CHEMICAL DOWNSTREAM ETCHING OF SILICON-NITRIDE AND POLYCRYSTALLINE SILICON USING CF4/O-2/N-2 - SURFACE CHEMICAL EFFECTS OF O-2 AND N-2 ADDITIVES

By comparing the etching characteristics of silicon and silicon nitride in CF4/O2/N2 microwave downstream plasmas we demonstrate clearly how low concentrations of energetic species can play a dominant role in remote plasma processing: Injection of 5% N2 to a CF4/O2 plasma increases the silicon nitride etch rate by a factor of 7, while not significantly affecting the bulk composition of the discharge. Downstream injection of N2 is ineffective. Using surface spectroscopies we directly show a dramatic enhancement of the reactivity of fluorine and oxygen atoms with silicon and silicon-nitride surfaces upon N 2 injection to the discharge. Our results can be explained by the production of energetic metastable species in the discharge region which transport energy to the gas-surface interface. © 1995 American Institute of Physics.