Polishing apparatus and polishing method

Abstract

To remove polishing waste generated by polishing a workpiece and adhering to an outer peripheral part of a chuck table.SOLUTION: A polishing device polishes a workpiece and includes: a chuck table which has a holding surface and suctions and holds the workpiece placed on the holding surface; a polishing unit which polishes the workpiece with a polishing pad while supplying slurry to the workpiece held by the chuck table; and a two-fluid nozzle which jets a fluid mixture of a liquid and a gas to the holding surface of the chuck table. The fluid mixture is jetted from the two-fluid nozzle to polishing waste deposited on an outer periphery part of the holding surface to remove the polishing waste from the holding surface.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer, and a polishing method for polishing the workpiece with the polishing apparatus. [Background technology]

[0002] In the manufacturing process of device chips used in electronic devices such as mobile phones and computers, first, multiple devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed on the surface of a semiconductor wafer. Next, the wafer is ground from the back side to thin it to a predetermined thickness, and the wafer is divided into individual devices to form individual device chips.

[0003] When the back side of a wafer is ground, minute irregularities are formed on the ground surface as grinding marks. Therefore, minute irregularities remain on device chips formed by dividing the wafer. These minute irregularities are a factor in reducing the flexural strength of the device chips. Therefore, it is known that after grinding, the back side of the wafer is polished by, for example, a chemical mechanical polishing (CMP) method (see Patent Document 1).

[0004] A polishing apparatus for polishing a workpiece such as a wafer includes a chuck table for holding the workpiece, and a polishing unit equipped with a polishing pad for polishing the workpiece held on the chuck table. When the workpiece is polished using the polishing apparatus, minute irregularities are removed and the workpiece is processed into a mirror surface.

[0005] In a polishing device, when polishing a workpiece, a slurry is supplied as a polishing liquid to the polished surface of the workpiece. The slurry is, for example, a chemical liquid in which abrasive grains are dispersed. The slurry not only contributes to polishing by acting chemically and mechanically, but also contributes to the discharge of polishing waste generated by polishing. The slurry is supplied from a supply path provided in the center of the polishing pad, and travels between the polishing pad and the workpiece to reach the outer periphery of the workpiece. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-99265 Summary of the Invention [Problem to be solved by the invention]

[0007] The slurry containing the polishing debris that reaches the outer periphery of the workpiece falls off the polished surface of the workpiece and accumulates and adheres to the outer periphery of the holding surface of the chuck table. When the polishing of the workpiece is completed and the workpiece is removed from the chuck table, the polishing debris remains adhered to the upper surface of the chuck table so as to surround the area where the workpiece was located.

[0008] When the workpiece to be polished next with the polishing pad is loaded onto the chuck table, the adhered polishing debris may get between the chuck table and the workpiece, hindering the loading. For example, it is conceivable to supply cleaning water to the outer periphery of the holding surface of the chuck table in order to remove the adhered polishing debris, but it is not easy to remove the adhered polishing debris.

[0009] In addition, in order to wash away the slurry containing polishing debris that reaches the outer periphery of the workpiece before the slurry adheres, it is possible to supply a sufficient amount of cleaning liquid to the outer periphery of the holding surface of the chuck table while the workpiece is being polished with the polishing pad. However, if the cleaning liquid gets mixed into the slurry supplied between the polishing pad and the workpiece and dilutes the slurry, the polishing process may not be performed properly.

[0010] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a polishing apparatus and a polishing method capable of removing polishing debris adhered to the outer periphery of a chuck table. [Means for solving the problem]

[0011] According to one aspect of the present invention, a polishing apparatus for polishing a workpiece includes a rotatable chuck table having a holding surface and suction-holding the workpiece placed on the holding surface, a polishing unit for polishing the workpiece held by the chuck table with a polishing pad while supplying a slurry to the workpiece, and a two-fluid nozzle for spraying a mixed fluid of liquid and gas onto an outer periphery of the holding surface of the chuck table, and the mixed fluid is sprayed from the two-fluid nozzle onto polishing waste accumulated on the outer periphery of the holding surface while rotating the chuck table. Polish The polishing device is characterized in that the polishing debris is removed from the outer periphery of the holding surface by jetting the debris in a direction opposite to the traveling direction of the debris.

