Evaluation of high pressure micro jet technology as an alternative pad conditioning method for silicon dioxide chemical mechanical planarization

In CMP, currently diamond conditioning is widely used to condition the polishing pad to maintain the pad asperity during planarization. However, diamond disc conditioning can create non-uniform thinning of the pad, leading to non-uniform contact pressures and polishing rates across the wafer. In addition, embedded diamond can be abraded away from the disc during conditioning, causing catastrophic defects, such as scratches on the wafer. In this study, a high pressure micro jet (HPMJ) technology is used as a novel pad conditioning method for silicon dioxide CMP applications. During the conditioning process, HPMJ sprays KOH solution at the pressure of 10 MPa onto the polishing pads to clean the residual slurry off the pad surface, remove embedded slurry particles and re-establish acceptable pad asperity heights. Coefficient of friction (COF), removal rate and pad flattening ratio (PFR) are used to evaluate the efficacy of the HPMJ system. Results are compared among conventional diamond conditioning, HPMJ conditioning, combination of HPMJ with diamond disc conditioning and no conditioning. It is bund that silicon dioxide removal rate, COF and PFR are closely correlated to one another. Results suggest that HMPJ conditioning has great potentials to become an alternative pad conditioning method in mainstream CMP processes.