Self-aligned STI process using nitride hard mask

摘要

A nitride hard mask (230) is used to isolate active areas of a DRAM cell. The shallow trench isolation (STI) method includes forming memory cells comprising deep trenches (216) on a semiconductor wafer (200). The memory cell deep trenches (216) are separated from active areas (212) by a region of substrate (212). A nitride hard mask (230) is formed over the semiconductor wafer (200). The wafer (200) is patterned with the nitride hard mask (230), and the wafer (200) is etched to remove the region of substrate (212) between the deep trenches and active areas to provide shallow trench isolation. An etch chemistry selective to the nitride hard mask (230) is used.