Trench sidewall isolation by polysilicon oxidation

Abstract From the Canadian patent

Disclosed is a process of growing a conformal and etch-resistant silicon dioxide on a surface by forming a conformal layer of polysilicon and subjecting the polysilicon to thermal oxidation to completely convert the polysilicon into (poly) silicon oxide. Disclosed also is a method of forming an isolation trench in a semiconductor substrate having a high integrity oxide sidewall. After forming the trench in the substrate surface using a suitable etch mask and RIE, a single (thermal) oxide or dual (thermal) oxide and (CVD) nitride liner is formed on all trench surfaces. A conformal layer of undoped polysilicon is then formed (by. e.g. LPCVD) on the liner. By subjecting to thermal oxidation, …