Self-Aligned Polysilicon Guard Ring for Schottky Barrier Diode
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
A proposal suggests that a polysilicon (PolySi) guard ring be formed around Schottky barrier diode (SBD) anodes by a self-aligned process. Such a ring would provide protection against any oxide etches used in subsequent processing steps. The method proposes to use the undercut-refill technique to achieve the PolySi ring. In the process a layer 1 of Si3N4 (Fig. 1) is deposited on an SiO2 layer 2 above an N- substrate 3. The area defining the SBD anode is opened by etching the Si3N4 and SiO2 . The SiO2 is purposely undercut 4. Chemical vapor deposition (CVD) is used to deposit a thin layer 5 of PolySi (Fig. 2). This may be doped or undoped P- type PolySi. The PolySi layer effectively fills the undercut.