8 - Relevance of Electrostatic Discharge Controls to Particle Contamination in Cleanroom Environments

Abstract

Reduction of product defects to levels acceptable in high quality, world-class clean-room manufacturing requires continuing attention to static charge control. Uncontrolled, static charge is responsible for increasing the number of particle-related defects, damaging products, and equipment by electrostatic discharge (ESD), and interfering with factory automation. As factory profitability increasingly depends on both high yields and high product throughput, minimizing or eliminating static-related problems in cleanrooms has become a necessity. Static charge control begins with the grounding of personnel, equipment, and any materials that come close to static sensitive products. Insulating materials should be removed, whenever possible, and replaced with static dissipative equivalent materials. When insulators must be used to satisfy other process requirements, ionizers are used to neutralize static charge on the insulators. It should be remembered that insulators are very often a part of the product itself and cannot be eliminated. Air ionization is one of the few methods available for controlling static charge in high-quality clean-room environments. In some cases it is the only method that can be used. Ionizers can reduce the number of contamination and ESD-related defects occurring in mini-environments and production equipment as well.