Understanding the origin and fate of plasma-enhanced chemical vapor deposition (CVD) contaminant particles is a critical issue in semiconductor manfacturing in order to improve thin film deposition on wafer surfaces. Several competing external forces will affect a particle's motion in the plasma field prior to either landing on the wafer or entering the exhaust line. Electrical forces dominate during plasma radio frequency (RF) activation creating regions of potential wells. If trapped, the nucleated particles can continue to grow and gain electron charges until gas or ion drag forces can overcome the potential barrier. Mutual electrostatic repulsion between particles can also cause the traps to "leak" out contaminants into the exhaust line. In this way, contaminants formed solely in the plasma volume are hypothesized to possess a distinctive size and charge distribution independent of condensation particles originating from gas compression by the oil-based rotary pump. For these reasons, a novel experimental aerosol sampling system was designed to continuously monitor submicron particles carried was designed to continuously monitor submicron particles carried during a thin film deposition cycle without disturbing the internal operation of the plasma. Sampling from the plasma enhanced chemical vapor deposition (PECVD) process exhaust gases using an oil-free mechanical piston pump parallel to the main vacuum line is considered to be an effective alternative to in situ probe measurement. Concentration and size distribution data were continuously measured using a condensation nucleus counter and an optical spectrometer. Results show that the particles in the reactor exhaust line are bimodal or made up of the fine and coarse sizes divided near 100 nm. Experimental results show the fine fraction incrases in the exhaust line afteer a certain time interal. This delay is hypothesized to be the initial period the nucleated particles were trapped inside the plasma's potential wells. Once trapped, reactor particles can continue to grow in agreement with free molecular coagulation models. A larger particle will experience greater gas drag to eventually overcome the electrical forces. The delay, or critical transport time, depends upon the reactor pressure and plasma power, which also affect the size of the trapping field. The second paper in the series "Exhaust Aerosol of a Plasma Enhanced CVD System" comares a computational charging model of the plasma sheath with experimental charge distribution measurements of contaminant particles carried through the CVD exhaust.
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