Abstract
Accurate and real-time thickness measurement of metal film on Si-based wafer improves the global planarization by adjusting the polishing pressure and avoids over-polishing and under-polishing during the chemical mechanical polishing (CMP) process. Nevertheless, the large lift-off distance between the sensor and the target film with low conductivity, such as the tungsten, bring great challenges to measure the metal film thickness precisely in the metal CMP process. In this paper, a novel eddy current sensor with Mn-Zn ferrite core is designed to improve sensitivity of eddy current thickness sensors at the large lift-off distance. And the measured results are compared with an air core coil.
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