Active gimbal ring with internal gel and methods for making same

• US 6,592,437 B1
• Filed: 12/26/2001
• Issued: 07/15/2003
• Est. Priority Date: 12/26/2001
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Lam Research Corporation
• Inventors: Boyd, John M., Paterson, Allan
• Primary Examiner(s): Hail, III, Joseph J.
• Assistant Examiner(s): Shakeri, Hadi
• Application Number:
  US10/033,479
• Time in Patent Office: 566 Days
• Field of Search: 451/285, 451/289, 451/397, 451/398, 451/364, 451/286, 451/287, 451/288, 451/290, 451/41, 451/63
• US Class Current: 451/285
• CPC Class Codes: B24B 37/30 for single side lapping of plane surfaces
• CPC Class Codes: B24B 41/007 Weight compensation; Temperature compensation; Vibration damping

Abstract

A chemical mechanical planarization (CMP) system having a polishing pad, a carrier plate and a wafer plate is provided with an active gimbal. The active gimbal is defined by a circular hollow ring having a wall thickness and a diameter. The circular hollow ring is configured by an elastomeric material for placement in a space between the carrier plate and the wafer plate, and the space preferably is defined in part by a cavity tightly receiving the ring. The circular hollow ring is filled with a gel-like material that flows from one portion of the ring that is squeezed and deformed when the wafer plate tilts relative to the carrier plate. The flow is to another portion of the ring that returns to an original configuration during such tilting. Methods of making the gimbal include operations for selecting materials for the hollow ring and the gel-like material.

Claims

1. In a chemical mechanical planarization (CMP) system having a carrier body for applying force along a central axis and a retainer body for holding a wafer centered on the axis, the wafer having a peripheral edge, the carrier body and the retainer body each defining a perimeter edge and a plane, the planes being separated by a space having a uniform dimension when the planes are parallel and having a non-uniform dimension when the planes are not parallel, and an active gimbal received in the space, the active gimbal comprising:

a hollow annular body configured with an arcuate wall structure, the body extending around and being radially spaced outwardly from the central axis, the body being co-axial with the peripheral edge of the wafer, the body being configured with a first section generally at one side of the axis and adjacent to the perimeter edges and with a second section generally at an opposite side of the axis and adjacent to the perimeter edges, the first and second sections being unevenly deformed when the space has the non-uniform dimension; and

a gel-like material received in and filling the hollow annular body so that when the first and second sections are unevenly deformed a portion of the gel-like material is caused by the deformed first section to flow in the hollow annular body from the one side of the axis to the second section at the opposite side of the axis to fill the deformed second section with the gel-like material while allowing the deformed first section to remain filled with another portion of the gel-like material.

2. An active gimbal as recited in claim 1, wherein:

the wall structure is fabricated from an elastomeric material;

the arcuate wall structure has a hollow generally circular cross section when the planes are parallel;

the wall structure has a first internal volume evenly distributed around the axis when the planes are parallel;

the first section has the hollow generally circular cross section in a first deformed configuration, the first configuration has a reduced internal volume when the planes are not parallel;

the second section has the hollow generally circular cross section in a second deformed configuration, the second configuration has an increased internal volume when the planes are not parallel;

the first and second configurations being unevenly deformed; and

the gel-like material is taken from the group consisting of silicone-based gel-like fluids and dimethyl fluids.

3. An active gimbal as recited in claim 2, wherein:

the gel-like material received in and filling the hollow generally circular cross section of the wall structure has a volume about equal to the first internal volume;

the gel-like material has a viscosity characteristic and a time constant flow characteristic; and

the time constant flow characteristic is variable according to a value of the viscosity characteristic, the time constant flow characteristic represents the amount of time required for the gel-like material to flow from the first section having the reduced internal volume and fill the second section having the increased internal volume.

4. An active gimbal as recited in claim 1, wherein:

each of the carrier body and the retainer body is provided with a groove that extends through the respective plane defined by the respective carrier body and retainer body and extends circularly around the central axis and having a diameter less that that of the respective perimeter edges so that each of the grooves is closely adjacent to the respective perimeter edge, each of the grooves having an outer wall and an inner wall, the respective outer wall and inner wall of one groove is disposed opposite to the respective outer wall and inner wall of the other groove to define a cavity, and

the hollow annular body is received in the cavity compressed into an evenly deformed configuration when the space has the uniform dimension.

5. An active gimbal as recited in claim 4, wherein a volume encompassed by the cavity has a first cavity volume portion adjacent to the first section and a second cavity volume portion adjacent to the second section, and wherein the first cavity volume portion is reduced and the second cavity volume portion is increased when the first and second sections of the body are unevenly deformed;

and wherein;

the reduced first cavity volume portion further compresses the first section and the second section is allowed to be decompressed by the increased second cavity volume portion; and

in response to the further compression of the first section and the decompression of the second section there is the flow of the gel-like material in the hollow annular body from the first section to the second section.

