JP2005088171A - Work holding head and polishing device having work holding head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a work holding head and a polishing device having the work holding head capable of unifying a polishing rate on a substantially whole surface of work, wherein pressure distribution in processing is unified even when an orientation flat or a notch is provided on the work. <P>SOLUTION: The work holding head 14 has a protective sheet 52, a ring-like member 28, and a carrier 24. The protective sheet 52 is composed of an elastic material, and presses the work W to a polishing pad 20. The ring-like member 28 abuts on the polishing pad 20 while holding a periphery of the protective sheet 52. The carrier 24 presses the protective sheet 52 of a part corresponding to a space of the work W to the work. A circular reinforcing member 80 is provided at the part corresponding to an outer peripheral space of the work of an upper face and/or a lower face of the protective sheet 52, and rigidity of the protective sheet 52 of the part is increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a work holding head and a polishing apparatus having the work holding head, and in particular, a work holding head suitable for polishing a wafer or the like by chemical mechanical polishing (CMP) and the work holding head. The present invention relates to a polishing apparatus having

  Polishing of a wafer by CMP is performed by pressing the wafer against a rotating polishing pad with a predetermined pressure while rotating the wafer, and supplying an abrasive slurry between the polishing pad and the wafer. At this time, the wafer is surrounded by a retainer ring, and the back side is held by the carrier and pressed against the polishing pad.

  In such polishing of a wafer by CMP, uniformity of polishing is strongly demanded, and in order to cope with this, proposals have been made for a substrate polishing apparatus that has been devised in various ways (for example, Patent Documents 1 to 3). reference.).

Among these, Patent Document 1 includes an adjustment mechanism that can independently control the pressing pressure of the retainer ring, thereby making the polishing state uniform. Patent Document 2 controls the guide ring pressing pressure to be smaller than the substrate pressing pressure, and makes the polishing rate uniform. Patent Document 3 attempts to obtain a wafer having no peripheral sagging or the like by making the polishing state uniform by pressing with a pressurized fluid.
JP-A-8-229808 JP-A-9-225818 Japanese Patent Laid-Open No. 7-124862

  Incidentally, an orientation flat or a notch is generally provided on a wafer processed by such a substrate polishing apparatus. This orientation flat is also referred to as an orientation flat, and refers to a flat surface provided on the outer periphery of the ingot and the wafer in order to facilitate discrimination and alignment of crystal orientation and conductivity type. A notch refers to a notch provided on the outer periphery of an ingot and a wafer in order to facilitate discrimination and alignment of crystal directions.

  However, even when processed by the conventional substrate polishing apparatus, there is a problem in that the polishing state at the orientation flat or notch portion of the wafer does not become the same state as other portions of the wafer.

  9 and 10 are conceptual diagrams showing an example of a conventional substrate polishing apparatus. In FIG. 9, the protective sheet 1 is attached to the retainer ring holder 3 disposed around the carrier 2 with the peripheral edge adhered, and the retainer ring 4 is attached to the lower part of the protective sheet 1 by adhesion. Compressed air is supplied between the protective sheet 1 and the carrier 2, and the protective sheet 1 acts as an airbag to press the wafer W and press the wafer W against the polishing pad 20 for polishing. FIG. 10 shows a substrate polishing apparatus having a configuration in which the protective sheet 1 is not provided. The carrier 2 directly presses the wafer W and presses the wafer W against the polishing pad 20 to perform polishing.

  In the case of the substrate polishing apparatus of FIG. 9, the protective sheet 1 is bent at the edge portion of the wafer W as shown in the enlarged view in the circle of FIG. It becomes. At that time, the polishing rate is locally different in the portion where the orientation flat or notch is provided. That is, as shown in FIG. 11, the polishing rate is high at both side portions O2 and O2 of the orientation flat, and the polishing rate is low at the central portion O1 of the orientation flat, resulting in poor polishing conditions.

  On the other hand, in the case of the substrate polishing apparatus of FIG. 10, although the carrier 2 is not deformed, a similar phenomenon occurs. That is, as shown in FIG. 12, the polishing rate is low at the center O1 of the orientation flat, resulting in a poor polishing state.

  The present invention has been made in view of such circumstances. Even when an orientation flat or notch is provided on a workpiece (wafer or the like), the pressure distribution during processing is uniform, and the polishing rate is uniform over substantially the entire surface of the workpiece. An object of the present invention is to provide a work holding head that can be used and a polishing apparatus having the work holding head.

