Self-Aligned Electrical Connection to Trench
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
A method is described to provide a self-aligned electrical connection between an insulated trench filled with highly doped polycrystalline silicon and a nearby doped silicon region. Referring to Fig. 1, a trench 2 is formed in a silicon substrate 4 by defining an opening having a width W in photoresist 8, and reactive ion etching (RIE) the exposed silicon after an isotropic etch removal of SiO2 layer 6. The isotropic etch time is extended to create an opening in the SiO2 wider than the photoresist opening W, as shown. Photoresist 8 is then removed, and, as shown in Fig. 2, insulating layer 10 is formed. Highly doped polycrystalline silicon 14 is next deposited conformally by chemical vapor deposition (CVD) to over-fill the trench to a level indicated by the dashed line 12.