Methods and apparatus for control of polishing pad conditioning for wafer planarization

• US 5,664,987 A
• Filed: 09/04/1996
• Issued: 09/09/1997
• Est. Priority Date: 01/31/1994
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Renteln, Peter Henry
• Primary Examiner(s): Rose, Robert A.
• Assistant Examiner(s): NGUYEN, GEORGE BINH MINH
• Application Number:
  US08/707,826
• Time in Patent Office: 370 Days
• Field of Search: 451/5, 451/21, 451/41, 451/56, 451/444, 451/443, 451/287
• US Class Current: 451/21
• CPC Class Codes: B24B 37/005 Control means for lapping machines or devices
• CPC Class Codes: B24B 53/017 Devices or means for dressing, cleaning or otherwise conditioning lapping tools
• CPC Class Codes: G05B 19/401 characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/37574 In-process, in cycle, machine part, measure part, machine same part
• CPC Class Codes: G05B 2219/37575 Pre-process, measure workpiece before machining
• CPC Class Codes: G05B 2219/37577 In-process and post-process measurement combined
• CPC Class Codes: G05B 2219/37602 Material removal rate
• CPC Class Codes: G05B 2219/45199 Polish
• CPC Class Codes: G05B 2219/50063 Probe, measure, verify workpiece, feedback measured values

Abstract

A method and apparatus for determining the amount of conditioning required to be applied to a polishing pad to achieve a desired removal rate during the polishing of a semiconductor wafer utilizes a rotating conditioning wheel in contact with a rotating polishing pad. Preselected points on just polished wafers are measured for removal rate and such measurements are used to calculate the removal rate as a function of wafer radius. When the removal rate changes by a preselected amount, the polishing pad is conditioned in accordance with the calculations.

Claims

1. A method for polishing a top layer of each of a plurality of semiconductor wafers, comprising the steps of:

measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer;

rotating a platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against successive rotating semiconductor wafers, a rotational axis of the semiconductor wafers offset from a rotational axis of the platen;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of the at least one measured semiconductor wafer; and

based at least upon the measured thickness and the remeasured thickness, calculating when a removal rate of the top layer changes from a desired value by a predetermined value at a predetermined radius of the at least one measured and remeasured semiconductor wafer and, in response thereto, conditioning each area of the pad corresponding to the predetermined radius for an interval corresponding to the change in the removal rate at such predetermined radius.

2. The method of claim 1, further comprising the steps of:

determining a number of wafers polished by the pad; and

governing the duration of the conditioning intervals for succeeding wafers to be polished as a function of the number of polished wafers to thereby control the average removal rate of each wafer.

3. An apparatus for polishing a top layer of each of a plurality of semiconductor wafers, comprising:

a rotatable platen having attached thereto a polishing pad for rotatable contact with a top layer of successive semiconductor wafers;

means for depositing an abrasive slurry onto a polishing surface of the polishing pad;

means for measuring and remeasuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer to determine a removal rate of the top layer at such points; and

means for conditioning the polishing surface of the polishing pad when the removal rate at a predetermined radius of the at least one measured and remeasured top layer, as determined by the means for measuring and remeasuring, changes from a desired value by a predetermined value, the means for conditioning rotatably creating channels within an area of the polishing surface of the polishing pad corresponding to the predetermined radius for an interval corresponding to the change in the removal rate at such predetermined radius.

4. A method for polishing a top layer of each of a plurality of semiconductor wafers, comprising the steps of:

measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer;

rotating a platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against successive rotating semiconductor wafers, a rotational axis of each semiconductor wafer offset from a rotational axis of the platen;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of the at least one semiconductor wafer; and

based at least upon the measured thickness and the remeasured thickness, calculating when a removal rate changes from a desired value by a predetermined value at a predetermined radius of the at least one semiconductor wafer and, in response thereto, conditioning each area of the pad corresponding to the predetermined radius for an interval corresponding to the change in the removal rate at such predetermined radius.

