Particle contamination on silicon wafers etched in an RF plasma.

Particle contamination and etch depth on silicon wafers etched in SF₆/Ar and CF₄/O₂/Ar plasmas are examined as a function of five critical plasma parameters using response surface methodology. The explored plasma parameters are 13.56 MHz RF power, 100 KHz wafer electrode power, pressure, process gas flow rate, and etch time. The experiments are conducted in a modified Tegal MCR-1 single wafer reactor operated in the triode mode. In both chemistries, particle contamination is a predictable function of the externally controlled plasma parameters. Particle deposition and etch depth have a linear dependence on 13.56 MHz RF power, 100 KHz power, and etch time. Also, the particle deposition and etch depth have quadratic dependence on process gas flow rate. In the pressure range explored, particle deposition on the wafers is independent of pressure. In addition, in each chemistry, the behavior of particle deposition and etch depth are similar suggesting that the mechanisms might be analogous. In the SF₆/Ar case, Auger and EDX chemical analysis of the particles reveal the presence of silicon, fluorine, oxygen, sulfur, and aluminum. In the CF₄/O₂/Ar case, particles contain only silicon with carbon and oxygen on the surface.