JP2007158255A - Retainer ring and wafer polishing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retainer ring of capable for reducing the formation of polishing dust and a wafer polishing apparatus. <P>SOLUTION: The retainer ring 10 is located on a polishing cloth 2 surrounding a wafer W when polishing the wafer W, pressing it against the polishing cloth 2, and a portion contacted with the polishing cloth 2 of the retainer ring 10 is composed of a plurality of tapered rollers 12 which rotate on the polishing cloth 2 with a perpendicular line a passing through the center of the wafer W as an axis. In such a structure, a friction force produced between the retainer ring 10 and polishing cloth 2 is reduced due to a rotation of the tapered rollers 12, whereby, the formation of polishing dust from the retainer ring 10 can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a retainer ring and a wafer polishing apparatus, and more particularly to a technique capable of reducing generation of polishing scraps.

  FIG. 8 is a cross-sectional view showing a configuration example of a wafer polishing apparatus 400 according to a conventional example. A wafer polishing apparatus 400 shown in FIG. 8 is an apparatus that performs CMP (chemical mechanical polishing) on the surface of the wafer W, and is attached to the polishing table 91 and a polishing table 91 that can be rotated about a rotation shaft (not shown). The polishing cloth 92, the retainer ring 93 that guides the periphery of the wafer W on the polishing table 91, and the wafer W and the retainer ring 93 are pressed onto the polishing cloth 92, and the wafer W and the retainer ring 93 are held in this state. The rotary head 94 and the spindle 95 rotate around a perpendicular line a passing through the center of the wafer W, and a nozzle (not shown) for supplying an abrasive slurry onto the polishing cloth 92.

  When the wafer polishing apparatus 400 is used to polish the surface of the wafer W, an abrasive slurry is discharged together with water onto a polishing cloth 92 from a nozzle (not shown). Next, the retainer ring 93 and the wafer W are pressed onto the polishing pad 92 by the rotary head 94. Then, while the periphery of the wafer W is guided by the retainer ring 93, the polishing table 91 is rotated around a rotation shaft (not shown) (that is, revolved), and the rotation head 94 is rotated around a perpendicular line a passing through the surface of the wafer. Rotate (ie, rotate). By such revolution of the polishing table 91 and rotation of the rotary head 94, the surface of the wafer W is scraped and polished by the polishing cloth 92.

Further, in this wafer polishing apparatus 400, when pressing the wafer W and the retainer ring 93 onto the polishing cloth 92, the force for pressing the retainer ring 93 is set larger than the force for pressing the wafer W. Yes. This is to improve the uniformity of the polishing amount on the wafer W surface. By greatly sinking the portion of the polishing cloth 92 that contacts the retainer ring 93, the portion of the polishing cloth 92 that contacts the wafer W is stretched, so that the polishing cloth 92 is uniformly applied to the surface of the wafer W. Can do.
JP 2005-5398 A JP 2001-121411 A

  By the way, in the wafer polishing apparatus 400 shown in FIG. 8, the retainer ring 93 is pressed firmly on the polishing cloth 92, and the retainer ring 93 is rotated together with the wafer W in this state. For this reason, the bottom surface of the retainer ring 93 is strongly polished in proportion to the pressing force and the rotation speed, and there is a problem that a large amount of the polishing waste is discharged onto the polishing table 91. When a large amount of polishing debris is discharged from the retainer ring 93, a part thereof may enter between the wafer W and the polishing cloth 92 to cause small scratches (that is, micro scratches) on the surface of the wafer W. .

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a retainer ring and a wafer polishing apparatus that can reduce generation of polishing debris.

[Invention 1] In order to achieve the above object, the retainer ring of Invention 1 is a retainer ring disposed on the polishing pad around the wafer when the wafer is pressed against the polishing pad for polishing. A portion of the retainer ring that contacts the polishing pad is composed of a plurality of rolling elements capable of rotating on the polishing pad around a vertical line passing through the center of the wafer. . With such a configuration, the frictional force acting between the retainer ring and the polishing pad is reduced by the rotating operation of the rolling element, so that the generation of polishing dust from the retainer ring can be reduced. Thereby, generation | occurrence | production of the micro scratch on a wafer surface can be suppressed.

