Correlating shear force and coefficient of friction to platen motor current in copper, cobalt, and shallow trench isolation chemical mechanical planarization at steady-state conditions

In a follow up from our earlier work that focused on highlighting the relationship among platen motor current (PMC), shear force (SF), and coefficient of friction (COF) in non-steady-state cases, we examined whether PMC was a reliable indicator that could be used in place of SF and COF data at steady-state conditions. For the 12 cases studied, we examined 60 distinct steady-state steps from their associated Stribeck+ curves. Data averaging, coupled with a trend matching algorithm, showed that for large time spans at steady-state, PMC was a reasonably good indicator of both SF and COF, as 68.5% of the time, PMC and SF trends matched (ranges between 62% to 86%) for all 60 cases. Regarding PMC and COF, we observed trend matching for 68.8% of the time (ranges between 62% and 86%) for all 60 cases. However, correlations between SF and PMC, and also between COF and PMC were found to be very poor (in most cases, non-existent) since at small timescales PMC was not sensitive enough to capture the instantaneous stick-slip occurrences and other important tribological and fluid dynamics phenomena present in CMP.