JP2006159383A - Carrier for double-disc polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large diameter carrier for double-disc polishing, which carrier is used in a single carrier type double-disc polishing apparatus and carries out the compound movement including a radial component, and can avoid the deformation of an overhung portion and the fracture and the deterioration of polishing accuracy due to the deformation. <P>SOLUTION: A ring shape supporting frame 20 formed to be thick so as to support a carrier body 10 is arranged on the outer peripheral side of the disk shape carrier body 10 having a workpiece retaining opening 11 for retaining a workpiece. Teeth 21 are formed on the outer peripheral surface of the supporting frame 20 so as to engage with a driving gear 30. The supporting frame 20 is composed of separated members independent of the carrier body, and dismountably supports the carrier body 10 by means of screws 40. The carrier body 10 is made of a fiberglass reinforced resin, etc. suitable for holding the workpiece. The supporting frame 20 is made of nylon 66, etc. suitable for being driven by the gear 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a double-side polishing carrier suitable for double-side polishing of a semiconductor wafer as a material of a semiconductor device, and more particularly to a double-side polishing carrier suitably used for a single-wafer double-side polishing apparatus.

  Conventionally, as a double-side polishing of a semiconductor wafer, which is a material of a semiconductor device, a planetary gear type double-side polishing apparatus has been widely used. The planetary gear type double-side polishing apparatus is a kind of batch type apparatus that simultaneously polishes a plurality of wafers on both sides simultaneously. In this type of double-side polishing apparatus, a plurality of carriers are arranged around the center of rotation between rotating upper and lower surface plates. The plurality of carriers are sufficiently smaller in diameter than the surface plate, and rotate around the center of rotation while rotating between the surface plates while holding one or more wafers. Due to the planetary movement of the carrier, the wafer held by each carrier is polished on both sides between the surface plates.

  By the way, the diameter of a semiconductor wafer subjected to double-side polishing has been rapidly increased in diameter in recent years and has reached 300 mm. It is expected that the diameter will be further increased in the future. When double-side polishing such a large-diameter wafer, a multi-carrier type double-side polishing apparatus that uses a plurality of carriers, such as a planetary gear system, has an extremely large apparatus scale to ensure machine accuracy and Maintenance performance such as maintenance inspection is deteriorated. In order to satisfy the high flatness required for a wafer, it is desired to change the processing conditions for each wafer. In these respects, a single wafer processing apparatus that processes wafers one by one is considered more advantageous for double-side polishing of large-diameter wafers.

  The greatest structural feature of the single-sided double-side polishing apparatus is a single carrier system that uses a single carrier whose outer diameter is larger than the rotating upper and lower surface plate diameter. A single wafer having a diameter smaller than the surface plate diameter is held by the single carrier, and the large diameter wafer is double-side polished by rotating the carrier between upper and lower surface plates. It goes without saying that the apparatus is downsized and advantageous in terms of price as compared to a multi-carrier type double-side polishing apparatus that simultaneously polishes both sides of a plurality of wafers using a plurality of carriers. Such a single-wafer double-side polishing apparatus is presented in Patent Document 1.

JP 2001-315057 A

  In the single-sided double-side polishing apparatus presented by Patent Document 1, the carrier holds the wafer at a position eccentric with respect to the center. The carrier is arranged concentrically between the upper and lower surface plates and rotates around the center. The wafer held eccentrically by the concentric rotation of the carrier with respect to the surface plate, that is, the rotation, rotates around the center of the carrier between the rotating surface plates and is polished on both sides.

  Note that the rotational peripheral speed at the center of the surface plate is 0, but this peripheral speed increases as the distance from the center of the surface plate increases and becomes maximum at the outer peripheral edge. As a result, the polishing rate by the surface plate is greatly different between the central portion and the outer peripheral portion from the viewpoint of peripheral speed.

  The single-wafer type double-side polishing apparatus, including the one described in Patent Document 1, is more stable than the multi-carrier type double-side polishing apparatus that uses a plurality of carriers at the same time, such as the planetary gear system, due to its polishing principle. Since a single wafer is polished using almost the entire surface of the plate at the same time, the amount of wafer polishing varies due to a large peripheral speed difference between the outside and inside of the surface plate, which is disadvantageous in ensuring wafer flatness. It can be said that there is.

