JP2009045685A - Pressing mechanism of polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressing mechanism for narrow zone capable of delicately pressing and controlling by arranging it near a wafer edge and accurately controlling against the variation of a polishing speed near the wafer edge. <P>SOLUTION: A polishing head 10 comprises a head body 11 disposed oppositely to a polishing pad 22 and rotatingly driven, a carrier so loosely supported on the head body 11 as to be vertically moved, and a retainer ring 13 so loosely supported on the head body 11 as to be vertically moved and brought into contact with the polishing pad 22 while surrounding the circumference of a wafer 20 during the polishing. An inner peripheral extension part 13d covering the upper surface of the outer peripheral part of a wafer is formed by extending the inner peripheral part of a retainer ring 13 inward. An airbag 31 for locally pressing the upper surface of the outer peripheral part of the wafer during the polishing is installed on the lower surface of the inner peripheral extension part 13d. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressurizing mechanism of a polishing apparatus, and in particular, in chemical mechanical polishing (CMP), a polishing head is provided with a local pressurizing unit to locally pressurize a wafer being polished. It is related with the pressurization mechanism of the polisher formed in this way.

  In recent years, fine processing of semiconductors has progressed, and a pattern is formed over multiple layers. It is inevitable that a certain degree of unevenness is generated on the surface of the layer on which the pattern is formed. Conventionally, the pattern of the next layer is formed as it is. However, as the number of layers increases and the width of a line or hole decreases, it becomes difficult to form a good pattern, and defects and the like easily occur.

  For this reason, the pattern of the next layer is formed after the surface of the layer on which the pattern is formed is polished and flattened. Thus, in order to polish the surface of a wafer such as a semiconductor, a polishing apparatus using a CMP process is used. This type of polishing apparatus generally has a configuration in which a wafer held by a polishing head is pressed against a polishing pad on a rotating platen and a slurry is supplied to the polishing pad to polish the wafer.

  The polishing head is rotatably supported by a head body that is disposed opposite to the polishing pad and rotationally driven, a carrier that is loosely supported by the head body so as to be vertically movable, and is freely loosely supported by the head body. And a retainer ring that surrounds the periphery of the wafer and contacts the polishing pad during polishing. In order to polish the wafer uniformly, it is necessary to press the wafer against the polishing pad with a uniform pressing force. For example, while pressing the carrier of the polishing head with the air pressure of a rubber sheet, A configuration is known in which a pressure air layer is formed by supplying air, and a pressing force from the rubber sheet is transmitted through the pressure air layer to polish the wafer (see Patent Document 1).

  Here, in order to produce a large number of chips from a single wafer, it is necessary to uniformly polish as close as possible to the edge (outer peripheral edge) of the wafer. However, in CMP, the polishing speed in the vicinity of the wafer edge varies greatly, and it is difficult to control the speed. For this reason, in the conventional polishing apparatus, the polishing head is equipped with a local pressurization mechanism called zone pressurization (hereinafter referred to as zone pressurization or zone pressurization mechanism).

For example, a plurality of air outlets are provided on the lower surface of the carrier of the polishing head, and an air chamber is formed between the rubber sheet disposed between the carrier and the wafer and the lower surface of the carrier. A structure of a polishing head is known in which a rubber sheet is inflated by air from an air outlet and the vicinity of the edge of a wafer is pressed against a polishing pad by the pressure of an air chamber (see Patent Document 2).
Japanese Patent Laid-Open No. 11-048136 JP 2001-212754 A

  Since Patent Document 1 is configured to polish a wafer by transmitting a pressing force from a rubber sheet through a pressure air layer, the wafer can be polished with a relatively uniform pressing force. However, the mechanism for locally pressurizing the wafer is not specifically described.

