13.

[0047] In the operation of each part of the grinding apparatus 1 described below, unless the primary control entity is specified, it shall be assumed that the operation is controlled by control signals sent from the control unit 30.

[0048] In the grinding apparatus 1 configured as described above, the robot hand 11 transports the wafer 90 (with a modified layer 96 formed by the laser processing apparatus 80) from the cassette C to the temporary storage table 12. Subsequently, with the back surface 92 of the wafer 90 held by the transport pad 40 of the first transport mechanism 15, the wafer 90 is loaded from the temporary storage table 12 onto the chuck table 14 by the first transport mechanism 15. When the wafer 90 is handed over from the transport pad 40 of the first transport mechanism 15, the chuck table 14 is positioned near the first transport mechanism 15 (closer to the front in the X-axis direction) by the movement of the moving plate 17.

[0049] As shown in Figure 8, the wafer 90 transported by the first transport mechanism 15 is placed on the holding surface 143 of the chuck table 14 with the modified layer 96 (surface 91) facing downwards and the back surface 92 facing upwards. In other words, during processing in the grinding apparatus 1, the protective tape 95 is on the bottom surface and the back surface 92 is on the top surface. The on / off valve 201 is opened and the suction source 20 communicates with the flow path 144, and a suction force acts on the holding surface 143 of the chuck table 14. This suction force causes the wafer 90 to be held in place on the holding surface 143.

[0050] The chuck table 14, which holds the wafer 90 by suction, is moved to the rear in the X-axis direction by the table moving mechanism and positioned below the grinding mechanism 24. Next, the grinding mechanism 24 is lowered by the lifting mechanism 25 to bring the grinding wheel 246 into contact with the back surface 92 of the wafer 90, and the grinding wheel 243 is rotated by the spindle unit 242 to grind the back surface 92 of the wafer 90 while pressing it with the grinding wheel 246. When the back surface 92 of the wafer 90 is ground to the desired thickness, the rotation of the grinding wheel 243 is stopped, and the grinding mechanism 24 is raised by the lifting mechanism 25 to separate the grinding wheel 246 from the wafer 90 on the chuck table 14, and the grinding process is completed.

[0051] After grinding, the chuck table 14 is moved forward in the X-axis direction by the table moving mechanism, positioning it at a transfer position near the second transport mechanism 16. The on / off valve 201 is closed, disconnecting it from the suction source 20, preventing suction force from acting on the wafer 90 from the holding surface 143 of the chuck table 14, and enabling the wafer 90 to be transferred from the chuck table 14 to the transport pad 40 of the second transport mechanism 16.

[0052] With the back surface 92 of the wafer 90 being held by the transport pad 40 of the second transport mechanism 16, the air supply source 21 is activated and the on / off valve 211 is opened to supply air from the holding surface 143 of the chuck table 14 toward the underside of the wafer 90 (protective tape 95). Alternatively, the water supply source 22 may be activated and the on / off valve 221 may be opened to supply water from the holding surface 143 of the chuck table 14 toward the underside of the wafer 90 (protective tape 95). As a result, the pressure of the mixed fluid of air and water from the holding surface 143 side pushes up the wafer 90, causing it to separate from the holding surface 143.

[0053] The second transport mechanism 16 removes the wafer 90 from the chuck table 14 and transports the wafer 90 to the spin cleaning mechanism 13. When the wafer 90 is placed on the spinner table 131, the second transport mechanism 16 terminates its suction holding of the wafer 90 by the transport pad 40, and the wafer 90 is transferred from the second transport mechanism 16 to the spin cleaning mechanism 13. The wafer 90 is then cleaned in the spin cleaning mechanism 13.

[0054] Next, the cleaned wafer 90 is removed from the spinner table 131 by the robot hand 11 and placed in cassette C. Although only one cassette C is shown in Figure 1, separate cassettes C may be provided: one for storing the wafer 90 before processing and another for storing the wafer 90 after processing.

