Concentrations of organic contaminants (hereafter abbreviated as ORCs) in cleanroom air were measured regularly since operations in a new cleanroom were started. Concentrations of ORCs in cleanroom air gradually decreased and attained steady state values after six months. The removal efficiency of a chemical filter for total ORCs was significantly reduced with time, however the efficiencies for di (2-ethylhexyl) phthalate (DOP) , di (isobutyl) phthalate and low molecular weight cyclosiloxanes (LMCSs) remained at a sufficiently high value for three years. The sticking probabilities of DOP and Trichloroethylphosphate onto Si surface were estimated to be 1 × 10-2 and 5 × 10-3 from the concentrations of ORCs in the air and the masses of ORCs deposited on Si wafers.
