JP2011083836A - Polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance in-surface uniformness by eliminating a clearance between a retainer ring and a wafer at a wafer polishing stage. <P>SOLUTION: The polishing device includes: a polishing pad used for polishing of the wafer; a polishing head capable of sucking/retaining the wafer and pressing the wafer to the polishing pad to perform polishing; and the retainer ring arranged on an outer periphery of the polishing head. The retainer ring includes: a first ring-like member 6a; a second ring-like member 6b joined to the inner periphery; and a third ring-like member 6c joined to an inner periphery of the second ring-like member 6b. The first ring-like member 6a is fixed onto an outer periphery of a surface for sucking the wafer of the polishing head. The second ring-like member 6b is formed of an expandable/contractable elastic member having a cavity 12. The third ring-like member 6c is a member movable in a diameter-contraction and diameter-enlargement direction according to motion of the second ring-like member 6b and has an area for sucking the wafer at an inner side of the member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polishing apparatus such as a CMP apparatus used for manufacturing a semiconductor device. In particular, the present invention relates to a retainer ring disposed in a polishing head of a CMP apparatus. Note that CMP is an abbreviation for Chemical Mechanical Polishing and is a technique for polishing and flattening the wafer surface.

  In a CMP apparatus, the back surface of a substrate such as a wafer is attracted to a polishing head, and the front surface of the substrate to be polished is pressed against a polishing pad positioned below and polished. In such a CMP apparatus, a retainer ring surrounding the substrate is provided on the periphery of the polishing head so that the substrate does not shift.

  FIGS. 10A to 10C are schematic sectional views of a polishing head equipped with a conventional retainer ring, and show operations from the wafer chuck to the wafer separation by the polishing head. FIG. 11 shows a cross-sectional structure of a conventional retainer ring.

  As shown in FIG. 10A, the retainer ring 104 is fixed to the periphery of the surface 101 a that attracts the wafer 102 of the polishing head 101. Regarding the operation of the conventional CMP apparatus, first, the wafer 102 is attracted to the inner region of the retainer ring 104 on the surface 101a of the polishing head 101 (FIG. 10B). Thereafter, the polishing head 101 moves onto the polishing pad 103 and presses the wafer 102 against the upper surface of the polishing pad 103 (FIG. 10C). At this time, high-pressure air is supplied to a space formed between the surface 101 a of the polishing head 101 and the wafer 102 to press the wafer 102 against the upper surface of the polishing pad. As the polishing pad 103 rotates, the polishing head 101 that presses the wafer 102 against the upper surface of the polishing pad 103 also rotates to polish the wafer 102.

  In such a conventional polishing head, the retainer ring 104 has a single-layer structure made of a hard material (see FIG. 11). Therefore, the distance between the inner peripheral end of the retainer ring 104 and the outer peripheral end of the wafer 102 cannot be changed, and a gap is formed between the retainer ring 104 and the wafer 102 during wafer polishing. Generally, the polishing pad 103 is elastic because it is made of polyurethane. Due to these factors, as shown in FIG. 12, when the retainer ring 104 is pressed against the surface of the polishing pad 103, the polishing pad portion 103a in the vicinity of the inner peripheral edge of the retainer ring 104 rises into the gap, and the wafer The polishing pad 103 makes excessive contact with the outer peripheral edge 102 a of the 102. As a result, the outer periphery of the wafer is excessively polished, and the uniformity of the polishing amount within the wafer surface (hereinafter referred to as in-plane uniformity) decreases.

JP 2007-307623 A JP2008-173741

  In recent years, with the miniaturization of semiconductor elements, the problem that polishing variation due to the above-described gap reduces the manufacturing yield has become apparent. For example, in OxCMP, there is a problem that the uniformity of polishing at the wafer edge portion is lowered, and in the metal CMP, the erosion and recess of the wafer edge portion are increased as the uniformity of polishing at the wafer edge portion is lowered.

  In Patent Documents 1 and 2, a member that fills the gap between the retainer ring and the wafer is disposed inside the retainer ring, and the peripheral edge of the wafer is effectively pressed against the upper surface of the polishing pad by such a member. Is disclosed. In Patent Documents 3 and 4, a plurality of ring bodies having different inner diameters are arranged between the inner periphery of the retainer ring and the outer periphery of the wafer, and the pressing force of each ring body against the polishing pad surface is individually adjusted. Thus, a technique for preventing excessive polishing of the outer peripheral edge of the wafer is disclosed.

