Processing and encapsulation of silver patterns by using reactive ion etchand ammonia anneal

Silver is a potential candidate for interconnect materials in advanced inte rconnect technology due to its excellent conductivity and better electromig ration resistance than aluminium. In this study, the fabrication of 10 mu m -linewidth silver patterns has been carried out by applying reactive ion et ch in an oxygen plasma. The influence of rf-power supply and etch time on t he etch effect has been investigated by the use of scanning electron micros copy (SEM) and Rutherford backscattering spectrometry (RBS). In this partic ular study, the etch condition of 50 W and 5 min can lead to complete remov al of the Ag film (100 nm thick) uncovered by the photoresist. The etch mec hanism has been discussed. The essential point for Ag etch in the oxygen pl asma is that the Ag film is oxidized and then the oxidized Ag film flakes o ff due to the strain-induced cracking and ion bombardment. In an attempt to address some major existing issues of silver as a good interconnect materi al, an encapsulation process has been successfully implemented by annealing silver patterns (with Ti/SiO2/Si stack structure as substrate) in a flowin g ammonia ambient. Upon anneal, the silver patterns are encapsulated with a thin TiN(O) layer due to the diffusion of the underlying Ti through the Ag layer to the surface and the reaction of Ti with ammonia. In the meantime, part of Ti reacts with SiO2 to form Ti5Si3 and Ti(O) at the original Ti/Si O2 interface. (C) 2000 Elsevier Science S.A. All rights reserved.