Holding surface formation method

Abstract

To form a preferable holding surface on a chuck table by performing self-grinding.SOLUTION: A holding surface formation method of grinding an upper surface of a chuck table by a grindstone to form a holding surface includes: a grinding step of grinding the upper surface of the chuck table by the grindstone to form the holding surface; and a high-pressure water supply step of supplying high pressure water to the holding surface, after the grinding step. In the grinding step, a brittle layer exposed to the holding surface is formed in the chuck table. In the high-pressure water supply step, the brittle layer is removed by the high pressure water. Preferably, in the high pressure water supply step, the high pressure water is supplied to the entire region of the holding surface.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a holding surface forming method for forming a holding surface by grinding the upper surface of a chuck table that sucks a workpiece.

Background Art

[0002] A grinding apparatus is known in which a plate-shaped workpiece such as a semiconductor wafer, a ceramic substrate, or a resin package substrate is sucked and held by a chuck table (holding table) and ground with a grinding wheel. The grinding wheel is disposed above the chuck table, and a grinding abrasive is fixed to the lower surface of the grinding wheel. When the chuck table and the grinding wheel are rotated around an axis substantially perpendicular to their contact surfaces, and the grinding wheel is lowered to press the grinding abrasive against the workpiece, the workpiece is ground and thinned.

[0003] The chuck table includes a disk-shaped porous member (porous member) that supports the workpiece on the upper surface (holding surface) side, and a ceramic frame having a recess that surrounds the periphery of the porous member and supports the lower surface side of the porous member. The porous member is formed of a material such as ceramics, for example.

[0004] The chuck table has an internal suction path for transmitting negative pressure to the upper surface of the porous member. The suction path is configured through the porous member, and a suction source such as a vacuum pump is connected to the start end of the suction path. When the workpiece is placed on the upper surface of the porous member and negative pressure is generated by the suction source, the workpiece is sucked and held by the chuck table. Thus, the upper surface of the porous member functions as a holding surface. In other words, the chuck table has a holding surface on its upper surface.

[0005] When a workpiece is sucked and held by a chuck table and the workpiece is ground with a grinding wheel, chips called grinding swarf are generated from the workpiece and the grinding wheel. The grinding swarf enters from the gap between the holding surface of the chuck table and the workpiece into the outer peripheral portion of the porous member, and reduces the suction force particularly at the outer peripheral portion of the holding surface. As a result, the chuck table cannot appropriately suck the workpiece at the outer peripheral portion of the holding surface. Then, when grinding is performed, the outer peripheral portion of the workpiece floats with respect to the holding surface, and there arises a problem that the grinding amount of the outer peripheral portion of the workpiece increases and becomes thinner compared to the central portion.

[0006] Therefore, a step of grinding the chuck table itself with a grinding wheel and removing the upper end of the porous member together with the grinding swarf is periodically performed. Further, when starting to use a new chuck table with a grinding device, a step of grinding the upper surface of the porous member with a grinding wheel is also performed to adjust the shape of the holding surface (see Patent Document 1). These steps are called self-grinding and the like.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] When self-grinding is performed and the upper surface of the ground porous member is brittle, the mechanical strength of the surface layer of the porous member becomes low. In other words, when self-grinding is performed, a thin embrittled layer (damage layer) is formed on the upper surface of the porous member. When a workpiece is placed on the porous member in this state and the workpiece is sucked and held by the chuck table, the workpiece is pressed against the holding surface due to negative pressure, a physical load is applied to the embrittled layer, and the embrittled layer collapses.

[0009] The collapse of the brittle layer of the porous member has a small adverse effect on the thickness uniformity of the workpiece to be ground. In recent years, with the improvement in performance of device chips manufactured by dividing semiconductor wafers ground by a grinding apparatus, the required thickness accuracy of the semiconductor wafer after grinding has also increased. Therefore, the influence of the brittle layer on the thickness uniformity of the workpiece cannot be ignored. Further, the fragments generated by the collapse of the brittle layer may adhere to the lower surface of the workpiece pressed against the holding surface due to negative pressure, which may cause deterioration of the quality of the workpiece.

[0010] Therefore, after self-grinding of the chuck table is performed, in order to remove the brittle layer of the porous member, it is conceivable to prepare a number of dummy wafers having the shape of a workpiece and sequentially suck and hold the dummy wafers with the chuck table. When the dummy wafer is sucked and held, the brittle layer collapses and fragments adhere to the dummy wafer. By repeating this many times, the brittle layer is gradually removed from the surface of the porous member. However, since the workpiece cannot be ground during this process, there is a problem that the operating efficiency of the grinding apparatus is greatly reduced.

