JP2008307674A - Split pressurizing type retainer ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent excessive polishing of an outer peripheral edge part of a wafer by a rebound part of a polishing pad, and to suppress dispersion of quality performance of the wafer after the polishing. <P>SOLUTION: This split pressurizing type retainer ring 19 is in a polishing head 11 polishing the wafer W by pressing the wafer W on the polishing pad 16. The retainer ring 19 is divided into a plurality of ring split bodies 19A, 19B and 19C having different diameter dimensions. Each of the ring split bodies 19A, 19B and 19C is mutually independently provided to be vertically movable. A pressurizing value of each of the ring split bodies 19A, 19B and 19C is separately set and controlled by air pressurizing mechanisms 21A, 21B and 21C. By independently controlling the pressurizing value of each of the ring split bodies 19A, 19B and 19C, height and position, etc. of the rebound part 30 of the polishing pad 16 are optimally controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a divided pressure type retainer ring, and more particularly to a divided pressure type retainer ring disposed in a CMP polishing head for polishing a wafer by pressing it against a polishing pad.

  Conventionally, this type of CMP apparatus has a polishing head that can be driven to rotate, which includes a carrier for holding a wafer by air pressure, and an annular retainer ring provided on the outer peripheral side of the carrier. During the CMP process, the wafer held by the polishing head is pressed against the polishing pad on the rotating platen, and the polishing agent is supplied to the upper surface of the polishing pad to polish the wafer.

  The wafer is surrounded by a retainer ring, and is pressed against the upper surface of the polishing pad together with the retainer ring to be polished. During polishing, the surface of the polishing pad is pressed by the retainer ring to cause a phenomenon that the upper surface bulges, that is, a so-called undulation phenomenon. Thus, a portion (hereinafter referred to as “rebound portion”) that rises in a substantially trapezoidal cross section is generated in the polishing pad corresponding to the outer peripheral edge portion of the wafer due to the wavy phenomenon.

  That is, as shown in FIG. 7, the upper surface of the polishing pad 1 is pressed by the retainer ring 2 so as to be slightly recessed, so that a rebound portion 3 is generated at a location corresponding to the outer peripheral edge of the wafer W on the upper surface of the polishing pad 1. To do. Reference numeral 4 in the figure denotes a carrier for pressing the wafer W against the polishing pad 1 through the elastic sheet 5 by air pressure.

  When the height (rebound amount) of the rebound portion 3 on the surface of the polishing pad 1 is increased, the polishing pressure for the wafer W is increased accordingly, so that the polishing rate (polishing rate) of the wafer W is increased and the polishing of the wafer W is performed. The surface may be adversely affected such as excessive polishing.

In order to eliminate the occurrence of excessive polishing, it is necessary to control the rebound amount of the polishing pad 1. In the prior art, for example, the rebound amount of the polishing pad 1 is changed and controlled by adjusting / setting the pressing force of the retainer ring 2 against the polishing pad 1 (see, for example, Patent Document 1).
JP 2003-124169 A

  When the pressing force of the retainer ring 2 with respect to the polishing pad 1 is adjusted as in the prior art, the height of the rebound portion 3 of the polishing pad 1 can be controlled to some extent. However, since the position and shape of the rebound part 3 cannot be controlled, the position of the rebound part 3 is fixedly formed below the outer peripheral edge of the wafer W as shown in FIG. Accordingly, a force that pushes up the wafer W by the rebound portion 3 acts. As a result, the polishing speed of the wafer W is affected by the pushing force of the rebound portion 3. Therefore, as shown in FIG. 8, the outer peripheral edge of the lower surface of the wafer W corresponding to the rebound portion 3 is excessively polished, and a ring-shaped poor polishing region (overpolishing region) E is generated. The effective area is reduced.

  In particular, the height, position, and / or shape of the rebound portion 3 of the polishing pad 1 varies depending on the type of polishing pad, for example, the structure, hardness, groove, etc. of the polishing pad. The position and / or shape cannot be freely controlled. Therefore, when the type of the polishing pad 1 is changed, the polishing speed of the wafer W is changed according to the height, position and / or shape of the rebound portion 3, and the quality performance varies among a plurality of polished wafers. There was a problem that occurred.

