Effect of chemicals and slurry particles on chemical mechamical polishing of polyimide

Abstract

The purpose of this study was to investigate the effect of chemicals and particles on chemical mechanical polishing (CMP) of polyimide (PI). The effect of particle size and its surface area on both the removal rates and the surface roughness was investigated as a function of the slurry content upon the addition of various chemicals. The optimal particle content was measured for silica, ceria and alumina slurries in terms of the removal rate and surface roughness. The removal rate was highest when deionized (DI)-water-based alumina slurry was used. However, the greatest surface roughness was measured when ceria slurry was used rather than alumina. Alkaline chemicals were added to the slurry to enhance the removal rates of PI during CMP. The addition of Tetramethyl Ammonium Hydroxide (TMAH) and Potassium Hydroxide (KOH) to ceria slurry but not to alumina and silica slurries increased the removal rate significantly at higher pH values. The addition of ethylenediamine and the presoaking of PI in hot DI water did not increase the removal rate in alkaline-chemical-based slurries. The addition of surfactant resulted in a decrease of the removal rate to half of that determined without the addition of surfactant.