REACTIVE ION ETCHING OF PECVD SILICON-NITRIDE IN SF6 PLASMA

The reactive ion etching of PECVD silicon nitride thin films has been investigated using SF6 plasma. Effects of variations of process parameters such as pressure (50-350 mTorr), RF power (50-250 W), gas flow rate (3-130 sccm) and additions of O2 and He (0-50%) in SF6, on the PECVD silicon nitride etch rate and selectivity to the AZ 1350J photoresist were examined. An etch rate of 1 mum/min has been obtained under the condition of 150 mTorr, 100 W and 60 sccm. Experimental results also indicated a maximum etch rate at approximately 30% O2 while addition of He showed only dilution effect. A nitride/photoresist selectivity ranging from 1 to 3:1 has been obtained.