Terraced Contact Holes With a Nitride Layer
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
Processing high density bipolar circuits (Fig. 1), which incorporate silicon nitride 11 as an etch or ionic mask, by conventional methods generates a silicon nitride ledge 12 overhanging the oxide 13. This overhang is difficult to cover with evaporated metal particularly when the deposition is done on cold substrates. Terraced contact hole edges with positive scopes provide good metal coverage. They can be fabricated as follows: 1. Apply the resist masking 14 for opening contact holes (Fig. 2). 2. The silicon nitride 11 is etched in a plasma of etching gas (non-directional system) for a sufficient time to undercut 15 the photoresist mask by approximately 0.5 mm (Fig. 3). 3. Spin coat wafers with dilute polymer (e.g., photoresist, poly or polyimide) to backfill 16 the resist undercut.