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324ChemInform Abstract The comparative study of the etching of tungsten using CF4/O2/He, CClF3/O2/He, and CBrF3/O2/He plasmas shows that CBrF3 is the most selective etching agent that etches anisotropically over the widest O2 concentration. The effectiveness of anisotropic etching of tungsten in a CBrF3/O2/He plasma is due to the more substantial polymer deposit which protects the tungsten sidewalls (Auger and XPS surface analysis, optical emission spectra).

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Recently, refractory metals such as tungsten have attracted considerable attention as materials suitable for high density, high speed VLSI interconnect structures. Producing submicron tungsten structures requires an etching process with high anisotropy and selectivity, such as can be achieved in RF glow discharge reactors. In this work, we compare three plasma chemistries, namely, CF4/O2/normalHe , CClF3/O2/normalHe , and CBrF3/O2/normalHe , for the etching of photoresist‐patterned tungsten over SiO2 . Optical emission spectroscopy of reactive fragments and nonreactive additives (Ar, Xe, N2 ) is used to identify plasma species suitable for use as endpoint monitors in each case. Of these three freons, the CBrF3 provides an etch process least dependent on oxygen concentration, with the best anisotropy and selectivity. Etch rates, optical emission intensities, Auger and XPS surface analyses are used to interpret differences in reaction mechanism among these plasmas. It is concluded that anisotropy is promoted by the deposition on the tungsten sidewalls of a polymer film, which is more substantial in CBrF3 than in CClF3 .