Reactive ion etch of patterned and blanket silver thin films in Cl-2/O-2 and O-2 glow discharges

Silver (Ag) is being investigated as a potential metal for interconnect tec hnology because it has the lowest bulk resistivity of any metal and higher electromigration resistance than aluminum. Silver dry etch is an important process step in the implementation of this metal as an interconnect. This a rticle demonstrates both blanket and pattern-ed etch of Ag films in a react ive ion-etch reactor using Cl-2/O-2 and O-2 glow discharges. X-ray diffract ion and scanning electron microscopy were used to analyze the postetch mate rials. Stress caused by volume expansion upon the formation of Ag2O, AgO, A gCl, and AgClOx, and possibly the sputtering and formation of volatile prod ucts, are also believed to induce the etch. The etch mechanism initiated by stress led to roughness and residues on the postetch surface for a blanket etch, and jagged edges for a line etch. It is not suitable to use the abov e chemistries for a blanket films etch; but for pattern etch, it showed sui table line formation after resist removal and clean. Further study will be needed to improve roughness, uniformity, and edges geometry of the line edg es. Corrosion of Ag in chlorine ambient is an essential issue to be conside red in future work. (C) 1999 American Vacuum Society.