  In order to achieve the object, the present invention according to claim 1 is a protective sheet made of an elastic material that presses a workpiece against a polishing pad, and a ring shape that holds the periphery of the protective sheet and abuts against the polishing pad. In a work holding head comprising a member and a carrier that presses a portion of the protective sheet corresponding to the region of the workpiece toward the workpiece, the portion corresponding to the outer peripheral region of the upper surface and / or the lower surface of the protective sheet includes: Provided is a work holding head characterized in that an annular reinforcing member is provided.

  According to the present invention, since the annular reinforcing member is provided in the portion corresponding to the work outer peripheral region on the upper surface and / or the lower surface of the protective sheet, the rigidity of the protective sheet in this portion increases, and the orientation flat portion And the bending of the protective sheet at the notch portion (hereinafter abbreviated as “orientation flat portion etc.”) are suppressed. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  In the present invention, it is preferable that a pressurized gas is supplied between the carrier and the protective sheet. Even if the carrier and the protective sheet are in mechanical contact with each other, the effect of the present invention can be obtained, but if a pressurized gas is supplied between the carrier and the protective sheet, The effects of the present invention can be obtained more suitably.

  The present invention according to claim 3 corresponds to a protective sheet made of an elastic material that presses the workpiece against the polishing pad, a ring-shaped member that holds the periphery of the protective sheet and abuts against the polishing pad, and a region of the workpiece A workpiece holding head comprising a carrier that presses a portion of the protective sheet toward the workpiece, and a pressurized gas is supplied between the carrier and the protective sheet. There is provided a work holding head characterized in that an orifice is formed between an outer edge and the protective sheet, or between an outer surface of the carrier and an inner surface of the ring-shaped member.

  According to the present invention, an orifice is formed between the outer edge of the lower surface of the carrier and the protective sheet, or between the outer surface of the carrier and the inner surface of the ring-shaped member. The sheet does not bend greatly below the edge of the orientation flat portion or the like. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  The term “orifice” refers to a fluid restriction in which a passage with a reduced area is relatively short compared to the cross-sectional dimension, and the pressure drop is not significantly affected by the fluid viscosity.

  As a specific configuration for forming such an orifice, the tension of the protective sheet (for example, the tension that supports the periphery of the protective sheet with a ring-shaped member) is made stronger than usual, and the outer edge of the lower surface of the carrier and the protective sheet A configuration in which an orifice is formed between them, a configuration in which the clearance between the outer side surface of the carrier and the inner side surface of the ring-shaped member is set to a predetermined value or less are conceivable.

  In this invention, it is preferable that the part applicable to the area | region of the workpiece | work outer periphery of the said protection sheet is provided with the several through-hole along the circumferential direction. If such a plurality of through holes are provided, the pressurized gas supplied between the carrier and the protective sheet leaks from the through holes. If the through hole is not blocked by the workpiece in the orientation flat part, etc., the pressurized gas leaks from the through hole, which causes the protective sheet to be greatly bent downward from the edge of the orientation flat part, etc. Disappears. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  The present invention according to claim 5 corresponds to the region of the workpiece, a protective sheet made of an elastic material that presses the workpiece against the polishing pad, a ring-shaped member that holds the periphery of the protective sheet and contacts the polishing pad, and And a carrier for pressing a portion of the protective sheet against the work, and a pressurized gas is supplied between the carrier and the protective sheet from a plurality of through holes provided in the carrier. In the part corresponding to the work area of the protective sheet, a plurality of through holes are provided, and the part corresponding to the work outer peripheral area is provided along the circumferential direction. Provided is a work holding head characterized in that positions of a plurality of through-holes and positions of a plurality of through-holes provided in the carrier substantially coincide with each other.

