CHEMICAL-MECHANICAL POLISHING FOR FABRICATING PATTERNED W METAL FEATURES AS CHIP INTERCONNECTS

Interconnect features of W metal, recessed in an SiO2 dielectric, can be formed using a novel chemical-mechanical polish process. Mechanical action, to continually disrupt a surface passivating film on W, and chemical action, to remove W, appear to be requirements for workability of the process. A trial process chemistry using a ferricyanide etchant is described. Removal of the W is discussed in terms of competition between an etching reaction which dissolves W and a passivation reaction to reform WO3 on the surface of the W. This novel processing technology is compared with earlier methods of fabricating metal interconnect structures.