  In the case of a multi-carrier type double-side polishing apparatus that uses a plurality of carriers, the plurality of carriers are arranged on the outer peripheral part between the upper and lower surface plates, so the difference in peripheral speed between the outer and inner peripheral parts of the outer peripheral part. Is small. As a result, the wafer held by the carrier is evenly polished in combination with the revolution of the carrier and the rotation of the wafer.

  In actual polishing using a single-sided double-side polishing machine, the wafer rotates within the carrier, and measures such as increasing the amount of polishing liquid supplied to the center to compensate for the difference in peripheral speed are taken. Although the flatness does not decrease as much as the difference in peripheral speed, it is still difficult to absorb this large peripheral speed difference, and it is difficult to ensure the flatness.

  In order to solve the problem of such a single-wafer type double-side polishing apparatus, it is effective to move the carrier in a complicated manner between the upper and lower surface plates. This complicates the movement trajectory of each part of the carrier, averages the peripheral speed of the surface plate acting on each part of the carrier, and improves the flatness of the wafer. From this viewpoint, the present applicant rotates the carrier in the circumferential direction, and at the same time, circularly moves the carrier around the position off the center, and further, if necessary, the surface plate is perpendicular to the rotation axis. Japanese Patent Application No. 2004-127074 filed a patent application for a double-side polishing method and apparatus for moving in any direction.

  However, when the carrier tries to perform such a complex motion including a radial motion component with respect to the surface plate, the carrier is not removed from the space between the surface plates due to the motion in the radial direction. It is necessary to make the diameter considerably larger than the outer diameter of the surface plate. For example, for a 380 mm surface plate for polishing a 300 mm wafer, a carrier exceeding 500 mm is required. As a result, it was found that the amount of carrier overhang that protrudes around the surface plate increases, which causes the following problems. Note that the overhang area is an area outside the surface plate 50 if shown in FIG.

  The thickness of the silicon wafer as the material of the semiconductor device is not increased as the diameter is increased, and the standard thickness of the 300 mm wafer is 0.775 mm. The thickness of the carrier finished to this thickness is generally about 0.75 mm, and such a thin and large-diameter carrier is an epoxy resin reinforced with glass fiber in order to ensure mechanical strength. It is made of high-rigidity material such as

  When such a large-diameter and thin gear-shaped carrier performs a composite operation between the upper and lower surface plates, the overhang portion is deformed due to an external force by the driving gear from the outer peripheral side. That is, when rotational torque is applied to the carrier from the driving gear, the carrier tries to escape in the thickness direction, resulting in a load in the thickness direction. When most of the carrier is held between the surface plates, the carrier is not deformed even if it receives a load in the thickness direction. However, when the diameter difference between the surface plate and the carrier is large and the constrained portion by the surface plate is limited to the center portion of the carrier, the wide unconstrained overhang portion is deformed by the load in the plate thickness direction. As a result, the carrier frequently breaks.

  Further, when the overhang portion of the carrier is deformed in the plate thickness direction, the surface plate receives a load accompanying the deformation of the carrier because the carrier has high rigidity. As a result, the load applied to the wafer from the surface plate becomes unstable, and the polishing accuracy also decreases.

  As another problem, when the carrier is an epoxy resin reinforced with glass fiber, fine fiber powder is generated as the carrier is driven by the driving gear on the outer peripheral side. This fiber powder also has an adverse effect on polishing such as causing scratches on the wafer surface.

  Further, as the carrier is repeatedly used, the inner surface of the holding hole for holding the wafer is damaged by friction with the wafer. As a result, the carrier is exchanged after several tens of uses, but the current carrier is relatively expensive because it is necessary to form teeth on the outer peripheral surface, and the increase in run rink cost due to exchange cannot be ignored. It has become.

  An object of the present invention is to use a single carrier type double-side polishing apparatus, and although it is a large-diameter type that performs a composite operation including a radial component, the deformation of the overhang portion, and the damage and polishing accuracy caused thereby. It is an object of the present invention to provide a carrier for double-side polishing that can effectively avoid a decrease in the thickness.

