Atomic force microscope measurement process for dense photoresist

Abstract

Accurate measurement of the sidewalls of photoresist features formed on a semiconductor substrate is achieved by a double mask exposure process. This allows probing the sidewalls of closely spaced photoresist features with the probe tip of an atomic force microscope, in spite of the small (submicron) physical dimensions involved. First a conventional line/space pattern is exposed onto the photoresist using the desired mask. Then a second exposure is made using a second mask which has a special space pattern to effectively remove the already exposed photoresist features along at least one side of one of the previously exposed features. Hence, at least that one side of that one feature is clear of any adjoining photoresist features when the photoresist is then developed after the two exposures. This allows easy access to the sidewall of that one photoresist feature by tilting the probe tip of the atomic force microscope. This allows the measurement of the photoresist feature sidewall characteristics, including for instance angle, curvature and any artifacts present.