[0011] The present invention has been made in view of such problems, and an object thereof is to provide a holding surface forming method for forming a good holding surface on a chuck table by performing self-grinding.

Means for Solving the Problems

[0012] According to one aspect of the present invention, there is provided a holding surface forming method for grinding the upper surface of a chuck table with a grinding wheel to form the holding surface, the method including: a grinding step of grinding the upper surface of the chuck table with the grinding wheel to form the holding surface; and a high-pressure water supply step of supplying high-pressure water to the holding surface to wash the holding surface after the grinding step. In the grinding step, a brittle layer exposed on the holding surface is formed on the chuck table, and in the high-pressure water supply step, the brittle layer is removed with the high-pressure water.

[0013] Preferably, in the high-pressure water supply step, the high-pressure water is supplied to the entire area of the holding surface.

Advantages of the Invention

[0014] In the holding surface forming method according to one aspect of the present invention, the upper surface of the chuck table is ground with a grinding wheel to form a holding surface, and then high-pressure water is supplied to the holding surface. The embrittled layer formed on the holding surface by grinding is removed by the high-pressure water. When the embrittled layer is removed, even if the workpiece is then sucked and held by the chuck table and ground with a grinding wheel, problems caused by the collapse of the embrittled layer do not occur. That is, a chuck table having a good holding surface can be obtained.

[0015] Therefore, according to one aspect of the present invention, there is provided a holding surface forming method for performing self-grinding to form a good holding surface on a chuck table.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0017] With reference to the accompanying drawings, embodiments according to one aspect of the present invention will be described. First, a grinding apparatus in which the holding surface forming method according to the present embodiment is implemented and a workpiece to be ground by the grinding apparatus will be described. FIG. 1 is a perspective view schematically showing a grinding apparatus 2 in which the holding surface forming method according to the present embodiment is implemented. FIG. 2 is a perspective view schematically showing the grinding apparatus 2 with some components separated. Further, FIG. 8 includes a cross-sectional view schematically showing the workpiece 1.

[0018] The workpiece 1 is, for example, a disk-shaped wafer made of a material such as silicon, and includes surfaces 1a and 1b that are generally parallel to each other. On the surface 1a of the workpiece 1, a plurality of division planned lines (not shown) arranged in a grid pattern so as to intersect each other are set. In each region partitioned by the division planned lines on the surface 1a of the workpiece 1, devices (not shown) such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed, respectively.

[0019] Note that there are no restrictions on the material, structure, size, shape, etc. of the workpiece 1. For example, the workpiece 1 may be a substrate made of a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), sapphire, glass (quartz glass, borosilicate glass, etc.), or the like. Further, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the devices, and the workpiece 1 may not have devices formed thereon.

[0020] When the workpiece 1 is ground from the back surface 1b side to be thinned and the workpiece 1 is divided along the division planned lines, a plurality of thin chips (device chips) each including a device are manufactured. When grinding the back surface 1b side of the workpiece 1, a tape-shaped protective member (not shown) having a diameter approximately the same as that of the workpiece 1 is attached to the surface 1a side of the workpiece 1 in order to protect the surface 1a side.

[0021] As shown in FIG. 1, the grinding apparatus 2 has a substantially rectangular parallelepiped base 4 that supports each component. Cassette mounting tables 6a and 6b are provided on the front side of the base 4. A cassette 8a containing the workpiece (wafer) 1 is placed on the cassette mounting table 6a, and a cassette 8b for containing the workpiece 1, for example, is placed on the cassette mounting table 6b. In the grinding apparatus 2, the workpieces 1 contained in the cassettes 8a and 8b are successively drawn out, ground, and returned to the cassettes 8a and 8b.

[0022] On the base 4, a wafer transfer robot 10 for transferring the workpiece 1 is provided adjacent to the cassette mounting tables 6a and 6b. Further, a positioning table 12 for determining the position of the workpiece 1 is provided behind the cassette mounting table 6a.

[0023] The base end portion of the loading arm 18 is provided behind the positioning table 12. A first suction holding unit for sucking and holding the workpiece 1 by negative pressure is provided at the tip of the loading arm 18. The loading arm 18 carries the workpiece 1 into a disk-shaped turntable 14 provided behind the base end portion of the loading arm 18.