  According to the present invention, pressurized gas is supplied between the carrier and the protective sheet from the plurality of through holes provided in the carrier. And the part corresponding to the area | region of the workpiece | work of a protection sheet is provided with several through-holes, Furthermore, the several through-hole provided along the circumferential direction in the part applicable to the area | region of workpiece | work outer periphery And the positions of the plurality of through holes provided in the carrier substantially coincide with each other. Therefore, the pressurized gas supplied between the carrier and the protective sheet leaks from the through hole, and is discharged from the outer peripheral portion of the work through the gap between the protective sheet and the work. In particular, since the through hole provided along the circumferential direction in the portion corresponding to the region of the outer periphery of the workpiece is in the same location as the position of the through hole provided in the carrier, the flow rate of the gas discharged from here is In many cases, the protective sheet in this portion does not bend greatly below the edge of the orientation flat portion or the like. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  As described above, according to the first aspect of the present invention, in the work holding head, a portion corresponding to the work outer peripheral region on the upper surface and / or the lower surface of the protective sheet that presses the work against the polishing pad has an annular shape. The reinforcing member is provided. Thereby, the rigidity of the protective sheet of this part increases and the bending of the protective sheet in an orientation flat part etc. is suppressed. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  According to the third aspect of the present invention, in the work holding head having a configuration in which a pressurized gas is supplied between the carrier and the protective sheet, and the protective sheet presses the work against the polishing pad, An orifice is formed between the protective sheet or between the outer surface of the carrier and the inner surface of the ring-shaped member. Due to the effect of the orifice, the protective sheet does not bend greatly below the edge of the orientation flat portion or the like. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  According to the fifth aspect of the present invention, a pressurized gas is supplied between the carrier and the protective sheet, and the protective sheet is provided on the carrier in the workpiece holding head configured to press the workpiece against the polishing pad. Pressurized gas is supplied from the plurality of through holes. And the part corresponding to the area | region of the workpiece | work of a protection sheet is provided with several through-holes, Furthermore, the several through-hole provided along the circumferential direction in the part applicable to the area | region of workpiece | work outer periphery And the positions of the plurality of through holes provided in the carrier substantially coincide with each other. Therefore, the pressurized gas supplied between the carrier and the protective sheet leaks from the through hole, and is discharged from the outer peripheral portion of the work through the gap between the protective sheet and the work. In particular, since the through hole provided along the circumferential direction in the portion corresponding to the region of the outer periphery of the workpiece is in the same location as the position of the through hole provided in the carrier, the flow rate of the gas discharged from here is In many cases, the protective sheet in this portion does not bend greatly below the edge of the orientation flat portion or the like. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  Hereinafter, preferred embodiments of a workpiece holding head and a polishing apparatus having the workpiece holding head according to the present invention will be described in detail with reference to the accompanying drawings. First, the basic configuration of the polishing apparatus will be described with a holding head (work holding head) as a main component, and then each embodiment will be described in detail.

  FIG. 1 is a perspective view showing the overall configuration of the polishing apparatus 10. As shown in the figure, the polishing apparatus 10 is mainly composed of a polishing surface plate 12 and a holding head (work holding head) 14.

  The polishing surface plate 12 is formed in a disk shape, and a rotating shaft 16 is connected to the center of the lower surface thereof. The polishing surface plate 12 rotates by driving a motor 18 connected to the rotating shaft 16. A polishing pad 20 is attached to the upper surface of the polishing surface plate 12, and abrasive slurry is supplied onto the polishing pad 20 from a nozzle (not shown).

  As shown in FIG. 2, the work holding head 14 is mainly composed of a main body (head main body) 22 of the holding head, a carrier 24, a carrier pressing means 26, a retainer ring 28 (corresponding to a lower ring), a retainer ring pressing means 30, and a protection. It comprises a seat 52, air control means, and the like.

  The head body 22 is formed in a disk shape, and a rotary shaft 32 is connected to the center of the upper surface thereof. The head main body 22 rotates by being driven by a motor (not shown) connected to the rotary shaft 32.

  The carrier 24 is formed in a disc shape and is arranged at the lower center of the head body 22. A cylindrical recess 34 is formed at the center of the upper surface of the carrier 24. A shaft portion 36 of the head body 22 is fitted into the recess 34 via a pin 38. The rotation is transmitted to the carrier 24 from the head main body 22 through the pin 38.

  Further, a carrier pressing member 40 is provided on the peripheral edge of the upper surface of the carrier 24. The carrier 24 receives a pressing force from the carrier pressing means 26 via the carrier pressing member 40.

  An air suction / blowout groove 42, which is an air supply path for injecting air to the protective sheet 52, is formed on the lower surface of the carrier 24. An air flow path 44 formed inside the carrier 24 is communicated with the suction / blowout groove 42. An intake pump and an air supply pump are connected to the air flow path 44 via an air pipe (not shown). The suction and blowing of air from the suction / blowing groove 42 is performed by switching between the intake pump and the air supply pump.

  The air suction / blowout groove 42, the air flow path 44, the air piping, the intake pump, the air supply pump, the switching means between the intake pump and the air supply pump, and the like constitute an air control means.