  However, in the inventions disclosed in these documents, the gap between the retainer ring and the wafer cannot be completely eliminated because it is necessary to attract the wafer to the polishing head. If there is no gap between the retainer ring and the wafer, a lot of time and advanced position control are required so that the wafer enters the inner area of the retainer ring when the wafer is attracted to the polishing head. Adsorption is not easy. In addition, it becomes an apparatus that makes it difficult to remove the polished wafer from the polishing head.

  Therefore, in the inventions of the cited documents 1 to 4 that do not change the gap between the retainer ring and the wafer, the problem of polishing variation due to the gap is not completely solved.

  The present invention seeks to improve the in-plane uniformity by eliminating the gap between the retainer ring and the wafer as described above at the wafer polishing stage.

  According to one aspect of the present invention, a polishing pad used for polishing a wafer, a polishing head capable of adsorbing and holding the wafer and pressing the wafer against the polishing pad for polishing, and a polishing head comprising: The present invention relates to a polishing apparatus including a retainer ring disposed on an outer periphery of a surface to be adsorbed. And in order to solve said subject, the retainer ring by this invention has the area | region for adsorb | sucking the said board | substrate inside, and contains the ring-shaped member which can move in the direction where an inner peripheral part shrinks and expands. It is characterized by.

  In the polishing apparatus configured as described above, when the wafer is attracted to the inner region of the ring-shaped member and the wafer is pressed against the polishing pad, the ring-shaped member is moved to the wafer side by moving the ring-shaped member in the direction of expanding the diameter. Since the wafer moves to contact the outer peripheral edge of the wafer, the gap between the outer periphery of the wafer and the inner periphery of the retainer ring can be reduced. As a result, the rising of the polishing pad portion to the outermost periphery of the wafer is reduced, and the entire surface of the wafer can be evenly pressed against the polishing pad. As a result, excessive polishing of the wafer edge portion is reduced, and in-plane uniformity is improved. The erosion and recess of the wafer edge portion can also be reduced.

  Furthermore, when the wafer is attracted and held on the polishing head or when the wafer is detached from the polishing head, the gap between the outer periphery of the wafer and the inner periphery of the retainer ring is widened when the ring-shaped member is moved in the direction of reducing the diameter. The wafer can be easily sucked and detached.

  According to the present invention, it is possible to improve the in-plane uniformity and reduce the erosion and recess of the wafer edge portion.

FIG. 2 is a top view schematically showing the constituent parts of a CMP apparatus according to an embodiment of the present invention. The top view which showed typically the mode of the grinding | polishing part in FIG. FIG. 3 is a schematic cross-sectional view of a state in which wafer polishing is performed by a top ring (polishing head) in FIG. 2. The side view which showed the mode of the washing | cleaning part in FIG. 1 typically. The side view which showed typically the mode of the drying part in FIG. The typical sectional view of the retainer ring applied to the CMP device of the present invention. The figure which looked at the retainer ring of FIG. 6 from the top. 1 is a schematic cross-sectional view showing a state in which a retainer ring of a top ring is pressed against a polishing pad together with a wafer in a stage where wafer polishing is performed by a CMP apparatus according to an embodiment of the present invention. It is a cross-sectional schematic diagram of the top ring provided with the retainer ring by one Example of this invention, and is a figure which shows the operation | movement from a wafer chuck | zipper by the top ring to wafer removal. It is a cross-sectional schematic diagram of a polishing head provided with a conventional retainer ring, and shows the operation from the wafer chuck to the wafer release by the polishing head. The figure showing the cross-section of the conventional retainer ring. The cross-sectional schematic diagram which shows a mode when the retainer ring of the conventional grinding | polishing head is pressed on the surface of the grinding | polishing pad.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the CMP apparatus of this embodiment dries a wafer, a polishing unit A that polishes a wafer with polishing abrasive grains, a cleaning unit B that removes polishing abrasive grains, scraps and metal contamination, and a wafer. A drying unit C and a transfer unit D for transferring a wafer across these units are included. Further, a mechanism is also provided for connecting a FOUP (Front-Opening Unified Pod) 15 that accommodates an unpolished wafer to be supplied to the polishing unit A and accommodates a wafer discharged from the apparatus via the drying unit C.

