Effect of ammonium molybdate concentration on chemical mechanical polishing of glass substrate

The effect of the ammonium molybdate concentration on the material removal rate (MRR) and surface quality in the preliminary chemical mechanical polishing (CMP) of a rough glass substrate was investigated using a silica-based slurry. Experimental results reveal that the ammonium molybdate concentration has a strong influence on the CMP behaviors of glass substrates. When the ammonium molybdate was added to the baseline slurry, polishing rates increased, and then decreased with a transition at 2 wt.%, and the root mean square (RMS) roughness decreased with increasing ammonium molybdate concentration up to 2 wt.%, after which it increased linearly up to 4 wt.%. The improvement in MRR and RMS roughness may be attributed to the complexation of hydrolysis products of the glass substrate with the ammonium molybdate so as to prevent their redeposition onto the substrate surface. It was found that there exists an optimal ammonium molybdate concentration at 2 wt.% for obtaining the highest MRR and the lowest RMS roughness within a particular polishing time.