Kinetics of particle formation in the sputtering and reactive ion etching of silicon

Particle formation from a Si substrate in an Ar sputtering plasma and a reactive ion etching plasma of 10% CCl2F2 in Ar has been investigated by laser light scattering. The kinetics of particle growth are studied as a function of rf power and chamber pressure. Threshold behavior for particle generation has been observed in that minimum values of both rf power and pressure are necessary for particles to appear. In both reactive ion etching and sputtering, the smallest particles detected on the wafer are ∼0.2 μm in size. In sputtering most particles are spherical and must have been deposited onto the substrate from the plasma. On the other hand, in reactive ion etching most particles are hemispherical or conical and seem to have grown on the substrate itself. Particle formation is correlated with significant redeposition in sputtering and with deposition of a surface film in reactive ion etching. Si atoms removed from the substrate are probably responsible for the nucleation of particles in both types of plasmas because particle formation is much slower, yet the etch rate is much higher, in reactive ion etching compared to sputtering.