[Invention 2] The retainer ring according to Invention 2 includes the retainer ring according to Invention 1, including a cage that holds the plurality of rolling elements individually so that the rolling elements are not brought into contact with each other. It is characterized by. With such a configuration, the spacing between the rolling elements can be kept constant at all times, and the position of the rolling elements can be prevented from being biased, so that the portion of the polishing pad that contacts the wafer is less uneven. Can be stretched.

[Invention 3] The retainer ring of Invention 3 is characterized in that, in the retainer ring of Invention 2, the rolling element is a “tapered roller”. With such a configuration, it is easy to secure a wider contact area between the rolling element and the polishing pad than in the fourth aspect.

[Invention 4] The retainer ring of Invention 4 is characterized in that, in the retainer ring of Invention 2, the rolling elements are “balls”. With such a configuration, the rolling element can rotate and move in any direction within the horizontal plane, and therefore, the frictional force acting between the retainer ring and the polishing pad is further reduced as compared with the third aspect. It is possible.

[Invention 5] The wafer polishing apparatus according to Invention 5 is the retainer ring according to any one of Inventions 1 to 4, and passes through the center of the wafer while pressing the polishing pad and the retainer ring and the wafer against the polishing pad. And a rotary head that rotates about a perpendicular line. With such a configuration, the retainer ring according to any one of the first to fourth aspects of the invention is applied, so that the generation of polishing dust from the retainer ring can be reduced, and the generation of micro scratches on the wafer surface can be reduced. Can be suppressed.

[Invention 6] The wafer polishing apparatus according to Invention 6 includes a retainer ring disposed on the polishing pad around the wafer when the wafer is pressed against the polishing pad to polish the retainer ring and the wafer. A rotating head that rotates around a vertical line passing through the center of the wafer while pressing against the polishing pad, and a bearing mechanism provided between the rotating head and the retainer ring, the bearing mechanism including the wafer A plurality of rolling elements capable of rotating on the retainer ring about a perpendicular line passing through the center of the retainer ring. Here, the retainer ring tends to be strongly polished in proportion to the force pressed by the rotary head and the number of rotations (that is, the rotation speed).

  According to the wafer polishing apparatus of the sixth aspect, the rolling element of the bearing mechanism rotates on the retainer ring while the rotary head is rotating. Therefore, the number of rotations of the retainer ring can be made smaller than the number of rotations of the rotary head, and the generation of polishing dust from the retainer ring can be reduced. Thereby, generation | occurrence | production of the micro scratch on a wafer surface can be suppressed.

Embodiments of the present invention will be described below with reference to the drawings.
(1) 1st Embodiment FIG. 1: is sectional drawing which shows the structural example of the wafer polishing apparatus 100 which concerns on 1st Embodiment of this invention.
The wafer polishing apparatus 100 is an apparatus that performs, for example, CMP (chemical mechanical polish) on the surface of a wafer. As shown in FIG. 1, the wafer polishing apparatus 100 includes a polishing table 1, a polishing cloth 2, a rotating head 4, a spindle 5, a membrane 9, a retainer ring 10, and an abrasive slurry on the polishing cloth 2. And a nozzle (not shown).