  Patent Document 2 describes a configuration in which a plurality of air outlets are provided on the lower surface of the carrier of the polishing head, and the amount of pressurization is changed by dividing into a central portion and an outer peripheral portion of the lower surface of the carrier. FIG. 7 is an explanatory diagram that simplifies the configuration in the vicinity of the outer peripheral portion of the conventional polishing head described in Patent Document 2, and air blowout ports 52 are provided in places on the lower surface of the carrier 51 of the polishing head 50. The outer peripheral edge 54 a of the rubber sheet 54 disposed between the carrier 51 and the wafer 53 is sandwiched by the holder 56 of the retainer ring 55, and an air chamber 57 is formed between the lower surface of the carrier 51 and the rubber sheet 54. Is formed. At the time of polishing, the rubber sheet 54 swells due to the air from the air outlet 52, and the vicinity of the edge of the wafer 53 is pressed against the polishing pad 58 by the pressure of the air chamber 57, thereby applying zone pressure.

  However, in the vicinity of the outer periphery of the carrier 51, the space of the air chamber 57 formed by the air outlet 52 is limited due to the relationship between the retainer ring 55 and the holder 56. It is difficult to control, and the fluctuation of the polishing rate in the vicinity of the edge of the wafer 53 may change within a narrow range, and it is a limit to dispose a narrow zone pressurizing mechanism in the vicinity of the outer periphery of the carrier 51. was there.

  Therefore, in order to provide a pressurization mechanism that can control minute pressurization by arranging a narrow zone pressurization mechanism in the vicinity of the wafer edge and can accurately control the fluctuation of the polishing speed in the vicinity of the wafer edge. Therefore, a technical problem to be solved arises, and the present invention aims to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 presses the wafer held by the polishing head against the polishing pad on the rotating platen and also applies the slurry to the polishing pad. And polishing the wafer, wherein the polishing head is arranged to be opposed to the polishing pad and rotationally driven, and the head main body is loosely supported to be freely movable in the vertical direction. A polishing apparatus comprising: a carrier; and a retainer ring that is loosely supported by the head main body so as to be freely movable in the vertical direction and surrounds the periphery of the wafer during polishing and contacts the polishing pad. An inner peripheral extending portion that covers the upper surface of the outer peripheral portion of the wafer is formed by extending the inner portion, and the lower surface of the inner peripheral extending portion is formed on the lower surface of the wafer during polishing. The part upper surface to provide a pressing mechanism of the polishing apparatus, characterized in that a local pressurizing means for pressurizing locally pressurizing.

  According to this configuration, the inner peripheral extending portion of the retainer ring is formed so as to cover the outer peripheral portion of the wafer from the upper surface, and the outer peripheral portion of the wafer is locally localized by the local pressurizing means provided in the inner peripheral extending portion. Therefore, zone pressure can be applied to the outermost periphery of the wafer edge. In addition, since there is a sufficient space on the retainer ring side, it is possible to provide a plurality of minute pressure mechanisms, and minute zone pressure control near the wafer edge can be performed.

  According to a second aspect of the present invention, there is provided the pressurizing mechanism of the polishing apparatus according to the first aspect, wherein the local pressurizing means is formed in a ring shape that is substantially concentric with the rotation center of the polishing head. provide.

  According to this configuration, the local pressurizing means is formed in a ring shape, and pressurizes the outer peripheral portion of the wafer evenly without being biased.

  According to a third aspect of the present invention, the local pressurizing means comprises a rubber sheet-made airbag, and an air supply mechanism for supplying air to the airbag is connected, and the air pressure of the airbag is arbitrarily adjusted. The pressurizing mechanism of the polishing apparatus according to claim 1, further comprising a control unit.

  According to this configuration, the local pressurizing unit is formed of a rubber sheet airbag, and the air pressure of the airbag is arbitrarily controlled by the control unit. Pressurization control can be performed.

  According to the first aspect of the present invention, since the local pressurizing means is provided at the inner peripheral extending portion of the retainer ring, the zone pressure can be applied to the outermost periphery of the wafer edge. In addition, since there is room on the retainer ring side, it is possible to provide a plurality of minute pressure mechanisms, and it is possible to perform fine zone pressure control near the wafer edge for even finer control. It becomes possible.