  In the polishing section A, as shown in FIG. 2, the front surface of the wafer is brought into contact with the polishing pad 1 for polishing the wafer while rotating in the direction of the arrow, and the back side of the wafer is adsorbed during wafer polishing. The top ring 2 (that is, the polishing head) that rotates in the direction of the arrow while pressing and holding the front surface of the wafer against the polishing pad 1, the dresser 3 that sharpens the polishing pad 1, and the abrasive grains flow down. Nozzle 4 is prepared. The polishing pad 1 is made of polyurethane on the polishing surface.

  The configuration of the top ring 2 will be described in detail. As shown in FIG. 3, the retainer ring 6 is fixed to the periphery of the surface 2 a of the top ring 2 that attracts the wafer 5. The retainer ring 6 prevents the wafer during polishing from jumping out from the outer periphery of the top ring 2. Further, the surface 2a is provided with a polishing pressure adjusting unit 7 including a membrane sheet for adjusting a pressure for pressing the wafer 5 against the polishing pad 1, and an adsorption unit 8 for adsorbing the wafer.

  In the cleaning section B, as shown in FIG. 4, the support 9 that supports the wafer 5 without being damaged and rotates in the direction of the arrow, and the cleaning chemical solution and pure water are applied to the wafer 5 supported by the support 9. A nozzle 10 for cleaning and a cleaning brush 11 such as a roll brush for performing physical cleaning are prepared.

  Further, in the drying section C, as shown in FIG. 5, a support 18 that supports the wafer 5 without damaging it and rotates in the direction of the arrow is prepared, thereby enabling spin dry drying.

  In order to perform polishing by the CMP apparatus of the present embodiment described above, the wafer 5 is first sucked by the top ring 2. Thereafter, the top ring 2 moves onto the polishing pad 1 and moves down so that the adsorbed wafer 5 comes into contact with the polishing pad 1. Then, while rotating the top ring 2, the front surface of the wafer 5 is pressed against the surface of the polishing pad 1 for polishing. After polishing, the top ring 2 sucks the wafer 5 again, moves the wafer 5 to the transfer unit D, and the wafer 5 is transferred to the cleaning unit B. Thereafter, chemical cleaning with the nozzle 10 is performed on the wafer 5 together with scrub cleaning using a roll brush to clean the front and back surfaces of the wafer 5. Finally, the wafer 5 moves to the drying unit C, spin dry drying is performed, and the CMP process ends.

  The present invention is characterized in that the retainer ring 6 of the top ring 2 of the CMP apparatus illustrated in FIGS. 1 to 5 has a structure in which three ring-shaped members having different inner diameters are arranged concentrically. . By using the retainer ring 6 having this structure in the CMP apparatus, the entire surface of the wafer can be pressed against the polishing pad uniformly, the excessive polishing of the wafer edge portion is reduced, and the in-plane uniformity is improved.

  Hereinafter, the retainer ring 6 according to the present invention will be described in detail.

  FIG. 6 is a schematic cross-sectional view of the retainer ring 6 applied to the CMP apparatus of the present invention. FIG. 7 is a view of the retainer ring 6 as viewed from above.

  As shown in FIG. 6A, the retainer ring 6 includes a first ring-shaped member 6a made of a hard material (for example, polyphenylene sulfide) and an elastic material joined to the inner periphery of the first ring-shaped member 6a. A second ring-shaped member 6b made of (for example, silicon rubber) and a third ring-shaped member 6c made of a hard material (for example, polyphenylene sulfide) joined to the inner periphery of the second ring-shaped member 6b. Composed. Moreover, the cavity 12 is vacant in the 2nd ring-shaped member 6b, and the 2nd ring-shaped member 6b swells by supplying air in the cavity 12, as shown in FIG.6 (b). It has become. This air supply timing is when the wafer 5 sucked and held by the top ring 2 is pressed against the polishing pad 1. When the wafer 5 is attracted to the top ring 2 or detached from the top ring 2, air is removed from the cavity 12.

