A Novel Method For Molybdenum Etching Using a Combination of Surface Oxidation By Ozone-Gas-Bake and Wet Selective Removal for Future Semiconductor Devices

Abstract

As semiconductor devices continue to scale, it is important to evaluate new metals for narrower trench or via structures. Mo is a candidate because of its lower resistivity compared to the conventional metals, Cu or W. Mo is etched with wet chemistry using an oxidizer but increase in surface roughness is a problem. The model for increase in roughness is water insoluble MoO2 partially remains whereas MoO3 dissolves in the water via simultaneous "oxidation-dissolution" reactions. We have developed a novel cyclic process with O3 gas bake followed by oxidizer free wet process to separate the oxidation and dissolution and verified that surface roughness does not increase. The new process was tested with patterned wafer to look at residue on sidewall, pattern loading and oxygen diffusion. This method is showing promising results and is expected to be applied for use in manufacturing of future semiconductor devices.