Patent ID: 6022766
Filing Date: 2000-02-08
Classification: H01L

Abstract:
A method of protecting metallic studs situated with an undoped cap oxide layer in a field effect transistor structure from chemical agents which are normally degradative of the metallic studs, comprising:applying an interfacial layer of polysilicon on an exposed surface of the metallic studs prior to deposition of subsequent materials utilized to form the transistor structure;wherein the step of applying the interfacial layer is preceded by the steps of forming an undoped cap oxide layer over the surface of an underlying insulator layer, forming the metallic studs in the undoped cap oxide layer and underlying insulator layer, wherein the exposed surface of the metallic studs is recessed below the top surface of the undoped cap oxide layer;wherein the interfacial layer is deposited across the entire top surface of the undoped cap oxide layer and exposed surface of the metallic studs;wherein a portion of the interfacial layer is removed from the top surface of the undoped cap oxide layer, leaving a portion of the interfacial layer on the metallic studs; andwherein the step of applying the interfacial layer is followed by a sequence of steps comprising;(a) forming a body-polysilicon layer directly onto the undoped cap oxide layer and interfacial layer; and(b) patterning the body-polysilicon layer; and(c) ion implanting dopants to form source and drain regions of a thin film transistor; andwherein the body-polysilicon layer is substantially free of metallic contaminants from the studs.