  In the basic configuration shown in FIG. 2, the air suction / blowout groove 42 is employed, but the function can be similarly obtained by using a plurality of through holes instead. In each embodiment described later, a plurality of through holes may be employed.

  The carrier pressing means 26 is disposed on the outer peripheral portion of the lower surface of the head body 22, and applies a pressing force to the carrier pressing member 40 to transmit the pressing force to the carrier 24 coupled thereto. The carrier pressing means 26 is preferably composed of a rubber sheet airbag 46 that expands and contracts by air intake and exhaust. An air supply mechanism 48 for supplying air is connected to the airbag 46, and the air supply mechanism 48 is provided with a regulator (not shown) that adjusts the pressure of air pumped from a pump (not shown).

  The retainer ring 28 is formed in a ring shape and is disposed on the outer periphery of the carrier 24. The retainer ring 28 is attached to a holder (retainer ring holder) 50 which is a ring-shaped member main body provided on the work holding head 14, and a protective sheet 52 is stretched around the inner periphery thereof.

  The retainer ring holder 50 which is a ring-shaped member main body is formed in a ring shape, and an annular recess 54 is formed on the lower surface thereof as shown in FIGS. On the other hand, a convex portion 56 that fits into the concave portion 54 is formed on the upper surface of the retainer ring 28. By fitting the convex portion 56 into the concave portion 54 of the retainer ring holder 50, the retainer ring 28 is retained by the retainer ring 28. Attached to the ring holder 50.

  As the material of the retainer ring holder 50, various metal materials can be used. In particular, stainless steel, anodized aluminum, and the like can be preferably used from the viewpoints of corrosion resistance to an abrasive and rust prevention effect.

  The material of the retainer ring 28 is preferably a material that has a wear resistance of a predetermined level or more that does not cause a problem even when mixed with an abrasive, considering that the retainer ring 28 is worn by the polishing pad 20. As a resin material such as resin, PET, polyethylene, polypropylene, PFA, PTFE and the like can be used, and as a resin material such as polyimide resin, PEEK, Vespel (trade name) and the like can be used. Of these, PEEK can be preferably used.

  The protective sheet 52 is formed in a circular shape and has a plurality of holes 52A. The protective sheet 52 is stretched inside the retainer ring 28 by sandwiching the peripheral edge portion between the retainer ring 28 and the retainer ring holder 50. That is, the protective sheet 52 is formed in a thin disk shape, and when the retainer ring 28 is attached, the peripheral portion thereof is sandwiched between the convex portion 56 of the retainer ring 28 and the concave portion 54 of the retainer ring holder 50. It is stretched inside the retainer ring 28. By stretching in this way, the protective sheet 52 is pulled in the outer circumferential direction at the same time as being attached, and is stretched uniformly over the entire surface. The protective sheet 52 has a plurality of holes (not shown) through which the bolts 58, 58,.

  The air ejected by the suction / blowing groove 42 of the carrier 24 forms an air layer between the carrier 24 and the protective sheet 52 by the pressing force applied by the carrier pressing means 26, and the principle of a so-called hydrostatic bearing ( The wafer W is pressed against the polishing pad 20 through the protective sheet 52 by the principle of the air bearing.

  The protective sheet 52 is an elastic member that is flexible enough to transmit the air dynamic pressure distribution formed by the air layer formed by the suction / blowout grooves 42 of the carrier 24 to the wafer W, and damages the wafer W. Therefore, it is required that the material does not contaminate.

  Further, when the retainer ring 28 is worn, it is necessary to have flexibility that can change the amount of deflection following the retainer ring 28 and sufficient strength against contact and friction with the wafer W during polishing.

  When the strength of the protective sheet 52 is insufficient, the protective sheet 52 is damaged or wrinkles occur in the protective sheet 52, making normal polishing work difficult. On the other hand, if the strength of the protective sheet 52 is too high, the flexibility is insufficient, and the retainer ring 28 cannot be followed when worn. As a result, the replacement frequency of the retainer ring 28 increases.

  There are two types of wafers W, a notch type and an orientation flat type. In the case of the orientation flat type, the hardness of the protective sheet 52 is preferably high in order to reduce the influence of the orientation flat portion.

  On the other hand, in the case of the notch type, the hardness of the protective sheet 52 is preferably low as long as it has sufficient strength to withstand friction with the wafer W during polishing. That is, if the protection sheet 52 is highly flexible, the attachment position of the protection sheet 52 to the retainer ring 28 can be sufficiently higher than the upper surface of the wafer W. Thereby, even if the wear amount of the retainer ring 28 is large, the retainer ring 28 can be used, and the replacement frequency of the retainer ring 28 can be reduced.

