US20060084371A1

US20060084371A1 - Wafer chuck

Info

Publication number: US20060084371A1
Application number: US11/241,928
Authority: US
Inventors: Takashi Yoshida; Shinichi Murakami; Hiroyuki Itou
Original assignee: BBS KINMEI Co Ltd
Current assignee: BBS KINMEI Co Ltd
Priority date: 2004-10-14
Filing date: 2005-10-04
Publication date: 2006-04-20
Also published as: JP4691667B2; JP2006114643A; TW200620527A

Abstract

The influence of the slurry generated when polishing an orientation notch and the like is minimized. The holding members 10, 20 for holding the outer periphery of the wafer W and the driving mechanism 30 for driving the holding members 10, 20 all together in the closing direction are integrally combined.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to wafer chucks suitably used particularly when polishing an orientation notch and the like of the outer periphery part of the semiconductor wafer.
2. Description of the Related Art
The semiconductor wafer (hereinafter referred to simply as a wafer) has a V-shaped or a circular arc shaped orientation notch formed on the outer periphery. It is to be noted that the notch may be a linear orientation flat.
When forming the orientation notch in the wafer, the polishing pad contacts the outer periphery of the wafer along a predetermined trajectory so as to create a predetermined angle, which wafer is normally attracted to and fixed to the vacuum chuck that uses vacuum, (e.g., Japanese Laid-Open Patent Publication No. 2-180554 and Japanese Laid-Open Patent Publication No. 2002-28840.). That is, a concentric or a radial groove communicating to the vacuum source is formed on the upper surface of the vacuum chuck, and the wafer is attracted and held at the upper surface of the vacuum chuck by operating the vacuum pump.
On the other hand, after grinding, the orientation notch has the internal part polished to realize an accurate positioning of the wafer. Thus, a similar vacuum chuck is also normally used in polishing.