[0012] According to another aspect of the present invention, there is provided a polishing method using a polishing apparatus including a rotatable chuck table which suction-holds a workpiece placed on a holding surface, and a polishing unit which polishes the workpiece held on the chuck table with a polishing pad while supplying a slurry to the workpiece, the method including a holding step of placing the workpiece on the holding surface and holding it on the chuck table, a polishing step of polishing the workpiece held on the chuck table with the polishing pad while supplying a slurry to the workpiece, a carrying step of carrying out the workpiece polished in the polishing step from the chuck table, and a polishing step of injecting a mixed fluid of liquid and gas onto polishing waste accumulated on an outer periphery of the holding surface of the chuck table while rotating the chuck table. Polish and a polishing debris removal step of jetting the polishing debris in a direction opposite to the direction of travel of the debris to remove the polishing debris. Effect of the Invention

[0013] In a polishing apparatus and method according to one aspect of the present invention, a workpiece is polished with a polishing pad while a slurry is supplied to the workpiece. Some of the polishing debris generated when the workpiece is polished accumulates and adheres to the outer periphery of the holding surface of the chuck table. When a mixed fluid of liquid and gas is sprayed onto the polishing debris adhered to the outer periphery of the holding surface, moisture is returned to the adhered polishing debris, softening it, and the force of the mixed fluid blows away the grinding debris, so that the polishing debris can be removed from the holding surface relatively easily. Once the polishing debris can be removed from the holding surface, a new workpiece can be placed on the holding surface without any hindrance.

[0014] Therefore, according to one aspect of the present invention, a polishing apparatus and a polishing method are provided that are capable of removing polishing debris adhered to the outer periphery of the chuck table. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a polishing apparatus. [Diagram 2] FIG. 2 is a perspective view showing a grinding wheel. [Diagram 3] FIG. 2 is a perspective view showing a schematic view of a state in which a protective member is attached to a surface of a workpiece. [Figure 4] FIG. 2 is a perspective view showing a state in which a workpiece is placed on a holding surface of a chuck table; [Diagram 5] FIG. 2 is a perspective view showing a schematic view of a workpiece being polished; [Figure 6] FIG. 13 is a perspective view showing a state in which the polished workpiece is carried out from the holding surface of the chuck table; [Figure 7] FIG. 7(A) is a perspective view that shows a schematic diagram of cleaning the outer periphery of the holding surface of the chuck table, and FIG. 7(B) is a perspective view that shows a schematic diagram of the chuck table whose holding surface has been cleaned. [Figure 8]Figure 8(A) is a flowchart showing the flow of each step of an example of a method for polishing a workpiece, Figure 8(B) is a flowchart showing the flow of each step of another example of a method for polishing a workpiece, and Figure 8(C) is a flowchart showing the flow of each step of yet another example of a method for polishing a workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. A workpiece to be polished by a polishing apparatus and a polishing method according to this embodiment will be described. Fig. 3 includes a perspective view showing a workpiece 1 such as a semiconductor wafer.

[0017] The workpiece 1 is, for example, a wafer made of silicon, SiC (silicon carbide), or other semiconductor materials, or a substantially disk-shaped substrate made of sapphire, glass, quartz, or other materials. The surface 1a of the workpiece 1 is partitioned into a plurality of regions by a plurality of planned division lines (streets) 5 arranged in a lattice pattern, and devices 7 such as ICs and LSIs are formed in each of the plurality of regions. Finally, the workpiece 1 is divided along the planned division lines 5 to form individual device chips.

[0018] The workpiece 1 is thinned by grinding the back surface 1b. The ground back surface 1b of the workpiece 1 has minute irregularities called grinding marks. If the workpiece 1 is divided along the division lines 5 to produce device chips in this state, the minute irregularities will remain on the device chips, which will cause a decrease in the flexural strength of the device chips. Therefore, the back surface 1b side of the workpiece 1 whose back surface 1b has been ground is polished to remove the minute irregularities on the back surface 1b and flatten it. Then, the minute irregularities will not remain on the device chips.

[0019] When polishing the back surface 1b side of the workpiece 1, a protective tape 3 is attached in advance to protect the front surface 1a side of the workpiece 1. The protective tape 3 protects the front surface 1a side of the workpiece 1 from impacts applied when the back surface 1b of the workpiece 1 is polished or when the workpiece 1 is transported, and prevents damage to the device 7.