[0055] Incidentally, as shown in Figure 5, the wafer 90 on which the modified layer 96 is formed has a curved shape with a concave (concave in the center) shape on the back surface 92 side and a convex (convex in the center) shape on the front surface 91 and protective tape 95 side. In other words, when the wafer 90 is with the front surface 91 facing downwards, the outer circumference tends to curl upwards. Furthermore, the wafer 90 on which the modified layer 96 is formed has a vulnerability that makes it easy to cleave along the modified layer 96 (planned division line 93) when external force is applied. The first transport mechanism 15 and the second transport mechanism 16 in the grinding apparatus 1 of this embodiment are equipped with transport pads 40 that can stably hold the wafer 90 with these characteristics and transport it while suppressing sagging and cleavage. The first transport mechanism 15 will be described in detail below, but the second transport mechanism 16 has a similar configuration to the first transport mechanism 15.

[0056] The transport pad 40 is a transport pad according to a first embodiment to which the present invention is applied. As shown in Figures 2 to 4, the transport pad 40 has a disc-shaped plate 41.

[0057] As shown in Figure 2, a cylindrical portion 42 protruding upward is provided in the center of the upper surface 411 of the plate 41. In addition, three slide shafts 43 are provided on the upper surface 411 of the plate 41, arranged to surround the cylindrical portion 42.

[0058] As shown in Figure 3, the lower surface 412 of the plate 41 is provided with a central suction section 44 that holds the central portion of the wafer 90 by suction, and a ring-shaped outer periphery suction section 45 that holds the outer periphery of the wafer 90 by suction. The central suction section 44 is located in the center of the lower surface 412, and the outer periphery suction section 45 is located on the outer periphery (outer edge) of the lower surface 412.

[0059] The central suction section 44 has a central suction port 441 that opens downward, and is provided with a plurality of cylindrical contact portions 442 concentrically surrounding the central suction port 441, and an annular portion 443 on the outside of the contact portions 442. In this embodiment, a double contact portion 442 is provided. The contact portions 442 and the annular portion 443 are made of a material such as rubber that is elastically deformable and blocks the passage of air.

[0060] The outer periphery suction portion 45 is provided by dividing the plate 41 into four arc-shaped regions in the circumferential direction. Each region of the outer periphery suction portion 45 has an outer periphery suction port 451 that opens downward and an arc-shaped annular portion 452 that surrounds the outer periphery suction port 451. The arc-shaped annular portion 452 protrudes downward from the lower surface 412 of the plate 41 and extends in the circumferential direction in an arc-shaped annular shape, and is a protruding portion that surrounds the inner circumferential side, outer circumferential side, and both ends in the circumferential direction of the outer periphery suction port 451. In other words, multiple (four) arc-shaped annular portions 452 that extend in the circumferential direction of the plate 41 are arranged, and an outer periphery suction port 451 that opens to the lower surface 412 of the plate 41 is formed inside each arc-shaped annular portion 452. The arc-shaped annular portions 452 are made of a material such as rubber that is elastically deformable and blocks the passage of air.

[0061] The lower surfaces (tips) of the contact portion 442 and the annular portion 443 and the lower surface (tips) of the arc-shaped annular portion 452 are located in approximately the same position in the Z-axis direction.

[0062] As shown in Figure 4, a central suction passage 46 and an outer peripheral suction passage 47 are formed inside the plate 41. The central suction passage 46 communicates with a suction passage 421 formed inside the cylindrical portion 42 and extending in the Z-axis direction, and a central suction port 441 is formed at the lower end of the central suction passage 46. The outer peripheral suction passage 47 extends radially from the suction passage 421 toward the outer circumference of the plate 41, and the tip of the outer peripheral suction passage 47 bends downward and communicates with the outer peripheral suction port 451. The outer peripheral suction passage 47, together with the outer peripheral suction port 451 and the arc-shaped annular portion 452, constitute the outer peripheral suction portion 45.

