Prevention of Birdsbeak Formation
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
To achieve greatest density in integrated bipolar technology, the isolation regions between devices must be made as narrow as possible. Generally, this is accomplished by reactive ion etching (RIE) of deep narrow trenches and their subsequent refill with silicon oxide deposited by chemical vapor deposition (CVD) after thin thermal oxidation. However, even the densest chips have isolation regions that are comparatively wide. These wide isolation regions cannot be easily refilled with CVD silicon oxide and birdsbeak-shaped structures can be formed at the device side of the trenches, when these wide areas are oxidized.