  In the invention of claim 2, since the local pressurizing means is formed in a ring shape, in addition to the effect of the invention of claim 1, it is possible to pressurize evenly without biasing the outer periphery of the wafer, Accurate edge control is possible.

  In the invention described in claim 3, since the local pressurizing means comprises an air bag made of rubber sheet, and the air pressure of the airbag is arbitrarily controlled by the control means, in addition to the effect of the invention described in claim 1 or 2 The polishing rate can be increased and a wide range of edge control is possible.

  Hereinafter, the pressurizing mechanism of the polishing apparatus according to the present invention will be described with reference to preferred embodiments. In order to achieve the object of enabling a fine pressure control by arranging a narrow zone pressure mechanism in the vicinity of the wafer edge, the present invention allows a wafer held by a polishing head to be moved on a rotating platen. A polishing apparatus that presses against a polishing pad and supplies slurry to the polishing pad to polish the wafer, wherein the polishing head is disposed to face the polishing pad and is driven to rotate, and the head body And a carrier ring that is loosely supported to be freely movable in the vertical direction, and a retainer ring that is loosely supported to be freely movable in the vertical direction on the head body and surrounds the periphery of the wafer during polishing. In the polishing apparatus, the inner peripheral portion of the retainer ring is extended inward to form an inner peripheral extension portion that covers the upper surface of the outer peripheral portion of the wafer, and the inner peripheral extension The lower surface of the parts, was realized by providing the local pressurization means locally pressurizing ring and the outer peripheral portion upper surface of the wafer during polishing.

  FIG. 1 is a cross-sectional view of the vicinity of the outer periphery of the polishing head showing the pressurizing mechanism of the polishing head according to the present invention. In this embodiment, the wafer 20 is polished as a substrate to be processed, and the wafer 20 held by the polishing head 10 is pressed against the polishing pad 22 on the rotating platen 21 and the slurry ( A polishing apparatus for supplying a wafer (not shown) to polish the wafer 20 will be described.

  The polishing head 10 includes a head body 11, a carrier 12, and a retainer ring 13. The head body 11 is disposed to face the polishing pad 22 and is driven to rotate by a motor (not shown).

  On the other hand, the carrier 12 is loosely supported by the head main body 11 so as to be movable in the vertical direction, and an airbag 14 is provided between the head main body 11 and the carrier 12. The carrier 12 includes a carrier body 12a that holds the wafer 20 by suction, and a carrier pressing member 12b that is provided on the carrier body 12a and transmits the pressing force from the airbag 14 to the carrier body 12a.

  The retainer ring 13 is loosely supported by the head main body 11 so as to be movable in the vertical direction, and an airbag 15 is provided between the head main body 11 and the retainer ring 13. The retainer ring 13 is provided on a retainer ring main body 13a that surrounds the periphery of the wafer 20 and contacts the polishing pad 22 during polishing, and an upper portion of the retainer ring main body 13a to reduce the pressing force from the airbag 15. It consists of retainer ring pressing members 13b and 13c that transmit to the retainer ring body 13a.

  The airbags 14 and 15 provided in the head body 11 are connected to an air supply means including an air pump 16 and regulators 17 and 18. The air pressures of the airbags 14 and 15 are controlled by a controller 30 which is a control means. Is arbitrarily adjusted, and the wafer pressure P1 and the retainer ring pressure P2 are respectively controlled.

  A plurality of air outlets (not shown) are provided on the lower surface of the carrier body 12a, and the outer peripheral edge 23a of the rubber sheet 23 disposed between the carrier body 12a and the wafer 20 is retained by the retainer ring 13. An air chamber 24 is formed between the lower surface of the carrier 12 and the rubber sheet 23 by being sandwiched.

  On the other hand, the retainer ring pressing member 13b has an inner peripheral portion extending inward to form an inner peripheral extended portion 13d, and the inner peripheral extended portion 13d covers the upper surface of the outer peripheral portion of the wafer 20. Is formed. Further, an air bag 31 made of a rubber sheet is provided as a local pressurizing means on the lower surface of the inner peripheral extending portion 13d of the retainer ring.