[0024] The base end portion of the unloading arm 20 is provided adjacent to the lateral direction of the base end portion of the loading arm 18. A second suction holding unit for sucking and holding the workpiece 1 by negative pressure is provided at the tip of the unloading arm 20. The unloading arm 20 unloads the workpiece 1 from the turntable 14.

[0025] The turntable 14 is configured to be rotatable around a predetermined rotation axis. On the upper surface of the turntable 14, three chuck tables 16 are arranged at substantially equal intervals along the circumferential direction of the turntable 14.

[0026] FIG. 3 includes a cross-sectional view schematically showing the chuck table 16. The chuck table 16 has a frame body 16b made of a material such as ceramics. A suction path (not shown) is provided in the frame body 16b, and a suction source (not shown) such as an ejector or a pump is connected to one end of this suction path.

[0027] The frame body 16b has a concave portion (accommodating concave portion) formed of a disk-shaped space on the upper surface side. A disk-shaped porous member 16c that supports the workpiece 1 on the upper surface side is accommodated in this concave portion. The porous member 16c is, for example, a porous plate made of a material such as ceramics.

[0028] The upper surface of the porous member 16c has an extremely gently inclined conical surface shape. Also, the diameter of the porous member 16c is substantially the same as the diameter of the workpiece 1. The other end of the suction path of the frame body 16b is connected to the lower surface side of the porous member 16c. When the suction source is operated, a negative pressure is generated on the upper surface of the porous member 16c, and the workpiece 1 is sucked and held on this upper surface. Therefore, the upper surface of the chuck table 16 functions as a holding surface 16a.

[0029] A disk-shaped table base 16d is connected to the lower surface side of the frame body 16b of the chuck table 16. The upper end of the spindle 17 is connected to the center of the lower surface of this table base 16d, and a rotation drive source (not shown) such as a motor for rotating the spindle 17 is provided at the lower end of the spindle 17. By operating this rotation drive source, the chuck table 16 rotates around a table rotation axis 16e (see FIG. 4 etc.) passing through the center of the holding surface 16a.

[0030] The upper surface side of the turntable 14 is partitioned into three fan-shaped regions by a plurality of linear partition plates (not shown) provided radially. The fan-shaped region closest to the base end portions of each of the loading arm 18 and the unloading arm 20 is a loading / unloading region A for loading or unloading the workpiece 1 to / from the turntable 14.

[0031] The fan-shaped area that is approximately 120 degrees clockwise from the loading and unloading area A in a top view becomes the rough grinding area B where the workpiece 1 is rough ground, and the fan-shaped area that is approximately 120 degrees counterclockwise from the loading and unloading area A in a top view becomes the finish grinding area C where the workpiece 1 is finish ground.

[0032] One chuck table 16 is provided in each fan-shaped area. The upper surface of the chuck table 16 functions as a holding surface 16a for sucking and holding the workpiece 1. Below the chuck table 16, a rotation drive source (not shown) such as a motor for rotating the chuck table 16 around a predetermined rotation axis is provided.

[0033] A wall portion 4a is provided behind the turntable 14. On the front surface of the wall portion 4a, ball screw type grinding feed mechanisms 22a, 22b are provided. The grinding feed mechanism 22a moves the grinding unit 24a along the Z-axis direction. The grinding unit (rough grinding unit) 24a is supported by the base 4 via the grinding feed mechanism 22a. Directly below the grinding unit 24a corresponds to the above-mentioned rough grinding area B.

[0034] Similar to the grinding feed mechanism 22a, the grinding feed mechanism 22b moves the grinding unit (finish grinding unit) 24b along the Z-axis direction. The grinding unit 24b is supported by the base 4 via the grinding feed mechanism 22b. Directly below the grinding unit 24b corresponds to the above-mentioned finish grinding area C.

[0035] FIG. 3 is a side view schematically showing the chuck table 16 and the grinding units 24a, 24b. The grinding unit 24a has a cylindrical spindle housing 26. Inside the spindle housing 26, a part of a cylindrical spindle 28 is rotatably accommodated.

[0036] At the upper end of the spindle 28, a rotation drive source 30 such as a motor is provided. The lower end of the spindle 28 protrudes below the bottom of the spindle housing 26, and a grinding wheel 34a is mounted on the lower end of the spindle 28 via a disk-shaped mount 32.