SUMMARY OF THE INVENTION

According to the conventional technique, when slurry (mixture of fluid polishing agent containing abrasive grain and powder polishing waste of the wafer) enters the lower surface side (attraction surface side) of the wafer, microscopic defects are unavoidably created at the wafer since the vacuum chuck attracts the wafer using vacuum.
The present invention, in view of the problem of the conventional art, aims to provide a wafer chuck that suppresses the influence of the slurry produced when polishing the orientation notch and the like of the outer periphery part to minimum by arranging holding members for mechanically holding the outer periphery part of the wafer.
The configuration of the present invention for achieving the above aim includes a plurality of holding members for pushing the outer periphery of the wafer in the radial direction and holding the wafer, and a driving mechanism for driving the holding members all together in the closing direction. It is to be noted that “closing direction” refers to the direction of moving each holding member forward towards the center of the wafer.
Each holding member is configured so as to hold the wafer by way of an elastic member.
Further, a V-shaped groove for sandwiching the outer peripheral part of the wafer in a snapping manner is formed in the elastic member, which V-shaped groove is further shaped into a circular arc shape so as to lie along the circumferential direction with respect to the outer peripheral edge of the wafer.
Moreover, the elastic member further includes a guide groove having an apex angle greater than the apex angle of the V-shaped groove on the opening direction side of the V-shaped groove.
The elastic member is configured from fluorocarbon resin or fluorocarbon rubber molded article.
When the holding members are arranged on both sides in the radial direction of the wafer with the wafer in between, a cylinder arranged in the radial direction of the wafer and connected to one of the holding members, and an interlocking mechanism for operating the other holding member in conjunction with the operation of the former holding member are arranged as the driving mechanism.
Further, as the driving mechanism, feed screws arranged in the radial direction of the wafer and having screw parts in the direction opposite to each other in order to screw each screw part to the holding member, and a motor for turning the feed screw may be arranged.
When a machining tool forward/backward path that approaches the wafer at a position orthogonal to the wafer and machines the outer peripheral edge of the wafer is formed in one of the holding members arranged on both sides in the radial direction of the wafer, the holding member is capable of holding the part near the machining portion of the wafer.
The present invention is suitable for polishing a V-notch or Orientation flat for defining the orientation of the wafer.
According to the configuration of the present invention, the holding member is driving all together in the closing direction towards the center of the wafer by way of the driving mechanism to push the outer periphery of the wafer in the radial direction and mechanically hold the wafer. That is, in such state, since the wafer is held with both surfaces floating in the air, even if slurry produced when polishing the orientation notch or orientation flat of the outer peripheral part is attached, the slurry can be easily removed in the post-process of washing and the like, and thus does not cause defects on the wafer. When a plurality of holding members are driven parallel to the wafer all together by the same stroke towards the center of the wafer by way of the driving mechanism, each holding member applies the same pushing force parallel to both surfaces of the wafer towards the central part of the wafer in the thickness direction, thereby preventing localized distortion or curve of the wafer.
Each holding member holds the wafer by way of the elastic member, and thus the pushing force is suitably dispersed and applied to the outer periphery of the wafer to minimize the localized distortion produced in the wafer. Further, the V-shaped groove formed in the elastic member sandwiches the outer peripheral part of wafer in a snapping manner and holds the wafer in a further stabilized manner. The guide groove formed in the opening direction of the V-shaped groove accurately guides the outer peripheral part of the wafer and allows the same to enter therein when the holding members are driven towards the center of the wafer.
The chuck according to the present invention does not require a vacuum chuck for fixing the wafer, and thus is configured to be light as a whole, and the V-notch or Orientation flat is particularly suitable in an application of polishing the notch. When polishing the internal part of the V-notch or Orientation flat, the wafer tends to perform a complex and precise movement by way of the chuck, and thus if the chuck is light weight, the driving mechanism for moving the chuck can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
FIG. 1 is a perspective view of the entire configuration;
FIG. 2 is a plan explanatory view of the entire configuration;
FIG. 3 is an enlarged cross sectional view of the main part of FIG. 2;
FIG. 4 is a frame format configuration view of a driving mechanism;
FIG. 5 is an explanatory view taken along line X-X of FIG. 2;
FIG. 6 is a view corresponding to FIG. 4 showing another embodiment of the present invention;
FIG. 7 is a plan view (1) of the main part showing another embodiment of the present invention; and
FIG. 8 is a plan view (2) of the main part showing another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will now be described with reference to the drawings.
The wafer chuck is made by integrally assembling a pair of holding members 10, 20 and a driving mechanism 30 (FIG. 1, FIG. 2). The holding members 10, 20 are driven in a closing direction-(direction of arrow K₁, K₁of FIG. 2) by way of the driving mechanism 30 to push the outer periphery of the wafer W towards the center Wo of the wafer W in a radial direction and hold the wafer W.
One of the holding members 10 is formed with a pair of left and right parallel fingers 12, 12 projecting horizontally from a distal end of the common base 11. The distal end of each finger 12 is bent upwards, and an elastic member 14 is attached in an exchangeable manner to the upper surface of each finger 12 by way of a press plate 13. V-shaped grooves 14 a that conforms to the outer peripheral part of the wafer W is formed at each elastic member 14, 14, and the V- shaped grooves 14 a, 14 a, opening in the horizontal direction, are continued in a circular arc shape so as to lie along the outer periphery of the wafer W.
The other holding member 20 is configured with the elastic member 22 attached in an exchangeable manner to the upper surface of the block shaped base 21. The elastic member 22 is fixed by way of the press plate 23 screw-fitted to the distal end face of the base 21, and a pair of left and right V- shaped grooves 22 a, 22 a are formed on the upper surface of the elastic member 22 so as to face the V- shaped grooves 14 a, 14 a of the holding member 10.
