Pre-polishing transient effects investigation for Chemical Mechanical Planarization processes

Abstract:
In this paper, we investigate the effects on process performances of transient phase in CMP that represents the short time the system spends to reach the steady state regime of polishing. While the responses on average CMP polish rate, as suggested by Preston’s equation, are modulated easily by table speed and downward pressure, the removal rate distribution across the wafer (non uniformity) has been demonstrated to be dependent on the transient phase too. By this way, the Preston’s coefficient could be considered a function of this transient as well as of process consumables and polished materials. Thus, the on-wafer response will be affected by a modulation of the starting phase, independently on table speed and downward pressure setup. The assumed model for this study considers as variables in the transient phase the spatial distribution of slurry on the pad surface, depending on dispensing time, table speed, pad roughness, design and fluid viscosity, and the capability of pad to capture it, depending on conditioning settings.