  In order to optimize the strength of the protective sheet 52, it is necessary to treat as follows. When the hardness of the protective sheet 52 is constant, when the pressing force of the wafer W is high, the thickness of the protective sheet 52 is increased to cope with the damage of the protective sheet 52 and the generation of wrinkles of the protective sheet 52. When the pressing force of the wafer W is low, the thickness of the protective sheet 52 is reduced so that the retainer ring 28 can follow the wear.

  On the other hand, when the thickness of the protective sheet 52 is constant, when the pressing force of the wafer W is high, the hardness of the protective sheet 52 is increased so that the protective sheet 52 is damaged and wrinkles of the protective sheet 52 occur. In response, when the pressing force of the wafer W is low, the hardness of the protective sheet 52 is lowered so that the retainer ring 28 can follow the wear.

  Considering the relationship between the protective sheet 52 and the polishing pad 20, when the polishing pad 20 is soft and the pressing force of the wafer W is high, the hardness of the protective sheet 52 should be reduced and the thickness of the protective sheet 52 should be increased. It is. However, even in this case, in the case of the orientation flat type, the hardness of the protective sheet 52 should be increased and the thickness of the protective sheet 52 should be decreased to ensure elasticity.

  On the other hand, when the polishing pad 20 is hard and the pressing force of the wafer W is low, the hardness of the protective sheet 52 should be lowered and the thickness of the protective sheet 52 should be reduced. Thereby, it can press to the outer peripheral part of the wafer W, there is little uneven tension of the protection sheet 52, and the impact force added to the edge of the wafer W is also small. However, even in this case, in the case of the orientation flat type, the protective sheet 52 having a high hardness that does not easily affect the orientation flat portion should be used.

  In order to cope with this, the hardness of the protective sheet 52 needs to be within an appropriate range. If the hardness of the protective sheet 52 is too high, there is a high possibility that the back surface of the wafer W will be damaged, and the function as the protective sheet cannot be exhibited. On the other hand, if the hardness of the protective sheet 52 is too low, the protective sheet 52 is wrinkled, the amount of polishing varies partially, and normal polishing work becomes difficult.

  The thickness of the protective sheet 52 is preferably 0.1 to 2 mm. If the thickness of the protective sheet 52 exceeds 2 mm, the radius of curvature of the protective sheet 52 increases in the vicinity of the outer peripheral portion of the wafer W, and the outer peripheral portion of the wafer W cannot be polished with an appropriate pressing force, making normal polishing work difficult. It becomes.

  On the other hand, if the thickness of the protective sheet 52 is less than 0.1 mm, the hardness of the protective sheet 52 must be increased in order to maintain the strength of the protective sheet 52, and as a result, the back surface of the wafer W is damaged. The possibility increases and the function as a protective sheet cannot be exhibited.

  In particular, since the strength of rubber-based materials is low, the thickness is increased to maintain the strength. However, when the thickness of the protective sheet 52 exceeds 2 mm, the radius of curvature of the protective sheet 52 increases and the curvature increases. The center also moves outward. Therefore, the outer peripheral portion of the wafer W cannot be polished with an appropriate pressing force, and normal polishing work becomes difficult.

  In addition, with a polyimide-based material, the polishing operation can be performed even if the thickness of the protective sheet 52 is less than 0.1 mm, but even a slight scratch on the protective sheet 52 is easy to tear, which is not preferable.

  Usually, the pressure of the wafer W is in the range of 20 to 70 kPa. For example, when a wafer W having an outer shape of 300 mm is polished with a pressing force of 70 kPa, a protective sheet 52 having a JIS-A hardness of 90 and a thickness of 1 mm can be used.

  As the material of the protective sheet 52, chloroprene rubber, nitrile rubber, etc. are used as rubber materials, and PET, polyethylene, polypropylene, PFA, PTFE, etc. are polyimide resins as resin materials such as tetrafluoroethylene resin. As a resin material such as PEEK, Vespel (trade name) or the like can be used.

  The retainer ring 28 is fixed to the retainer ring holder 50 by fitting the convex portion 56 into the concave portion 54 of the retainer ring holder 50 and then screwing it with bolts 58, 58. Therefore, screw holes 60, 60,... Are formed in the retainer ring 28 at regular intervals, and through holes 62, 62,... Are formed in the retainer ring holder 50 at regular intervals.

