Plasmas (partially ionized gases) are the workhorse of modification of materials for low and high value processing. Plasmas are used to modify commodity polymers, to fabricate microprocessors and now to treat human tissue. The development of technologies for plasma modification of surfaces requires controlling the plasma sources to deliver the desired fluxes of radicals and ions as activation energy to surfaces. Doing so ultimately rests on the ability to control the energy and velocity distributions of charged and neutral particles. Controlling electron energy distributions, f(e), specifies the production rates of radicals and ions. Controlling the velocity distributions, f(v), of ions and neutrals specifies the activation energy delivered to surfaces. There has been an evolution of techniques to control f(e) and f(v) utilizing different types of plasma excitation schemes. These techniques are being challenged to provide the specificity required for nano-scale processing. Control of f(e) and f(v) becomes even more challenging in biological applications of plasmas and plasma medicine, typically performed at atmospheric pressure, where timescales for plasma formation are shorter than conventional control techniques can address. In this talk, techniques to control f(e) and f(v) in plasma sources in the context of plasma modification of biological and nano-scale surfaces will be discussed. Examples will be drawn from pulsed and remote plasma processing.
* Work supported by the Department of Energy Office of Fusion Energy Sciences, Semiconductor Research Corp., Applied Materials, Tokyo Electron. Ltd. and HP Research Labs.