Chemical mechanical polishing of PSG and BPSG dielectric films: The effect of phosphorus and boron concentration

Abstract

Chemical-mechanical polishing of blanket and patterned oxide films doped with phosphorus and boron has been studied. FTIR was used to characterize the film microstructure. Experimental results show that an increase of phosphorus level promoted the polish rate of PSG film. We also found that increasing the boron content enhanced the polish rate of BPSG films although phosphorus contents is decreased. This implies that boron is more effective than phosphorus in enhancing the polishing rate of BPSG films. However, the hardness of these doped films is slightly affected by doping level. Excellent planarity achieved by CMP is demonstrated for patterned wafers. Here, we also identify inversion patterns for the composite dielectric formed by a thin hard film on the top of a thick soft film. Such inversion phenomenon can be used for monitoring CMP process as a means of end point detection.