The V-shaped groove 14 a of each elastic member 14 is formed with a cross section symmetrical in the up-and-down direction (FIG. 3), and a guide groove 14 b, symmetrical in the up-and-down direction, is formed in the opening direction of the V-shaped groove 14 a. Since each groove 22 a of the elastic member 22 also has the same shape, the V-shaped groove 14 a will be herein described. Assuming the apex angles of the V-shaped groove 14 a and the guide groove 14 b as θ1, θ2, respectively, and the bevel angle of the outer peripheral part of the wafer W as θ, θ1≦θ, θ2>θ1. Therefore, when the outer peripheral part of the wafer W enters, the V-shaped groove 14 a snaps the upper and lower bevel parts W1, W1 of the wafer W. It is to be noted that the outer peripheral surface W2 of the wafer W preferably contacts the bottom surface 14 a 1 of the V-shaped groove 14 a, and both surfaces of the wafer W are in a state completely floating in air and thus does not contact any part. The elastic members 14, 14, 22 are made of materials that has an appropriate elasticity, has chemical-proof property, and that does not contain metal ion, such as fluorocarbon resin or fluorocarbon rubber.
The holding members 10, 20 are each connected to the distal end of the rod 31 and the guide rod 32 projecting out from both ends of the driving mechanism 30 (FIG. 2, FIG. 4). Each of the rod 31 and the guide rod 32 are combined with one of the air cylinders 33, 33, installed adjacent to each other within the driving mechanism 30. The rod 31, 31 is projected out from the one of the end of the air cylinder 33, 33, and the guide rods 32, 32 is projected out from the opposing other end of the air cylinder 33, 33. The air cylinders 33, 33 have the air pressure from the air source AC introduced in the opposite direction by way of a switching valve V and regulators R1, R2 with respect to the port of each end. When the switching valve V is operated, the holding members 10, 20 are driven in an opening direction in which the distance with respect to each other are opened at once, or a closing direction in which the distance between each other is narrowed by way of the air cylinders 33, 33. The switching valve V has an exhaustion port for exhausting the return air from the air cylinders 33, 33 outward.
The racks 34, 34 connected to the holding members 10, 20 and a pinion 35 commonly engaging with the racks 34, 34 are built in the driving mechanism 30 to align the stroke of the holding members 10, 20 so as to be the same. The rack 34 and the pinion 35 function as an interlocking mechanism.
In FIG. 4, each rack 34 is shown to be configured directly connected to the holding member 10 or the holding member 20, but is not limited thereto, and the racks 34, 34 may be directly connected to the rods 31, 31 (or guide rod 32, 32) by way of a connection fitting.
Further, the arrangement relationship between the racks 34, 34 and the cylinder 33, 33 is not particularly limited, and the racks 34, 34 may be arranged in any direction of above, below, left or right of the cylinders 33, 33. It is to be noted that in FIG. 4, the racks 34, 34 are shown in a state arranged in the longitudinal direction so that the operation of a plurality of cylinders 33, 33 can be clearly seen.
An attachment bracket 42 is screw fitted to the left and right of the driving mechanism 30 by way of the spacer bracket 41 (FIG. 1, FIG. 2). Each spacer bracket 41 is screw fitted to the base bracket 43 annexed to the lower surface of the driving mechanism 30. One or two attachment screw hole 42 b is formed at positioning depression 42 a. The positioning depression 42 a is formed at the distal end of each bracket 42.
The wafer chuck mechanically holds the wafer W by way of the elastic members 14, 14, 22 by driving the holding members 10, 20 in the closing direction (direction of arrow K₁, K₁of FIG. 2, FIG. 4) towards the center Wo of the wafer W by way of the driving mechanism 30. The holding members 10, 20 allow the outer peripheral part of the wafer W to enter the V-shaped grooves 14 a, 14 a, 22 a, 22 a and push the outer periphery of the wafer W in the radial direction. The pushing force with respect to the wafer W is suitably set by adjusting the air pressure in the closing direction of the holding members 10, 20 with the regulator R₁(FIG. 4). It is to be noted that the regulator R₂sets the air pressure of when driving the holding members 10, 20 in the opening direction to release the wafer W.
The wafer W on the chuck contacts the outer periphery of the polishing pad G and the internal part of the orientation notch N of the wafer W is polished (FIG. 2, FIG. 5). The polishing pad G is rotated about the axis center Go, and is entered into the gap 10 a serving as a machining tool forward/backward path between the fingers 12, 12, of the holding member 10 to contact the internal part of the notch N of the outer periphery of the wafer W positioned in the gap 10 a. The outer peripheral shape of the polishing pad G conforms to the shape of the notch N, and the wafer W being polished is swung in a reciprocating manner about the axis center Go of the polishing pad G with the chuck (direction of arrow K, K of FIG. 5) to finish the internal surface of the notch N to a predetermined shape. It is to be noted that the notch N is not limited to a circular arc shape as shown, and may be a V shape. The wafer W may, in addition to the swinging motion about the axis center Go of the polishing pad G, also perform a predetermined movement such as changing the relative distance with the axis center Go, or inclining the relative angle with the axis center Go by way of the chuck.
The driving mechanism 30 may have ball screw shafts 36, 36 that are reverse-rotatably driven by the motor M as the main member (FIG. 6). Each ball screw shaft 36 has a screw part of the same pitch in a direction opposite from each other, and is screwed to the nut member 15, 25 on the holding member 10 side and the holding member 20 side, respectively. When the ball screw shafts 36, 36 are rotated by way of the motor M, the holding members 10, 20 are driven all together in the closing direction by the same stroke to hold the wafer W (direction of arrow K₁, K₁of FIG. 6).
According to the above description, the wafer chuck polishes the orientation flat W₃of the wafer by being suitably relatively moved with respect to the polishing pad G (FIG. 7, FIG. 8). However, the holding members 10, 20 of FIG. 7 are able to further stably hold the wafer W by arranging three of each elastic members 14, 22 on the outer peripheral direction of the wafer W. In FIG. 8, the wafer W is held by way of three sets of holding members 10, 10 . . . arranged at equidistance on the outer periphery. The holding members 10, 10 . . . of FIG. 8 are also driven all together in the closing direction towards the center Wo of the wafer W by way of the driving mechanism, not shown (direction of arrow K₁, K₁. . . of FIG. 8).
It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

