Apparatus and method to determine the coefficient of friction of a chemical mechanical polishing pad during a pad conditioning process and to use it to control the process
First Claim
1. An apparatus for controlling a chemical mechanical polishing (CMP) pad conditioning device, comprising:
- (a) a disk-shaped body having a bottom surface in contact with a top surface of a rotating CMP pad undergoing a CMP pad conditioning process;
(b) a bracket for restraining the disk-shaped body so as to prevent the disk-shaped body from moving along with the rotating CMP pad;
(c) force sensing means for sensing a restraining force which is exerted by the bracket on the disk-shaped body and which is substantially parallel to the top surface of the CMP pad, the force sensing means generating an output signal indicative of the restraining force; and
(d) means for causing the CMP pad conditioning device to terminate the CMP pad conditioning process whenever the output signal from the force sensing means indicates a prescribed threshold has been exceeded.
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Accused Products
Abstract
An apparatus and method for detecting the roughness of a CMP pad surface, in situ, during pad conditioning by measuring and making use of surface friction effects. The effect is advantageously exploited to determine an endpoint for the pad conditioning process i.e. when the surface roughness of the pad is within a desired range, to facilitate the qualification of conditioning process parameter changes by determining their effect on the conditioning process, and to optimize these parameters. Also, the effect is employed to measure non-uniformities in the pad'"'"'s surface roughness, and to guide corrective measures. Generally, these objectives are accomplished using an apparatus which includes a floating head having its bottom surface in contact with the top surface of a rotating CMP pad undergoing a CMP pad conditioning process. A bracket is employed to restrain the floating head so as to prevent the head from moving along with the rotating CMP pad. A force sensing device is used to sense a restraining force exerted by the bracket on the floating head and to output a signal indicative of the restraining force. This restraining force is indicative of the friction between the floating head and the pad, and can be used to determine the coefficient of friction. The coefficient of friction is directly related to the surface roughness of the pad.
118 Citations
31 Claims
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1. An apparatus for controlling a chemical mechanical polishing (CMP) pad conditioning device, comprising:
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(a) a disk-shaped body having a bottom surface in contact with a top surface of a rotating CMP pad undergoing a CMP pad conditioning process; (b) a bracket for restraining the disk-shaped body so as to prevent the disk-shaped body from moving along with the rotating CMP pad; (c) force sensing means for sensing a restraining force which is exerted by the bracket on the disk-shaped body and which is substantially parallel to the top surface of the CMP pad, the force sensing means generating an output signal indicative of the restraining force; and (d) means for causing the CMP pad conditioning device to terminate the CMP pad conditioning process whenever the output signal from the force sensing means indicates a prescribed threshold has been exceeded. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An apparatus for controlling a chemical mechanical polishing (CMP) pad conditioning device, comprising:
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(a) a body having a bottom surface positionable in contact with a top surface of a rotating CMP pad during a CMP pad conditioning process; (b) a bracket for restraining the body so as to prevent it from moving along with the rotating CMP pad; (c) a sensor to measure a restraining force which is exerted by the bracket on the body and which is substantially parallel to the top surface of the CMP pad, the sensor generating an output signal indicative of the restraining force; and (d) circuitry configured to cause the CMP pad conditioning device to terminate the CMP pad conditioning process whenever the output signal from the sensor exceeds a prescribed threshold. - View Dependent Claims (18, 19, 20, 30)
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21. An apparatus for controlling a chemical mechanical polishing (CMP) pad conditioning device, comprising:
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(a) a body having a bottom surface positionable in contact with a top surface of a rotating CMP pad during a CMP pad conditioning process; (b) a bracket for restraining the body so as to prevent it from moving along with the rotating CMP pad, the bracket including a right angle portion having a first arm and a second arm which form an interior corner to face against the direction of rotation of the CMP pad, the body being disposed within the interior corner and restrained by the arms; (c) a sensor to measure a restraining force which is exerted by the bracket on the body and generating an output signal indicative of the restraining force, the sensor comprising a first load cell and a second load cell, the first load cell being attached to the first arm of the bracket at a position coincident with a first point of contact of the body and the second load cell being attached to the second arm of the bracket at a position coincident with a second point of contact of the body; and (d) circuitry configured to cause the CMP pad conditioning device to terminate the CMP pad conditioning process if the output signal from the sensor indicates a prescribed threshold has been exceeded. - View Dependent Claims (22, 23, 24, 25, 27, 28)
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26. An apparatus for controlling a chemical mechanical polishing (CMP) pad conditioning device, comprising:
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(a) a body having a bottom surface positionable in contact with a top surface of a rotating CMP pad during a CMP pad conditioning process; (b) a bracket for restraining the body so as to prevent it from moving along with the rotating CMP pad; (c) a sensor to measure a restraining force which is exerted by the bracket on the body and generating an output signal indicative of the restraining force; and (d) circuitry configured to compute a coefficient of friction between the bottom surface of the body and the top surface of the rotating CMP pad using the output signal from the sensor, and to cause the CMP pad conditioning device to terminate the CMP pad conditioning process if the output signal from the sensor indicates a prescribed threshold has been exceeded, wherein the prescribed threshold corresponds to an expected coefficient of friction which is expected to be exhibited whenever the top surface of the CMP pad has been conditioned to a desired surface roughness.
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29. An apparatus for controlling a chemical mechanical polishing (CMP) pad conditioning device, comprising:
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(a) a body having a bottom surface positionable in contact with a top surface of a rotating CMP pad during a CMP pad conditioning process; (b) a bracket for restraining the body so as to prevent it from moving along with the rotating CMP pad; (c) a sensor to measure a restraining force which is exerted by the bracket on the body and generating an output signal indicative of the restraining force, the sensor including a first tension sensor and a second tension sensor, each tension sensor being attached to the bracket and having a filament extending therefrom which is attached at a distal end to the body so that the body is spaced from the bracket by the filaments in the direction of the rotation of the CMP pad; and (d) circuitry configured to cause the CMP pad conditioning device to terminate the CMP pad conditioning process if the output signal from the force sensing means indicates a prescribed threshold has been exceeded output signal from the sensor exceeds a prescribed threshold. - View Dependent Claims (31)
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Specification