Specific to 1,1,1 Trichloroethane, Furnace Grade, Tier A. Tier A refers to first generation Guidelines. Tier A Guidelines are intended to describe the quality required to produce IC's whose critical dimensions lie in the range of 0.8 to 1.2 microns and greater, with most trace metal specifications near 10 ppb. They are designated by "SEMI C7._", and in general become Grade 2 standards upon approval of a validated analytical quality control method. Tier A guidelines were developed by the North American Process Chemicals Committee, and approved through SEMI's International ballot methods.