  Further, the convex portion 56 formed on the retainer ring 28 and the concave portion 54 formed on the retainer ring holder 50 have inner circumferential wall surfaces 54A and 56A formed in a tapered shape (having a tapered portion). Thus, the fitting operation can be easily performed.

  As shown in FIG. 2, an air layer is formed between the carrier 24 and the protective sheet 52 under the carrier 24 on which the protective sheet 52 is stretched. The wafer W is pressed against the carrier 24 through the air reservoir 74. The air reservoir 74 is increased in internal pressure by blowing air from the suction / blowing groove 42 of the carrier 24. The holes 52A formed in the protective sheet 52 act as suction holes when the wafer W is held and transported, and act as air ejection holes during polishing.

  The retainer ring holder 50 is attached to an attachment member 64 formed in a ring shape via a snap ring 66. The snap ring 66 is formed in a ring shape, and a groove 66A is formed on the inner periphery thereof as shown in FIG. The snap ring 66 is cut and formed so that it can be expanded and contracted. The retainer ring holder 50 and the mounting member 64 are integrated with each other by fitting the outer peripheral flange portions 50A and 64A formed on the outer periphery of the upper end portion and the outer periphery of the lower end portion into the groove 66A formed in the snap ring 66. Fixed.

  An inner peripheral flange portion 50B is formed on the inner peripheral portion of the retainer ring holder 50, and a flange portion 24A formed on the outer peripheral portion of the carrier 24 is loosely inserted into the inner peripheral flange portion 50B. Thereby, an air layer is formed between the carrier 24 and the protective sheet 52.

  The retainer ring pressing member 68 of FIG. 2 is connected to the mounting member 64. The retainer ring 28 is transmitted with a pressing force from the retainer ring pressing means 30 via the retainer ring pressing member 68.

  The retainer ring pressing means 30 is disposed on the peripheral edge of the central portion of the lower surface of the head main body 22, and applies a pressing force to the retainer ring pressing member 68 to press the retainer ring 28 coupled thereto against the polishing pad 20. The retainer ring pressing means 30 is also preferably formed of a rubber sheet airbag 70 in the same manner as the carrier pressing means 26. An air supply mechanism 72 for supplying air is connected to the airbag 70, and the air supply mechanism 72 is provided with a regulator (not shown) that adjusts the pressure of air pumped from a pump (not shown).

  The polishing method of the polishing apparatus 10 configured as described above is as follows. First, the wafer W is held by the wafer holding head 14 and placed on the polishing pad 20. At this time, the wafer W is sucked and held by using the sucking / blowing grooves 42 formed on the lower surface of the carrier 24. For this suction, the protective sheet 52 has a plurality of holes 52A (see FIG. 3). The wafer W is sucked and held through the hole 52A.

  Next, air is supplied to the airbags 46 and 70 from a pump (not shown). At the same time, air is blown out from the suction / blowing groove 42 of the carrier 24. As a result, the internal pressure of the air reservoir 74 is increased and the airbags 46 and 70 are inflated, and the wafer W and the retainer ring 28 are pressed against the polishing pad 20 with a predetermined pressure. In this state, the polishing surface plate 12 is rotated in the direction A in FIG. 1, and the wafer holding head 14 is rotated in the direction B in FIG. Then, slurry is supplied onto the rotating polishing pad 20 from a nozzle (not shown). Thereby, the lower surface of the wafer W is polished by the polishing pad 20.

  Since the protective sheet 52 has a plurality of holes 52A (see FIG. 3), the air supplied to the air reservoir 74 presses the back surface of the wafer W through the protective sheet 52 from the holes 52A. To do. No direct pressing force acts between the protective sheet 52 present in the air layer and the back surface of the wafer W. Therefore, the thickness unevenness of the protective sheet 52 is not affected by the processing accuracy of the wafer W.

  The above is the description of the basic configuration of the polishing apparatus 10 and the operation method (polishing method) thereof, mainly the holding head (work holding head) 14. Next, each embodiment of the present invention will be described in detail.

  First, a first embodiment of the present invention will be described. FIG. 4 is a view for explaining this embodiment, and is a cross-sectional view showing the structure of the clamping portion of the protective sheet 52. This figure is almost the same as FIG. 3 described above. Since the numbers of the respective constituent elements are the same as those in FIG. 3, detailed description thereof is omitted.