[0020] The protective tape 3 has a flexible film-like substrate and a glue layer (adhesive layer) formed on one side of the substrate. For example, the substrate may be made of polyolefin, polyethylene terephthalate, polyvinyl chloride, polystyrene, or the like. For example, the glue layer (adhesive layer) may be made of silicone rubber, an acrylic material, an epoxy material, or the like.

[0021] Next, a polishing apparatus according to this embodiment for polishing the back surface 1b of the workpiece 1 will be described. Fig. 1 is a perspective view showing a polishing apparatus 2. The polishing apparatus 2 has a base 4 for supporting each component. Cassette mounting tables 6a and 6b are provided on the upper surface of the front portion of the base 4.

[0022] For example, a cassette 8a containing a workpiece 1 before polishing is placed on the cassette mounting stage 6a. For example, a cassette 8b for containing a workpiece 1 after polishing is placed on the cassette mounting stage 6b. A workpiece transport robot 10 for transporting the workpiece 1 is installed on the base 4 adjacent to the cassette mounting stages 6a and 6b.

[0023] Further provided on the upper surface of the front portion of the base 4 are a positioning table 12 which adjusts the position of the workpiece 1 by clamping the workpiece 1 with a plurality of positioning pins, and a workpiece carry-in mechanism (loading arm) 14 which places the workpiece 1 on the chuck table 20. Further provided are a workpiece removal mechanism (unloading arm) 16 which removes the workpiece 1 from the chuck table 20, and a spinner cleaning device 52 which cleans and spin-dries the polished workpiece 1.

[0024] An opening 4a is provided on the upper surface of the rear portion of the base 4. An X-axis moving table 18 is provided inside the opening 4a, on whose upper surface a chuck table 20 that suction-holds the workpiece 1 is placed. The X-axis moving table 18 can be moved in the X-axis direction by an X-axis moving mechanism (not shown). The X-axis moving table 18 is positioned, by the function of the X-axis moving mechanism, between a carry-in / out area 22 where the workpiece 1 is attached / detached on the chuck table 20 and a processing area 24 where the workpiece 1 held by suction on the chuck table 20 is polished.

[0025] A disk-shaped porous member having the same diameter as the workpiece 1 is exposed on the upper surface of the chuck table 20. The upper surface of the chuck table 20 serves as a holding surface 20a for holding the workpiece 1. The chuck table 20 includes an internal suction path (not shown) having one end connected to the porous member and the other end connected to a suction source (not shown). When the suction source is activated, negative pressure acts on the workpiece 1 placed on the holding surface 20a, and the workpiece 1 is sucked and held on the chuck table 20. The chuck table 20 can also rotate around an axis perpendicular to the holding surface 20a.

[0026] A polishing unit 26 for polishing the workpiece 1 is disposed above the processing area 24. A support part 28 is provided at the rear end of the base 4 of the polishing device 2, and the polishing unit 26 is supported by the support part 28. A pair of Z-axis guide rails 30 extending in the Z-axis direction are provided on the front surface of the support part 28, and a Z-axis moving plate 32 is slidably attached to each of the Z-axis guide rails 30.

[0027] A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 32, and a Z-axis ball screw 34 parallel to the Z-axis guide rail 30 is screwed into this nut portion. A Z-axis pulse motor 36 is connected to one end of the Z-axis ball screw 34. When the Z-axis pulse motor 36 rotates the Z-axis ball screw 34, the Z-axis moving plate 32 moves in the Z-axis direction along the Z-axis guide rail 30. The polishing unit 26 is fixed to the lower part on the front side of the Z-axis moving plate 32. When the Z-axis moving plate 32 is moved in the Z-axis direction, the polishing unit 26 can be moved in the Z-axis direction.

[0028] The polishing unit 26 includes a spindle 40 that is rotated by a motor connected to the base end, and a polishing wheel 44 that is fixed by a fastener 46 to a mount 42 disposed on the tip side of the spindle 40. The motor is provided in the spindle housing 38, and when the motor is operated, the polishing wheel 44 rotates in accordance with the rotation of the spindle 40.

