Nonhomogeneous pattern formation in the dissolution processes of novolak-diazonaphthoquinone resists

The development mechanisms of irradiated novolak-diazonaphthoquinone resists have been studied on the basis of the atomic force microscopy (AFM) data of resist surface images. The characteristic surfaces with large holes or island structures, that is, nonhomogeneous surfaces, have been observed at the exposure doses near the beginning of the film thickness reduction. The changes in the size of holes and island structures roughly correspond to the changes of cluster size estimated by percolation theory. From the dissolution pattern changes which depend on exposure dose, it is considered that an adequate exposure dose is indispensable for high-precision patterns and such an exposure dose determines the sensitivity of positive-type resists.