Novel technique to pattern silver using CF[sub 4] and CF[sub 4]/O[sub 2] glow discharges

Abstract

Silver is being studied as a potential metal for future interconnects in integrated circuits. Under appropriate conditions, Ag thin films can be removed at reasonable rates using a CF4 or CF4/O2 glow discharge followed by a conventional resist strip process. This is not a typical “dry-etch” process where the formation of volatile products is the main removal mechanism. Rather, it is novel in that the glow discharge is employed to form reactive byproducts of Ag. There are simultaneous sputtering and desorption of the byproducts during the plasma exposure; but the primary film removal mechanism is in the subsequent resist strip process. Two-level-factorial design, and one-factor-at-a-time experiments are employed to study the effects of process conditions on the etch rate, and postetch surface roughness. It is found that Ag removal rate in CF4 or CF4/O2 glow discharges depends strongly on applied power. Postetch surface roughness depends on both power and pressure.