Shallow trench isolation with self aligned PSG layer

摘要

A method for forming trench isolation and in specific shallow trench isolation(STI) using SiO2 plugs is proposed. The SiO2 plugs of the STI have a buried phosphorus (P) rich layer introduced during and subsequent to the trench formation to tie up any sodium ionic contamination from processes prior to gate formation. P impurity layer is formed below the surface of the deposited SiO2 layer. A preferred method for forming the buried P layer is by shallow implantation in a vertical direction into the deposited SiO2 layer prior to planarization. The process is self aligned to the trench isolation regions.