  In order to achieve the above object, the double-side polishing carrier of the present invention sandwiches a single carrier holding a workpiece between upper and lower rotating surface plates, and radiates the first motion in the circumferential direction with respect to the carrier. A carrier used in a single-carrier-type double-side polishing apparatus that polishes both sides of the workpiece by performing a combined operation that combines a second motion including a directional motion component, A disc-shaped carrier main body provided with a work accommodation hole to be accommodated, and a tooth portion which is provided on the outer peripheral side to support the main body, is formed thicker than the main body, and meshes with a driving gear. And a ring-shaped support frame formed on the outer peripheral surface.

  Since the double-side polishing carrier of the present invention is used in a single-carrier type and complex-motion type double-side polishing apparatus, the amount of overhang with respect to the surface plate becomes large. However, since a thick support frame for supporting the carrier body is provided on the outer peripheral side of the disk-shaped carrier body provided with a work accommodation hole for accommodating the work, even if rotational torque is applied from the driving gear, The torque is received by the thick support frame. For this reason, deformation in the thickness direction is suppressed. Incidentally, the dimension of the support frame on the outer peripheral side is, for example, 10 mm with respect to the main body thickness of 1 mm or less, and the radial width is 15 mm including the tooth portion.

  The support frame on the outer peripheral side can be formed integrally with the inner carrier body or can be formed of a separate member independent of the inner carrier body. By using a separate member, it is possible to change the material of the support frame, and by changing to 66 nylon or the like that does not generate fiber powder, it is possible to avoid adverse effects on polishing by fiber powder.

  In addition, by using the support frame as a separate member, the carrier body can be removably supported with respect to the support frame. As a result, only the carrier body can be replaced, and the support frame can be used for a long time. When the support frame is thick, wear due to meshing with the drive gear is reduced, and the service life is extended. By using the support frame for a long time and replacing only the carrier body, the carrier cost is reduced. Since the carrier body does not have a tooth portion on the outer peripheral surface, the cost is lower than that of a conventional carrier.

  The dimensions of the double-side polishing carrier of the present invention will be described. The outer diameter D2 of the thin carrier body sandwiched between the surface plates is suitably (1.2 to 1.8) × D1 where the surface plate diameter is D1. , (1.3 to 1.5) × D1 is particularly preferable (see FIG. 2). When the outer diameter D2 of the carrier body is not so large with respect to the surface plate diameter D1, the overhang portion is small, and its deformation is slight and does not cause a big problem. The fact that the outer diameter D2 of the carrier body is extremely large with respect to the surface plate diameter D1 is unnecessary and impractical for polishing, and even if such a carrier is realized, deformation cannot be sufficiently suppressed.

  The thickness d2 of the support frame is suitably (10-30) × d1 with the thickness of the carrier body being d1, and is particularly preferably (15-20) × d1 (see FIG. 1). If the thickness d2 of the support frame is not sufficiently large with respect to the thickness d1 of the carrier body, the insufficient strength of the entire carrier is not eliminated, and the effect of suppressing the deformation becomes insufficient. If the thickness d2 of the support frame is too large with respect to the thickness d1 of the carrier body, the weight and volume increase and handling becomes difficult. Incidentally, the thickness d1 of the carrier body is determined according to the finished thickness of the workpiece, and is currently about 0.7 mm in the case of a silicon wafer.

  The width W of the support frame in the radial direction (the width including the tooth portion) is appropriately expressed as a ratio to the outer diameter D2 of the carrier body (0.05 to 0.1) × D2, and (0.07 to 0.08) × D2 is particularly preferred. If the width W of the support frame is too narrow, insufficient strength of the entire carrier is not eliminated, and the effect of suppressing the deformation becomes insufficient. When the width W of the support frame is too wide, the weight and volume increase, and handling becomes difficult. In addition, downsizing of the apparatus, which is a feature of the sheet-fed machine, is hindered.