[0029] 2 is a perspective view showing a schematic view of the polishing surface side of the polishing wheel 44. The polishing wheel 44 includes a polishing pad 44b made of, for example, polyurethane, nonwoven fabric, or the like, having a diameter larger than that of the rear surface 1b of the workpiece 1, and a wheel base 44a to which the polishing pad 44b is fixed.

[0030] The wheel base 44a is provided with a plurality of fixing holes (not shown) into which the fixing device 46 enters on the surface opposite to the surface on which the polishing pad 44b is fixed. A through hole is formed in the wheel base 44a and the polishing pad 44b of the polishing wheel 44, penetrating through the center in the thickness direction, and the end of the through hole on the polishing pad 44b side serves as a polishing liquid supply port 54.

[0031] 1, a polishing liquid supply path 50 is formed inside the polishing unit 26, penetrating the polishing unit 26 in the Z-axis direction. The upper end side of the polishing liquid supply path 50 is connected to a polishing liquid supply source 48, and when the workpiece 1 is polished, a polishing liquid called a slurry is supplied from the polishing liquid supply source 48 through the polishing liquid supply path 50 to a polishing liquid supply port 54 (see FIG. 2) formed in the center of the polishing pad 44b.

[0032] The slurry is a chemical solution in which abrasive grains (loose abrasive grains) are dispersed, and the material of the abrasive grains, the particle size of the abrasive grains, the type of dispersion medium, etc. are appropriately selected according to the material of the workpiece 1, etc.

[0033] Examples of the abrasive grains that can be used include silica, alumina, zirconia, manganese dioxide, ceria, clodal silica, fumed silica, boehmite, bayerite, and diamond. Examples of the dispersion medium that can be used include an alkaline aqueous solution in which potassium acetate, potassium chloride, potassium hydroxide, sodium hydroxide, ammonium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, imidazole, pyrazole, and pyrazine are dissolved. However, the components contained in the slurry are not limited to these, and other additives may be added.

[0034] When polishing the workpiece 1 held on the chuck table 20 positioned in the processing region 24, the polishing pad 44b is disposed above the workpiece 1. Then, the polishing wheel 44 and the chuck table 20 are rotated about their respective axes along the Z-axis direction, and the polishing wheel 44 is lowered to bring the polishing pad 44b into contact with the workpiece 1. At this time, in order to supply slurry between the workpiece 1 and the polishing pad 44b, the polishing liquid supply source 48 is operated to send the slurry to the polishing liquid supply path 50.

[0035] 5 is a perspective view showing a schematic diagram of polishing the workpiece 1. When polishing the workpiece 1, for example, the rotation speed of the chuck table 20 is set to about 300 rpm, and the rotation speed of the polishing wheel 44 is set to about 1000 rpm.

[0036] The position of the chuck table 20 is adjusted in advance so that the polishing liquid supply port 54 of the polishing pad 44b is blocked by the workpiece 1. Therefore, the slurry supplied from the polishing liquid supply port 54 remains on the workpiece 1. When the polishing pad 44b and the workpiece 1 are rotated about an axis along the Z-axis direction while being in contact with each other, the slurry enters between the polishing pad 44b and the surface to be polished (rear surface 1b) of the workpiece 1.

[0037] When the workpiece 1 is polished by the polishing pad 44b, polishing debris is generated from the polished surface (rear surface 1b). The polishing debris is taken up into the slurry and discharged toward the outside of the polishing pad 44b. The slurry 56 that has taken up the polishing debris eventually reaches the outer periphery of the rear surface 1b of the workpiece 1 and falls onto the outer periphery 20b of the holding surface 20a of the chuck table 20.

[0038] Thereafter, a part of the slurry 56 falls off the chuck table 20 and is discharged from a drainage port 4b formed in the opening 4a of the base 4 of the polishing apparatus 2. Meanwhile, another part of the slurry that has fallen onto the outer periphery 20b of the holding surface 20a of the chuck table 20 dries on the outer periphery 20b and adheres to the outer periphery 20b together with the grinding debris. On the back surface 1b of the workpiece 1, processing heat is generated by polishing and the temperature of the slurry is kept relatively high, but the temperature of the slurry that has fallen onto the outer periphery 20b of the holding surface 20a drops rapidly, so that adhesion is likely to progress.