[0063] The suction passage 421 is connected to the suction source 48 via an on / off valve 481 and to the air supply source 49 via an on / off valve 491. By opening the on / off valve 481, the central suction port 441 and the outer suction port 451 are connected to the suction source 48. By opening the on / off valve 491, the central suction port 441 and the outer suction port 451 are connected to the air supply source 49. When the suction source 48 is driven with the on / off valve 481 open, air is drawn in from the central suction port 441 and the outer suction port 451 towards the central suction passage 46 and the outer suction passage 47. When the air supply source 49 is driven with the on / off valve 491 open, air is ejected from the central suction port 441 and the outer suction port 451 via the central suction passage 46 and the outer suction passage 47.

[0064] On the lower surface 412 side of plate 41, an atmospheric release area 50 is formed in the region between the central suction portion 44 and the outer peripheral suction portion 45. As shown in Figure 3, the atmospheric release area 50 is a region enclosed by the lower surface 412 of plate 41, the outer peripheral surface of the annular portion 443, and the inner peripheral surface of the arc-shaped annular portion 452. The atmospheric release area 50 is connected to the atmosphere on the outer peripheral side of plate 41 through the gaps 51 between the arc-shaped annular portions 452, which are divided into four sections in the circumferential direction.

[0065] With the central suction section 44 and the outer peripheral suction section 45 in contact with the wafer 90 (Figures 6 to 8), the atmospheric release area 50 is separated from the central suction port 441 and the outer peripheral suction port 451 by the annular section 443 and the arc-shaped annular section 452. Therefore, when air is drawn in from the central suction port 441 and the outer peripheral suction port 451, the wafer 90 is drawn in only at the locations of the central suction section 44 and the outer peripheral suction section 45, and no suction force acts on the atmospheric release area 50. Furthermore, since the atmospheric release area 50 is connected to the atmosphere through the gap 51, even if there is some leakage of suction force from the central suction port 441 and the outer peripheral suction port 451, the internal pressure of the atmospheric release area 50 does not change significantly, and the state in which no suction force acts on the atmospheric release area 50 can be maintained.

[0066] The first transport mechanism 15 includes a moving mechanism 60 that moves the transport pad 40. The movement of the transport pad 40 performed by the moving mechanism 60 consists of a vertical movement in the Z-axis direction and a rotational movement about a vertical axis extending in the Z-axis direction. The rotational movement performed by the moving mechanism 60 allows the transport pad 40 to be moved to a position above the temporary storage table 12 and to a position above the chuck table 14 (the chuck table 14 at the front transfer position in the X-axis direction). In addition, the vertical movement performed by the moving mechanism 60 allows the transport pad 40 to be moved closer to or further away from the temporary storage table 12 and the chuck table 14 in the Z-axis direction.

[0067] The moving mechanism 60 includes an arm 61 that supports the transport pad 40. The arm 61 extends horizontally, and a ring portion 611 is provided at the tip of the arm 61, surrounding the cylindrical portion 42 of the transport pad 40 (see Figure 2). Three through holes 612 (only two are shown in Figures 4 to 8) are formed in the ring portion 611, penetrating in the Z-axis direction. The three through holes 612 are arranged at approximately equal intervals in the circumferential direction centered on a vertical axis passing through the center of the transport pad 40. A slide shaft 43 passes through each through hole 612. The upper end of the slide shaft 43 has a large diameter head 431, and the head 431 can contact the upper surface of the ring portion 611.

[0068] A cylindrical coil spring 62 is positioned between the upper surface 411 of the plate 41 on the transport pad 40 and the lower surface of the ring portion 611 on the arm 61, surrounding each slide shaft 43. Each coil spring 62 biases the transport pad 40 downward relative to the arm 61, pressing the head 431 of the slide shaft 43 against the upper surface of the ring portion 611. This holds the transport pad 40 in a fixed position in the Z-axis direction relative to the arm 61. Furthermore, when the transport pad 40 receives downward pressure, it is possible for the transport pad 40 to move closer to the arm 61 (upward) while the coil spring 62 is contracted.