The polishing table 1 is coupled to a rotation shaft (not shown) and can rotate (i.e., revolve) around the rotation shaft. The polishing cloth 2 is affixed on the polishing table 1. A rotating head 4 that presses the wafer W and the retainer ring 10 onto the polishing cloth 2 is provided above the polishing table 1 to which the polishing cloth 2 is attached.
As shown in FIG. 1, a membrane 9 for adjusting the pressing of the wafer W is inserted between the rotary head 4 and the wafer W. The membrane 9 is made of, for example, rubber. The wafer W to be polished is, for example, a semiconductor wafer W or a glass wafer W on which a wiring layer such as Al, Cu, or polycrystalline silicon, or an insulating layer such as a silicon oxide film or a silicon nitrogen film is formed. Can be mentioned. The rotary head 4 is coupled to the spindle 5 and is configured to rotate (ie, rotate) about a perpendicular line a passing through the center of the wafer W while pressing the wafer W and the retainer ring 10 on the polishing pad 2. Yes.

  The retainer ring 10 guides the periphery of the wafer W (that is, suppresses movement in the horizontal direction), and when the wafer W is pressed against the polishing cloth 2 and polished, the polishing cloth around the wafer W is provided. 2 is arranged. As shown in FIG. 1, a portion of the retainer ring 10 that contacts the polishing cloth 2 has a plurality of tapered rollers 12 that can rotate and move on the polishing cloth 2 about a perpendicular line a passing through the center of the wafer W. It consists of

FIG. 2 is a plan view showing a configuration example of the bottom surface of the retainer ring 10. As shown in FIG. 2, the retainer ring 10 includes a plurality of tapered rollers 12, a retainer 14 that individually holds the tapered rollers 12 so that the tapered rollers 12 can rotate and do not contact each other. The frame 16 that supports these cages 14 is included.
The tapered rollers 12 are all of the same shape and the same size, and are arranged so that the inner ring 12a having a small diameter faces the center of the wafer W and the outer ring 12b having a large diameter away from the center of the wafer W. Thus, the difference between the outer and inner rings can be made substantially zero, and slipping of the outer ring 12b can be prevented. The tapered roller 12 is made of, for example, PEEK (polyether ether ketone), PPS (polyphenylene sulfide), ceramic, or the like. Further, the same number of cages 14 that hold the tapered rollers 12 as the tapered rollers 12 are prepared, and one of the tapered rollers 12 is held by one of the cages 14. These cages 14 are attached to the bottom surface of the frame body 16 (that is, the surface facing the polishing pad 2) at regular intervals. As shown in FIG. 1, the frame body 16 is detachably attached to the rotary head 4.

  Next, the case where the surface of the wafer W is polished using the wafer polishing apparatus 100 shown in FIG. 1 will be described. When polishing the surface of the wafer W, a polishing cloth 2 is attached on the polishing table 1 and an abrasive slurry is discharged onto the polishing cloth 2. The retainer ring 10 and the wafer W are pressed onto the polishing cloth 2 by the spindle 5 and the rotary head 4, and the polishing table 1 and the rotary head 4 are rotated while guiding the periphery of the wafer W with the retainer ring 10.

  Here, when the wafer W and the retainer ring 10 are pressed onto the polishing cloth 2, the polishing cloth 2 is compressed by the pressing of the wafer W and the retainer ring 10, and sinking occurs. For this reason, when the wafer W and the retainer ring 10 are pressed onto the polishing cloth 2, the thickness, material, and the like of the membrane 9 are adjusted so that the press of the retainer ring 10 is larger than the press of the wafer W. As a result, the portion of the polishing cloth 2 that contacts the retainer ring 10 sinks greatly, and the portion of the polishing cloth 2 that contacts the wafer W is stretched, so that the polishing cloth 2 can be uniformly applied to the surface of the wafer W. And the uniformity of the polishing amount on the surface of the wafer W can be improved.

  In the first embodiment, the portion of the retainer ring 10 that comes into contact with the polishing pad 2 is composed of a plurality of tapered rollers 12, as if they are “thrust bearing”. While the rotary head 4 is rotating, a large amount of water is supplied together with the abrasive slurry from a nozzle (not shown), and water enters between the tapered roller 12 and the retainer 14 and is in a lubricated state (ie, squeezed). Therefore, the tapered roller 12 can rotate with little resistance.

