AMC Control and Chemical Filters

In addition to the common industrial pollution, in the semiconductor high-end wafer manufacturing plants, the concentration of Airborne Molecular Contamination (AMC), which is ten times smaller than a virus, has been a concern for a long time. Aside from personnel safety concerns, wafer yields can be easily affected. However, AMCs come from a wide range of sources, so how to effectively control them is becoming a major issue for the related industries.

Classification of AMC

  • MA (Molecular Acids)
  • MB (Molecula Bases)
  • MC (Molecula Condensables)
  • MD (Molecula Dopands)

Why is AMC important?

The impact of AMC on the yield of semiconductor processes has actually been prevented by the relevant industries for a long while, but in the past, it was only being focused on large particles. With the improvement of process fineness, the standards have become more stringent, and the AMC test items have gradually expanded from acid and base substances to include organic substances. What is more, the monitoring of organic species has also gradually expanded from the dozen that were emphasized by the semiconductor industry to include new unknown organic species. 

Common sources of AMC:

  • Chemicals used in the manufacturing process, resulting in reduced efficiency or release of chemical filters.
  • Organic sulfide emissions from neighboring factories using sulfur-containing organic solvents.
  • Volatile organic compounds (VOCs) and photochemical reactants emitted from petrochemical processes.
  • Sulfur oxides and nitrogen oxides in the atmosphere.
  • VOCs from building materials, machinery, equipment and other related items in the clean room.

Importance of Chemical Filters

Chemical filters are usually made of activated carbon and coconut charcoal, which are effective in controlling AMCs. For this reason, clean rooms install chemical filters (or gas phase filters) on MAUs, RAUs, FFUs, or inside process machines, while general buildings install gas phase filters in air conditioning boxes or indoor cleaning units to effectively control and reduce AMC concentrations.

As semiconductor technology moves towards advanced processes below 7nm, the need for chemical filters that can effectively control AMC has increased dramatically. After all, it only takes 5 to 25 gaseous molecules to deposit on the surface to fill up the 7nm linewidth, which in turn affects wafer yields, and thus demonstrates the importance of chemical filters.