  The upper surface level of the carrier body may be the same as the upper surface level of the support frame, or may be lower than the upper surface level of the support frame. In the former case, the polishing liquid supplied to the surface of the carrier is discharged smoothly and the surrounding support frame does not become a factor that hinders the discharge of the polishing liquid. On the other hand, in the latter case, the polishing liquid supplied to the surface of the carrier is accumulated on the carrier body, and the workpiece is polished in the accumulated polishing liquid. That is, in the latter case, polishing in liquid is possible.

  In the single-wafer type double-side polishing apparatus described in Patent Document 1, the outer peripheral portion of the carrier is formed thick, but this positions the carrier that rotates concentrically with the surface plate in the radial direction with respect to the surface plate. In order to do so, a concave portion into which the surface plate is fitted is formed in the carrier, and the thin portion surrounded by the thick outer peripheral portion has the same outer diameter as the surface plate. Therefore, the thin portion does not overhang from the surface plate, and no deformation occurs. Further, the thick part and the ridge are also slightly thicker than the thin part. There is no idea of reinforcement here, and it is natural that the purpose is to form a recess for fitting a platen for positioning. Therefore, the use, configuration and operational effects are clearly different from the double-side polishing carrier of the present invention.

  The double-side polishing carrier of the present invention is particularly effective for a single-wafer double-side polishing method in which a single wafer holds a single wafer, but a multi-carrier type holding a plurality of wafers in a single carrier. It can also be applied to a double-side polishing method.

  The carrier for double-side polishing of the present invention is a single carrier system and has a workpiece receiving hole for receiving a workpiece, although the carrier is a large-diameter carrier used in a double-side polishing apparatus that performs a composite operation including a radial motion component. Since a thick ring-shaped support frame that supports the main body is provided on the outer periphery of the provided disc-shaped carrier main body, deformation of the large overhang portion is suppressed, and damage caused by the deformation and polishing accuracy Can be avoided. Therefore, there is an effect that both sides of a large-diameter workpiece can be polished with high accuracy at low cost.

  Embodiments of the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view of a main part of a carrier for double-side polishing showing an embodiment of the present invention, FIG. 2 is a plan view and a longitudinal sectional view of a carrier body in the carrier, and FIG. 3 is a plan view of a support frame in the carrier. FIG.

  The double-side polishing carrier of this embodiment includes a carrier main body 10 made of a thin disk and a ring-shaped support frame 20 attached to the outer periphery of the carrier main body 10 in order to support it. The support frame 20 is separated and independent from the carrier body 10 and is detachably coupled to the carrier body 10 by screwing.

  This double-side polishing carrier is for a 300 mm wafer, and a circular work accommodation hole 11 for accommodating the wafer is provided at the center of the carrier body 10. The work accommodation hole 11 is formed at a position concentric with the carrier body 10 or at a position slightly decentered from the center. A plurality of screw insertion holes 12, 12 are provided on the outer peripheral portion of the carrier body 10 at predetermined intervals in the circumferential direction for fixing to the support frame 20.

  Since the carrier body 10 moves between the upper and lower surface plates in a plane perpendicular to the center line, it has the same thickness over the entire surface, and the thickness is set slightly smaller than the finished thickness of the wafer. For example, when the finished thickness of the wafer is 0.775 mm, the thickness of the carrier body 10 is selected to be about 0.75 mm. Thereby, a predetermined load is applied to both surfaces of the wafer until the final stage of polishing.

  In order to provide such a thin carrier body 10 with sufficient mechanical strength (rigidity), for example, an epoxy resin (GFRP) reinforced with glass fiber is used as the material. In addition to this, it is possible to use metal such as SK material in addition to CFRP. In any case, since it is necessary to give high strength to a thin member, the degree of freedom in selecting a material is small.

  The outer diameter D2 of the carrier main body 10 is determined by the momentum of the carrier between the upper and lower surface plates, particularly the radial momentum in a plane perpendicular to the central axis, and for example, 480 to 490 mm with respect to the workpiece receiving hole 11 of slightly more than 300 mm. Selected. If the momentum in the radial direction is small, the outer diameter D2 of the carrier body 10 may be reduced. If the momentum in the radial direction is increased, the outer diameter D2 of the carrier body 10 needs to be increased.