[0037] The grinding wheel 34a has an annular wheel base 35a formed of a metal such as an aluminum alloy. On one side of the wheel base 35a, a plurality of segmental grinding wheels 36a are arranged at substantially equal intervals along the circumferential direction of the wheel base 35a. The grinding wheel 36a is formed, for example, by mixing abrasive grains such as diamond and cBN (cubic boron nitride) with a binder such as vitrified or resinoid, and sintering the mixture.

[0038] FIG. 2 is a perspective view of the grinding apparatus 2 with the rough grinding chamber cover 38 and the finish grinding chamber cover 40 removed, and FIG. 1 is a perspective view of the grinding apparatus 2 with the rough grinding chamber cover 38 and the finish grinding chamber cover 40 attached. In FIG. 3, the rough grinding chamber cover 38 and the finish grinding chamber cover 40 are omitted.

[0039] The grinding unit (rough grinding unit) 24a grinds (rough grinds) the back surface side of the workpiece 1 sucked and held by the chuck table 16 disposed in the rough grinding region B. The chuck table 16 and the grinding wheel 34a disposed in the rough grinding region B are covered by a rough grinding chamber cover 38 formed of a metal such as stainless steel.

[0040] The grinding unit (finish grinding unit) 24b also has a spindle housing 26, a spindle 28, a rotational drive source 30, and a mount 32. A grinding wheel 34b is attached to the lower end of the spindle 28 of the grinding unit 24b via the mount 32.

[0041] On one side of the wheel base 35b of the grinding wheel 34b, a plurality of segmental grinding wheels 36b are arranged at substantially equal intervals along the circumferential direction of the wheel base 35b. The grinding wheel 36b has abrasive grains with an average particle size smaller than that of the abrasive grains of the grinding wheel 36a of the grinding wheel 34a, and a binder for fixing the abrasive grains.

[0042] The grinding unit 24b grinds (finishing grind) the back surface 1b side of the workpiece 1 sucked and held by the chuck table 16 arranged in the finishing grind area C. The chuck table 16 and the grinding wheel 34b arranged in the finishing grind area C are covered by the finishing grind chamber cover 40.

[0043] For example, as shown in FIGS. 1 and 2, the rough grind chamber cover 38 and the finishing grind chamber cover 40 are continuously incorporated into the grinding device 2. A partition wall 37 is provided between the rough grind area B covered by the rough grind chamber cover 38 and the finishing grind area C covered by the finishing grind chamber cover 40.

[0044] A cleaning unit 48 for cleaning the ground workpiece 1 is provided behind the cassette mounting table 6b on the base 4. The cleaning unit 48 includes, for example, a spinner table for holding the workpiece 1 and an injection nozzle (not shown) for injecting a cleaning liquid such as pure water onto the workpiece 1 held by the spinner table.

[0045] When grinding the workpiece 1 with the grinding device 2, the workpiece 1 with the protective member attached to the surface 1a is carried out from the cassettes 8a, 8b, the position is adjusted by the positioning table 12, and it is conveyed to the chuck table 16 positioned in the loading / unloading area A. Then, the workpiece 1 is placed on the holding surface 16a of the chuck table 16 via the protective member, the workpiece 1 is sucked and held by the chuck table 16, and the back surface 1b that becomes the machined surface of the workpiece 1 is exposed upward. Then, the turntable 14 is operated to move the chuck table 16 to the rough grind area B.

[0046] Thereafter, as shown in FIG. 8, the grinding wheel 34a of the grinding unit 24a is rotated around the wheel rotation axis 28a, and the chuck table 16 is rotated around the table rotation axis 16e. Then, the grinding feed mechanism 22a is operated to start the descent of the grinding unit 24a. Thereafter, when the lower surface of the grinding wheel 36a moving on the annular track hits the back surface 1b of the workpiece 1, the workpiece 1 is ground (rough ground).

[0047] Next, operate the turntable 14 to move the chuck table 16 to the finish grinding area C. Thereafter, rotate the grinding wheel 34b of the grinding unit 24b around the wheel rotation axis 28a and rotate the chuck table 16 around the table rotation axis 16e. Then, operate the grinding feed mechanism 22b to start the descent of the grinding unit 24b. Thereafter, when the lower surface of the grinding wheel 36b moving on the annular track contacts the back surface 1b of the workpiece 1, the workpiece 1 is ground (finish ground).

[0048] Note that the grinding apparatus 2 is provided with a height gauge (not shown) capable of measuring the thickness of the workpiece 1, and continues the descent of the grinding units 24a and 24b while monitoring the thickness of the workpiece 1 with the height gauge. Then, when the thickness of the workpiece 1 reaches a predetermined finish thickness, the descent of the grinding units 24a and 24b is terminated and the grinding units 24a and 24b are raised. Then, the workpiece 1 thinned to a predetermined thickness is obtained.