  The airbag 31 provided in the inner ring extending portion 13d of the retainer ring is formed in a ring shape that is substantially concentric with the center of rotation of the polishing head 10, and the airbag 31 includes the air pump 16 and the regulator 19. The air pressure supplied to the airbag 31 can be arbitrarily adjusted by the control of the controller 30.

  FIG. 2 is an enlarged view of a portion A in FIG. 1. By supplying air to the airbag 31 provided in the inner peripheral extending portion 13d of the retainer ring and inflating, the outer peripheral portion of the wafer 20 is locally expanded. Pressurized. Compared with the configuration in which the pressure mechanism is provided in the vicinity of the outer peripheral portion of the carrier as in the prior art, by providing the pressure mechanism in the inner peripheral extending portion 13d of the retainer ring as in the present invention, the wafer 20 Zone pressurization (P3) can be performed up to the outermost periphery of the edge, and finer control becomes possible. Further, since the pressurizing mechanism is formed by the continuous ring-shaped airbag 31, the outer peripheral portion of the wafer 20 can be evenly pressurized without being biased, and accurate edge control can be performed.

  In the illustrated example, a ring-shaped airbag 31 having a width of 5 to 10 mm is used. However, the size and installation position of the airbag are not limited to this, and the retainer ring pressing member 13b is replaced. Thus, the airbag can be easily changed to another ring shape.

  FIG. 3 is an explanatory view showing another embodiment of the zone pressurizing mechanism. For example, FIG. 3 (a) shows that two airbags 31, 31 are continuously arranged on the inner peripheral extending portion 13d of the retainer ring. By independently pressurizing each of them, variation in edge rate can be suppressed, and finer zone pressurization control can be performed.

  FIG. 3B shows a configuration in the case where the outermost edge of the wafer 20 is zone-pressed, and FIG. 3C shows a zone where the inner peripheral extending portion 13d of the retainer ring is located at a substantially inner position slightly inside of FIG. FIG. 3D shows a configuration in the case of pressurizing, and FIG. 3D shows a configuration in the case where the inner peripheral position of the inner peripheral extending portion 13d of the retainer ring is zone-pressed further inside than FIG. 3B. FIG. 3E shows a configuration in which a wide position is zone-pressurized from the inner circumference to the outer circumference of the inner circumference extending portion 13d of the retainer ring.

  In this manner, by replacing the retainer ring pressing member 13b according to the control contents, zone pressurizing mechanisms at different positions can be easily obtained by the various ring-shaped airbags 31. And since it became possible to polish to the outermost edge of the wafer 20 with high precision, the polishing area of the wafer 20 is increased, and the number of chips that can be taken from one wafer 20 is increased, which can contribute to improvement of productivity.

  In the first embodiment, the configuration in which the airbag 31 that is the zone pressurizing mechanism is provided in the inner peripheral extending portion 13d of the retainer ring has been described. However, in the second embodiment, a conventional type in which the carrier is provided with the airbag. A description will be given of a result of an experiment in which the air seal position is moved inward with the polishing head.

  4A shows a conventional polishing head 40, in which an air bag 42 is provided in the vicinity of the outer peripheral portion of the carrier 41, and an air seal 43 is mounted on the lower surface of the outermost peripheral portion of the carrier 41 at an outer position thereof. Reference numeral 44 is an air film, and 45 is a membrane sheet.

  FIG. 4B shows a test polishing head 40A in which the air seal 43A is moved and mounted inside the airbag 42A. As described above, the zone pressurizing mechanism is not provided in the retainer ring but is provided in the carrier 41A, but the polishing principle is very close to that of the present invention.