5. The method of claim 4, further comprising the steps of:

determining the number of wafers polished by the pad; and

governing the duration of the conditioning intervals for succeeding wafers to be polished as a function of the number of wafers.

6. An apparatus for polishing a top layer of each of a plurality of semiconductor wafers, comprising:

a rotatable platen having attached thereto a polishing pad for rotatable contact with a top layer of each of a plurality of successive semiconductor wafers;

means for depositing an abrasive slurry onto a polishing surface of the polishing pad;

means for measuring and remeasuring a thickness of the top layer of at least one of the semiconductor wafers at a predetermined number of points of the top layer of the at least one of the semiconductor wafers to determine the removal rates of the top layer at such points; and

means for conditioning the polishing surface of the polishing pad when the removal rate at a predetermined radius of the polished top layer of the at least one semiconductor wafer changes from a desired value by a predetermined value, the means for conditioning rotatably creating channels within an area of the polishing surface of the polishing pad for an interval corresponding to the change in the removal rate, the area corresponding to the predetermined radius.

7. A method for polishing a top layer of a semiconductor wafer, comprising the steps of:

measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer;

rotating a platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against a rotating semiconductor wafer, a rotational axis of the semiconductor wafer offset from a rotational axis of the platen;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of the at least one semiconductor wafer polished by the pad; and

based at least upon the measured thickness and the remeasured thickness, calculating the removal rate at predetermined radii of the semiconductor wafer, calculating a weighted average value of the removal rates, subtracting each removal rate from the weighted average value to derive a residual for each predetermined radius of the semiconductor wafer, determining the sign of each residual, creating a first array of the resultant ones, minus ones and zeros, the ones corresponding to positive sign residuals surrounded by neighboring residuals having a positive sign, the minus ones corresponding to negative sign residuals surrounded by neighboring residuals having a negative sign and the zeros corresponding to one of a positive sign residual having at least one neighboring residual having a negative sign and a negative sign residual having at least one neighboring residual having a positive sign, mapping the first array into a second array and into a third array, multiplying the second and third arrays to generate a fourth array, multiplying the fourth array by a sensitivity factor to derive a conditioning recipe correction, adding the conditioning recipe correction to an initial recipe to generate a new conditioning recipe, and conditioning the pad in accordance with the new conditioning recipe.

8. A method for polishing a top layer of a plurality of semiconductor wafers, comprising the steps of:

measuring a thickness of a top layer of a plurality of semiconductor wafers at a predetermined number of points of the top layer of the plurality of semiconductor wafers;

rotating a platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against successive rotating semiconductor wafers, a rotational axis of the semiconductor wafers offset from a rotational axis of the platen;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one of the plurality of semiconductor wafers polished by the pad; and

based at least upon the measured thickness and the remeasured thickness, calculating the removal rates at predetermined radii of the at least one semiconductor wafer and,

if the removal rate for at least one of the predetermined radii changes by a first predetermined value, calculating a correction to a conditioning recipe, determining within wafer uniformity of removal rate, and

in response to a deviation from the within wafer uniformity greater than a second predetermined value, modifying the correction to the conditioning recipe, and

conditioning the pad in accordance with the modified corrected conditioning recipe, the modified corrected conditioning recipe utilized for conditioning each area of the pad corresponding to the predetermined radii for respective intervals corresponding to changes in removal rates at such radii.

9. An apparatus for polishing a top layer of each of a plurality of semiconductor wafers, comprising:

a rotatable platen, the rotatable platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against successive rotating semiconductor wafers, a rotational axis of the semiconductor wafers offset from a rotational axis of the platen;

means for measuring and remeasuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of a top layer of at least one semiconductor wafer polished by the pad; and

means for calculating, based at least upon the measured thickness and the remeasured thickness, when a removal rate at a predetermined radius of at least one semiconductor wafer changes from a desired value by a predetermined value and, in response thereto, conditioning each area of the pad corresponding to the predetermined radius for an interval corresponding to the change in removal rate at such radius.