[0049] The ground workpiece 1 is conveyed from the chuck table 16 to the cleaning unit 48 by the unloading arm 20 and is cleaned by the cleaning unit 48. Thereafter, the workpiece 1 is housed in the cassettes 8a and 8b. Then, when the cassettes 8a and 8b are carried out of the grinding apparatus 2, the workpiece 1 is carried out of the grinding apparatus 2.

[0050] Here, when starting the use of the chuck table 16 in the grinding apparatus 2 or when performing maintenance work on the grinding apparatus 2, a correction operation is performed in which the upper surface (holding surface 16a) of the porous member 16c is ground by the grinding wheels 34a and 34b. This correction operation is called self-grinding or the like. FIG. 5 includes a cross-sectional view schematically showing the chuck table 16 being self-ground.

[0051] When the workpiece 1 is placed on the self-ground porous member 16c and held by the chuck table 16, and the workpiece 1 is ground with the grinding wheels 34a and 34b, the unevenness on the upper surface (back surface 1b) and the lower surface (front surface 1a) of the workpiece 1 is reduced, and both surfaces become similar in shape, making the thickness of the workpiece 1 uniform throughout.

[0052] However, the upper surface of the ground porous member 16c is brittle, and the mechanical strength of the surface layer of the porous member 16c is reduced. In other words, when self-grinding is performed, a thin brittle layer (damage layer) 16f is formed on the upper surface of the porous member 16c. FIG. 6 includes a cross-sectional view schematically showing the porous member 16c with the brittle layer 16f formed. However, in FIG. 6, the shape, thickness, etc. of the brittle layer 16f are emphasized for the sake of explanation.

[0053] When the workpiece 1 is sucked and held by the chuck table 16 including the brittle layer 16f on the upper surface of the porous member 16c, a negative pressure acts, the workpiece 1 is pressed against the holding surface 16a, and a physical load is applied to the brittle layer 16f, causing the brittle layer 16f to collapse.

[0054] The collapse of the brittle layer 16f of the porous member 16c has an adverse effect on the uniformity of the thickness of the workpiece 1 to be ground. In addition, the fragments generated by the collapse of the brittle layer 16f may adhere to the lower surface of the workpiece 1 pressed toward the holding surface 16a due to the negative pressure, which may cause deterioration of the quality of the workpiece 1.

[0055] Therefore, in the holding surface forming method according to the present embodiment, after the chuck table 16 is self-ground so that a good holding surface 16a can be formed on the chuck table 16, high-pressure water is supplied to the chuck table 16. Hereinafter, the holding surface forming method according to the present embodiment in which the upper surface of the chuck table 16 is ground with the grinding wheels 36a and 36b to form the holding surface 16a will be described. FIG. 9 is a flowchart showing the flow of each step of the holding surface forming method according to the present embodiment.

[0056] In the holding surface forming method according to this embodiment, first, a grinding step S10 of grinding the upper surface of the chuck table 16 with grinding wheels 36a and 36b to form a holding surface 16a is performed. That is, the upper surface of the chuck table 16 is ground to perform self-grinding. In the grinding step S10, the chuck table 16 may be ground by the grinding unit 24a, may be ground by the grinding unit 24b, or may be ground by both.

[0057] FIG. 4 is a side view schematically showing the chuck table 16 and the grinding units 24a and 24b in the preparation stage of the grinding step S10. FIG. 4 includes a cross-sectional view schematically showing a part of the chuck table 16.

[0058] In the grinding step S10, first, as shown in FIG. 4, the chuck table 16 to be the object of self-grinding is positioned below the grinding units 24a and 24b used for grinding. Next, the grinding wheels 34a and 34b are rotated around the wheel rotation axis 28a, and the chuck table 16 is rotated around the table rotation axis 16e. Then, the lowering of the grinding units 24a and 24b is started.

[0059] When the grinding units 24a and 24b are lowered, the bottom surfaces of the grinding wheels 36a and 36b traveling on the annular orbit come into contact with the upper surface of the chuck table 16, and the chuck table 16 is ground. That is, self-grinding is performed. FIG. 5 is a cross-sectional view schematically showing the chuck table 16 and the grinding units 24a and 24b in the grinding step S10.