[0069] An arm support portion 63 extending in the Z-axis direction is connected to the end of the arm 61 opposite to the ring portion 611. The arm support portion 63 is moved up and down in the Z-axis direction by a lifting drive unit. As shown in Figures 5 to 8, the lifting drive unit comprises a guide portion 64, a ball screw 65, a motor 66, and an encoder 67.

[0070] The guided portion 631 of the arm support portion 63 is supported so as to be movable in the Z-axis direction relative to the guide portion 64 which extends in the Z-axis direction. The threaded portion 632 of the arm support portion 63 is screwed onto a ball screw 65 which extends in the Z-axis direction. The ball screw 65 rotates due to the driving force of a motor 66 connected to one end of the ball screw 65. When the ball screw 65 rotates and force is applied to the threaded portion 632, the arm support portion 63 moves along the guide portion 64 in the Z-axis direction.

[0071] The driving direction and amount of the motor 66 are detected via the encoder 67. The detection signal from the encoder 67 is input to the control unit 30.

[0072] Referring to Figures 5 to 8, the transport of the wafer 90 by the first transport mechanism 15 equipped with a transport pad 40 will be described. This transport is the operation from placing the wafer 90 on the temporary storage table 12 to transferring it to the chuck table 14.

[0073] As shown in Figure 5, the wafer 90 is placed on the temporary placement table 12 with the surface 91 to which the protective tape 95 is attached facing downwards and the back surface 92 facing upwards. The wafer 90 on which the modified layer 96 is formed has a curved shape with a concave back surface 92 side and a convex front surface 91 (protective tape 95) side, and the outer circumference curves upwards.

[0074] The transport pad 40 is positioned above the temporary storage table 12 on which the wafer 90 is placed. Then, the motor 66 of the moving mechanism 60 is driven to rotate the ball screw 65, moving the arm 61 and arm support 63 downward. This movement causes the transport pad 40 to descend and approach the back surface 92 of the wafer 90 on the temporary storage table 12.

[0075] As the transport pad 40 descends, the contact portion 442 and annular portion 443 of the central suction portion 44 and the arc-shaped annular portion 452 of the outer peripheral suction portion 45 of the transport pad 40 come into contact with the back surface 92 (top surface) of the wafer 90. From the moment the contact portion 442, annular portion 443, and arc-shaped annular portion 452 come into contact with the back surface 92 of the wafer 90, the moving mechanism 60 further moves the arm 61 and arm support portion 63 downward. As a result, as shown in Figure 6, the arm 61 moves downward along the slide axis 43, reducing the gap between the lower surface of the ring portion 611 and the upper surface 411 of the plate 41, which contracts the coil spring 62 and presses the wafer 90 against the temporary storage table 12 with the transport pad 40.

[0076] The wafer 90 is pressed toward the temporary storage table 12 by the contact portion 442, the annular portion 443, and the arc-shaped annular portion 452 of the transport pad 40, thereby correcting its curvature. However, the area between the annular portion 443 and the arc-shaped annular portion 452 is an open-air area 50 that does not come into contact with the wafer 90. Therefore, the wafer 90 is not subjected to pressure from the transport pad 40 except for the central portion where the contact portion 442 and the annular portion 443 make contact, and the outer peripheral portion where the arc-shaped annular portion 452 makes contact. As a result, no force is applied that would forcibly flatten the entire wafer 90, and the occurrence of cracking in the fragile wafer 90 is suppressed.

[0077] Furthermore, since both the annular portion 443 and the arc-shaped annular portion 452 are made of an elastically deformable material such as rubber, the annular portion 443 and the arc-shaped annular portion 452 adhere tightly to the back surface 92 of the wafer 90 in an airtight manner, preventing the central suction port 441 and the outer peripheral suction port 451 from communicating with the atmosphere or the atmospheric opening area 50, and ensuring that the wafer 90 is securely held by the central suction portion 44 and the outer peripheral suction portion 45.

[0078] The motor 66 is stopped when the contact portion 442, the annular portion 443, and the arc-shaped annular portion 452 are pressed against the wafer 90 with appropriate pressure. The amount of movement of the transport pad 40 and the arm 61 until pressing against the wafer 90 is complete is managed by detecting and controlling the amount of drive of the motor 66 based on a signal from the encoder 67.

