Development of an Anisotropic, Highly Selective Tungsten Silicide Dry Etch Process

The development of an anisotopic Tungsten Suicide etch that will provide good selectivity to photoresist as well as an underlying oxide has been studied. It has been found that by reducing the amount of fluorine (SF6) in the system and increasing the chlorine concentration, slightly tapered sidewalls can be achieved without the use of a polymer forming gas. An optimum process was developed on an Applied Materials P-5000 MxP system. A condition of 10 sccm SF6, 40 sccm Cl2, 20 sccm 11e02 at 30 mTorr, and 400W presents slightly tapered sidewalls with within wafer uniformity of 4.85%. The selectivity of Tungsten Silicide to photoresist and oxide is 0.89, and 3.07 respectively. An experiment was also conducted in which comparable etch rates of 57A/sec were obtained using a first order approximation of power densities between the P-5000 MxP and a GEC Plasma Cell located at the Rochester Institute of Technology