[0060] In the grinding step S10, the grinding units 24a and 24b are fed for grinding by a predetermined amount so that self-grinding is performed under predetermined conditions, and self-grinding is performed for a predetermined time. Thereby, a holding surface 16a is formed on the upper surface of the chuck table 16.

[0061] When self-grinding is performed, grinding chips are generated from the chuck table 16 and the grinding wheels 36a and 36b. Also, heat is generated due to the contact between the chuck table 16 and the grinding wheels 36a and 36b. Therefore, it is preferable that a grinding fluid such as pure water is supplied to the chuck table 16 and the grinding wheels 36a and 36b while self-grinding is being performed. The generated grinding chips and heat are removed to a certain extent by the grinding fluid.

[0062] When the chuck table 16 is ground under predetermined conditions, the grinding units 24a and 24b are raised and separated from the chuck table 16. When the grinding step S10 is performed, the upper surface of the porous member 16c becomes brittle. That is, a brittle layer (damage layer) 16f exposed on the holding surface 16a of the chuck table 16 is formed on the chuck table 16.

[0063] In the holding surface forming method according to the present embodiment, in order to remove this brittle layer 16f, after the grinding step S10, a high-pressure water supply step S20 is performed in which high-pressure water is supplied to the holding surface 16a to wash the holding surface 16a. FIG. 7 is a cross-sectional view schematically showing the chuck table 16 and the grinding units 24a and 24b in the high-pressure water supply step S20.

[0064] Here, the grinding device 2 may include a high-pressure water supply unit 50 that supplies high-pressure water to the chuck table 16. In the high-pressure water supply step S20, high-pressure water 54 is supplied from the high-pressure water supply unit 50 to the holding surface 16a of the chuck table 16. The high-pressure water supply unit 50 includes a flow path (not shown) having one end connected to a high-pressure water supply source (not shown) and a high-pressure water supply nozzle 52 connected to the tip of the flow path.

[0065] For example, the high-pressure water supply unit 50 is disposed on the base 4 outside the chuck table 16 positioned in the loading / unloading area A. For example, the high-pressure water supply unit 50 is composed of a pipe-shaped member including a support shaft portion along a substantially vertical direction and an arm portion along a substantially horizontal direction. The lower end of the support shaft portion is accommodated in the base 4, the upper end of the support shaft portion is connected to the base end of the arm portion, and a high-pressure water supply nozzle 52 is disposed at the tip of the arm portion. A rotary drive source such as a motor for rotating the support shaft portion around a rotation axis along a substantially vertical direction and a high-pressure water supply source such as a pump for supplying high-pressure water 54 are connected to the lower end of the support shaft portion. When the support shaft portion is rotated, the high-pressure water supply nozzle 52 can be swung above the chuck table 16.

[0066] Also, the high-pressure water supply nozzle 52 may be attached to the tip of the loading arm 18 or the unloading arm 20. In this case, by rotating the loading arm 18 or the unloading arm 20, the high-pressure water supply nozzle 52 can be swung above the chuck table 16.

[0067] In the high-pressure water supply step S20, while moving the high-pressure water supply nozzle 52 above the chuck table 16, high-pressure water 54 is supplied from the high-pressure water supply nozzle 52 to the holding surface 16a of the chuck table 16. At this time, the chuck table 16 may be rotated around the table rotation axis 16e.

[0068] The high-pressure water supply nozzle 52 preferably reciprocates in a region overlapping the center of the holding surface 16a, for example. Also, for example, one end of this region preferably overlaps the center of the holding surface 16a, and the other end of this region preferably overlaps the end of the holding surface 16a. Here, the supply pressure of the high-pressure water 54 is, for example, 2.0 MPa or more. The high-pressure water 54 is composed of pure water, for example. However, the high-pressure water 54 and its supply pressure are not limited to this.

[0069] When the high-pressure water 54 is supplied to the embrittled layer (damage layer) 16f formed on the holding surface 16a of the chuck table 16, the embrittled layer 16f is removed by the physical impact caused by the collision of the high-pressure water 54. Therefore, in the grinding device 2, no problems caused by the embrittled layer 16f occur thereafter. That is, if the embrittled layer 16f formed on the holding surface 16a by self-grinding is removed in advance, even when the workpiece 1 is sucked and held by the chuck table 16, no problems caused by the collapse of the embrittled layer 16f occur.

[0070] The target area to which the high-pressure water 54 is supplied is preferably the entire surface of the holding surface 16a. When the high-pressure water 54 is supplied to the entire surface of the holding surface 16a, it is difficult for the embrittled layer 16f to remain on the holding surface 16a. However, the target area to which the high-pressure water 54 is supplied is not limited to the entire surface of the holding surface 16a.