[0079] With the contact portion 442, annular portion 443, and arc-shaped annular portion 452 of the transport pad 40 pressed against the wafer 90, the suction source 48 is activated and the on / off valve 481 is opened. As a result, air is drawn in through the central suction passage 46 and the outer suction passage 47 from the central suction port 441 and the outer suction port 451, and the suction force acting on the central suction portion 44 and the outer suction portion 45 causes the back surface 92 of the wafer 90 to be sucked and held by the transport pad 40. More specifically, the suction force causes the back surface 92 of the wafer 90 to be in close contact with the undersides of the contact portion 442, annular portion 443, and arc-shaped annular portion 452, respectively. The atmospheric release area 50 is separated from the central suction port 441 and the outer suction port 451 by the annular portion 443 and the arc-shaped annular portion 452, and is also in communication with the atmosphere through the gap 51, so no suction force acts on the wafer 90 in the atmospheric release area 50. In this way, only the central and outer portions of the wafer 90 are held in place by the transport pad 40.

[0080] Next, as shown in Figure 7, the motor 66 of the moving mechanism 60 is driven to rotate the ball screw 65, moving the arm 61 and the arm support 63 upward. This movement causes the transport pad 40, which is holding the back surface 92 of the wafer 90 by suction, to rise, and the wafer 90 is separated from the temporary storage table 12.

[0081] The wafer 90, held by the transport pad 40 and separated from the temporary storage table 12, is transported without its central portion, which is held by the central suction unit 44, or its outer peripheral portion, which is held by the outer peripheral suction unit 45, hanging down.

[0082] The first transport mechanism 15 moves the transport pad 40, which is holding the wafer 90 by suction, above the temporary storage table 12, and then the moving mechanism 60 performs a rotational movement to position the transport pad 40 above the chuck table 14. At this time, the chuck table 14 is positioned at a transfer position close to the first transport mechanism 15 in the X-axis direction.

[0083] When the transport pad 40 reaches above the chuck table 14, the motor 66 of the moving mechanism 60 is driven to rotate the ball screw 65, moving the arm 61 and arm support 63 downwards. Then, as shown in Figure 8, the side of the wafer 90 held by the transport pad 40 with the protective tape 95 facing downwards is placed on the holding surface 143 of the chuck table 14.

[0084] When the transport pad 40 is placed on the holding surface 143 of the chuck table 14, the suction source 20 is activated and the on / off valve 201 is opened. As a result, air from the porous plate 142 side is drawn in through the flow path 144, and a suction force acts on the holding surface 143, holding the wafer 90 on the holding surface 143.

[0085] In this state, the suction force acting on the central suction section 44 and the outer peripheral suction section 45 of the transport pad 40 is released by either closing the on / off valve 481 or stopping the operation of the suction source 48. As a result, the transport pad 40 is no longer in a state of suction holding the wafer 90.

[0086] Furthermore, the on / off valve 491 is opened and the air supply source 49 is activated. As a result, air is ejected from the central suction port 441 and the outer suction port 451 through the central suction passage 46 and the outer suction passage 47, and the wafer 90 is released from the transport pad 40.

[0087] As described above, the first transport mechanism 15, to which the transport pad 40 is attached, transports the wafer 90 from the temporary storage table 12 to the chuck table 14.

[0088] The transport pad 40 uses a central suction section 44 and an outer peripheral suction section 45 to hold both the central and outer peripheral portions of the wafer 90 by suction. As a result, the wafer 90 is transported without either the central or outer peripheral portion sagging, allowing the wafer 90 to be transferred from the transport pad 40 to the holding surface 143 of the chuck table 14 without any problems.

[0089] Furthermore, the transport pad 40 does not suction and hold the wafer 90 in the atmospheric open area 50 between the central suction section 44 and the outer peripheral suction section 45. In other words, since the curvature of the wafer 90 is not corrected in the atmospheric open area 50, the load applied to the wafer 90 while it is held by the transport pad 40 is reduced, thereby suppressing the occurrence of cracking of the wafer 90 along the modified layer 96.

