Alternative to H3PO4 for Si3N4 Removal by Using Chemical Downstream Etching

Abstract

Silicon Nitride is with SiO2, one of the most used material in the VLSI. Most of the time it is deposited as a sacrificial layer: etch stop and CMP buffer layers, temporary or permanent spacers, hard masks for epitaxies, etc… In the present work we have been able to remove Si3N4 without the use of conventional H3PO4 chemistry. We managed to integrate a chemical downstream etching (CDE) process to 28nm and 14nm FDSOI wafers. Aspects of uniformity, selectivity and defectivity will be discussed in this paper.