[0071] As described above, in the formation of the holding surface according to the present embodiment, the upper surface of the chuck table 16 is ground by the grinding wheels 36a and 36b to form the holding surface 16a, and then the high-pressure water 54 is supplied to the holding surface 16a to wash the holding surface 16a. When the upper surface of the chuck table 16 is ground by the grinding wheels 36a and 36b, the embrittled layer 16f exposed on the holding surface 16a is formed on the chuck table 16, but the embrittled layer 16f is removed by the high-pressure water 54.

[0072] When the embrittled layer 16f formed on the holding surface 16a is removed by the high-pressure water 54, even when the workpiece 1 is sucked and held by the chuck table 16, no problems caused by the collapse of the embrittled layer 16f occur. That is, a good chuck table 16 can be obtained as the holding surface 16a on which the workpiece 1 to be ground is placed.

[0073] After performing self-grinding by the holding surface forming method according to the present embodiment to form a high-quality holding surface 16a on the upper surface of the chuck table 16, in the grinding device 2, grinding of the workpiece 1 is performed by the grinding units 24a and 24b. Hereinafter, the procedure of grinding the workpiece 1 performed by the grinding device 2 will be described.

[0074] First, in order to load the workpiece 1 into the grinding device 2, cassettes 8a and 8b for accommodating a plurality of workpieces 1 are placed on cassette mounting tables 6a and 6b. Next, the workpiece 1 is unloaded from the cassettes 8a and 8b, the position of the workpiece 1 is adjusted by the positioning table 12, and the workpiece 1 is placed on the holding surface 16a of the chuck table 16 positioned in the loading / unloading area A, and the workpiece 1 is sucked and held by the chuck table 16. At this time, the surface to be ground of the workpiece 1 faces upward.

[0075] For example, when the workpiece 1 is a wafer having a device or the like formed on the surface 1a and the back surface 1b of the workpiece 1 is the surface to be ground, the workpiece 1 is placed on the chuck table 16 with the back surface 1b side facing upward. When a device or the like is formed on the surface 1a which is the lower surface of the workpiece 1, it is preferable that a tape-shaped protective member for protecting the device or the like is previously disposed on the surface 1a of the workpiece 1. In this case, the workpiece 1 is sucked and held by the chuck table 16 via the protective member.

[0076] Next, the turntable 14 is rotated, and in order to perform grinding (rough grinding) of the workpiece 1 by the grinding unit 24a, the chuck table 16 that sucks and holds the workpiece 1 is moved to the rough grinding area B. Then, the chuck table 16 and the grinding wheel 34a are rotated respectively, the grinding unit 24a is lowered, and the grinding wheel 36a is brought into contact with the back surface 1b of the workpiece 1 to rough grind the workpiece 1.

[0077] After the rough grinding of the workpiece 1 is completed, the turntable 14 is rotated, and in order to perform grinding (finish grinding) of the workpiece 1 by the grinding unit 24b, the chuck table 16 that sucks and holds the workpiece 1 is moved to the finish grinding area C. Then, the chuck table 16 and the grinding wheel 34b are rotated respectively, the grinding unit 24b is lowered, and the grinding wheel 36b is brought into contact with the back surface 1b of the workpiece 1 to finish grind the workpiece 1.

[0078] After the finish grinding of the workpiece 1, the turntable 14 is rotated, the chuck table 16 is returned to the loading / unloading area A, the suction holding of the workpiece 1 by the chuck table 16 is released, and the workpiece 1 is moved to the cleaning unit 48. Then, the workpiece 1 is cleaned by the cleaning unit 48 and the workpiece 1 is accommodated in the cassettes 8a, 8b. In the grinding device 2, a plurality of workpieces 1 accommodated in the cassettes 8a, 8b are successively ground and returned to the cassettes 8a, 8b.

[0079] FIG. 8 is a cross-sectional view schematically showing a state in which the workpiece 1 is ground by the grinding units 24a, 24b. When the holding surface forming method according to the present embodiment is implemented in the grinding device 2, the embrittlement layer (damage layer) 16f formed on the holding surface 16a by self-grinding is removed. Therefore, problems caused by the collapse of the embrittlement layer 16f when the workpiece 1 is suction-held by the chuck table 16 are less likely to occur.