[0039] 6 is a perspective view that shows a schematic diagram of a state in which the polished workpiece 1 is carried out from the chuck table 20. As shown in FIG. 6, polishing debris 9 remains adhered to the outer periphery 20b of the holding surface 20a of the chuck table 20.

[0040] In the polishing device 2, a plurality of workpieces 1 stored in a cassette 8a are successively carried out and placed on the chuck table 20, polished by the polishing unit 26, carried out from the chuck table 20, cleaned by the spinner cleaning device 52, and stored in the cassette 8b. Then, the next workpiece 1 to be polished is placed on the holding surface 20a on which the polishing debris 9 remains adhered to the outer periphery 20b.

[0041] When multiple workpieces 1 are repeatedly polished, polishing debris 9 accumulates one after another on the outer periphery 20b of the holding surface 20a. If the amount of polishing debris 9 adhering to the outer periphery 20b increases, there is a risk that the polishing debris 9 will get in between the workpiece 1 and the holding surface 20a when a new workpiece 1 is placed on the chuck table 20. In this case, the workpiece 1 cannot be properly held by the chuck table 20, and the polishing unit 26 will not be able to properly polish the workpiece 1.

[0042] For example, it is conceivable to wash the holding surface 20a of the chuck table 20 by spraying water onto the polishing debris 9, but simply spraying water has a low cleaning effect and is unable to completely remove the polishing debris 9. It is also conceivable to mechanically polish the holding surface 20a of the chuck table 20, but there is a risk that the polishing debris 9 adhering to the holding surface 20a will be dragged and the holding surface 20a will be scratched.

[0043] Therefore, in the polishing apparatus 2 according to this embodiment, the chuck table 20 having the polishing debris 9 adhered to the outer circumferential portion 20b of the holding surface 20a is washed with a mixed fluid obtained by mixing a liquid such as pure water and a gas such as high-pressure air. In the polishing apparatus 2, for example, a two-fluid spraying unit 58 is provided near the loading / unloading area 22 where the workpiece 1 is loaded and unloaded.

[0044] 7(A) is a perspective view that shows a schematic diagram of the chuck table 20 onto which the mixed fluid 60 is sprayed by the two-fluid spray unit 58. The two-fluid spray unit 58 is, for example, a pipe-shaped member including a shaft portion 58a extending in the Z-axis direction, an arm portion 58b extending in the horizontal direction from the upper end of the shaft portion 58a, and a two-fluid nozzle 58c provided at the tip of the arm portion 58b. In the two-fluid spray unit 58, for example, the shaft portion 58a may rotate to rotate the arm portion 58b, and the two-fluid nozzle 58c may be positioned at a predetermined position.

[0045] A liquid supply source and a gas supply source (not shown) are connected to the lower end of the shaft portion 58a. The liquid supply source is composed of, for example, a tank that contains liquid such as pure water, and a liquid delivery pump that sends the liquid from the tank to the two-fluid jetting unit 58. The gas supply source is composed of, for example, a cylinder that contains high-pressure nitrogen gas or air, and a regulator that adjusts the pressure of the gas supplied from the cylinder to the two-fluid jetting unit 58.

[0046] A mixed fluid obtained by mixing liquid supplied from a liquid supply source and gas supplied from a gas supply source is supplied to the shaft portion 58a. The mixed fluid reaches the two-fluid nozzle 58c through the arm portion 58b, and is forcefully ejected from the two-fluid nozzle 58c toward the chuck table 20 below. The diameter of the ejection port of the two-fluid nozzle 58c is preferably about 20 mm. The liquid is preferably ejected from the two-fluid nozzle 58c at a pressure of about 0.3 MPa and an ejection rate of about 1 L per minute.

[0047] When cleaning the outer periphery 20b of the holding surface 20a of the chuck table 20, for example, the chuck table may be rotated at a rotation speed of about 30 rpm, whereby the mixed fluid 60 is sprayed over the entire circumference of the outer periphery 20b of the holding surface 20a.

[0048] When the mixed fluid 60 is sprayed onto the polishing debris 9 adhered to the outer periphery 20b of the holding surface 20a, the water penetrates into the polishing debris 9, softening the polishing debris 9. Then, as the spraying of the mixed fluid 60 continues, the polishing debris 9 is eventually detached from the outer periphery 20b of the holding surface 20a by the force of the mixed fluid 60 and is removed.