  The present embodiment is the work holding head 14 in which an annular reinforcing member 80 is provided in a portion corresponding to the outer peripheral area of the work (wafer W) on the upper surface of the protective sheet 52. According to this embodiment, since the reinforcing member 80 is provided in a portion corresponding to the outer peripheral region of the wafer W on the upper surface of the protective sheet 52, the rigidity of the protective sheet 52 in this portion increases, The bending of the protective sheet 52 is suppressed. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the wafer W, and the polishing state at the orientation flat portion or the like can be made uniform.

  That is, when the rigidity of the entire surface of the protective sheet 52 is increased, as described above, it is difficult to make the shape of the edge portion appropriate, and it is difficult to properly control the uniformity of the polished state in the surface of the wafer W. It is. On the other hand, since the reinforcing member 80 is provided only in the part corresponding to the orientation flat part or the like and corresponding to the peripheral area of the wafer W as in this embodiment, only this part of the protective sheet 52 has high rigidity. And the other part of the protection sheet 52 can be kept as before.

  The size (inner diameter, outer shape, thickness) of the reinforcing member 80 used in the present embodiment, the material of the reinforcing member 80, the fixing method of the reinforcing member 80 to the protective sheet 52, etc. ), An appropriate material, a value, and the like can be selected according to the material of the wafer W, the polishing speed (rotation speed of the surface plate), the polishing pressure, and the like.

  Next, a second embodiment of the present invention will be described. FIG. 3 described above is also a view for explaining this embodiment, and is a cross-sectional view showing the structure of the clamping portion of the protective sheet 52.

  In the present embodiment, the workpiece holding head 14 forms an orifice between the outer edge of the lower surface of the carrier 24 and the protective sheet 52 or between the outer surface of the carrier 24 and the inner surface of the ring-shaped member (retainer ring holder 50). It is. According to this embodiment, since the orifice (82 in FIG. 3) is formed, this prevents the protective sheet 52 from being greatly bent below the edge of the orientation flat portion or the like. As a result, the polishing state at the orientation flat portion or the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat portion or the like can be made uniform.

  The details will be described below with reference to FIG. 5A and 5B are schematic cross-sectional views illustrating the second embodiment. FIG. 5A shows the relationship between the protective sheet 52 and the normal edge of the wafer W. FIG. 5B shows the relationship between the protective sheet 52 and the wafer W. The relationship with the edge of the orientation flat O part is shown. Although there is a pressure difference between the upstream and downstream of the orifice 84, the protective sheet 52 bends more greatly than that of FIG. However, the opening of the orifice 84 widens, so that excessive pressurization in the orientation flat O portion is avoided. In addition, each arrow in FIG. 5 shows the flow of air.

  3 is formed between the outer surface of the carrier 24 and the inner surface of the retainer ring holder 50, and the orifice 84 of FIG. 5 is formed between the outer edge of the lower surface of the carrier 24 and the protective sheet 52. Is formed.

  Next, a third embodiment of the present invention will be described. 6 and 7 are views for explaining this embodiment. FIG. 6 is a bottom view of the holding head (work holding head) 14 holding the wafer W. FIG. 7 shows the third embodiment. It is a schematic sectional drawing to explain. Each arrow in FIG. 7 shows the flow of air.

  This embodiment is the work holding head 14 in which a plurality of through holes 52A, 52A,... Are provided along the circumferential direction in a portion corresponding to the work outer peripheral region of the protective sheet 52. According to this embodiment, the pressurized gas supplied between the carrier 24 and the protective sheet 52 leaks from the through holes 52A, 52A. If the through holes 52A, 52A, etc. are not blocked by the workpiece (wafer W) in the orientation flat O portion or the like, the pressurized gas leaks from the through holes 52A, 52A, and thereby the protective sheet. 52 does not bend greatly below the edge of the orientation flat O portion or the like. As a result, the polishing state at the orientation flat O portion and the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat O portion and the like can be made uniform.

  In addition, when this embodiment is applied in combination with the second embodiment of the present invention, a synergistic effect can be obtained, and it is preferable, but the effect can be sufficiently obtained even when this embodiment is applied alone.

  Next, a fourth embodiment of the present invention will be described. FIG. 8 is a schematic sectional view for explaining this embodiment. Each arrow in the figure indicates the flow of air.