Therefore, the frictional force acting between the retainer ring 10 and the polishing pad 2 is reduced by the rotating operation of the tapered roller 12. Thereby, compared with the prior art as shown in FIG. 8, generation | occurrence | production of the grinding | polishing waste from a retainer ring can be reduced, and generation | occurrence | production of the microscratch on the wafer W surface can be suppressed.
In the first embodiment, the polishing cloth 2 corresponds to the “polishing pad” of the present invention, and the tapered roller 12 corresponds to the “rolling element” of the present invention.

(2) Second Embodiment In the first embodiment, the case where the tapered roller 12 is used as the “rolling element” of the present invention has been described. However, the “rolling element” of the present invention is not limited to the tapered roller. For example, it may be a ball that can rotate and move in an arbitrary direction in a horizontal plane. In the second embodiment, a case where a ball is used as the “rolling element” will be described.

  FIG. 3 is a cross-sectional view showing a configuration example of a wafer polishing apparatus 200 according to the second embodiment of the present invention. 3, parts having the same configurations and functions as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 1, the wafer polishing apparatus 200 includes a polishing table 1, a polishing cloth 2, a rotating head 4, a spindle 5, a membrane 9, a retainer ring 20, and an abrasive slurry on the polishing cloth 2. And a nozzle (not shown).

Among these, the retainer ring 20 guides the periphery of the wafer W, and is disposed on the polishing cloth 2 around the wafer W when the wafer W is pressed against the polishing cloth 2 for polishing. It is. And the rolling element with which the retainer ring 20 is provided is not the tapered roller but the ball 22.
FIG. 4 is a plan view showing a configuration example of the bottom surface of the retainer ring 20. As shown in FIG. 4, the retainer ring 20 includes a plurality of balls 22, a retainer 24 that individually holds the balls 22 so that the balls 22 can rotate and do not contact each other, and the holding thereof. And a frame body 26 that supports the container 24. The balls 22 have the same shape and the same dimensions, and are made of, for example, PEEK, PPS, or ceramic. Further, the same number of cages 24 that hold the balls 22 as the balls 22 are prepared, and one cage 22 is configured to hold one ball 22. These retainers 24 are attached to the bottom surface of the frame body 26 (that is, the surface facing the polishing pad 2) at a constant interval. As shown in FIG. 3, the frame body 26 is detachably attached to the rotary head 4.

  As described above, according to the second embodiment of the present invention, the ball 22 can rotate in any direction within a horizontal plane, and both the rotational force transmitted from the rotary head 4 and the rotational force transmitted from the polishing table 1 can be obtained. It is configured to roll on the polishing cloth 2 under the force. Further, while the rotary head 4 is rotating, a large amount of water is supplied together with the abrasive slurry from a nozzle (not shown), and water enters between the balls 22 and the retainer 24 to be in a lubricating state. 22 can rotate with little resistance.

Therefore, compared with the first embodiment, the frictional force acting between the retainer ring 20 and the polishing pad 2 can be further reduced, and the generation of polishing dust from the retainer ring 20 can be further reduced. is there. In the second embodiment, the ball 22 corresponds to the “rolling element” of the present invention.
In the second embodiment, as shown in FIG. 3, the case where only one row of balls 22 is arranged from the inside to the outside of the retainer ring 20 has been described. However, the arrangement of the balls 22 is not limited to one row. . For example, as shown in FIG. 5, the balls 22 may be arranged in three rows from the inside to the outside of the retainer ring 20. With such a configuration, the number of contact points between the balls 22 and the polishing pad 2 can be increased, and the total contact area between the balls 22 and the polishing pad 2 can be increased. It is.

(3) Third Embodiment FIG. 6 is a cross-sectional view showing a configuration example of a wafer polishing apparatus 300 according to a third embodiment of the present invention. 6, parts having the same configurations and functions as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 6, the wafer polishing apparatus 300 includes a polishing table 1, a polishing cloth 2, a rotating head 4, a spindle 5, a membrane 9, a bearing mechanism 30, a retainer ring 40, and a polishing cloth 2. And a nozzle (not shown) for supplying an abrasive slurry thereon.