Claims

1. A wafer chuck comprising a plurality of holding members for pushing an outer periphery of a wafer in a radial direction and holding the wafer, and a driving mechanism for driving the holding members all together in a closing direction.

2. The wafer chuck as claimed in claim 1, wherein each holding member is configured so as to hold the wafer by way of an elastic member.

3. The wafer chuck as claimed in claim 2, wherein the elastic member is formed with a V-shaped groove for sandwiching the outer peripheral part of the wafer in a snapping manner.

4. The wafer chuck as claimed in claim 3, wherein the V-shaped groove of the elastic member is formed into a circular arc shape so as to lie along the circumferential direction of the outer peripheral edge of the wafer.

5. The wafer chuck as claimed in claim 3, wherein the elastic member further includes a guide groove having an apex angle greater than the apex angle of the V-shaped groove on an opening direction side of the V-shaped groove.

6. The wafer chuck as claimed in claim 2, wherein the elastic member is made of fluorocarbon resin or fluorocarbon rubber molded article.

7. The wafer chuck as claimed in claim 1, wherein the holding member is arranged on both sides in the radial direction of the wafer with the wafer sandwiched in between; and

the driving mechanism includes cylinders arranged in the radial direction of the wafer and connected to one of the holding members, and an interlocking mechanism for operating the other holding member in conjunction with the operation of the former holding means.

8. The wafer chuck as claimed in claim 1, wherein the holding member is arranged on both sides in the radial direction of the wafer with the wafer sandwiched in between; and

the driving mechanism, feed screws arranged in the radial direction of the wafer and having screw parts in the direction opposite to each other in order to screw each screw part to the holding member, and a motor for rotating the feed screw may be arranged.

9. The wafer chuck as claimed in claim 7, wherein a machining tool forward/backward path for approaching the wafer at a position orthogonal to the wafer and machining the outer peripheral edge of the wafer is formed on one of the holding members arranged on both sides in the radial direction of the wafer.

10. The wafer chuck as claimed in claim 1, being used for polishing the V-notch or Orientation flat for determining the orientation of the wafer.

11. The wafer chuck as claimed in claim 8, wherein a machining tool forward/backward path for approaching the wafer at a position orthogonal to the wafer and machining the outer peripheral edge of the wafer is formed on one of the holding members arranged on both sides in the radial direction of the wafer.

12. The wafer chuck as claimed in claim 2, being used for polishing the V-notch or Orientation flat for determining the orientation of the wafer.

13. The wafer chuck as claimed in claim 3, being used for polishing the V-notch or Orientation flat for determining the orientation of the wafer.

14. The wafer chuck as claimed in claim 4, being used for polishing the V-notch or Orientation flat for determining the orientation of the wafer.

15. The wafer chuck as claimed in claim 5, being used for polishing the V-notch or Orientation flat for determining the orientation of the wafer.

16. The wafer chuck as claimed in claim 6, being used for polishing the V-notch or Orientation flat for determining the orientation of the wafer.