a test method for measuring adsorbed molecular contamination uses a test structure that includes a substrate comprising a plurality of separated test sites having a plurality separate thicknesses having a base design thickness and a designed thickness interrelationship . the test structure is exposed to a molecular contaminant environment to provide an adsorbed molecular contaminant layer upon each of the plurality of separated test sites . the plurality of separated test sites with the adsorbed molecular contaminant layer thereon is measured . an appropriate algorithm that considers the designed thickness interrelationship is used to determine at least one of : the base design thickness ; and a thickness of the adsorbed molecular contaminant layer .