[0090] Even if the wafer 90 is fractured in the area corresponding to the open-air area 50 while being held on the transport pad 40, no suction force acts on the open-air area 50, making it difficult for the debris generated by the fracture to adhere to the transport pad 40. Therefore, the debris generated by the fracture of the wafer 90 is less likely to remain attached to the transport pad 40, and there is less risk of the debris causing damage during the transport of the next wafer 90. In other words, frequent cleaning to remove debris from the transport pad 40 is not required.

[0091] Unlike the transport pad 40 of this embodiment, in a transport pad that only suction-holds and transports the central portion of the wafer 90 (for example, the one described in Patent Document 1 above), the portion of the wafer other than the central portion is prone to vertical vibration, making it easier for the wafer 90 to fracture along the modified layer 96. Furthermore, if the wafer 90 fractures in an area not held by the transport pad, the outer periphery of the wafer 90 may sag, potentially preventing the chuck table 14 from properly suction-holding the wafer 90.

[0092] To prevent the outer edge of the wafer 90 from sagging, it is conceivable to use a transport pad that suction-holds and transports only the outer edge of the wafer 90. However, if such a transport pad is used, the impact applied to the outer edge of the wafer 90 may cause it to fracture in multiple pieces along the modified layer 96 inside the outer edge. As a result of this fracture, the central part of the wafer 90 may sag, causing adjacent chips 94 on the wafer 90 to come into contact with each other and potentially causing damage (such as chipping) to the chips 94.

[0093] Furthermore, in order to prevent the wafer 90 from partially sagging, it is conceivable to use a transport pad that uses a suction surface to hold the entire back surface 92 of the wafer 90. However, when such a transport pad is used, the entire wafer 90 is held in suction while being straightened from a curved shape to a flat shape, which tends to increase the load on the wafer 90 and increases the risk of fracture occurring along the modified layer 96. When fracture occurs, the debris generated may adhere to the suction surface of the transport pad, and when the next wafer 90 is held in suction, the debris may cause problems. For example, debris adhering to the suction surface of the transport pad may come into contact with the chip 94 on the wafer 90, causing chipping at the corner of the chip 94.

[0094] Unlike comparable transport pads, the transport pad 40 of this embodiment prevents the central and outer portions of the wafer 90 from sagging, allowing the wafer 90 to be transported in a stable state and handed over to the chuck table 14. Furthermore, the transport pad 40, which has an air-opening area 50 between the central and outer portions, makes it less likely for the wafer 90 to crack along the modified layer 96 during transport. Even if cracking does occur in the wafer 90, the configuration makes it less likely for the debris generated by the cracking to adhere to the transport pad 40, thus preventing manufacturing defects of the chip 94 caused by debris.

[0095] The outer periphery suction portion 45 of the transport pad 40 prevents the outer periphery of the wafer 90 from sagging during transport by suction, and when the wafer 90 is placed on the chuck table 14, the downwardly protruding arc-shaped annular portion 452 presses the outer periphery of the wafer 90 against the chuck table 14. This makes it possible to reliably hold a warped wafer 90, as shown in Figure 5, in the chuck table 14 by suction.

[0096] The central suction section 44 of the transport pad 40 is equipped with a contact section 442 around the central suction port 441. When a wafer 90 is sucked up, the lower surface of the contact section 442 contacts the back surface 92 (upper surface) of the wafer 90. The contact section 442 can suppress deformation of the wafer 90 in the region where the suction force from the central suction port 441 acts, thereby increasing the stability of the central part of the wafer 90. Specifically, if the central part of the wafer 90, which is subjected to the suction force from the central suction port 441, is recessed towards the central suction port 441 inside the annular section 443, local deformation can easily cause the wafer 90 to crack. However, the contact section 442, provided inside the annular section 443, contacts the back surface 92 of the wafer 90, thereby preventing such local deformation of the wafer 90. In addition, similar to the contact section 442, the annular section 443 also plays a role in preventing local deformation of the central part of the wafer 90.

