Basics of Contamination by Electrostatic Attraction
Now You’ll Know Your ESDs , Douglas W. Cooper, Texwipe.
Excess electrical charge plays a significant role in contamination. It can cause an energetic
discharge (“electrostatic discharge” or “ESD”) that causes damage, and it can attract particles, by means of “electrostatic attraction” or “ESA,” that can lead to damage.
The presence of excess charge on a surface can create an electrostatic field that causes the
formation of a spark (ESD), which can damage microelectronic components and give rise to
electromagnetic signals that disrupt, for example, robotic equipment. The presence of excess
charge on a surface also creates an electrostatic field that will accelerate deposition of oppositely charged particles and thus accelerate contamination.
The dominant type of ESA is almost always the “Coulombic” interaction: the attraction or
repulsion of a charged particle by a charged surface. The number of particles deposited on a
surface is proportional to:
- particle charge and concentration,
- the electrostatic charge per area on the surface, and
- the duration of exposure.
This article reviews just the basics, using semiconductor manufacturing as the example
application. More information on electrostatic attraction of particles in cleanroom conditions is
available in the articles and book listed in the bibliography.