RIE planarization process for magnetic bubble devices

A reactive ion etching process, which planarizes the silicon dioxide film deposited over steps in AlCu conductor patterns, has been developed for Permalloy magnetic bubble devices. A conventional fabrication sequence was used through deposition of the spacer SiO2layer which isolates AlCu conductors from Permalloy propagate elements. Prior to Permalloy deposition, however a thick photoresist layer was spin-coated on the SiO2layer and hard-baked to form a planar surface. The photoresist was then etched-back in a NF3,-CHF3, plasma, in the reactive ion etching (RIE) mode, under conditions that etch photoresist and SiO2at nearly identical rates. The planar resist surface profile was thus transferred into the underlying SiO2film. Etch rates for photoresist and SiO2were determined as a function of feed gas composition, and the degree of planarization and thickness uniformity of the remaining SiO2were characterized.