Abstract: A method of measuring the linewidth of an electrical conductor on a semiconductor substrate includes preparing mutually separated test and interconnection areas on a surface of a semiconductor substrate; forming an electrical interconnection conductor on the surface of the substrate in the interconnection area with a substantially uniform linewidth electrically interconnecting elements on the surface; simultaneously with forming the interconnection conductor, forming in the test area a test structure having a plurality of closed loops of the electrical conductor having the same linewidth as the interconnection conductor; measuring the impedance or complex reflection coefficient of the test structure using a head disposed opposite the test area, spaced from the surface, and coupled to the test structure without directly contacting the test structure; and correlating the measured impedance or complex reflection coefficient of the test structure with measurements of geometrically identical structures of conducto