Particle trapping, transport, and charge in capacitively and inductively coupled argon plasmas in a Gaseous Electronics Conference Reference Cell

Particle trapping has been observed for both a capacitively coupled and an inductively coupled Gaseous Electronics Conference Reference Cell. Particles in the system were formed by introducing 10% CCl2F2 into an argon discharge for 5-10 min and sputtering the resulting film during argon-only experiments. The particles generated were 200-600 nm in diameter. Particle transport was observed in the postplasma regime for both capacitively and inductively coupled cases. For the capacitively coupled plasma, particles of positive, negative and neutral charge were found during the postplasma and shown to be affected by the presence of a de field during the postplasma period. The charge on these particles was determined to be between 1.4 and 12.4 electron charges based on a study of particle motion. This compares to a theoretical value of 800-2600 while the plasma is ignited. For the inductively coupled plasma both a low density mode and a high density mode were observed, being distinguished by a sudden increase in the emission from the plasma as rf power to the inductive coil was increased. In the high density mode of the inductively coupled plasma, the particle cloud was observed to reside less than a millimeter from the powered electrode as the high density plasma mode was established. This was distinguished from a trap height of 4-7 mm for the capacitively coupled plasma which corresponds to the sheath thickness. (C) 1996 American Vacuum Society.