[0080] In the above embodiment, the case where the high-pressure water supply unit 50 mounted on the grinding device 2 is used for removing the embrittlement layer (damage layer) 16f formed on the holding surface 16a has been described, but one aspect of the present invention is not limited thereto. That is, the use of the high-pressure water supply unit 50 mounted on the grinding device 2 is not limited to the removal of the embrittlement layer 16f.

[0081] For example, the high-pressure water supply unit 50 may be used for cleaning the workpiece 1 ground by the grinding device 2. When the workpiece 1 is ground by the grinding device 2, chips are generated from the workpiece 1 and the grinding wheels 36a, 36b and adhere to the workpiece 1. The workpiece 1 is cleaned by the cleaning unit 48 after grinding, but the chips adhering to the workpiece 1 may detach from the workpiece 1 between when the workpiece 1 is ground and when it is cleaned by the cleaning unit 48. Then, the detached chips may scatter inside the processing chamber of the grinding device 2 and become a source of contamination.

[0082] Therefore, in the grinding apparatus 2, high-pressure water 54 may be supplied to the grinding surface of the workpiece 1 by the high-pressure water supply unit 50 before the workpiece 1 is unloaded from the chuck table 16 after grinding the workpiece 1. The supply conditions of the high-pressure water 54 in this case do not necessarily have to match the supply conditions of the high-pressure water 54 in the high-pressure water supply step S20.

[0083] Further, the high-pressure water supply unit 50 may be used for other purposes. The high-pressure water supply unit 50 may be used, for example, to clean the holding surface 16a of the chuck table 16 that holds the workpiece 1 to be ground and from which the workpiece 1 is unloaded after grinding. Chips generated when the workpiece 1 is ground by the grinding apparatus 2 may enter the porous member 16c by penetrating between the workpiece 1 and the holding surface 16a. Further, chips may adhere to the upper surface of the frame body 16b of the chuck table 16.

[0084] In this case, when the next workpiece 1 to be ground is placed on the holding surface 16a of the chuck table 16, the chips are sandwiched between the workpiece 1 and the holding surface 16a, and the workpiece 1 is not properly sucked and held by the chuck table 16. Then, the workpiece 1 cannot be properly ground.

[0085] Therefore, when the workpiece 1 is ground by the grinding apparatus 2 and the workpiece 1 is unloaded from the chuck table 16, high-pressure water 54 may be supplied from the high-pressure water supply unit 50 to the holding surface 16a of the chuck table 16 to clean the holding surface 16a of the chuck table 16.

[0086] When the chuck table 16 is cleaned by the high-pressure water supply unit 50, problems caused by chips during grinding of the workpiece 1 are less likely to occur. Note that the supply conditions of the high-pressure water 54 in this case do not necessarily have to match the supply conditions of the high-pressure water 54 in the high-pressure water supply step S20.

[0087] In addition, the structures, methods, etc. according to the above embodiments can be appropriately changed and implemented without departing from the scope of the object of the present invention.

Description of Reference Numerals

[0088] 1 Workpiece 1a Surface 1b Back surface 2 Grinding device 4 Base 4a Wall portion 6a, 6b Cassette mounting table 8a, 8b Cassette 10 Wafer transfer robot 12 Positioning table 14 Turntable 16 Chuck table 16a Holding surface 16b Frame body 16c Porous member 16d Table base 16e Table rotation axis 16f Brittle layer 17 Spindle 18 Loading arm 20 Unloading arm 22a, 22b Grinding feed mechanism 24a, 24b Grinding unit 26 Spindle housing 28 Spindle 28a Wheel rotation axis 30 Rotation drive source 32 Mount 34a, 34b Grinding wheel 35a, 35b Wheel base 36a, 36b Grinding stone 38 Rough grinding chamber cover 40 Finish grinding chamber cover 48 Cleaning unit 50 High-pressure water supply unit 52 High-pressure water supply nozzle 54 High-pressure water

Claims

1. A method for forming a holding surface by grinding the upper surface of a chuck table with a grinding wheel to form the holding surface, comprising a grinding step of grinding the upper surface of the chuck table with the grinding wheel to form the holding surface, and a high-pressure water supply step of supplying high-pressure water to the holding surface after the grinding step, wherein in the grinding step, a brittle layer exposed on the holding surface is formed on the chuck table, and in the high-pressure water supply step, the brittle layer is removed with the high-pressure water. A method for forming a holding surface, characterized by the above.

2. The method for forming a holding surface according to claim 1, wherein in the high-pressure water supply step, the high-pressure water is supplied to the entire area of the holding surface.

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