  The support frame 20 is a ring attached to the outer periphery of the carrier body 10. The support frame 20 is designed to be sufficiently thicker than the carrier body I0. For example, when the thickness of the carrier body 10 is 0.75 mm, the support frame 20 is designed to be about 10 mm. Further, the radial width W is designed to be, for example, about 20 mm so that sufficient self-strength can be secured together with the thickness d2.

On the outer peripheral surface of the support frame 20, tooth portions 21 that mesh with the plurality of driving gears 30 are provided over the entire circumference. On the back surface of the support frame 20 (the surface facing downward when in use), an annular recess 22 is provided that opens to the inner surface side of the L-shaped cross section into which the outer peripheral edge of the carrier body 10 is fitted. Along with the provision of the annular recess 22, an annular projection 23 is provided on the surface side as a support portion of the carrier body 10. The annular protrusion 23 has a plurality of screw holes 24, 24 penetrating in the thickness direction.
Is provided so as to correspond to the screw insertion holes 12, 12 of the carrier body 10.

  When the thickness d2 of the support frame 20 is 10 mm, the depth of the annular recess 22 is, for example, 4 mm. In that case, the thickness of the annular convex portion 23 is 6 mm.

Regarding the material of the support frame 20, since there are few dimensional restrictions, it is easy to ensure the mechanical strength, and the degree of freedom in selecting the material is great. An example is 66 nylon, which is relatively high in strength and inexpensive, and does not generate fiber powder even when engaged with the driving gear 30. Other than this, it is also possible to use a resin such as polycarbonate or PVC, or a metal such as stainless steel.

  Such a double-sided polishing carrier is completed by fitting the outer peripheral edge of the carrier body 10 into the annular recess 22 of the support frame 20 and fixing it to the annular protrusion 23 with screws 40.

  In the double-side polishing, the wafer is accommodated in the work accommodating hole 11 of the carrier main body 10, and the carrier main body 10 is sandwiched between the upper and lower surface plates 50 (see FIG. 2) in this state, and the outer peripheral side of the tooth portion 21 of the support frame 20. The carrier is rotated in the circumferential direction by a plurality of driving gears 30 meshing with each other. At the same time, the plurality of driving gears 30 are rotated synchronously, thereby causing the carrier to circularly move around a position off the center. As a result, the carrier performs a combined operation in which the first motion in the circumferential direction is combined with the second motion including the motion component in the radial direction, and the flatness of the wafer is improved.

  Here, the carrier receives rotational torque from a plurality of driving gears 30 on the outer peripheral side. At the same time, the diameter is larger than that of the surface plate, and a considerably large overhang is caused by the radial movement. Although the carrier main body 10 holding the wafer is thin, it is supported by a thick support frame 20 on the outer peripheral side, and sufficient rigidity is given by reinforcement by this support. For this reason, deformation in the thickness direction due to the application of the rotational torque from the driving gear 30 hardly occurs in the overhang portion.

  Therefore, damage due to deformation of the carrier is prevented. Specifically, in the case of single-sided double-side polishing of a 300 mm wafer, the present inventor has confirmed that the frequency of breakage is 0.1% or less compared to a carrier having the same thickness on the entire surface. Further, a situation in which the load applied to the wafer from the surface plate 50 changes due to the deformation of the carrier is avoided, and the polishing accuracy is also the same by stabilizing the load.

  In addition, in the double-side polishing carrier of this embodiment, a circular recess 14 is formed on the carrier body 10 by being surrounded by the annular protrusion 23 of the support frame 20. The polishing liquid supplied at the time of polishing accumulates in the circular recess 14. As a result, it is possible to cope with in-liquid polishing of the wafer.

  Moreover, the contact thickness with the driving gear 30 is increased by increasing the thickness of the tooth portion 21 for driving the carrier. As a result, wear of both is suppressed and the life is extended. When the entire carrier is thin and the tooth portion is thin, not only the tooth portion is heavily worn, but also the tooth portion hits the drive gear 30 locally, so the wear of the drive gear 30 is also intense.

