Synchronous, In Situ Measurements in Chemical Mechanical Planarization

Abstract

Achieving device- and wafer-scale planarity in integrated circuit manufacturing is increasingly challenging as device sizes are reduced to and smaller, and wafer sizes are increased from . Hence a better understanding of chemical mechanical planarization (CMP) processes is needed. We report the synchronous, in situ measurement of wafer forces [coefficient of friction (CoF)] and wafer orientation during CMP polishing of BK7 glass wafers and the ex situ measurement of material removal rate (MRR) over a wide range of applied vertical loads and relative rotational velocities. MRR appears to be Prestonian and was significantly reduced by moving the slurry injection location to the outer edge of the wafer track leading to slurry starvation. Both positive and negative wafer pitch angles were measured, indicating that apparently contradictory modeling reports in the literature may not be in conflict. A phenomenological linkage between wafer orientation and frictional behavior was observed with positive pitch angles (from to ) corresponding to smooth polishing and nose-down angles (from to ) corresponding to stick-slip. Spectral signal analysis shows that the variation of CoF is due to platen rotation effects, while wafer orientation variation is affected by both platen and wafer rotations.