Dry etch method for in situ top corner rounding of shallow trench isolation

This work presents a new dry etching technique for creating top corner rounding (TCR) in shallow trench isolation (STI). This method has been successfully used to fabricate TCR structures with curvature diameters of approximately 65 and 105 nm. The entire process is completed in situ within the STI etching sequence. The key is to synchronize the consumption rate of the polymer layer with the rounding etch rate of the silicon top corner, thereby naturally forming TCR structures without observable silicon loss. Scanning electron microscopy results demonstrate that distinct and smooth TCR morphologies can be obtained at different critical dimensions without compromising gate width. This method eliminates the need for additional process steps, saving time and reducing cost, and providing an efficient STI process integration solution.