  Then, while preventing excessive polishing of the outer peripheral edge of the wafer by the rebound portion of the polishing pad, there arises a technical problem to be solved in order to suppress variations in quality performance of the wafer. The purpose is to solve.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a divided pressure type disposed in a CMP polishing head for holding a wafer and pressing it against a polishing pad for polishing. A retainer ring, the retainer ring is divided into a plurality of annular shapes having different diameters, and each ring divided body is provided so as to be vertically movable, and each ring divided body is pressed against the upper surface of the polishing pad. There is provided a split pressurizing type retainer ring which has a pressurizing mechanism for adjusting the pressing force of each ring split body against the polishing pad and can be independently adjusted and set.

  According to this configuration, when the wafer is pressed against the upper surface of the polishing pad and polished, the pressing force of each ring divided body against the polishing pad is arbitrarily adjusted and set by the pressurizing mechanism. Therefore, by adjusting and setting the pressing force of each ring divided body independently, the distribution state of the pressing force received from each ring divided body can be changed, and the dimension of the rebound portion formed on the upper surface of the polishing pad and the corresponding The position changes.

  Further, when the type of the polishing pad is changed, by changing the setting of the pressure value of each ring divided body of the retainer ring, the pressure value of each ring divided body with respect to the polishing pad depends on the type of the polishing pad. Adjusted and set. Therefore, the height, position and / or shape of the rebound portion corresponding to the type of polishing pad can be easily obtained.

  According to a second aspect of the present invention, the pressure value of the ring divided body arranged on the innermost circumferential side among the plurality of ring divided bodies is smaller than the pressure value of the ring divided body arranged on the outer circumferential side thereof. The split pressure type retainer ring according to claim 1 is set.

  According to this configuration, during polishing, the lower surface of the innermost ring segment among the plurality of ring segments is positioned above the lower surface of the outer ring segment, and the outer ring segment is divided. The lower surface of the body presses the upper surface of the polishing pad. In this case, since a gap is formed between the lower surface of the innermost ring segment and the upper surface of the polishing pad, the rebound portion of the polishing pad moves to the gap position.

  The invention according to claim 3 is that the number of the ring divided bodies is three or more, and the pressure values of the two ring divided bodies arranged on the first and second inner circumferential sides are on the outer circumferential side thereof. The divided pressure type retainer ring according to claim 1 or 2, wherein the pressure value is set to be smaller than a pressure value of the arranged ring divided body.

  According to this configuration, during polishing, the lower surfaces of the two ring division bodies on the inner circumferential side among the plurality of ring division bodies are positioned above the lower surfaces of the ring division bodies on the outer circumferential side, and the outer ring The lower surface of the divided body presses the upper surface of the polishing pad. In this case, since a gap is formed between the lower surface of the two ring division bodies on the inner peripheral side and the upper surface of the polishing pad, the rebound portion of the polishing pad moves to the position of the gap. Therefore, since the rebound portion is positioned away from the outer peripheral end surface of the wafer, the influence of the rebound portion on the polishing rate of the wafer is completely eliminated (cancelled).

  The invention according to claim 4 is the divided pressurization type according to claim 1, 2 or 3, wherein the width dimension in the radial direction of each of the plurality of ring divided bodies is set to be different from each other according to the polishing conditions and the like. Provide retainer ring.

  According to this configuration, since the width dimension in the radial direction of each of the plurality of ring division bodies is set to be different from each other in consideration of polishing conditions and the like, depending on the radial position corresponding to each ring division body, The pressing force and the pressing area with respect to the polishing pad by each ring division body differ. Accordingly, since the distribution state of the pressing force received from each ring divided body can be changed more finely, the size and position of the rebound portion generated in the polishing pad can be controlled more precisely.

  Since the invention according to claim 1 can control the height, position, etc. of the rebound portion of the polishing pad by changing the pressing force of each ring divided body against the polishing pad, the outer peripheral edge portion of the wafer caused by the rebound portion It is possible to reduce or alleviate the influence of the polishing rate and the like. Therefore, excessive polishing at the outer peripheral edge of the wafer can be prevented, and the effective area of the wafer can be increased by that amount compared to the prior art.

