Abstract
A novel technology utilizing energetic ionized gas cluster ion beams (GCIB) has been successfully used to reduce the surface roughness of SiC for electronic applications. In GCIB, a high-pressure gas, such as argon, is supersonically expanded through a nozzle into vacuum. This adiabatic expansion results in the condensation of clusters consisting of tens to thousands of gas atoms weakly held together by Van der Waals forces. These clusters are then ionized and accelerated towards the target substrate. Upon impact, they create a strong lateral sputtering effect resulting in a net smoothing of the surface. The surfaces of commercial, single-crystal, research grade SiC wafers were exposed to a series of Ar and O2 gas cluster ion treatments of varying doses and energies. After processing, atomic force microscope measurements indicated a reduction of surface roughness and removal of pre-existing CMP polishing scratches. Enhanced GCIB smoothing was achieved by using sequential doses of gas clusters with different energies, and in some cases different gases. Higher cluster energies removed scratches but added a high spatial-frequency roughness component, which could be in turn reduced by lower energy clusters. It was found that oxygen clusters produced a greater degree of smoothing than argon clusters. RBS ion channeling measurements were also conducted, and showed that processing with lower energy clusters as the final step of a series of doses minimized the creation of defects near the surface.
The Mechanism of Layer Stacked Clamping (LSC) for Polishing Ultra-Thin Sapphire Wafer