  This embodiment is the work holding head 14 in which the position of the through hole 52 </ b> A of the protective sheet 52 and the position of the through hole 86 of the carrier 24 substantially coincide with each other. According to this embodiment, part of the gas supplied between the carrier 24 and the protective sheet 52 passes through the gap between the back surface of the workpiece (wafer W) and the protective sheet 52 through the through hole 52A of the protective sheet 52. Is discharged from the outer periphery of the workpiece. This gas flow prevents the protective sheet 52 from being greatly bent downward from the edge of the orientation flat O portion or the like. In particular, since the position of the through hole 52A of the protective sheet 52 and the position of the through hole 86 of the carrier 24 substantially coincide with each other, this effect becomes remarkable. As a result, the polishing state at the orientation flat O portion and the like becomes substantially the same as the other portions of the workpiece, and the polishing state at the orientation flat O portion and the like can be made uniform.

  In the case where a plurality of through holes 86 are provided in the carrier 24, particularly when the through holes 86 are provided so as to cover substantially the entire surface of the workpiece, the through holes that substantially coincide with the positions of the through holes 52 </ b> A of the protective sheet 52. The effect of the present embodiment can be obtained if 86 is provided in a portion corresponding to the outer peripheral area of the workpiece.

  The configuration described above is an example of an embodiment of the present invention, but the configuration of the present invention is not limited to these, and various configurations can be adopted.

  For example, in the example of the embodiment, the retainer ring 28 sandwiching the protective sheet 52 and the retainer ring holder 50 are fixed by the bolts 58, but may be fixed by bonding with an adhesive.

Perspective view showing the overall structure of the polishing apparatus Longitudinal sectional view showing the configuration of the work holding head Sectional drawing which shows the structure of the clamping part of a protection sheet Sectional drawing which shows 1st Embodiment Schematic sectional view for explaining the second embodiment Bottom view of the work holding head that holds the work Schematic sectional view for explaining a third embodiment Schematic sectional view for explaining the fourth embodiment Longitudinal sectional view showing the configuration of a conventional wafer holding head Longitudinal sectional view showing the configuration of a conventional wafer holding head Conceptual diagram showing the polishing rate of the orientation flat part of the wafer Conceptual diagram showing the polishing rate of the orientation flat part of the wafer

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Polishing apparatus, 12 ... Polishing surface plate, 14 ... Work holding head, 20 ... Polishing pad, 24 ... Carrier, 28 ... Retainer ring (lower ring), 42 ... Suction / blowing groove, 44 ... Air flow path, 46 ... Air bag 48 ... Air supply mechanism 50 ... Retainer ring holder (ring-shaped member main body) 52 ... Protective sheet 72 ... Air supply mechanism 74 ... Air reservoir part W ... Wafer

Claims (6)

A protective sheet made of an elastic material that presses the workpiece against the polishing pad;
A ring-shaped member that holds the periphery of the protective sheet and is in contact with the polishing pad;
In a work holding head comprising a carrier that presses a protective sheet corresponding to a work area toward the work,
A work holding head, wherein an annular reinforcing member is provided in a portion corresponding to a work outer peripheral region on the upper surface and / or the lower surface of the protective sheet.   The work holding head according to claim 1, wherein a pressurized gas is supplied between the carrier and the protective sheet. A protective sheet made of an elastic material that presses the workpiece against the polishing pad;
A ring-shaped member that holds the periphery of the protective sheet and is in contact with the polishing pad;
In a work holding head comprising a carrier that presses a protective sheet corresponding to a work area toward the work,
A pressurized gas is supplied between the carrier and the protective sheet, and between the outer edge of the carrier lower surface and the protective sheet, or the outer surface of the carrier and the ring-shaped member. A workpiece holding head, wherein an orifice is formed between the inner surface of the workpiece.   The work holding head according to claim 3, wherein a plurality of through holes are provided along a circumferential direction in a portion corresponding to a work outer peripheral region of the protective sheet. A protective sheet made of an elastic material that presses the workpiece against the polishing pad;
A ring-shaped member that holds the periphery of the protective sheet and is in contact with the polishing pad;
In a work holding head comprising a carrier that presses a protective sheet corresponding to a work area toward the work,
From a plurality of through holes provided in the carrier, pressurized gas is supplied between the carrier and the protective sheet,
Positions of the plurality of through-holes provided along the circumferential direction in the portion corresponding to the work outer periphery area, in the portion corresponding to the work area of the protective sheet. And a position of a plurality of through holes provided in the carrier substantially coincide with each other. A polishing apparatus comprising the work holding head according to claim 1.

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