  Regarding the life of the carrier body 10, the use limit is reached by damaging the inner peripheral surface of the work receiving hole 11 as in the prior art. In that case, the carrier body 10 is removed from the support frame 20 and replaced with a new one. By doing so, the support frame 20 can be used repeatedly, and can be reused by replacing the carrier body 10. Unlike the conventional carrier, the carrier body 10 does not have a tooth portion on the outer peripheral surface, and is thus relatively inexpensive. For this reason, compared with the conventional carrier, the cost required for replacement is reduced.

  FIG. 4 is a plan view of a carrier body used in a double-side polishing carrier according to another embodiment of the present invention. Compared to the carrier main body 10 described above, a plurality of small holes 13 and 13 are provided around the work accommodation hole 11. The small holes 13 and 13 promote the discharge of the polishing liquid. That is, although the upper surface of the support frame 20 is set at a higher level than the upper surface of the carrier body 10, the discharge of the polishing liquid is promoted. As an advantage of promoting the discharge of the polishing liquid, polishing is always performed with a new polishing liquid, the polishing time is shortened, and the quality of the finished surface can be improved.

  A similar function can be obtained by setting the upper surface of the support frame 20 to the same level as or lower than the upper surface of the carrier body 10. By the combination of both, the discharge of the polishing liquid from the carrier body 10 is further promoted. However, depending on the type of polishing, the above-described submerged polishing may be preferable.

  FIG. 5 is a plan view of a carrier body used for a double-side polishing carrier according to still another embodiment of the present invention. Compared with the carrier main body 10 described above, a difference is that a plurality of workpiece accommodating holes 11 are provided. Here, in order to simultaneously polish three 200 mm wafers, three work receiving holes 11, 11, 11 having an inner diameter of slightly over 200 mm are provided at equal intervals around the center. The surface plate diameter D1 is 230 to 240 mm which is slightly larger than the wafer diameter. The outer diameter D2 of the carrier body 10 and the dimensions of the support frame 20 are the same as in the previous embodiments.

  Thus, if the support frame 20 is separated from the carrier body 10, the support frame 20 can be shared even when the type of carrier is changed, and the advantage is great.

It is a longitudinal cross-sectional view of the principal part of the carrier for double-side polishing which shows one Embodiment of this invention. (A) is a top view of the carrier main body in the carrier, (b) is a bb arrow directional cross-sectional view of (a). (A) is a top view of the support frame in the carrier, (b) is a cross-sectional view taken along line bb of (a). It is a top view of the carrier main body used for the carrier for double-side polishing of another embodiment of this invention. It is a top view of the carrier main body used for the carrier for double-sided polishing of another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Carrier main body 11 Work accommodation hole 12 Screw insertion hole 13 Small hole 14 Recess 20 Support frame 21 Tooth part 22 Annular recessed part 23 Annular convex part 24 Screw hole 30 Driving gear 31 Annular support part 40 Screw 50 Surface plate

Claims (6)

  One carrier holding a workpiece is sandwiched between upper and lower rotating surface plates, and the carrier is caused to perform a combined operation in which a first motion in the circumferential direction is combined with a second motion including a radial motion component. A carrier used in a double-side polishing apparatus of a single carrier method and a composite operation method for polishing the work on both sides, and a disc-shaped carrier body provided with a work receiving hole for receiving the work; A ring-shaped support frame provided on the outer peripheral side to support the main body, formed thicker than the main body, and a tooth portion with which a driving gear meshes is formed on the outer peripheral surface. Characteristic carrier for double-sided polishing.   The double-sided polishing carrier according to claim 1, wherein the support frame is a separate member independent of the inner carrier body, and supports the carrier body in a detachable manner.   The double-side polishing carrier according to claim 2, wherein the support frame is made of a material different from that of the carrier body.   The double-side polishing carrier according to claim 1, wherein the upper surface of the carrier body is located at the same level as or higher than the upper surface of the support frame.   The double-side polishing carrier according to claim 1, wherein an upper surface of the carrier body is positioned at a level lower than an upper surface of the support frame. A method for polishing a semiconductor wafer, wherein the carrier for double-side polishing according to any one of claims 1 to 5 is used.

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