Cl. Nelson et al., Effects of process parameter variations on the removal rate in chemical mechanical polishing of 4H-SiC, J ELEC MAT, 30(10), 2001, pp. 1271-1275
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.