Chemi-Mechanical Polishing of On-Axis Semi-Insulating SiC Substrates

Abstract

Conventional colloidal silica (CS) chemi-mechanical polishing (CMP) of Si-face SiC substrates typically results in a low material removal rate (MRR<0.1µm/h). In this study, the chemical surface oxidation and mechanical removal of the oxide layer during CMP of on-axis semi-insulating (SI) 6H SiC substrates, and the effect on material removal rate and surface roughness were investigated separately by addition of (a) compatible oxidizers, (b) abrasives and (c) both oxidizers and abrasives to the CS slurry. Neither oxidizer nor soft abrasive addition individually resulted in a significant MRR increase, yet both increased the substrate surface roughness. The addition of nano-size diamond abrasive (0.1µm grain size) to the CS slurry resulted in a MRR of 0.60µm/h, a 10x increase over CS CMP, and produced substrates with a Ra surface roughness of 5.5Å. The addition of 0.1µm diamond abrasive and sodium hypochlorite oxidizer to the CS slurry resulted in a MRR increase to 0.92µm/h and produced substrates with a Ra surface roughness of 5.2Å.

Extended study of the atomic step-terrace structure on hexagonal SiC (0001) by chemical-mechanical planarization

“…Defects on the substrate surface could be replicated into the epilayer, thus surface preparation of the substrate wafer will play a critical role in electronic integration fabrication [5]. Due to the extreme hardness and strong stability against chemicals of SiC [6,7], it is more difficult to realize ideal planarization with high removal rate and good surface quality [3]. Chemical mechanical polishing (CMP) is applied to the surface as an efficient treatment to produce atomic level surface flatness by removing the irregularities and the damage on or near the surface due to mechanical polishing [8,9].…”

Effects of ultra-smooth surface atomic step morphology on chemical mechanical polishing (CMP) performances of sapphire and SiC wafers

“…Currently, chemical mechanical polishing (CMP) is still one method of the most effective technology to achieve global planarization [5][6][7]. However, owing to the super-high hardness and super-strong chemical innerness, CMP removal of sapphire and SiC wafer is very difficult [8][9][10][11][12][13][14][15][16]. Moreover, the relative research on CMP characteristics of sapphire and SiC wafer is very few, especially CMP mechanism.…”

Investigation on the Material Removal and Surface Generation of a Single Crystal SiC Wafer by Ultrasonic Chemical Mechanical Polishing Combined with Ultrasonic Lapping

“…On considering improving the material removal rate (MRR) of SiC during CMP, the reported literature mainly focuses on CMP slurry [ 5 , 6 , 7 , 8 , 9 , 10 ]. On the one hand, CARE (catalyst-referred etching) [ 11 ] using different oxidants and catalysts was studied to replace the high temperature.…”

“…On the other hand, the addition of a high-hardness abrasive combined with an oxidizer to the slurry is another method to increase MRR. Heydemann et al [ 5 ] increased the MRR to about 900 nm/h by addition of a nano-diamond and H 2 O 2 . Jeong et al [ 6 ] increased the MRR to about 500 nm/h also by addition of a nano-diamond.…”