6. An active gimbal as recited in claim 1, wherein:

the planes are not parallel in response to a first force applied to the body on one side of the central axis and a second force applied to the body on another side of the central axis,

the first and second sections of the body and the gel-like material in the body receive unbalanced forces in response to the first and second forces;

the active gimbal further comprising;

a heater, the heater and the gel-like material being positioned in heat transfer relationship; and

wherein;

the gel-like material received in and filling the hollow annular body has a viscosity, wherein the viscosity is greater than that of water and varies according to the temperature of the gel-like material;

the gel-like material has a temperature that is selected according to the amount of heat transferred to the material by the heater that is in heat transfer relationship with the material, and

the gel-like material has a characteristic that the flow of the gel-like material in the hollow annular body has a time constant selected according to the viscosity of the gel-like material to impede but still permit the flow of the portion of the gel-like material from the first section to the second section, the time constant representing a period of time after the first and second forces are applied to the body in which the material flows from the deformed first section to the deformed second section until the first and second forces become balanced.

7. An active gimbal for allowing a carrier plate-wafer support plate space to vary in configuration as the carrier plate and the wafer support plate tilt relative to a central axis during CMP processing, the active gimbal comprising:

a hollow toroidally-shaped body configured for reception in the carrier plate-wafer support plate space and between a carrier plane defined by the carrier plate and a support plane defined by the wafer support plate, the configuration of the body being a generally circular shape that extends around and is radially spaced from a co-axial center of the carrier plate and the wafer support plate, the toroidally-shaped body being configured so that a diameter of the body divides the body into a first hollow half that is squeezed when the planes are not parallel and into a second hollow half that is permitted to expand when the planes are not parallel, the respective first and second hollow halves being configured to encompass substantially equal volumes when the planes are parallel and to encompass substantially unequal volumes when the planes are not parallel, wherein the sum of the unequal volumes substantially equals the sum of the equal volumes; and

a gel-like material taken from the group consisting of silicone-based gel-like fluids and dimethyl fluids, the material filling the hollow toroidally-shaped body, the gel-like material being substantially incompressible so that as the first and second hollow halves encompass the substantially unequal volumes when the planes are not parallel a portion of the gel-like material is caused to flow in the hollow body from the first hollow half to the second hollow half to fill the encompassed unequal volumes, the gel-like material in the unequal volumes maintaining the hollow toroidally-shaped body in contact with each of the carrier plate and the wafer support plate when the planes are not parallel.

8. An active gimbal as recited in claim 7, wherein:

the carrier plane and the support plane define opposed sides of a gimbal motion space;

each of the opposed sides is provided with a groove extending in a circular cavity path;

the respective grooves also extend through the respective planes defined by the respective carrier plane and support plane;

the respective grooves are directly opposed to each other and define a circular cavity extending around the central axis so that each groove receives a portion of the hollow toroidally-shaped body;

the first and second halves of the body and the respective grooves defining the cavity are configured so that when the planes are parallel the cavity defined by the directly opposed grooves equally compresses and confines the respective received first and second halves of the body to allow the equally compressed halves to encompass the substantially equal volumes;

the first and second halves of the body and the respective grooves defining the cavity are further configured so that when the planes are not parallel the cavity further compresses and confines the first half and allows the second half of the body to decompress to allow the respective first and second halves to encompass the respective substantially unequal volumes; and

the gel-like material filling the unequally compressed and decompressed respective first and second halves of the body flows in the hollow body from the first half to the second half.

9. An active gimbal as recited in claim 7, wherein:

the gel-like material filling the hollow toroidally-shaped body has a gel volume about equal to a first internal volume encompassed by the substantially equal volumes so that as the first half is squeezed by a first force a portion of the gel-like material flows in the hollow body from the first half to the second half that is subject to a second force less that the first force to reduce the volume of the gel-like material in the first half and increase the volume of the gel-like material in the second half to keep the active gimbal tightly received in the space when the planes are not parallel;

the gel-like material has a viscosity characteristic and a time constant flow characteristic; and

the time constant flow characteristic is variable according to a value of the viscosity characteristic, the time constant flow characteristic represents the amount of time, from an initial time of application of the first and second forces to the respective first half and second half, to a later time at which the gel-like material has flowed from the squeezed first half into the expanded second half, which later time occurs when the first and second forces have become balanced.

10. An active gimbal as recited in claim 7:

wherein a first force applied to the body on one side of the central axis and a second force applied to the body on another side of the central axis cause the carrier plane and the support plane to not be parallel;

wherein the first and second halves of the body and the material in the body receive unbalanced forces in response to the first and second forces;

the active gimbal further comprising;

a heater, the heater and the gel-like material being positioned in heat transfer relationship; and

wherein;

wherein the gel-like material filling the hollow toroidally-shaped body has a viscosity that is greater than that of water and varies with the temperature of the material;

the gel-like material has a temperature selected according to the amount of heat transferred by the heater to the gel-like material; and

the gel-like material has a time constant flow characteristic, the time constant flow characteristic represents the duration of a period of time starting at a first time upon application of the first and second forces to the body and ending when the first and second forces become balanced, which time constant flow characteristic governs the duration of response of the body to the unbalanced force.