[0049] While the mixed fluid 60 is being sprayed from the two-fluid spray unit 58, water may be sprayed from the porous member forming the holding surface 20a of the chuck table 20. In this case, the polishing debris 9 peeled off from the outer circumferential portion 20b does not enter the porous member and is discharged to the outside of the holding surface 20a of the chuck table 20, thereby preventing problems such as re-adhesion of the peeled polishing debris 9 to the holding surface 20a.

[0050] Here, the two-fluid nozzle 58c of the two-fluid jetting unit 58 may be directed, for example, downward in the vertical direction (Z-axis direction). When the mixed fluid 60 is jetted from directly above onto the outer circumferential portion 20b of the holding surface 20a, the mixed fluid 60 can be made to act on the polishing debris 9 efficiently.

[0051] Furthermore, the bi-fluid nozzle 58c of the bi-fluid jetting unit 58 may be inclined at a predetermined angle with respect to the Z-axis direction so as to face the rotation direction of the chuck table 20 at the jetted position on the outer periphery 20b of the holding surface 20a of the chuck table 20. In this case, the mixed fluid 60 is jetted from a direction opposite to the traveling direction of the polishing debris 9 that is rotating and moving on the outer periphery 9b of the holding surface 9a, so that the mixed fluid 60 is likely to act strongly on the polishing debris 9. However, in the polishing apparatus 2 according to this embodiment, the orientation of the bi-fluid nozzle 58c is not limited to this.

[0052] As described above, in the polishing apparatus 2 according to this embodiment, a mixed fluid of liquid and gas can be sprayed onto the polishing debris 9 adhered to the outer periphery 20b of the holding surface 20a of the chuck table 20, and the polishing debris 9 can be easily removed. Fig. 7(B) is a perspective view showing a schematic view of the chuck table 20 from which the polishing debris 9 has been removed from the outer periphery 20b of the holding surface 20a. The chuck table 20 with the cleaned holding surface 20a can suck and hold a new workpiece 1 without any problems, so that the workpiece 1 can be properly polished by the polishing unit 26.

[0053] Next, a description will be given of a polishing method according to this embodiment in which the workpiece 1 is polished by the polishing device 2 and the outer circumferential portion 20b of the holding surface 20a of the chuck table 20 is cleaned. Fig. 8(A) is a flow chart that shows a schematic flow of each step of the polishing method according to this embodiment.

[0054] In the polishing method according to this embodiment, first, a holding step S10 is performed in which the workpiece 1 is placed on the holding surface 20a and held by the chuck table 20. Fig. 4 is a perspective view that typically shows the holding step S10.

[0055] In the holding step S10, the X-axis moving table 18 is positioned in the carry-in / out area 22, and the workpiece 1 positioned at a predetermined position by the positioning table 12 is carried onto the holding surface 20a by the workpiece carrying-in mechanism 14. At this time, the front surface 1a of the workpiece 1 to which the protective tape 3 is attached faces the holding surface 20a, and the back surface 1b, which will be the surface to be polished, faces upward. Then, the suction source of the chuck table 20 is operated to suction and hold the workpiece 1 on the chuck table 20. Then, the X-axis moving table 18 is moved to the processing area 24.

[0056] Next, a polishing step S20 is performed in which the workpiece 1 held by the chuck table 20 is polished with a polishing pad while a slurry is supplied to the workpiece 1. Fig. 5 is a perspective view showing the polishing step S20. In the polishing step S20, the chuck table 20 and the polishing wheel 44 are rotated around their respective axes. Then, while a slurry is supplied from the polishing liquid supply source 48 through the polishing liquid supply path 50 to the back surface 1b of the workpiece 1, the polishing unit 26 is lowered to bring the polishing pad 44b into contact with the back surface 1b.

[0057] At this time, the slurry gets into between the polishing pad 44b and the back surface 1b of the workpiece 1, and the back surface 1b of the workpiece 1 is polished and flattened. Polishing debris generated from the workpiece 1, etc. is taken up by the slurry and carried to the outer periphery of the workpiece 1. Then, the slurry 56 that has taken up the polishing debris falls onto the outer periphery 20b of the holding surface 20a of the chuck table 20, and some of the polishing debris, etc., adheres to the outer periphery 20b.