  FIG. 5A is a graph showing the fluctuation of the polishing rate at each position of the polishing head. FIG. 5B shows an enlarged view of the vicinity of the outer peripheral portion (B portion) of the polishing head in FIG. When polishing is performed without applying zone pressure with the test polishing head 40A, the outer peripheral portion has a lower polishing rate than the position where the air seal 43A is mounted as in L1. If zone pressurization is performed from this state, the polishing rate can be increased sequentially with L2, L3, L4, and L5 as the zone pressurization increases, and wide edge control can be performed.

The conditions in this experiment are as follows.
○ Rubber thickness: 0.4-1.0mm
○ Rubber hardness: JIS A scale 20-60
○ Rubber material: EPD, silicon rubber, urethane rubber, NBR
○ Supply pressure range: 1kPa to 100kPa
○ Ring material: PEEK, PPS
○ Ring holder (pressing member) material: PEEK, PPS, SUS, AL
□ PAD: ROHM & HAAS IC1000A21
□ Slurry ： Cabot Microelectronics Semi-Sperse 25 (2 Times dilution) / 300ml / min
□ Wafer: PETEOS
□ Platen Speed / Head Speed: 100rpm / 100rpm
□ Wafer Pressure / Retainer Pressure: 3.5psi / 1.0psi

  FIG. 6 is a pressure distribution model diagram of the wafer edge based on the experimental results. In an area where there is no air film layer, the pressure decreases as it goes to the outer periphery. However, it is possible to perform pressure control like “Pressure 1”, “Pressure 2”, and “Pressure 3” by zone pressurizing the area. In this experiment, it was possible to control the pressure to the tip of the wafer edge.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

Sectional drawing of the polishing head outer peripheral part vicinity in Example 1 which concerns on this invention. The enlarged view of the A section of FIG. Explanatory drawing which shows other embodiment of the zone pressurization mechanism in Example 1. FIG. FIG. 6 is a cross-sectional view of the vicinity of the outer periphery of a polishing head in Example 2. 9 is a graph showing fluctuations in the polishing rate of the polishing head in Example 2. FIG. 6 is a pressure distribution model diagram of a wafer edge in the second embodiment. Explanatory drawing of the conventional polishing head outer periphery vicinity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polishing head 11 Head main body 12 Carrier 12a Carrier main body 12b Carrier press member 13 Retainer ring 13a Retainer ring main body 13b, 13c Retainer ring press member 13d Inner peripheral extension part 14, 15 Air bag 16 Air pump 17, 18, 19 Regulator 20 Wafer 21 Platen 22 Polishing pad 23 Rubber sheet 23a Outer peripheral edge 24 Air chamber 30 Controller 31 Air bag 40, 40A Polishing head 41, 41A Carrier 42, 42A Air bag 43, 43A Air seal 44 Air film 45 Membrane sheet

Claims (3)

A polishing apparatus that presses a wafer held by a polishing head against a polishing pad on a rotating platen and supplies slurry to the polishing pad to polish the wafer, the polishing head facing the polishing pad A head body that is arranged and rotationally driven; a carrier that is loosely supported by the head body so as to be movable in a vertical direction; and a loosely supported and supported by the head body so as to be movable in a vertical direction. In a polishing apparatus comprising a retainer ring that surrounds and contacts the polishing pad,
Forming an inner peripheral extending portion that covers the upper surface of the outer peripheral portion of the wafer by extending the inner peripheral portion of the retainer ring inward;
A pressurizing mechanism of a polishing apparatus, wherein a local pressurizing means for locally pressurizing the upper surface of the outer peripheral portion of the wafer during polishing is provided on the lower surface of the inner peripheral extending portion.   2. The pressurizing mechanism of a polishing apparatus according to claim 1, wherein the local pressurizing means is formed in a ring shape that is substantially concentric with respect to the center of rotation of the polishing head.   The local pressurizing means is made of a rubber sheet airbag, and is connected to an air supply mechanism for supplying air to the airbag and is provided with a control means for arbitrarily adjusting the air pressure of the airbag. The pressurizing mechanism of the polishing apparatus according to claim 1 or 2.

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