JP2017191886A - Wafer end surface polishing pad, wafer end surface polishing apparatus, and wafer end surface polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer end surface polishing pad capable of suppressing scattering of slurry and reducing LPD on the rear surface of a wafer after polishing of an end surface.SOLUTION: The wafer end surface polishing pad is a pad for polishing an end surface of a wafer. A main surface composed of a front surface and a back surface has a substantially rectangular shape. A plurality of grooves opened at both ends in a lateral direction of the pad are arranged along a short direction of the pad with a space in a longitudinal direction of the pad.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wafer end surface polishing pad, a wafer end surface polishing apparatus, and a wafer end surface polishing method.

  One of the manufacturing processes of a polished wafer made of various materials such as a semiconductor such as a silicon wafer is a process of polishing a wafer end surface sandwiched between the front surface and the back surface of the wafer. This wafer end surface polishing step is performed as schematically shown in FIG. 8 of the present application using a polishing apparatus as described in Patent Document 1, for example.

  Referring to FIG. 8, wafer W is vacuum-sucked and held on a rotatable stage 60. A wafer holding pad 62 is provided on the main surface of the stage. Three types of wafer end surface polishing pads (polishing cloths) 70A, 70B, and 70C are arranged at positions where they can come into contact with the wafer end surface. The polishing pad 70A polishes the lower bevel region adjacent to the wafer suction surface among the end surfaces of the wafer. The polishing pad 70B polishes the upper bevel area adjacent to the surface opposite to the wafer suction surface of the wafer end surface. The polishing pad 70 </ b> C polishes the outermost peripheral region sandwiched between the lower bevel region and the upper bevel region in the end surface of the wafer. In FIG. 8, these polishing pads are schematically drawn to overlap each other, but are actually arranged at different positions along the wafer outer peripheral direction. Slurry is supplied from the nozzle 68 to the wafer surface. In this state, while rotating the wafer W in a predetermined direction, the polishing pads 70A, 70B and 70C are brought into contact with the wafer end surface and rotated in the opposite direction, whereby the wafer end surface is polished. The slurry is supplied to the wafer end surface by the rotation of the wafer W.

JP 2009-297842 A

  The present inventors carefully observed the situation of the end surface polishing. As schematically shown in FIG. 8, the slurry supplied to the wafer end surface is polished by polishing pads 70A, 70B, and 70C (especially polishing for polishing the lower bevel region). It was discovered that the pad 70A) was scattered in the direction of the outer peripheral edge of the stage 60. The slurry thus scattered enters between the wafer W and the wafer holding pad 62, and a part of the slurry is solidified and accumulated without being discharged from the space. It was found that the slurry solidified and accumulated by the wafer holding pad 62 rubs against the newly held wafer W and causes scratches on the back surface thereof. This flaw is detected as LPD (Light Point Defect) in the wafer inspection process and degrades the wafer quality. Particularly in recent years, reducing the LPD on the backside of the wafer has been demanded as one of important wafer qualities.

  Therefore, in view of the above problems, the present invention provides a wafer end surface polishing pad, a wafer end surface polishing apparatus, and a wafer end surface polishing method that can suppress the dispersion of slurry and reduce LPD on the back surface of the wafer after end surface polishing. With the goal.

  The inventors of the present invention focused on solving the above problems from the viewpoint of devising the shape of the end face polishing pad, and conducted intensive studies. As a result, by providing a groove on the end surface polishing pad, most of the slurry is guided by the groove and easily falls below the pad, and as a result, the slurry is less likely to scatter toward the outer peripheral edge of the stage. I found. The technology to increase the slurry supply efficiency by providing grooves on the polishing pad that polishes the front and back surfaces of the wafer is well known, but in the case of wafer end surface polishing, the slurry is easily supplied to the processing point. Conventionally, the necessity of providing grooves on the wafer end surface polishing pad has not been recognized. The present inventors have completed the present invention based on the idea of providing a groove in the end surface polishing pad based on the recognition of a new problem of suppressing slurry scattering.

This invention is based on the said knowledge, The summary structure is as follows.
(1) The shape of the main surface consisting of the front surface and the back surface is substantially rectangular, and is a pad for polishing the end surface of the wafer,
A wafer end surface polishing pad, wherein a plurality of grooves opened at both ends in the short side direction of the pad are arranged along the short side direction of the pad at intervals in the longitudinal direction of the pad. .