[0058] Next, an unloading step S30 is performed in which the workpiece 1 polished in the polishing step S20 is unloaded from the chuck table 20. In the unloading step S30, the X-axis moving table 18 is moved to the unloading area 22, the suction holding of the workpiece 1 by the chuck table 20 is released, and the workpiece 1 is transported by the workpiece unloading mechanism 16 to the spinner cleaning device 52. The workpiece 1 is then cleaned and dried by the spinner cleaning device 52, and the workpiece transport robot 10 stores the workpiece 1 in the cassette 8b.

[0059] In the polishing method according to this embodiment, after the workpiece 1 is removed from the chuck table 20, a polishing debris removal step S40 is performed in which a mixed fluid 60 is sprayed onto the polishing debris 9 accumulated on the outer periphery 20b of the holding surface 20a of the chuck table 20 to remove the polishing debris 9. Fig. 7(A) is a perspective view that typically shows the polishing debris removal step S40.

[0060] In the polishing debris removal step S40, the bi-fluid nozzle 58c of the bi-fluid jetting unit 58 is directed toward the outer periphery 20b of the holding surface 20a of the chuck table 20. Then, the bi-fluid nozzle 58c jets the mixed fluid 60 onto the outer periphery 20b of the holding surface 20a. At this time, the chuck table 20 is rotated at a predetermined rotation speed. Then, the polishing debris 9 adhered to the outer periphery 20b is heated and exposed to water, softening it, and is removed by further jetting of the mixed fluid 60.

[0061] Furthermore, in the polishing debris removal step S40, water is sprayed from the porous member constituting the holding surface 20a, thereby preventing the polishing debris 9 removed from the outer periphery 20b of the holding surface 20a from entering the porous member. Fig. 7(B) is a schematic perspective view of the chuck table 20 after being washed and the polishing debris 9 has been removed. As described above, in the polishing method according to this embodiment, the polishing debris 9 can be easily removed from the outer periphery 20b of the holding surface 20a.

[0062] In the polishing apparatus 2 according to this embodiment, a two-fluid ejection unit 58 that ejects the mixed fluid 60 onto the holding surface 20a of the chuck table 20 may be provided in the vicinity of the processing region 24. In the polishing method according to this embodiment, a polishing debris removal step S40 may be performed during the polishing step S20. Fig. 8(B) is a flowchart showing the flow of each step of the polishing method according to this embodiment when the polishing debris removal step S40 is performed in the polishing step S20.

[0063] If the two-fluid jetting unit 58 is provided near the processing region 24, the mixed fluid 60 can be jetted from the two-fluid jetting unit 58 to the outer periphery 20b of the holding surface 20a of the chuck table 20 while the workpiece 1 is being polished by the polishing unit 26. In this case, the slurry containing polishing debris that has reached the outer periphery 20b can be removed from the outer periphery 20b by the mixed fluid 60 before it dries and adheres to the outer periphery 20b.

[0064] In this case, after the polished workpiece 1 is removed from the chuck table 20, a new workpiece 1 can be immediately loaded onto the chuck table 20, so that multiple workpieces 1 can be polished efficiently.

[0065] Furthermore, in the polishing method according to this embodiment, the polishing debris removing step S40 may be performed before the holding step S10. Fig. 8(C) is a flow chart showing a flow of each step of the polishing method for a workpiece in the case where the polishing debris removing step S40 is performed before the holding step S10.

[0066] For example, when multiple workpieces 1 are polished one after another by the polishing device 2, a problem occurs when a new workpiece 1 is carried into the chuck table 20 if polishing debris 9 from the previous workpiece 1 polished by the polishing unit 26 adheres to the outer periphery 20b of the holding surface 20a. Therefore, a polishing debris removal step S40 may be performed before the holding step S10, and the holding surface 20a may be washed by spraying the mixed fluid 60.

[0067] That is, the grinding debris removal step S40 can be considered as a step that is carried out in advance to properly grind the workpiece 1. The grinding debris removal step S40 can also be considered as a step that removes grinding debris 9 that is generated by grinding the workpiece 1 in the grinding step S20 and adheres to the outer circumferential portion 20b of the holding surface 20a.

