| abstract |
A CHF3-based RIE etching process is disclosed using a nitrogen additive to provide high selectivity of SiO2 or PSG to Al2O3, low chamfering of a photoresist mask, and low RIE lag. The process uses a pressure in the range of about 200-1,000 mTorr, and an appropriate RF bias power, selected based on the size of the substrate being etched. The substrate mounting pedestal is preferably maintained at a temperature of about 0 degrees C. Nitrogen can be provided from a nitrogen-containing molecule, or as N2. He gas can be added to the gas mixture to enhance the RIE lag-reducing effect of the nitrogen. |