Strengthening the case for Plasma Polish

Three pioneering metrology techniques confirm that the Plasma Polish production process eradicates subsurface damage in SiC substrates while improving crystal quality.

BY GRANT BALDWIN AND JAMES SAGAR, OXFORD INSTRUMENTS PLC

Back in September 2022 at the International Conference for Silicon Carbide and Related Materials (ICSCRM), held in Davos, Oxford Instruments, launched Plasma Polish. Originally conceived as either a replacement or a complementary process to a chemical mechanical polish (CMP), this alternative plasma-based process has been attracting significant interest from leading substrate manufacturers and vertically integrated device manufacturers. Wafers that have undergone Plasma Polish during processing into diodes and MOSFETs have a performance that’s in line with industry standard CMP, according to full wafer electrical measurements and yield results (see Figure 1).

The non-contact, dry Plasma Polish process has several key benefits including lower cost, a reduced environmental impact and the ability to remove subsurface damage.

Plasma Polish requires low levels of consumables and creates no toxic slurry, leading to an operating cost reduction of up to 85 percent, resulting from the removal of these process requirements and their associated costs. The absence of the slurry also means that there are no disposal issues and removes the significant water use typically associated with CMP, making Plasma Polish better for the environment. Plasma Polish uses industry standard non-toxic process gasses, making it unproblematic to install in production facilities.

The third benefit, subsurface damage removal, is unique to Plasma Polish. This great strength, discussed further below, comes without having to make any changes to either upstream or subsequent processes.