  (2) The wafer end surface polishing pad according to (1), wherein the groove extends straight.

  (3) The wafer end surface polishing pad according to (2), wherein an angle formed by the extending direction of the groove and the short direction of the pad is 0 to 60 degrees.

  (4) The wafer end surface polishing according to any one of (1) to (3), wherein the length of the pad in the short direction is 23 to 27 mm, and the length of the pad in the longitudinal direction is 62 to 66 mm. pad.

  (5) The wafer end surface polishing pad according to any one of (1) to (4), wherein the main surface has a rectangular shape.

  (6) The shape of the main surface is a shape in which a pair of long sides are parallel to each other, and an angle formed by two short sides and the long side of the long sides is 85 to 95 degrees, respectively ( The wafer end surface polishing pad according to any one of 1) to (4).

  (7) The shape of the main surface is a shape in which the outer long side and the inner long side are a part of a circle centered at the intersection of the extension lines of the two short sides. The wafer end surface polishing pad according to any one of claims.

(8) a stage capable of rotating while holding the wafer by vacuum suction;
A pad disposed at a position in contact with an end face of the wafer;
A slurry supply mechanism for supplying slurry to the end face of the wafer;
A wafer end surface polishing apparatus that polishes the end surface of the wafer rotated by the stage with the pad,
The pad is the wafer end surface polishing pad according to any one of the above (1) to (7), wherein the rotation direction of the wafer and the longitudinal direction of the wafer end surface polishing pad coincide with each other. Wafer edge polishing equipment.

(9) The pad is a first pad that polishes a lower bevel region adjacent to the wafer suction surface of the wafer end surface, and the wafer end surface opposite to the wafer suction surface. A second pad for polishing an upper bevel region adjacent to the surface, and a third pad for polishing an outermost peripheral region sandwiched between the lower bevel region and the upper bevel region, of the end surface of the wafer. Have
The wafer end surface polishing apparatus according to (8), wherein at least the first pad is the wafer end surface polishing pad according to any one of (1) to (7) above.

(10) having a stage that can be rotated while holding the wafer by vacuum suction, a pad disposed at a position where it can come into contact with the end face of the wafer, and a slurry supply mechanism for supplying slurry to the end face of the wafer. A wafer end surface polishing method for polishing an end surface of the wafer rotated by the stage with the pad using a wafer end surface polishing apparatus,
The pad is the wafer end surface polishing pad according to any one of the above (1) to (7), wherein the rotation direction of the wafer and the longitudinal direction of the wafer end surface polishing pad coincide with each other. Wafer end face polishing method.

  According to the wafer end surface polishing pad, the wafer end surface polishing apparatus, and the wafer end surface polishing method of the present invention, since slurry scattering is suppressed, LPD on the back surface of the wafer after end surface polishing is reduced.

(A) is a schematic perspective view of the wafer end surface polishing pad 10 by one Embodiment of this invention, (B) is a schematic top view of the said pad 10. FIG. It is a model top view of the wafer end surface polishing pad 20 by other embodiment of this invention. It is a schematic top view of the wafer end surface polishing pad 30 by further another embodiment of this invention. It is a model top view of the wafer end surface polishing pad 40 by further another embodiment of this invention. It is a model top view of the wafer end surface polishing pad 50 by further another embodiment of this invention. (A) is a schematic top view of the wafer end surface polishing apparatus 100 according to one embodiment of the present invention, (B) is a cross-sectional view taken along line II in (A), and (C) is II- in (A). It is II sectional drawing, (D) is III-III sectional drawing in (A). (A) is a schematic top view of a wafer end surface polishing apparatus 200 according to another embodiment of the present invention, and (B) is an I-O-I cross-sectional view in (A). It is a schematic diagram of a conventional wafer end surface polishing apparatus 300.

(Wafer end face polishing apparatus and wafer end face polishing method)
First, a wafer end surface polishing apparatus and a wafer end surface polishing method according to an embodiment of the present invention will be described with reference to FIGS.

