US Patent 7851369 Hardmask trim method

A method for forming features in a polysilicon layer is provided. A hardmask layer is formed over the polysilicon layer. A photoresist mask is formed over the hardmask layer. The hardmask layer is etched through the photoresist mask to form a patterned hardmask. The patterned hardmask is trimmed by providing a non-carbon containing trim gas comprising oxygen and a fluorine containing compound, forming a plasma from the trim gas, and trimming the hardmask. Features are etched into the polysilicon layer through the hardmask.