Effects of process parameter variations on the removal rate in chemical mechanical polishing of 4H-SiC

The effects of temperature, slurry pH, applied pressure, and polishing rota tion rate on the material removal rate during chemical mechanical polishing (CMP) of 4H-silicon carbide wafers using colloidal silica slurry and polyu rethane/polyester fiber polishing pads have been studied. Measured removal rates varied from around 100 Angstrom /hr to nearly 2500 Angstrom /hr depen ding on the values of the various parameters. The amount of material remove d was determined by measuring the wafer mass before and after polishing. Va riations in temperature and slurry pH did not produce significant changes i n the measured removal rates. Highernolishing pressures resulted in increas ed material removal rates from 200 to 500 Angstrom /hr but also produced ex cessive polishing pad damage. Variations in pad rotational speeds produced the largest changes in material removal rates, from around 200 to around 20 00 Angstrom /hr for rotational speeds between 60 and 180 rpm, but the varia tions were non-linear and somewhat inconsistent. This CMP formula is shown to consistently produce damage free surfaces but the optimum removal rate i s slow.