  Further, even when the type of the polishing pad is changed, the height, position, etc. of the rebound portion corresponding to this can be obtained, so that it is possible to reliably suppress a decrease in quality of the wafer or a variation in quality.

  In the second aspect of the invention, the rebound portion of the polishing pad moves to the lower side of the innermost ring division body, thereby more reliably reducing or mitigating the influence of the rebound portion on the polishing rate of the wafer. Therefore, in addition to the effect of the first aspect of the invention, it is possible to prevent the occurrence of excessive polishing at the outer peripheral edge of the wafer without deteriorating the wafer holding function by the retainer ring.

  The invention according to claim 3 can completely eliminate the influence of the rebound portion on the polishing rate of the wafer, etc. In addition to the effect of the invention according to claim 1 or 2, polishing using a soft polishing pad. Even in this case, the occurrence of excessive polishing at the outer peripheral edge of the wafer can be prevented more reliably.

  In the invention according to claim 4, since the size, position and / or shape of the rebound portion generated in the polishing pad can be controlled more precisely, in addition to the effect of the invention according to claim 1, 2 or 3, the polishing conditions, etc. Even when is changed, the occurrence of excessive polishing at the outer peripheral edge of the wafer can be more reliably prevented.

  The present invention prevents excessive polishing of the outer peripheral edge of the wafer due to the rebound portion of the polishing pad, and suppresses variation in quality performance between wafers, and poor polishing due to excessive polishing of the outer periphery of the wafer due to rebound of the polishing pad In order to achieve the purpose of suppressing or preventing the generation of a region, a split pressure type retainer ring disposed in a CMP polishing head for holding a wafer and pressing it against a polishing pad for polishing, the retainer ring comprising: Divided into a plurality of annular shapes having different diameter dimensions, each ring segment is provided so as to be vertically movable, and has a pressurizing mechanism for pressing each ring segment against the upper surface of the polishing pad, This was achieved by configuring the ring divided body so that the pressing force against the polishing pad could be adjusted and set independently of each other.

  A preferred embodiment of the present invention will be described below with reference to FIGS. In this embodiment, the retainer ring provided on the outer periphery of the lower surface of the polishing head for the CMP apparatus is formed by dividing the retainer ring into three annular shapes having different diameters in concentric circles. The number may be two or four or more depending on the design matters.

  FIG. 1 is a perspective view showing an outline of the CMP apparatus 1. In the figure, a CMP apparatus 11 is mainly composed of a disk-shaped platen 12 and a polishing head 13. A rotation shaft 14 is connected to the center of the lower surface of the platen 12, and the rotation shaft 14 rotates in the direction of arrow A by driving a motor 15. A polishing pad 16 is attached to the upper surface of the platen 12, and a polishing agent is supplied onto the polishing pad 16 from a nozzle (not shown).

  As shown in FIG. 3, the lower surface of the polishing head 13 includes a carrier 17 for mainly holding the wafer W, an elastic sheet 18 provided on the lower side of the carrier 17, and a lower outer peripheral portion of the carrier 17. An annular retainer ring 19 is provided. The polishing head 13 rotates in the direction of arrow B in FIG. 1 by driving the rotating shaft 14 by a motor (not shown).

  On the lower surface of the carrier 17, an air outlet and / or a hole for pressurizing and jetting air and, if necessary, pure water (DIW) is formed on the upper surface of the elastic sheet 18.

  A circular elastic sheet 18 made of a soft material is disposed below the carrier 17. The elastic sheet 18 is stretched inside the retainer ring 19. A plurality of holes (not shown) are opened in the elastic sheet 18, and the holes function as wafer suction holes when the wafer W is conveyed, and also function as air pressure supply holes when polishing.

  The retainer ring 19 is disposed on the outer periphery of the carrier 17 and attached to a retainer ring holder (not shown). A plurality of abrasive passages (grooves) (not shown) are formed on the lower surface of the retainer ring 19.

