Abstract: A CHF.sub.3 -based RIE etching process is disclosed using a nitrogen additive to provide high selectivity of SiO.sub.2 or PSG to Al.sub.2 O.sub.3, 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.degree. C. Nitrogen can be provided from a nitrogen-containing molecule, or as N.sub.2. He gas can be added to the gas mixture to enhance the RIE lag-reducing effect of the nitrogen.

Abstract: Patterned conductive lines are formed simultaneously with stud via connections through an insulation layer to previously formed underlying patterned conductive lines in multilevel VLSI chip technology. A first planarized layer of insulation is deposited over a first level of patterned conductive material to which contacts are to be selectively established. The first layer then is covered by an etch stop material. Contact holes are defined in the etch stop material at locations where stud connectors are required. The first layer of insulation is not etched at this time.Next, a second planarized layer of insulation, is deposited over the etch stop material. The second layer insulation, in turn, is etched by photolithography down to the etch stop material to define desired wiring channels, some of which will be in alignment with the previously formed contact holes in the etch stop material.