Evaluation of Electrostatic Charges on Aerosol Particle Attractiveness to Silicon Wafers in Class-1 Cleanrooms

摘要

A series of tests were performed to define the required ion emitter balancing and cleaning frequencies. The voltage drift and discharge time drift were used to determine acceptable maintenance servicing schedules. The ion emitter operating limits were determined experimentally by measuring the maximum electrostatic charge that would build up on a wafer before it was at risk of attracting particles out of the airstream. A site survey was performed on cleanroom equipment and processes using a noncontact field meter to identify critical areas with greater than 1000 V of surface charge. Programs have been initiated which require "at risk" processes to perform specific testing to determine whether ionization emitters are needed.