Yield enhancement through defect reduction for post wet silicon nitride etch applications

Silicon etching in hot phosphoric acid is not new to the semiconductor manufacturing field. It has been used for decades to remove silicon nitride after LOCOS processes while preserving the integrity of the previously grown oxide. The etch has a high selectivity resulting in a good fit for this purpose. This paper will present an innovative cleaning technique for post hot phosphoric acid nitride strip applications that provide yield improvement through particle and defect reduction. The application developed at Fairchild Semiconductor, uses ammonium hydroxide, ozone, and water introduced in controlled amounts to promote the dissolution and removal of organic silicon nitride etch residues. This removal prevents downstream defect formation, improving product yields and long-term device reliability.