  Next, the divided structure of the retainer ring 19 which is a characteristic part of the present invention will be described in detail. The retainer ring 19 is divided into three annular shapes having different diameters, and the three ring divided bodies 19A, 19B, and 19C are arranged concentrically. In the illustrated example, the radial widths of the ring divided bodies 19A, 19B, and 19C are set to be the same as each other, but may be set to be non-identical with each other according to the polishing conditions and the like.

  And each ring division body 19A, 19B, 19C is each provided so that a vertical motion is possible. Further, air pressurization mechanisms 21A, 21B, and 21C shown in FIG. 2 are connected to the upper portions of the ring split bodies 19A, 19B, and 19C, respectively. 19B and 19C can be pressed against the upper surface of the polishing pad 16 independently of each other.

  Each air pressurization mechanism 21A, 21B, 21C is connected to an air pump (air source) 23 via air passages 22A, 22B, 22C, respectively. On-off valves 24A, 24B, 24C, pressure regulators 25A, 25B, 25C and flow regulators 26A, 26B, 26C are installed in the air passages 22A, 22B, 22C, respectively.

  A controller 27 is electrically connected to the on-off valves 24A, 24B, 24C, the pressure regulators 25A, 25B, 25C and the flow regulators 26A, 26B, 26C, and the air pressure mechanisms 21A, 21B are connected by the controller 27. , 21C, the air supply timing, the air pressure and the air supply amount are adjusted and controlled independently of each other.

  When polishing the wafer W by the CMP apparatus 11, first, the polishing head 13 is moved to a predetermined position on the unpolished wafer W on standby. Next, after vacuuming the air chamber 28 between the carrier 17 and the elastic sheet 18 by a vacuum line (not shown) and holding the wafer W by suction, the polishing head 13 is moved directly above the polishing pad 16, The wafer W and the retainer ring 19 are placed on the upper surface of the polishing pad 16.

  Thereafter, the wafer W and the retainer ring 19 are pressed against the upper surface of the polishing pad 16 by supplying air at a set pressure to the air chamber 28 and the air pressurizing mechanisms 21A, 21B, 21C. In this state, the platen 12 is rotated in the direction of arrow A in FIG. 1 and the polishing head 13 is rotated in the direction of arrow B in FIG.

  When the pressure values of the air pressurization mechanisms 21A, 21B, and 21C are all set to be equal at the time of polishing, as shown in FIG. 3, the lower surfaces of the three ring division bodies 19A, 19B, and 19C are polishing pads. 16 All contact with the top surface. In this case, a rebound portion 30 having a substantially trapezoidal cross section is generated at the location of the polishing pad 16 corresponding to the lower surface of the outer peripheral edge of the wafer W.

  Here, when the set pressure of the air pressurizing mechanism 21A is made smaller than the set pressure of the air pressurizing mechanisms 21B and 21C, the lower surface of the innermost ring segment 19A is removed from the polishing pad 16 as shown in FIG. Move upward from the upper surface and move away. As a result, the rebound portion 30 moves to the outside of the wafer W, and only the inclined surface of the rebound portion 30 comes into contact with the inclined lower surface of the wafer W edge portion.

  In this state, since the rebound part 30 has moved from the lower surface of the outer peripheral edge of the wafer W to the inclined lower surface of the edge part, the influence of the rebound part 30 on the wafer W, such as the polishing rate, is reduced or alleviated. Therefore, the retainer ring 19 securely holds the wafer W and prevents over-polishing at the outer peripheral edge of the wafer W.

  In the state of FIG. 4, when the set pressure of the air pressurizing mechanism 21B is made smaller than the set pressure of the air pressurizing mechanism 21C, in addition to the innermost ring segment 19A, as shown in FIG. The lower surface of the second inner peripheral ring segment 19B also moves upward from the upper surface of the polishing pad 16 and is separated.

  As a result, the upper surface of the polishing pad 16 is pressed only by the lower surface of the outermost ring segment 19C. In this case, the rebound part 30 moves and displaces outward of the wafer W, and is positioned directly below the ring division body 19B.

  Therefore, since the rebound part 30 is further moved away from the edge part of the wafer W, the influence of the polishing speed on the wafer W by the rebound part 30 is completely canceled. Therefore, the occurrence of overpolishing at the outer peripheral edge of the wafer W can be prevented more reliably.

