Approach for forming a buried stack capacitor structure featuring reduced polysilicon stringers

摘要

A process for forming a buried stack capacitor structure in a recessed region of a shallow trench isolation (STI) region, has been developed. The process features a unique sequence of procedures eliminating possible polysilicon stringers or residuals which if left remaining would result in leakage or shorts between conductive elements. The unique sequence of procedures include: deposition of a silicon oxide layer on the polysilicon layer from which the storage node structure will be defined from; photoresist plugs used to protect the portions of the silicon oxide and the underlying polysilicon layer located in the recessed region, during definition of the polysilicon storage node structure; and definition of the polysilicon storage node structure via a wet etch procedure, using the silicon oxide layer for protection of the underlying polysilicon storage node structure.