Gas utilization in remote plasma cleaning and stripping applications

Nitrogen trifluoride (NF3) is a likely candidate to replace perfluorocompou nds (PFCs) in stripping and reactor cleaning applications. In this article, the performance of NF3 for the etching of silicon, silicon dioxide (SiO2), and silicon nitride (Si3N4) is compared with that of CF4, C2F6, and C3F8 T he performance measures emphasized in this article are the dissociation eff iciency of the parent molecule in the discharge, the etch rate, and the gas utilization. The destruction efficiency of NF3 in the discharge as determi ned by mass spectrometry is typically 100%. The maximum destruction of the PFC gases for the parameters used in this investigation is approximately 75 % for CF4, and can approach 100% for C2F6 and C3F8. The removal rates for N F3 obtained at optimum settings of O-2 addition and microwave power are sig nificantly higher than those for PFC gases. The gas utilization, which desc ribes the degree of conversion of the parent molecules into etch products a nd is defined in this article, is also higher for NF3 than for the other ga ses investigated. (C) 2000 American Vacuum Society.