10. The apparatus of claim 9, further comprising:

means for determining a number of wafers polished by the pad; and

means for governing the duration of the conditioning intervals for succeeding wafers to be polished as a function of the number of wafers to thereby control the average removal rate of each wafer.

11. An apparatus for polishing a top layer of each of a plurality of semiconductor wafers, comprising:

means for measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of a top layer of the at least one semiconductor wafer;

a rotatable platen, the rotatable platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against successive rotating semiconductor wafers, a rotational axis of each semiconductor wafer offset from a rotational axis of the rotatable platen;

means for remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of the at least one semiconductor wafer; and

means for calculating, based at least upon the measured thickness and the remeasured thickness, when a removal rate at a predetermined radius of the at least one semiconductor wafer changes from a desired value by a predetermined value and, in response thereto, conditioning each area of the pad corresponding to the predetermined radius for an interval corresponding to the change in removal rate at such radius.

12. The apparatus of claim 11, further comprising:

means for determining a number of wafers polished by the pad; and

governing the duration of the conditioning intervals for succeeding wafers to be polished as a function of the number of wafers.

13. An apparatus for polishing a top layer of a semiconductor wafer, comprising:

means for measuring a thickness of the top layer of the semiconductor wafer at a predetermined number of points of the top layer of at least one semiconductor wafer;

a rotatable platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against a rotating semiconductor wafer, a rotational axis of the semiconductor wafer offset from a rotational axis of the rotatable platen;

means for remeasuring the predetermined number of points of the top layer of at least one semiconductor wafer polished by the pad; and

means for calculating, based at least upon the measured thickness and the remeasured thickness, the removal rate at predetermined radii of at least one semiconductor wafer by calculating a weighted average value of the removal rates, subtracting each removal rate from the weighted average value to derive a residual for each predetermined radius of the semiconductor wafer, determining the sign of each residual, creating a first array of the resultant ones, minus ones and zeros, the ones corresponding to positive sign residuals surrounded by neighboring residuals having a positive sign, the minus ones corresponding to negative sign residuals surrounded by neighboring residuals having a negative sign and the zeros corresponding to one of a positive sign residual having at least one neighboring residual having a negative sign and a negative sign residual having at least one neighboring residual having a positive sign;

means for mapping the first array into second and third arrays, and for multiplying the second and third arrays to generate a fourth array, and for multiplying the fourth array by a sensitivity factor to derive a conditioning recipe correction and adding the conditioning recipe correction to an initial recipe to generate a new conditioning recipe; and

means for conditioning the pad in accordance with the new conditioning recipe.

14. An apparatus for polishing a top layer of a plurality of semiconductor wafers, comprising:

means for measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of a top layer of the at least one of a plurality of semiconductor wafers;

a rotatable platen, the rotatable platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against successive rotating semiconductor wafers, a rotational axis of the semiconductor wafers offset from a rotational axis of the rotatable platen;

means for remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of the at least one of the semiconductor wafers polished by the pad; and

means for calculating, based at least upon the measured thickness and the remeasured thickness, the removal rate at predetermined radii of the at least one semiconductor wafer and, if the removal rate for adjacent radii changes from a desired value by a first predetermined value, calculating a correction to a conditioning recipe, determining within wafer uniformity of removal rate, and in response to a deviation from within wafer uniformity greater than a second predetermined value, modifying the correction to the conditioning recipe; and

means for conditioning each area of the pad corresponding to those predetermined radii whose removal rate changes by the first predetermined value, in accordance with the modified corrected conditioning recipe.