[0097] The annular portion 443 is in contact with the back surface 92 of the wafer 90 along its entire circumference. This configuration, in which the annular portion 443 extends along its entire circumference outside the central suction port 441, prevents the suction force from the central suction port 441 from reaching the atmospheric exposure area 50. The contact portion 442 is configured to partially contact the back surface 92 of the wafer 90 in the circumference. For example, the height of the contact portion 442 may be lower in the Z-axis direction in a part of the circumference. The contact portion 442 only needs to act as a support to suppress deformation when the central part of the wafer 90 is about to deform towards the central suction port 441, so partial contact is sufficient to achieve the desired effect.

[0098] In this embodiment, the central suction port 441 is surrounded by a double cylindrical contact portion 442, but the number and shape of the contact portions 442 are not limited thereto. Also, in this embodiment, the contact portions 442 partially contact the back surface 92 of the wafer 90 in the circumferential direction, but the contact portions 442 may contact the back surface 92 of the wafer 90 over the entire circumferential direction.

[0099] The above describes the transport pad 40 mounted on the first transport mechanism 15, but the same effect can be obtained for the transport pad 40 mounted on the second transport mechanism 16. In the second transport mechanism 16, the transport pad 40 operates in roughly the same way as the transport pad 40 in the first transport mechanism 15, as described with reference to Figures 5 to 8, except that the target to which the transport pad 40 receives the wafer 90 is the chuck table 14, and the target to which the transport pad 40 transfers the wafer 90 is the spinner table 131. Therefore, a detailed explanation of the operation of the transport pad 40 in the second transport mechanism 16 will be omitted.

[0100] In the second transport mechanism 16, the wafer 90, after being thinned on the back surface 92 side by grinding in the grinding mechanism 24, is transported from the chuck table 14. This means that the wafer 90 is transported in a situation where it is even more likely to break, highlighting the usefulness of the transport pad 40 in this embodiment.

[0101] In this invention, transporting a wafer to a chuck table is a concept that includes both loading the wafer into the chuck table (the role of the first transport mechanism 15) and unloading the wafer from the chuck table (the role of the second transport mechanism 16).

[0102] The transport pad 70 shown in Figures 9 and 10 is a transport pad of a second embodiment to which the present invention is applied. In the transport pad 70, components that are common with the transport pad 40 of the first embodiment described above are denoted by the same reference numerals as the components of the transport pad 40, and their description is omitted.

[0103] As shown in Figure 10, a ring-shaped outer periphery suction portion 71 is positioned on the outer periphery (outer edge) of the lower surface 412 of the plate 41 to suction and hold the outer periphery of the wafer 90. The outer periphery suction portion 71 is configured as a complete annular shape that is continuous without interruption in the circumferential direction of the plate 41.

[0104] More specifically, the outer peripheral suction portion 71 has an outer peripheral suction port 711 that opens downward and an annular projection portion 712 that protrudes from the lower surface 412 of the plate 41 and extends in an annular shape in the circumferential direction. The annular projection portion 712 surrounds the inner and outer sides of the outer peripheral suction port 711. The outer peripheral suction port 711 is connected to an outer peripheral suction passage within the plate 41 (a suction passage similar to the outer peripheral suction passage 47 of the transport pad 40). The annular projection portion 712 is made of a material such as rubber that is elastically deformable and blocks the passage of air.

[0105] On the lower surface 412 side of the plate 41, the region between the central suction section 44 and the outer peripheral suction section 71 is an atmospheric release area 72. In the transport pad 70, since the annular projection 712 of the outer peripheral suction section 71 is continuous without interruption in the circumferential direction, an atmospheric release hole 73 is provided that penetrates the plate 41 in the thickness direction to connect the atmospheric release area 72 to the atmosphere. As shown in Figures 9 and 10, the atmospheric release hole 73 opens on the upper surface 411 and the lower surface 412 of the plate 41, connecting the atmospheric release area 72 formed on the lower surface 412 side with the atmosphere on the upper surface 411 side of the plate 41.

