Measures of Resist Contrast

A PR is characterized by its ability to distinguish between light and dark portions of a mask. To achieve high contrast, the chemical response to the irradiation must be highly nonlinear. The intensity profile of a photoresist exposed through a mask window is shown in Fig. 3.59. The corresponding contrast curves for ideal positive and negative is given in Fig.3.60. In case of high contrast resists, sharpened regions are achieved instead of blurred regions close to the exposed areas. The slope of the exposure response is a measure of contrast.