Reactive ion etch of patterned and blanket silver thin films in Cl2/O2 and O2 glow discharges

Abstract

Silver (Ag) is being investigated as a potential metal for interconnect technology 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 article demonstrates both blanket and patterned etch of Ag films in a reactive ion-etch reactor using Cl2/O2 and O2 glow discharges. X-ray diffraction and scanning electron microscopy were used to analyze the postetch materials. Stress caused by volume expansion upon the formation of Ag2O, AgO, AgCl, and AgClOx, and possibly the sputtering and formation of volatile products, 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 above chemistries for a blanket films etch; but for pattern etch, it showed suitable line formation after resist removal and clean. Further study will be needed to improve roughness, uniformity, and edges geometry of the line edges. Corrosion of Ag in chlorine ambient is an essential issue to be considered in future work.