SI3N4 Plasma Etch Study for Optimized Morphology Performance

Si3N4 etch control is one of the most critical processes for profile angle, uniformity and selectivity. We investigated the morphology and selectivity of Si3N4 etch in inductively coupled plasmas (ICP) and capacitively-coupled plasmas (CCP), which are standardly used in fabrication industry for the etching process with Lam conductor etch (CE) Kiyo^® series and dielectric etch (DE) Flex^® series tool, respectively. In our study, Si3N4 etching was performed by using CF4/CHF3based plasma and combining O2 plasma to balance passivation when mixed with diluted gas AR or helium. We have focused on tuning ESC temperature, O2 flow, total flow, gas ratio and power splits to improve profile angle and uniformity. In addition, the wafer edge tilting issue has also been optimized to improve extreme edge profile tilting process window in extreme edge area.