A radiation-sensitive coating material, in addition to a base polymer, has
a solvent and a radiation-active substance which forms an acid on
irradiation by light (including energetic electrons or ions), a
fluorescent substance which alters its fluorescence property subject to a
change in the acid content of its surroundings. In a process for exposing
a substrate coated with the coating material at least one sensor in the
exposure chamber of the exposure apparatus measures the intensity of the
change in fluorescence spectrum as a function of time during the exposure
operation. From the course of intensity at the time of an individual line
of the fluorescence spectrum or the intensity integrated over a
wavelength interval it is possible to determine the endpoint of the
exposure operation by way of electronic algorithms. Deviations from
experimentally determined ideal curves of the intensity course provide
information on erroneous functions in the course of coating material
application and exposure.