Role of NO in highly selective SiN/SiO2 and SiN/Si etching with NF3/O2 remote plasma: Experiment and simulation

This paper describes the study of mechanisms of highly selective silicon nitride etching, in particular, the role of NO in silicon nitride etching by atomic fluorine. This paper presents experimental and simulation data about SiN, SiO2, and Si etching with NF3/O2 remote plasma. Quantum chemistry simulations show that NO reacts with the F–N bond in a SiN cluster with lower activation energy than the F-atom. Thus, NO increases the rate of fluorine migration on the silicon nitride surface from the nitrogen atom to the silicon atom during the etching process. In the absence of NO, such migration proceeds with relatively high activation energy, which limits the etching rate. The analytical model based on the SiN etching mechanism taking into account the fluorine migration is proposed. The results of calculations with the analytical model show a good agreement with the experimental SiN, SiO2, and Si etch rates.