Selective interhalogen etching of tantalum compounds and other semiconductor materials

Abstract

We find that gaseous ClF3 is an effective and selective etchant for a variety of transition metals and metal compounds. Kinetics were studied for etching α-Ta (13–16 atom % N), Ta2N, and Ta2O5 in this gas, as a function of temperature and pressure, to provide effective activation energies of 4.0, 4.4, 7.7 kcal/mole, respectively. Relative etch rates measured in CF4/O2 and NF3 plasmas indicate that ClF3 gaseous etching has more than an order of magnitude better selectivity for nonoxidic metal compounds over the corresponding oxide. At 100 °C, selectivity for etching α-Ta or Ta2N over Ta2O5 is more than 160:1. Other materials used in semiconductor manufacture, such as SixNy, W, TaSi2, and photoresist, were also briefly surveyed and the results suggest ClF3 holds promise for isotropic etching applications that require high selectivity.