Detection of residual photoresist with the atomic force microscope

We report the use of the atomic force microscope (AFM) for local measurements of photoresist thickness and for the detection of residual photoresist in semiconductor processing. By scraping the photoresist off a small portion of a sample with the AFM stylus, and then imaging a larger area at low force, we have been able to measure the depth of a residual, photoresist masking layer. In addition, the AFM has been used to qualitatively judge the efficiency of three common methods of removing photoresist: a hot acetone bath left the most residual photoresist, a commercial stripper left less, and an oxygen plasma etch left none under our test conditions.