Dust nucleation and growth in reactive ion etching discharges

Summary form only given. Particle contamination of wafers in plasma processing reactors is a continuing concern in the semiconductor fabrication community. With feature sizes approaching -0.1 /spl mu/m, particles as small as 10s of nm could result in killer defects. The transport of large particles (100s nm to 10s /spl mu/m in radius) in plasma discharges has been well characterized by considering the dominant forces of electrostatic, ion drag, thermophoretic and fluid drag. For example, in reaction ion etching discharges (RIEs), moderate ion fluxes (10/sup -5/-10/sup -4/ A/cm/sup 2/) and biases (few to 10s V) lead to a balance in electrostatic and ion-drag forces on large particles near the plasma-sheath boundaries, resulting in particles trapping above the substrate. For the same conditions, intermediate sized particles may be trapped near the peak in the plasma potential. Small particles (a few nm in size) behave more like large charged clusters and, under certain conditions, may have large fluxes onto the substrate. The rate of growth of these particles, as well as the transition between neutral and charged states, are therefore important in evaluating particle contamination. A 2 dimensional Monte Carlo simulation has been developed to address particle growth and transport in RIE discharges. The Particle Nucleation and Transport Simulation (PNTS) calculates the rate of particle growth due to gas-phase collisions with radicals and ions, and particle charging due to electron and ion collisions.