  6A to 6D, a wafer end surface polishing apparatus 100 according to an embodiment of the present invention includes a stage 60 that can rotate while holding the wafer W by vacuum suction, and an end surface of the wafer W. Pads 66 </ b> A, 66 </ b> B, and 66 </ b> C (end surface polishing pads) disposed at positions where they can come into contact with each other, and a slurry supply mechanism that supplies slurry to the end surface of the wafer W. The nozzle 68 constitutes a part of the slurry supply mechanism and drops the slurry onto the wafer surface.

  The stage 60 has a wafer holding pad 62 attached to its main surface, and holds the wafer W by vacuum suction. Three types of wafer end surface polishing pads (polishing cloths) 66A, 66B, and 66C are arranged at positions that can come into contact with the wafer end surface. The first polishing pad 66A polishes the lower bevel area adjacent to the suction surface of the wafer among the end faces of the wafer. The second polishing pad 66B polishes the upper bevel region adjacent to the surface opposite to the wafer suction surface of the wafer end surface. The third polishing pad 66C polishes the outermost peripheral region sandwiched between the lower bevel region and the upper bevel region in the end surface of the wafer. The polishing pads 66A, 66B, and 66C are attached and fixed to the first pad holding body 64A, the second pad holding body 64B, and the third pad holding body 64C, respectively.

  As shown in FIG. 6A, the polishing pads 66A, 66B, 66C are arranged at different positions along the wafer outer peripheral direction. In the present embodiment, a total of 12 polishing pads are arranged so as to surround the outer periphery of the wafer, the first polishing pad 66A for the lower bevel region, the second polishing pad 66B for the upper bevel region, and the outermost peripheral region. Four third polishing pads 66C are arranged at equal intervals. This is suitable when the diameter of the wafer W is 300 mm. The polishing pads 66A, 66B, and 66C are arranged curved along the outer periphery of the wafer in order to maximize the contact area with the wafer end surface. The order of arrangement of the polishing pads 66A, 66B, and 66C is not limited to that shown in FIG.

  The angle of inclination of the polishing pads 66A, 66B, and 66C with respect to the vertical direction is not particularly limited. However, in the case of the second polishing pad 66B in FIG. In the case of the first polishing pad 66A in 4 (C), it is about 45 to 65 degrees, and in the case of the third polishing pad 66C in FIG. 4D, it is about -5 to 5 degrees, preferably 0 degree.

  The diameter of the stage 60 is not particularly limited, but can be about 280 ± 5 mm when polishing the end face of a wafer with a diameter of 300 mm, and 430 ± 5 mm when polishing the end face of a wafer with a diameter of 450 mm.

  In this state, while rotating the stage 60 and rotating the wafer W in a predetermined direction, the polishing pads 66A, 66B, and 66C are brought into contact with the wafer end surface and rotated in the opposite direction, whereby the polishing pads 66A, 66B, The wafer end surface is polished by 66C. The slurry is supplied to the wafer end surface by the rotation of the wafer W. The mechanism for bringing the polishing pads 66A, 66B, and 66C into contact with the wafer end surface is not particularly limited, and for example, a known one as described in JP-A-2009-297842 can be used.

  The arrangement of the end surface polishing pad is not limited to this embodiment, and as a modification, for example, the one shown in FIG. In the wafer end surface polishing apparatus 200 shown in FIG. 7, a total of six polishing pads are arranged so as to surround the outer periphery of the wafer, and a first polishing pad 66A for the lower bevel region and a second polishing pad 66B for the upper bevel region. Two third polishing pads 66C for the outermost peripheral region are arranged at equal intervals, two each. This is also suitable when the diameter of the wafer W is 300 mm.

  In addition, when the diameter of the wafer W is 450 mm, a total of 18 polishing pads are arranged so as to surround the outer periphery of the wafer, and the first polishing pad, the second polishing pad, and the third polishing pad are Each of them may be arranged at six equal intervals.

  This embodiment is characterized in that at least one of the above-described polishing pads 66A, 66B, 66C is a wafer end surface polishing pad according to an embodiment of the present invention described below.

