Characterization of a Silicon Nitride Plasma Etch: Selectivities and Uniformity

A silicon nitride plasma etch process with good nitride-to-oxide selectivity has been developed at RIT. Two fluorine etchant gases, CF4 and SF6, were characterized for etch rate and selectivities, and the effects of oxygen and hydrogen loading determined. It was found that the $~b stoh provided a selectivity of 6:1 (with a nitride etch rate of about 700 A/minute) when no loading was applied. The 3:1 CF4:02 etch demonstrated a comparable nitride etch rate, but with a poorer selectivity (about 5:2). The uniformity of the Tegal 700 plasma etching system was determined to be the limiting factor during the etch