| 摘要 |
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.
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