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 parame ters such as pressure (50-350 mTorr), RF power (50-250 W), gas flow ra te (3-130 sccm) and additions of O2 and He (0-50%) in SF6, on the PECV D silicon nitride etch rate and selectivity to the AZ 1350J photoresis t 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 o f He showed only dilution effect. A nitride/photoresist selectivity ra nging from 1 to 3:1 has been obtained.