15. A method for polishing a top layer of a plurality of semiconductor wafers, comprising the steps of:

rotating the plurality of semiconductor wafers about a first rotational axis;

measuring a thickness of the top layer of at least one semiconductor wafer at a plurality of points of the top layer of the at least one of a plurality of semiconductor wafers;

rotating a platen about a second rotational axis, the second rotational axis offset from the first rotational axis, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against a rotating semiconductor wafer;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one of the plurality of semiconductor wafers polished by the pad;

based at least upon the measured thickness and the remeasured thickness, calculating a removal rate at predetermined radii for at least one of the plurality of semiconductor wafers, arranging the removal rates into a matrix, determining a first order coefficient regression of removal rates, in response to a determination that a slope at a given radius is at least a predetermined value determining whether a common sign exists for adjacent radii, in response to a determination that a common sign exists for adjacent radii, generating a scale amount of conditioning of the pad; and

determining for at least one wafer whether a standard deviation of removal rate is greater than a predetermined value and, in response to such determination, calculating the average value of removal rates for such wafer, subtracting each removal rate for such wafer from the average value to derive residuals, determining the sign of each residual, determining whether a plurality of adjacent radii have the same sign residual and, in response to such determination, changing a conditioning recipe in accordance with the scale amount of conditioning.

16. An apparatus for polishing a top layer of a plurality of semiconductor wafers, comprising:

means for rotating the plurality of semiconductor wafers about a first rotational axis;

means for measuring a thickness of the top layer of at least one semiconductor wafer at a plurality of points of the top layer of the at least one of a plurality of semiconductor wafers;

means for rotating a platen about a second rotational axis, the second rotational axis offset from the first rotational axis, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against a rotating semiconductor wafer;

means for remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one of the plurality of semiconductor wafers polished by the pad;

means for calculating, based at least upon the measured thickness and the remeasured thickness, a removal rate at predetermined radii for at least one of the plurality of semiconductor wafers, arranging the removal rates into a matrix, determining a first order coefficient regression of removal rates, in response to a determination that a slope at a given radius is at least a predetermined value determining whether a common sign exists for adjacent radii, in response to a determination that a common sign exists for adjacent radii, generating a scale amount of conditioning of the pad; and

means for determining for at least one wafer whether a standard deviation of removal rate is greater than a predetermined value, and in response to such determination, calculating the average value of removal rates for such wafer, subtracting each removal rate for such wafer from the average value to derive residuals, determining the sign of each residual, determining whether a plurality of adjacent radii have the same sign residual, and in response to such determination, changing a conditioning recipe in accordance with the scale amount of conditioning.

17. A method for polishing a top layer of a semiconductor wafer, comprising the steps of:

measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer;

rotating a platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against a rotating semiconductor wafer, a rotational axis of the semiconductor wafer offset from a rotational axis of the platen;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one semiconductor wafer polished by the pad; and

based at least upon the measured thickness and the remeasured thickness, calculating the removal rate at predetermined radii of the semiconductor wafer, calculating a weighted average value of the removal rates, subtracting each removal rate from the weighted average value to derive a residual for each predetermined radius of the semiconductor wafer to generate a new conditioning recipe, wherein a conditioning time at those areas of the pad which most affect specific radii on the semiconductor wafer in which the removal rate is below the weighted average value is increased, and the conditioning time at those areas on the pad which most affect the specific radii on the semiconductor wafer in which the removal rate is above the weighted average is decreased, and conditioning the pad in accordance with the new conditioning recipe.

18. An apparatus for polishing a top layer of a semiconductor wafer, comprising:

means for measuring a predetermined number of points of the top layer of at least one semiconductor wafer;

a rotatable platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against a rotating semiconductor wafer, a rotational axis of the semiconductor wafer offset from a rotational axis of the rotatable platen;

means for remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one semiconductor wafer polished by the pad;

means for calculating, based at least upon the measured thickness and the remeasured thickness, the removal rate at predetermined radii of the at least one semiconductor wafer by calculating a weighted average value of the removal rates, subtracting each removal rate from the weighted average value to derive a residual for each predetermined radius of the semiconductor wafer to generate a new conditioning recipe, wherein a conditioning time at those areas of the pad which most affect specific radii on the semiconductor wafer in which the removal rate is below the weighted average value is increased, and the conditioning time at those areas on the pad which most affect the specific radii on the semiconductor wafer in which the removal rate is above the weighted average is decreased; and

means for conditioning the pad in accordance with the new conditioning recipe.

