METHOD OF FORMING AN ISOLATION LAYER AND METHOD OF MANUFACTURING A TRENCH CAPACITOR

摘要

A two-step etch process is used to form a vertical collar oxide (174) within the upper portion (13) of a trench capacitor. The first step uses CF4/SiF4/O2 chemistry and ends when the bottom of the collar within the trench is opened although a thin oxide layer still remains on the surface of the PAD-nitride (18). The second etch step uses C4F8 chemistry to completely remove the remaining silicon oxide layer (17). The process provides good uniformity in thickness of the PAD-nitride layer (18) and sufficient collar oxide thickness in the very top section (173) of the collar oxide. The process is applicable for manufacturing deep trench capacitors for DRAM devices.