The bearing mechanism 30 supports a plurality of tapered rollers 12, retainers 14 that individually hold the tapered rollers 12 so that the tapered rollers 12 can rotate and do not contact each other, and support these retainers 14. The frame body 16 is configured to be included. The frame body 16 is detachably attached to the rotary head 4.
FIG. 7 is a plan view showing a configuration example of the upper surface of the retainer ring 40. As shown in FIG. 7, the upper surface of the retainer ring 40 (that is, the surface in contact with the tapered roller 12) has a raceway surface 41 for rolling the tapered roller 12 on the retainer ring 40, and both side ends of the raceway surface 41. An inner collar 42 and an outer collar 43 are provided. While the rotary head 4 shown in FIG. 6 is rotating, the tapered roller 12 of the bearing mechanism 30 rolls on the raceway surface 41 while being guided by the inner collar 42 and the outer collar 43. .

  As described above, according to the third embodiment of the present invention, the tapered roller 12 of the bearing mechanism 30 rotates on the retainer ring 40 while the rotary head 4 is rotating. Therefore, the number of rotations of the retainer ring 40 can be reduced, and generation of polishing scraps from the retainer ring 40 can be reduced. Thereby, generation | occurrence | production of the micro scratch on the wafer W surface can be suppressed. In the third embodiment, the tapered roller 12 corresponds to the “rolling element” of the present invention.

1 is a cross-sectional view showing a configuration example of a wafer polishing apparatus 100 according to a first embodiment. FIG. 3 is a plan view illustrating a configuration example of a bottom surface of the retainer ring 10. Sectional drawing which shows the structural example of the wafer grinding | polishing apparatus 200 which concerns on 2nd Embodiment. The top view which shows the structural example of the bottom face of the retainer ring 20. FIG. Sectional drawing which shows the other structural example of the wafer grinding | polishing apparatus 200. FIG. Sectional drawing which shows the structural example of the wafer grinding | polishing apparatus 300 which concerns on 3rd Embodiment. The top view which shows the structural example of the upper surface of the retainer ring 40. FIG. Sectional drawing which shows the structural example of the wafer polishing apparatus 400 which concerns on a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Polishing table, 2 Polishing cloth, 4 Rotating head, 5 Spindle, 9 Membrane, 10, 20, 40 Retainer ring, 22 balls, 30 Bearing mechanism, 12 Tapered roller, 14, 24 Cage, 16, 26 Frame, 41 Track surface, 42 inner brim, 43 outer brim, 100, 200, 300 Wafer polishing equipment, W wafer

Claims (6)

A retainer ring disposed on the polishing pad around the wafer when polishing the wafer against the polishing pad;
A portion of the retainer ring that comes into contact with the polishing pad comprises a plurality of rolling elements capable of rotating on the polishing pad around a vertical line passing through the center of the wafer.   The retainer ring according to claim 1, further comprising: a holder that holds the plurality of rolling elements individually so that the rolling elements are not brought into contact with each other.   The retainer ring according to claim 2, wherein the rolling element is a “cone roller”.   The retainer ring according to claim 2, wherein the rolling element is a “ball”. The retainer ring according to any one of claims 1 to 4,
A polishing pad;
A wafer polishing apparatus comprising: a rotating head that rotates about a perpendicular passing through the center of the wafer while pressing the retainer ring and the wafer against the polishing pad. A retainer ring disposed on the polishing pad around the wafer when polishing the wafer against the polishing pad;
A rotating head that rotates about a normal passing through the center of the wafer while pressing the retainer ring and the wafer against the polishing pad;
A bearing mechanism provided between the rotary head and the retainer ring,
2. The wafer polishing apparatus according to claim 1, wherein the bearing mechanism includes a plurality of rolling elements capable of rotating on the retainer ring about a vertical line passing through the center of the wafer.

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