Forming tungsten structures.

摘要

A method and system for forming tungsten structures 26 in a semiconductor device 10 which uses a chromium protective layer 14 to protect underlying semiconductor layers during the etching process and a chromium mask layer 24 so that tungsten structures 26 can be formed with high aspect ratios using a reactive ion etcher to etch the tungsten 16 with a carbon tetrachloride oxygen plasma in a reactive ion etcher. Long overetches can be achieved because of the high selectivity of chromium to the carbon tetraflouride/oxygen plasma. The anisotropic nature of the reactive ion etcher prevents undercut during long overetches of the tungsten 16 to further decrease losses in linewidth or increases in resistance as a result of overetching. The tungsten structures 26 are not susceptible to electromigration problems so that high circuit densities can be achieved. Low pressure chemical vapor deposition techniques of depositing the tungsten layer 16 are employed to provide a uniform layer of tungsten 16 which penetrates deep holes and trenches to ensure that full contact between multiple layers occurs for high circuit topologies. By-products of the carbon tetraflouride/oxygen plasma etch do not cause corrosion of the resulting tungsten structures 26 formed in accordance with the process of the present invention.