11. A method of making a gimbal for use in a chemical mechanical planarization (CMP) carrier head, the gimbal being configured to be positioned between the carrier head and a wafer carrier, the carrier head and the wafer carrier each defining a plane, the planes normally being spaced and parallel, the method comprising the operations of:

selecting an elastomeric material having compression and decompression characteristics suitable for response to CMP forces;

configuring each of the carrier head and the wafer carrier with an annular groove, each groove having a wall provided with a semi-circular cross section, the respective grooves being directly opposed to each other so that the walls define a cavity having a uniform cavity cross sectional area and a uniform cavity volume around a circumference of the cavity when the planes are parallel and having a non-uniform cavity volume around the circumference when the planes are not parallel;

configuring a hollow toroidally-shaped ring for reception in the cavity, the ring being configured from the selected elastomeric material, the configuring of the ring being such as to define a hollow generally circular uniform ring cross section having a uniform ring cross sectional area that is greater than the uniform cavity cross sectional area;

selecting a gel-like material from the group consisting of silicone-based gel-like fluids and dimethyl fluids, the fluids having a viscosity suitable for dampening the CMP forces applied to the carrier head and the wafer carrier; and

filling the hollow toroidally-shaped ring with the selected gel-like material.

12. A method as recited in claim 11, comprising the further operation of:

placing the filled hollow toroidally-shaped ring into the cavity between the carrier head and the wafer carrier to cause the uniform ring cross section to be compressed by the walls so that the uniform ring cross sectional area is reduced uniformly along the length of the ring around the circumference of the cavity.

13. A method as recited in claim 11, wherein:

the selected silicone-based gel-like material has a viscosity that is greater than that of water and that varies with temperature;

the silicone-based material has a time constant flow characteristic;

in the use of the gimbal unevenness of the CMP forces may cause the planes to not be parallel so that the non-uniform cavity volume exists around the circumference of the cavity;

the cavity having the non-uniform cavity volume reduces the volume of the silicone-based material in a first compressed configuration of the toroidally-shaped ring and allows an increase in the volume of the silicone-based material in a second decompressed configuration of the toroidally-shaped ring;

the time constant flow characteristic represents the amount of time measured from a first time at which the CMP forces become uneven, the amount of time being that required for the silicone-based material to flow from the first compressed configuration to the second decompressed configuration and fill the second decompressed configuration; and

heating the silicone-based material in the toroidally-shaped ring to adjust the temperature and the time constant flow characteristic of the silicone-based material.

14. A method as recited in claim 11, wherein:

the selected elastomeric material is taken from the group consisting of synthetic rubber, olefin, fluoroplastic, and polysulfone.

15. A method of making an active gimbal for allowing a wafer support to tilt with respect to a carrier plate during CMP processing, the method comprising the operations of:

configuring a hollow body for reception in a space between the carrier plate and the wafer support, the configuring providing the body with a hollow ring shape extending around and radially spaced from co-axial centers of the carrier plate and the wafer support, the ring-shaped body being configured so that a diameter of the body divides the body into a first half that is compressed when planes defined by the respective carrier plate and wafer support are not parallel and into a second half that is permitted to decompress when the planes are not parallel, the configuring allowing the first and second halves to encompass substantially equal volumes when the planes are parallel and to encompass substantially unequal volumes when the planes are not parallel, wherein the sum of the unequal volumes substantially equals the sum of the equal volumes; and

filling the hollow ring-shaped body with a gel-like silicone-based fluid that is substantially incompressible, that has a viscosity characteristic that is greater than that of water, the viscosity characteristic being variable with temperature and having a time constant flow characteristic, the time constant flow characteristic being variable according to a value of the viscosity characteristic, the time constant flow characteristic representing an amount of time after a first time at which a force causes the planes to be not parallel, the amount of time being that required for the gel-like silicone-based fluid to flow in response to the compressed first half and fill the decompressed second half, wherein the gel-like silicone-based fluid having the viscosity characteristic and time constant flow characteristic impedes but still permits flow of the gel-like silicone-based fluid from the compressed first half to the second decompressed half when the planes are not parallel.

16. A method as recited in claim 15, wherein:

the viscosity of the gel-like silicone-based material is in the range from about 200 cP to about 20,000 cP.

17. A method as recited in claim 15, further comprising the operation of:

controlling the temperature of the gel-like silicone-based fluid in the hollow ring-shaped body to provide a desired viscosity and time constant flow characteristic of the gel-like silicone-based fluid.