Sidewall-Defined Self-Aligned Reach-Up Isolation
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
This article describes a bipolar isolation scheme in which a sidewall process is used to produce self-aligned and closely spaced subcollector and isolation diffusions prior to epi deposition. The process is shown in Figs. 1-4. The starting material is a p-type substrate 1. P+ polysilicon 2 and thick silicon dioxide or nitride 3 are deposited, patterned with standard photolithographic processes, and reactive ion etched to obtain the vertical walled structure shown in Fig. 1. A thick layer of chemical vapor deposited oxide is then deposited which tends to follow the contours of the existing structure. It is then blanket reactive ion etched until the substrate is again exposed. The directional effect of the etching leaves a sidewall of oxide 4 covering the polysilicon 2.