(Wafer edge polishing pad)
Referring to FIGS. 1A and 1B, an end surface polishing pad 10 for polishing an end surface of a wafer according to an embodiment of the present invention has a shape of a main surface including a front surface 11A and a back surface 11B. Is a rectangular shape, and a plurality of grooves 14 opened at both ends 12A and 12B of the pad in the short direction X of the pad are arranged along the short direction X of the pad with an interval in the longitudinal direction Y of the pad. It is characterized by that. The end surface polishing pad is used as at least one of the first polishing pad 66A, the second polishing pad 66B, and the third polishing pad 66C in the end surface polishing apparatuses 100 and 200. In particular, the first polishing pad 66A for the lower bevel portion region is preferably used. At this time, the end surface polishing pad 10 is arranged so that the rotation direction of the wafer W and the longitudinal direction Y of the pad coincide. Of the two main surfaces of the end surface polishing pad 10, when the surface provided with the groove is the front surface 11A and the opposite surface is the back surface 11B, the front surface 11A is opposed to the wafer end surface. To do. By polishing the end face of the wafer W in this state, most of the slurry is guided by the groove 14 and easily falls below the end face polishing pad 10, and as a result, the slurry is scattered toward the outer peripheral end of the stage. It becomes difficult to do. Therefore, LPD on the back surface of the wafer W after end surface polishing is reduced. Furthermore, since the service life of the wafer holding pad 62 is extended, the material cost can be reduced, and the reduction in productivity associated with pad replacement can be prevented. As for the second polishing pad 66B and the third polishing pad 66C, a conventional end surface polishing pad may be used, but it is preferable to use the end surface polishing pad 10 of this embodiment because the scattering of slurry can be further suppressed.

  The material of the end surface polishing pad 10 may be a general material such as a non-woven fabric. For example, the end surface polishing pad 10 may be formed by impregnating a polyester fiber with a polyurethane resin and has a hardness (Asker-C) of about 70 to 85. It is preferable to do.

  The dimension of the end surface polishing pad 10 is not particularly limited as long as it is smaller than the front surface and the back surface of the wafer, but the length D in the short direction of the pad is preferably 23 to 27 mm. The end surface polishing apparatus has a mechanism for swinging the stage 60 in the vertical direction to swing the angle of the end surface polishing pad 10, and within a region of a predetermined width in the lateral direction X of the pad according to the swing width. The wafer travels (end surface polishing region S described later). Therefore, if the length D is too short, the ratio of the end surface polishing region S occupying the pad 10 becomes high, and stable polishing may not be performed. On the other hand, if the length D is too long, the pad 10 may interfere with the stage 60 or the like, or the slurry may be scattered on the stage. Further, although the length L in the longitudinal direction of the pad depends on the type of the end surface polishing apparatus, it is preferably 62 to 66 mm when the pad 10 is applied to the end surface polishing apparatus of FIG. 6 for a 300 mm wafer. In this case, the thickness is preferably 124 to 132 mm. Further, in the case of using a total of 18 polishing pads in an end surface polishing apparatus for a 450 mm wafer, the thickness is preferably 62 to 66 mm. The thickness of the end surface polishing pad 10 can be about 2.8 to 3.2 mm.

The shape of the end surface polishing pad is not particularly limited as long as the shape of the main surface is substantially rectangular. For example, as shown in the end surface polishing pad 20 of FIG. 2, the shape of the main surface is such that a pair of long sides 13A and 13B are parallel to each other, the two short sides 13C and 13D, and the long side 13B among the long sides The angles θ ₁ and θ _{2 formed} by each may be 85 to 95 degrees (a shape in which the short side is inclined within a range of ± 5 degrees with respect to the rectangle).

Moreover, as shown in the end surface polishing pad 30 of FIG. 3, the shape of the main surface may be a Baumkuchen shape. In this case, the outer long side 13A and the inner long side 13B are part of a circle centered at the intersection O of the extension lines of the two short sides 13C and 13D, and the major axis R ₁ (the center O and the outer long side) 13A) is 188 to 192 mm, the short diameter R ₂ (distance between the center O and the inner long side 13B) is 149 to 151 mm, and the center angle θ ₃ is preferably 37.5 to 39.5 degrees.

