A novel approach for the problem of in-situ and real time monitoring processes in thin film
photoresists is presented. The approach is based on the fact that all the essential
processing steps, such as softbaking, exposure, hardbaking, and development, can be
monitored by the induced spectral modifications in the infrared spectrum of the resist film.
The technique of fiber-optic-based evanescent field spectroscopy, is proposed as the method
for measuring these spectral changes. The technique is demonstrated using a silver halide
infrared transmitting optical fiber coated with thin photoresist film, as the sensing
element, and a tunable lead salt diode laser, as the infrared monochromatic source. As an
example, immense changes in the resist IR spectrum, induced by thermolysis, are measured.
The advantages of using all-fiber technology for remote real time sensing is further
discussed, and the possibility to monitor the resist film temperature and thickness, using
the same silver halide fibers, is emphasized.