  In addition, the lower surface of the second ring-shaped member 6b made of an elastic material is not arranged at the same height as the lower surfaces of the ring-shaped members 6a, 6b made of a hard material so as not to be scraped off by the friction of the polishing pad 1. Is preferred. That is, it is preferable that the lower surface of the second ring-shaped member 6b is positioned at such a height that the rebound polishing pad portion does not contact when the retainer ring 6 is pressed against the polishing pad 1.

  Moreover, as shown in FIG. 7, the groove | channel 13 is cut in eight places of the circumferential direction of the 3rd ring-shaped member 6c at equal intervals, and the 3rd ring-shaped member 6c is divided into 8 parts. Furthermore, about one of the eight groove | channels 13, not only the 3rd ring-shaped member 6c but the 2nd ring-shaped member 6b is also divided (refer the code | symbol L in a figure). Therefore, the divided third ring-shaped member 6c is movable in the direction of diameter reduction and diameter expansion according to the movement of the second ring-shaped member 6b.

  In the retainer ring 6 having such a structure, since the third ring-shaped member 6c inside the second ring-shaped member 6b can move in the radial contraction direction by inflating the second ring-shaped member 6b, A gap between the outer periphery of the wafer 5 and the inner periphery of the retainer ring 6 can be filled. Thereby, the rising of the polishing pad portion to the outermost periphery of the wafer 5 is reduced, and the entire surface of the wafer can be pressed against the polishing pad evenly. As a result, excessive polishing of the wafer edge portion is reduced, and in-plane uniformity is improved. The erosion and recess of the wafer edge portion can also be reduced.

  In order to prevent the wafer from cracking due to the wafer shift when filling the gap, at least one convex portion 14 is formed on the inner surface of the third ring-shaped member 6c as shown in FIG. Is preferably disposed. In the example of FIG. 7, convex portions 14 are provided in every other portion of the eight portions constituting the third ring-shaped member 6 c.

  FIG. 8 is a schematic cross-sectional view showing a state in which the retainer ring 6 of the top ring 2 is pressed against the polishing pad 1 together with the wafer 5. As shown in this figure, magnetic bodies 16a and 16b are contained in the first ring-shaped member 6a and the third ring-shaped member 6c, respectively. The magnetic bodies 16a and 16b are, for example, permanent magnets having different magnetic poles. Therefore, when air is supplied from the air supply port 17 provided in the top ring 2 to the cavity 12 of the second ring-shaped member 6b, the second ring-shaped member 6b expands in the direction of the arrow and the third ring-shaped member 6c. Is moved to the wafer 5 side, and the magnetic body 16a of the first ring-shaped member 6a and the magnetic body 16b of the third ring-shaped member 6c are separated from each other against the magnetic attractive force. On the other hand, when the air in the cavity 12 is sucked from the air supply port 17, the second ring-shaped member 6b contracts, and the magnetic body 16a of the first ring-shaped member 6a and the magnetic body 16b of the third ring-shaped member 6c Approaches the magnetic attraction force. By such an action of the magnetic bodies 16a and 16b, the distance between the wafer 5 and the retainer ring 6 can be reliably returned to the same distance as that during wafer chucking.

  Further, a protective film (for example, silicon rubber) 17 is attached to the outer surface of the convex portion 14 (four convex portions 14 shown in FIG. 7) so as not to damage the wafer. For this reason, the third ring-shaped member 6 c can be brought into contact with the outer peripheral end of the wafer 5 without damaging the wafer 5. Further, in the state of FIG. 8, the gap between the wafer 5 and the retainer ring 6 is reduced. As a result, it can be seen that the rebound of the polishing pad 1 (that is, the rising of the polishing pad portion due to the pressing of the retainer ring 6) is reduced as indicated by the symbol E in FIG.

  Next, the operation from the wafer chuck to the wafer detachment by the top ring 2 having the retainer ring 6 according to the present invention will be described. Such an operation is shown in FIG.

  Referring to FIG. 9, the wafer 5 is attracted to the inner region (polishing pressure adjusting unit 7) of the retainer ring 6 on the surface 2a of the top ring 2 (see FIGS. 9A and 9B). Thereafter, the top ring 2 moves onto the polishing pad 1 and presses the wafer 5 against the upper surface of the polishing pad 1 (see FIG. 9C). At this time, high-pressure air is supplied to the polishing pressure adjusting unit 7 provided between the surface 2 of the top ring 2 and the wafer 5 to press the front surface of the wafer 5 against the upper surface of the polishing pad 1.