  Referring to FIG. 1B, the end surface polishing region S (that is, the contact region with the wafer end surface in the front surface 11A of the pad) has a center line that is equidistant from both ends in the lateral direction X of the pad. As a reference, it extends to a region having a length of 50 to 60% of the length D in the short direction of the pad. The present inventors have confirmed that although the groove 14 is arranged so as to intersect with the end surface polishing region S, the polishing rate is hardly reduced by the groove.

  The shape of the groove, the cross-sectional shape perpendicular to the extending direction of the groove, the groove width, the interval between adjacent grooves, the number of grooves, and the like may be appropriately set in consideration of the efficiency of discharging the slurry.

  Regarding the shape of the groove, as shown in FIGS. 1 to 3, it is preferable that the groove extends straight from the viewpoint of slurry discharge efficiency and the easiness of the groove forming process. However, the present invention is not limited to this, and the groove may be curved.

  The cross-sectional shape perpendicular to the extending direction of the groove is a shape composed of a groove bottom parallel to the main surface of the pad and two groove walls perpendicular to the main surface of the pad, as in the present embodiment. It is preferable from the viewpoint of the slurry discharge efficiency and the easiness of the groove forming process. However, the present invention is not limited to this, and the cross-sectional shape may be curved like a semicircle or a semi-ellipse.

  The groove width is preferably 0.5 to 2.0 mm. By setting the thickness to 0.5 mm or more, the slurry discharge efficiency can be sufficiently obtained. By setting the thickness to 2.0 mm or less, transfer (polishing unevenness) due to the presence or absence of grooves does not occur.

  The interval between adjacent grooves (interval between groove bottom center lines) is preferably 5 to 20 mm. By setting it to 5 mm or more, the strength of the pad is maintained, and by setting it to 20 mm or less, the slurry discharge efficiency can be sufficiently obtained. The plurality of grooves are preferably arranged at equal intervals.

In the end surface polishing pad 10 shown in FIG. 1, the angle formed by the extending direction of the groove 14 and the short side direction X of the pad is 0 degree, which is from the viewpoint of slurry discharge efficiency and the easiness of the groove forming process. To preferred. However, the present invention is not limited to this, and the grooves 16 and 18 extending in a straight manner are inclined with respect to the lateral direction X of the pad as in the end surface polishing pads 40 and 50 shown in FIGS. May be. At this time, the angle θ ₄ formed by the extending direction of the groove and the short direction of the pad is preferably 0 to 60 degrees, and more preferably 30 degrees or less. By setting it to 60 degrees or less, the slurry discharge efficiency can be sufficiently obtained, and the end face of the wafer W does not fit into the groove.

(Invention Example 1)
The end surface polishing pad 10 having a rectangular main surface shown in FIG. 1 is held by the pad of the end surface polishing apparatus shown in FIG. 6 so that one end 12A in the short direction is positioned on the upper side in the vertical direction and the other end 12B is positioned on the lower side in the vertical direction. The test which affixed on the body 64A and grind | polished the end surface of a 300 mm diameter silicon wafer was done. The end surface polishing pad was formed by impregnating a polyester fiber with a polyurethane resin, and had a thickness of 3.0 mm, a lateral length D of 25 mm, and a longitudinal length L of 64 mm. The groove width was 1 mm, the distance between adjacent grooves was 7 mm, and the number of grooves was seven. Under such conditions, an aqueous solution (pH: 10 to 11.2) prepared by adjusting colloidal silica (SiO ₂ ) 5% with potassium hydroxide (KOH) 1500 ppm is supplied as a slurry to the wafer end face, and the wafer rotation speed is 10 rpm, the end face. End surface polishing was sequentially performed at a polishing pad rotation speed of 350 rpm, and a total of 300 silicon wafers were subjected to end surface polishing.

(Invention Example 2)
The test was performed in the same manner as in Example 1 except that the rectangular end surface polishing pad 40 shown in FIG. 4 was used. The groove inclination angle θ ₄ was 30 degrees. The groove width, the interval between adjacent grooves, and the number of grooves are the same as in Invention Example 1.

(Comparative example)
The test was performed in the same manner as in Invention Example 1 except that a rectangular end face polishing pad without grooves was used.