[0068] In any case, the polishing method according to this embodiment provides the effect of properly holding the workpiece 1 on the chuck table 20 and properly polishing the workpiece 1 for all workpieces 1 polished by the polishing device 2. The number of steps required for replacing and cleaning the chuck table 20 is reduced, and the downtime of the polishing unit 26 is also reduced, so the processing efficiency of the workpiece 1 is improved.

[0069] The present invention is not limited to the above-described embodiment, and can be modified in various ways. For example, in the above-described embodiment, the workpiece 1 is polished by the polishing device 2, but one aspect of the present invention is not limited to this. For example, the polishing device 2 may have a grinding unit (not shown) that grinds the workpiece 1, in addition to the polishing unit 26 that polishes the workpiece 1. The workpiece 1 held by the chuck table 20 may be ground by the grinding unit and then polished by the polishing unit 26.

[0070] In this case, grinding debris will accumulate in addition to polishing debris 9 on the outer periphery 20b of the holding surface 20a of the chuck table 20. Even in this case, by spraying a mixed fluid onto the outer periphery 20b from the two-fluid jetting unit 58, the grinding debris can be removed together with the polishing debris 9. Therefore, when a new workpiece 1 is placed on the chuck table 20, the polishing debris 9 and grinding debris will not hinder the chuck table 20 from properly holding the workpiece 1.

[0071] Furthermore, the mixed fluid ejected from the two-fluid nozzle 58c may be preheated by a heating source (heater) such as an electric heating wire, and the heated mixed fluid may be supplied to the outer periphery 20b of the holding surface 20a of the chuck table 20. In this case, the polishing debris 9 adhered to the outer periphery 20b of the holding surface 20a is more likely to be softened, and is more easily removed by the mixed fluid.

[0072] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0073] 1 Workpiece 1a surface 1b back side 3 Protective tape 5. Planned division line 7 Devices 9 Polishing dust 2 Polishing equipment 4 Foundation 4a aperture 4b Drain port 6a, 6b Cassette placement table 8a,8b Cassette 10 Workpiece transport robot 12 Positioning table 14 Workpiece loading mechanism (loading arm) 16 Workpiece removal mechanism (unloading arm) 18 X-axis moving table 20 Chuck table 20a Holding surface 22 Loading / unloading area 24 Processing area 26 Polishing unit 28 Support part 30 Z-axis guide rail 32 Z-axis moving plate 34 Z-axis ball screw 36 Z-axis pulse motor 38 Spindle housing 40 Spindle 42 Mount 44 Abrasive Wheel 44a Wheelbase 44b Polishing pad 46 Fixtures 48 Polishing liquid supply source 50 Polishing liquid supply path 52 Spinner cleaning device 54 Polishing liquid supply port 56 Slurry 58 Two-fluid injection unit 58a Shaft 58b Arm 58c Two-fluid nozzle

Claims

1. A polishing apparatus for polishing a workpiece, comprising: a rotatable chuck table having a holding surface and suction-holding the workpiece placed on the holding surface; a polishing unit that polishes the workpiece held by the chuck table with a polishing pad while supplying a slurry to the workpiece; a two-fluid nozzle that injects a mixed fluid of liquid and gas onto an outer periphery of the holding surface of the chuck table; Equipped with a polishing apparatus comprising: a polishing member for removing a polishing debris from a peripheral portion of the holding surface by injecting the mixed fluid from the two-fluid nozzle in a direction opposite to a traveling direction of the polishing debris while rotating the chuck table;

2. A polishing method using a polishing apparatus including a rotatable chuck table that suction-holds a workpiece placed on a holding surface, and a polishing unit that polishes the workpiece held by the chuck table with a polishing pad while supplying a slurry to the workpiece, comprising: a holding step of placing the workpiece on the holding surface and holding it on the chuck table; a polishing step of polishing the workpiece held by the chuck table with the polishing pad while supplying a slurry to the workpiece; a carrying-out step of carrying out the workpiece polished in the polishing step from the chuck table; a polishing debris removing step of spraying a mixed fluid of liquid and gas onto polishing debris accumulated on an outer periphery of the holding surface of the chuck table in a direction opposite to a moving direction of the polishing debris while rotating the chuck table, thereby removing the polishing debris; A polishing method comprising:

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