The variability in functional performance of polishing pads, slurries, conditioners and retaining rings (guides) is one of the major factors limiting the lot-to-lot uniformity of polishing and process yield. Both the yield and output of polished wafers are improved when the proper incoming inspection is put in place and no faulty consumables are used in planarization. Performing incoming inspection on the production polishers is expensive and unrealistic. A bench-top controlled (with in-situ process monitoring) polisher mod. CP-4 provides an inspection solution, which is both time and cost effective. By polishing small (from 4" to 1") wafer monitors on small (from 9" to 3") pad coupons, utilizing the same process parameters (linear speed and pressure) and thus providing the same wafer removal rate as on the production polishers, it allows for fast screening of consumables. A lot of experimental data on screening various pads, slurries and conditioners has been obtained for planarization of three types of wafers, with copper, tungsten and oxide films. The "good" (that is, within the process qualification window) CMP materials exhibited repeatable and reproducible CMP process characteristics, while the "bad" (that is, outside the process qualification window) ones exhibited different process parameters and so would produce out-of-spec wafer surfaces. The incoming inspection and failure analysis of consumables represent the next step in how the major fabs utilize, optimize and maintain the CMP technology.
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