(Evaluation of backside LPD)
The number of LPDs on the back surface of the polished silicon wafer was evaluated by the following method. Using a surface defect inspection system (KLA-Tencor: Surfscan SP-2), the back side of the silicon wafer is observed and evaluated in DWO mode (Dark Field Wide Oblique mode: dark field, wide, oblique incidence mode), and the size (diameter) ) Was examined for the occurrence of LPD of 120 nm or more. The results are shown in Table 1.

  As is apparent from Table 1, the number of LPDs increased as the number of polished sheets increased in the comparative example, whereas in Examples 1 and 2, the number of LPDs was kept low even when the number of polished sheets increased.

  According to the wafer end surface polishing pad, wafer end surface polishing apparatus, and wafer end surface polishing method of the present invention, the dispersion of slurry is suppressed, so that LPD on the back surface of the wafer after end surface polishing is reduced.

10, 20, 30, 40, 50 Wafer edge polishing pad 11A Front surface 11B Back surface 12A, 12B Both ends in short direction 14, 16, 18 Groove X Short direction of pad Y Longitudinal direction of pad Y Extension of _four grooves The angle between the direction and the short direction of the pad L The length in the longitudinal direction of the pad D The length in the short direction of the pad S The end polishing area (the contact area with the end face)
100, 200 Wafer edge polishing apparatus 60 Stage 62 Wafer holding pad 64A First pad holding body (for lower bevel area)
64B second pad holder (for upper bevel area)
64C Third pad holder (for outermost peripheral area)
66A First polishing pad (for lower bevel area)
66B Second polishing pad (for upper bevel area)
66C Third polishing pad (for outermost peripheral area)
68 nozzles (slurry supply mechanism)
W wafer

Claims (10)

The shape of the main surface consisting of the front surface and the back surface is substantially rectangular, and is a pad for polishing the end surface of the wafer,
A wafer end surface polishing pad, wherein a plurality of grooves opened at both ends in the short side direction of the pad are arranged along the short side direction of the pad at intervals in the longitudinal direction of the pad. .   The wafer end surface polishing pad according to claim 1, wherein the groove extends straight.   The wafer end surface polishing pad according to claim 2, wherein an angle formed by an extending direction of the groove and a short direction of the pad is 0 to 60 degrees.   The wafer end surface polishing pad according to any one of claims 1 to 3, wherein a length of the pad in a short direction is 23 to 27 mm, and a length of the pad in a longitudinal direction is 62 to 66 mm.   The wafer end surface polishing pad according to claim 1, wherein the main surface has a rectangular shape.   The shape of the main surface is a shape in which a pair of long sides are parallel to each other, and an angle between two short sides and a long side of the long sides is 85 to 95 degrees, respectively. The wafer end surface polishing pad according to any one of the above.   5. The shape of the main surface is a shape in which an outer long side and an inner long side are a part of a circle centering on an intersection of two extended short lines. Wafer edge polishing pad. A stage that can rotate while holding the wafer by vacuum suction;
A pad disposed at a position in contact with an end face of the wafer;
A slurry supply mechanism for supplying slurry to the end face of the wafer;
A wafer end surface polishing apparatus that polishes the end surface of the wafer rotated by the stage with the pad,
The wafer end surface polishing pad according to claim 1, wherein the rotation direction of the wafer and the longitudinal direction of the wafer end surface polishing pad coincide with each other. apparatus. The pad is adjacent to a first pad that polishes a lower bevel region adjacent to the suction surface of the wafer among the end surfaces of the wafer, and a surface opposite to the suction surface of the wafer among the end surfaces of the wafer. A second pad for polishing the upper bevel region, and a third pad for polishing an outermost peripheral region sandwiched between the lower bevel region and the upper bevel region, of the end surface of the wafer,
The wafer end surface polishing apparatus according to claim 8, wherein at least the first pad is the wafer end surface polishing pad according to claim 1. Wafer end surface polishing comprising: a stage that is rotatable while vacuum-adsorbing and holding a wafer; a pad that is disposed at a position in contact with the end surface of the wafer; and a slurry supply mechanism that supplies slurry to the end surface of the wafer. A wafer end surface polishing method for polishing an end surface of the wafer rotated by the stage with the pad using an apparatus,
The wafer end surface polishing pad according to claim 1, wherein the rotation direction of the wafer and the longitudinal direction of the wafer end surface polishing pad coincide with each other. Method.