[0106] With the back surface 92 of the wafer 90 being held by the central suction section 44 and the outer peripheral suction section 71, the air-opening area 72 is separated from the central suction port 441 and the outer peripheral suction port 711 by the annular section 443 and the annular projection 712. Therefore, when the transport pad 70 holds the wafer 90 by suction, the wafer 90 is sucked only in the central part where the central suction section 44 is located and the outer peripheral part where the outer peripheral suction section 71 is located, and no suction force acts on the air-opening area 72 in between.

[0107] Furthermore, since the atmospheric opening area 72 is connected to the atmosphere via the atmospheric opening hole 73, even if there is some leakage of suction force from the central suction port 441 or the outer periphery suction port 711, the internal pressure of the atmospheric opening area 72 will not change significantly, and a state in which no suction force acts on the atmospheric opening area 72 can be maintained.

[0108] The transport pad of the present invention is suitable for transporting wafers in a grinding apparatus as described in the above embodiment, but it can also be applied to transporting wafers in processing apparatuses other than grinding apparatuses, and to transporting wafers between different processing apparatuses.

[0109] Furthermore, the embodiments of the present invention are not limited to the embodiments and modifications described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Moreover, if the technical idea of ​​the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial applicability]

[0110] As described above, the transport pad of the present invention has the effect of being able to stably transport fragile wafers and is particularly useful in grinding equipment and the like that performs grinding on fragile wafers. [Explanation of symbols]

[0111] 1: Grinding device 12: Temporary placement table 13: Spin cleaning mechanism 14: Chuck Table 15: First conveying mechanism 16: Second conveying mechanism 20: Suction source 21: Air supply source 22: Water supply source 24: Grinding mechanism 25: Lifting mechanism 40: Conveyor pad 41: Plate 44: Central suction part 45: Outer suction part 46: Central suction path 47: Peripheral suction path 48: Suction source 50: Open-air area 51: Gap 60: Movement mechanism 61: Arm 70: Transport pad 71: Peripheral suction part 72: Open-air area 73: Atmospheric vent 80: Laser processing equipment 90: Wafer 91 :Surface 92: Backside (top side of the wafer) 93: Planned division line 94: Tip 95: Protective tape 96: Modified layer 131: Spinner Table 142: Porous board 143: Holding surface 243: Grinding Wheel 246: Grinding Wheel 411: Top surface (top surface of the plate) 412: Bottom surface (bottom surface of the plate) 441: Central suction port 442: Contact area 443: Ring section 451: Peripheral suction port 452: Arc-shaped annular section 711: Peripheral suction port 712: Annular projection

Claims

1. A transport pad comprising a grid of planned division lines and division starting points formed along the planned division lines, wherein the upper surface of a wafer having a weakness is held by suction at the division starting points and transported to a chuck table, The device comprises a central suction unit for holding the central portion of the wafer, a ring-shaped peripheral suction unit for holding the outer edge of the wafer, a plate on which the central and peripheral suction units are positioned, and an atmospheric release area for releasing the upper surface of the wafer that is not being held in suction by the central and peripheral suction units to the atmosphere. The central suction portion comprises a central suction port opening on the lower surface of the plate and communicating with a suction source, an annular portion disposed on the lower surface of the plate so as to surround the central suction port and in contact with the upper surface of the wafer to apply suction force to the center of the wafer, and a contact portion disposed on the lower surface of the plate inside the annular portion and in contact with the upper surface of the wafer, wherein the contact portion suppresses deformation of the center of the wafer.

2. The outer peripheral suction portion protrudes downward from the lower surface of the plate and extends in a circular arc in the circumferential direction, and comprises a plurality of circular arc annular portions arranged in the circumferential direction, an outer peripheral suction port that opens inside the circular arc annular portion to the lower surface of the plate and is capable of communicating with a suction source, and an outer peripheral suction path that connects the outer peripheral suction port to a suction source, as described in claim 1.

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