  As described above, according to the present embodiment, when the wafer W is pressed against the upper surface of the polishing pad 18 together with the retainer ring 19, the pressing force of each of the ring divided bodies 19A, 19B, and 19C against the polishing pad 16 is the pressurizing mechanism. It is adjusted and changed separately by 21A, 21B, and 21C. Therefore, the height, position, and / or shape of the rebound portion 30 of the polishing pad 16 can be controlled to an optimum state according to the set value of the pressing force of each ring divided body 19A, 19B, 19C.

  Thus, since the influence of the polishing rate on the wafer W by the rebound portion 30 is reduced, alleviated or eliminated, excessive polishing of the outer peripheral edge portion of the wafer W can be prevented. Therefore, as shown in FIG. 6, it is possible to reliably suppress the occurrence of a ring-shaped polishing failure region E due to excessive polishing, which has occurred in the past, and the effective area of the wafer W increases accordingly.

  Further, when the type of the polishing pad 16, for example, the structure, hardness, groove, or the like of the polishing pad 16 changes, the rebound can be achieved by appropriately changing the pressure values of the ring divided bodies 19A, 19B, 19C accordingly. The height, position, etc. of the part 30 can be controlled to the optimum state. Therefore, even when the type of the polishing pad 16 is changed, it is possible to prevent the quality performance from being varied in the polished wafer W.

  In addition, the radial width dimension of each ring divided body 19A, 19B, 19C can be varied depending on the polishing conditions and the like. In this case, only the pressing force against the polishing pad 16 depends on the radial position of the retainer ring 19. The pressing areas are also different from each other. Therefore, since the height, position, etc. of the rebound portion 30 generated in the polishing pad 16 are controlled more precisely, excessive polishing of the outer peripheral edge portion of the wafer W is more reliably suppressed.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified one.

1 is a perspective view of a CMP apparatus according to an embodiment of the present invention. The air circuit diagram of the air pressurization mechanism of the division | segmentation pressurization type retainer ring which concerns on one Example. Sectional drawing explaining an example of the grinding | polishing state by the grinding | polishing head which has the division | segmentation pressurization type retainer ring which concerns on one Example. Sectional drawing explaining another example of the grinding | polishing state by the grinding | polishing head which has the division | segmentation pressurization type retainer ring which concerns on one Example. Sectional drawing explaining another example of the grinding | polishing state by the grinding | polishing head which has the division | segmentation pressurization type retainer ring which concerns on one Example. The top view which shows the grinding | polishing surface of the wafer which concerns on one Example. Sectional drawing explaining an example of the grinding | polishing state by the conventional grinding | polishing head. The top view which shows the grinding | polishing surface of the wafer by a prior art.

Explanation of symbols

11 CMP apparatus 13 Polishing head (wafer holding head)
16 Polishing pad 19 Retainer ring 19A-19C Ring division body 21A-21C Air pressurization mechanism 30 Rebound part (swell part)

Claims (4)

  A split pressure type retainer ring disposed in a CMP polishing head for holding a wafer and pressing it against a polishing pad for polishing, wherein the retainer ring is divided into a plurality of annular shapes having different diameters, and each ring Each divided body is provided so as to be movable up and down, and has a pressurizing mechanism for pressing each ring divided body against the upper surface of the polishing pad, and independently adjusts the pressing force of each ring divided body against the polishing pad. -Divided pressure type retainer ring, characterized in that it can be set.   The pressure value of the ring divided body arranged on the innermost circumferential side among the plurality of ring divided bodies is set to be smaller than the pressure value of the ring divided body arranged on the outer circumferential side thereof. The split pressure type retainer ring according to claim 1.   The number of the ring divided bodies is 3 or more, and the pressure values of the two ring divided bodies arranged on the first and second inner circumferential sides are the applied values of the ring divided bodies arranged on the outer circumferential side. The split pressure type retainer ring according to claim 1 or 2, wherein the retainer ring is set smaller than a pressure value. 4. The split pressure type retainer ring according to claim 1, wherein width dimensions of the plurality of ring divided bodies in a radial direction are set to be different from each other according to polishing conditions and the like.

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