19. A method for polishing a top layer of a semiconductor wafer, comprising the steps of:

measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer;

rotating a platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

depositing an abrasive slurry onto the upper surface of the pad;

pressing the upper surface of the pad against a rotating semiconductor wafer, a rotational axis of the semiconductor wafer offset from a rotational axis of the platen;

remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one semiconductor wafer polished by the pad; and

based at least upon the measured thickness and the remeasured thickness, calculating the removal rate at predetermined radii of at least one semiconductor wafer, calculating a weighted average value to derive a residual for each predetermined radius of the semiconductor wafer to thereby generate a first array consisting of residuals, determining the sign of each residual to thereby generate a second array consisting of ones, minus ones and zeros, each of the ones, minus ones and zeros corresponding to the sign of each residual, mapping the second array to a third array, the third array smaller than the second array, the third array consisting of ones, minus ones and zeros, the ones corresponding to positive sign residuals surrounded by neighboring residuals having a positive sign, the minus ones corresponding to negative sign residuals surrounded by neighboring residuals having a negative sign and the zeros corresponding to one of a positive sign residual having at least one neighboring residual having a negative sign and a negative sign residual having at least one neighboring residual having a positive sign, mapping the third array into a fourth array in which the first mapping obeys an algorithm designed to reflect the geometric relationship of specific areas on the pad to specific radii on the wafer, mapping the first array into a fifth array in which the mapping obeys the algorithm designed to reflect the geometric relationship of specific areas on the pad to specific radii on the wafer, multiplying the fourth array and the fifth array to generate a sixth array, multiplying the sixth array by a sensitivity factor to derive a conditioning recipe correction, and adding the conditioning recipe correction to an initial recipe to generate a new conditioning recipe; and

conditioning the pad in accordance with the new conditioning recipe.

20. An apparatus for polishing a top layer of a semiconductor wafer, comprising:

means for measuring a thickness of the top layer of at least one semiconductor wafer at a predetermined number of points of the top layer of the at least one semiconductor wafer;

a rotatable platen, the platen including a pad covering a planar surface of the platen, the pad having an upper surface;

means for depositing an abrasive slurry onto the upper surface of the pad;

means for pressing the upper surface of the pad against a rotating semiconductor wafer, a rotational axis of the semiconductor wafer offset from a rotational axis of the rotatable platen;

means for remeasuring the thickness of the top layer of the at least one semiconductor wafer at the predetermined number of points of the top layer of at least one semiconductor wafer polished by the pad; and

means for calculating, based at least upon the measured thickness and the remeasured thickness, the removal rate at predetermined radii of at least one semiconductor wafer, calculating a weighted average value to derive a residual for each predetermined radius of the semiconductor wafer to thereby generate a first array consisting of residuals, determining the sign of each residual to thereby generate a second array consisting of ones, minus ones and zeros, each of the ones, minus ones and zeros corresponding to the sign of each residual, mapping the second array to a third array, the third array smaller than the second array, the third array consisting of ones, minus ones and zeros, the ones corresponding to positive sign residuals surrounded by neighboring residuals having a positive sign, the minus ones corresponding to negative sign residuals surrounded by neighboring residuals having a negative sign and the zeros corresponding to one of a positive sign residual having at least one neighboring residual having a negative sign and a negative sign residual having at least one neighboring residual having a positive sign, mapping the third array into a fourth array in which the first mapping obeys an algorithm designed to reflect the geometric relationship of specific areas on the pad to specific radii on the wafer, mapping the first array into a fifth array in which the mapping obeys the algorithm designed to reflect the geometric relationship of specific areas on the pad to specific radii on the wafer, multiplying the fourth array and the fifth array to generate a sixth array, multiplying the sixth array by a sensitivity factor to derive a conditioning recipe correction, and adding the conditioning recipe correction to an initial recipe to generate a new conditioning recipe; and

means for conditioning the pad in accordance with the new conditioning recipe.