CONTAMINATION: Sources of contamination: air, people, chemicals, processing in furnaces.

• There are also a few types of special contaminants:
  • metallic contaminants (causes leakage current)
  • organic contaminatation
  • oxides (can cause bad contact between metal lines)
  • electrostatic discharge - ESD (charge transferred from humans on very small devices results in huge currents for very small time, destroying the device)
• A solution for the contamination problem is to introduce robot handling of wafer to minimize human contamination (people are creating 5-10 million particles per minute in a cleanroom). This is an expensive solution, but suitable for industry.
• In cleanrooms, temperature, humidity and the number of dust particles are fixed and controlled.
• The quality of the cleanroom is defined as the number of particles 0.5 microns or greater in a cubic foot of air. It varies from 1 (highest quality) to 10000 (service area) in a cleanroom, while for outdoors is around 1 million. It can be observed in the following picture how small are the particles that cause problems, compared to humain air.