Measurement of Particle Deposition on Wafers in Vacuum Chambers

Abstract

To determine the applicability of electrical fields to control particle deposition on wafers in vacuum chambers, particle deposition experiments were conducted in an idealized vacuum chamber and in an e-beam evaporator in the metallization section of the fab line of the Microelectronics Center of North Carolina (MCNC). For the evaporator, particles created naturally during the pumpdown and venting operation of the chamber were used to measure particle deposition on wafers. Bias voltages were applied to the wafer to control particle deposition during pumpdown and venting. In the idealized chamber, monodisperse particles of known size, charge, and concentration, generated at low pressres by a modified Vibrating Orifice Aerosol Generator (VOAG), were used to carry out particle deposition experiments. The effectiveness of dc deflection plates in minimizing particle deposition on wafers was studied in this chamber. Results from both chambers and the predictions from a two dimensional, particle deposition model for a low pressure chamber are presented here