  Further, air is supplied from the air supply port 17 to the cavity 12 of the second ring-shaped member 6b of the retainer ring 6 in response to a command from a control device (not shown), and the second ring-shaped member 6b expands. As a result, the third ring-shaped member 6c moves to the wafer 5 side, and the convex portion 14 on the inner peripheral portion of the third ring-shaped member 6c and the outer peripheral end of the wafer 5 come into contact with each other, and the wafer 5 is fixed. (See FIG. 9 (d)). For this reason, the gap between the retainer ring 6 and the wafer 5 is reduced, and pressure can be applied uniformly to the entire front surface of the wafer 5. In such a state, the polishing pad 1 rotates, and the top ring 2 that presses the wafer 5 against the upper surface of the polishing pad 1 also rotates to polish the wafer 5. As a result, the excessive polishing of the edge portion, which has been difficult to improve even if the polishing pressure of the wafer edge is adjusted in the prior art, is eliminated, and the in-plane uniformity is improved.

  After polishing, the air in the cavity 12 is sucked from the air supply port 17 according to the command of the control device, so that the second ring-shaped member 6b is contracted and the first ring-shaped member 6a and the third ring-shaped member 6c. The magnetic bodies 16a and 16b are closest to each other by the magnetic attraction force, and the distance between the wafer 5 and the retainer ring 6 is opened at the same distance as when the wafer is attracted (see FIG. 9E). Thereafter, the wafer 5 is detached.

  Although the embodiments of the present invention have been described with reference to the drawings, it is not limited to the illustrated structure and shape without departing from the technical idea of the present invention, and the above embodiments may be appropriately modified and implemented. Is possible.

A Polishing part B Cleaning part C Drying part D Transport part 1 Polishing pad 2 Top ring (polishing head)
2a Surface 3 Dresser 4 Nozzle 5 Wafer 6 Retainer ring 6a First ring-shaped member 6b Second ring-shaped member 6c Third ring-shaped member 7 Polishing pressure adjusting unit 8 Adsorbing units 9, 18 Support 10 Nozzle 11 Cleaning brush 12 Cavity 13 Groove 14 Protrusion 15 FOUP
16a, 16b Magnetic body 17 Air supply port

Claims (7)

A polishing pad used for polishing a substrate, a polishing head capable of holding the substrate by suction and polishing the substrate by pressing the substrate against the polishing pad, and an outer periphery of the surface of the polishing head that sucks the substrate A polishing apparatus comprising:
2. The polishing apparatus according to claim 1, wherein the retainer ring includes a ring-shaped member having a region for adsorbing the substrate on the inner side and movable in a direction in which an inner peripheral portion is reduced in diameter and increased in diameter. A polishing pad used for polishing a substrate, a polishing head capable of holding the substrate by suction and polishing the substrate by pressing the substrate against the polishing pad, and an outer periphery of the surface of the polishing head that sucks the substrate A polishing device comprising:
The retainer ring is
A first ring-shaped member fixed to the surface;
A second ring-shaped member capable of expanding and contracting joined to the inner periphery of the first ring-shaped member;
A third ring-shaped member joined to the inner periphery of the second ring-shaped member and movable in a direction of diameter reduction and diameter expansion according to the movement of the second ring-shaped member; A third ring-shaped member having a region for adsorbing the substrate inside the ring-shaped member;
A polishing apparatus comprising:   3. The polishing apparatus according to claim 2, wherein the second ring-shaped member is formed of an elastic member having a cavity, and is expanded by supplying air to the cavity and contracted by sucking air in the cavity.   The polishing apparatus according to claim 3, wherein the polishing head includes an air supply port that supplies air to the cavity of the second ring-shaped member when the substrate held in the region is pressed against the polishing pad.   The polishing apparatus according to claim 1, wherein the ring-shaped member of the younger brother 3 is divided into a plurality of members in the circumferential direction.   The polishing apparatus according to claim 1, wherein a plurality of convex portions are disposed on an inner peripheral portion of the ring-shaped member of the younger brother 3.   7. The method according to claim 1, wherein the first ring-shaped member has a magnetic body, and the third ring-shaped member has a magnetic body having a polarity different from that of the magnetic body. The polishing apparatus as described.

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