Preparation of Fe-doped colloidal SiO_2 abrasives and their chemical mechanical polishing behavior on sapphire substrates

Abstract

Abrasives are one of key influencing factors on surface quality during chemical mechanical polishing (CMP). Silica sol, a widely used abrasive in CMP slurries for sapphire substrates, often causes lower material removal rate (MRRs). In the present paper, Fe-doped colloidal SiO₂ composite abrasives were prepared by a seed-induced growth method in order to improve the MRR of sapphire substrates. The CMP performance of Fe-doped colloidal SiO₂ abrasives on sapphire substrates was investigated using UNIPOL-1502 CMP equipment. Experimental results indicate that the Fe-doped colloidal SiO₂ composite abrasives exhibit lower surface roughness and higher MRR than pure colloidal SiO₂ abrasives for sapphire substrates under the same testing conditions. Furthermore, the acting mechanism of Fe-doped colloidal SiO₂ composite abrasives in sapphire CMP was analyzed by x-ray photoelectron spectroscopy. Analytical results show that the Fe in the composite abrasives can react with the sapphire substrates to form aluminum ferrite (AlFeO₃) during CMP, which promotes the chemical effect in CMP and leads to improvement of MRR.

Effect of Sr(OH)2 as a pH Regulator on Different Plane Sapphire Substrate Chemical Mechanical Polishing

“…16 Lei et al reported when doping La/Co/Fe/Ni/Cu ions in water-based SiO 2 slurry for c-plane sapphire AlLaO 3 /CoAl 2 O/AlFeO 3 /NiAl 2 O 4 /Al 2 CuO 4 were found to form and removed easily. [17][18][19] For removal rates of different plane sapphire substrate, a-and r-plane's was much lower than that of c-plane reported by E.A.Vovk. 20 Due to moderate hardness and obtaining high quality polishing surface, SiO 2 sol is preferred for sapphire polishing abrasive.…”

Effect of ZnO-SiO2 Composite Abrasive on Sapphire Polishing Performance and Mechanism Analysis

“…), and found AlLaO 3 /CoAl 2 O/AlFeO 3 / NiAl 2 O 4 /Al 2 CuO 4 /Al 2 ZnO 4 which are softer and easier to remove were formed. [18][19][20][21][22][23] Yin et al confirmed that solid-solid reaction occurred and aluminum silicate was formed, which has lower hardness and can be removed easily than sapphire itself during the CMP process. 24 Through preliminary investigations, it is found that ZnO can react with Al 2 O 3 under certain conditions to form ZnAl 2 O 4 .…”

Study on Chemical Mechanical Polishing Performances of Sapphire Wafer (0001) Using Silica-Based Slurry

“…All of its applications require the no damaged near-surface layer, no surface defects and a low working surface roughness. 3,4 At present, chemical mechanical polishing (CMP) process of silica-based slurry has become a widely accepted global planarization technology. However, the CMP process of silica-based slurry for 2 inch (0001) plane sapphire wafer still needs at least 3∼6 hours to remove sub-damaged layer and achieve atom-scale surface roughness.…”

“…Nevertheless, with silica sol as polishing abrasives for sapphire, the Roughness Average (Ra) is lower, but the corresponding MRR is also lower. Lei et al 4,[8][9][10] synthesized a series of metal-doped silica composite abrasive particles and investigated the CMP performance on sapphire. The results suggest that metal-doped silica composite abrasives can enhance the MRR and reduce the Ra.…”

“…Single colloidal silica abrasive is widely regarded as an ideal polishing abrasive for sapphire CMP since it can get best surface quality. 4 Presently, there are few studies devoted to investigating the effects of the chemical agents on the sapphire CMP. In this account, our group studies the regularities of influence of different chemicals like salts, alkaline agents and chelating agents on chemical mechanical polishing performances of sapphire wafer.…”