Trapping and Behavior of Particulates in a Radio Frequency Magnetron Plasma Etching Tool

Particle contamination has been studied in a commercial, magnetron reactive ion etching tool using rastered laser light scattering. Particles present in the plasma were imaged in real time, showing their spatial position and motion. The effect of the rotating magnetic field was also studied. In the absence of the magnetic field, particles were trapped near the inside circumference of the wafer clamp ring directly over the edge of the wafer, near the protruding “fingers” contacting the wafer. With the rotating magnetic field, particles moved in a wave like motion within the confines of the clamp ring and near the interior tool walls. Magnetron operation also resulted in a decrease of the sheath thickness, suspending particles closer to the wafer. Several process changes were shown to promote particle removal from the plasma. © 1993, American Vacuum Society. All rights reserved.