Robert R. Jackson

Postexposure bake as a process-control parameter for chemically amplified photoresist

A new method is described for the real-time in-line control of critical dimensions for positive- tone chemically amplified resist systems. The technique relies on the generation of a diffraction grating in the resist film when a latent image appears during the post-exposure bake. A simple optical illumination/collection arrangement allows the diffracted signal to be measured during the post-exposure bake. This signal can be correlated to linewidths when measured by a non-destructive SEM. The result is a post-exposure bake time that can be used to correct for exposure-and-bake temperature variations to conveniently provide overall process control. Results generated by a prototype system are presented for a variety of 0.5- micrometers mask levels and process conditions.

Latent image measurements in electron beam exposed polymethylmethacrylate

Undeveloped and unbaked paterns or latent images (LI) in polymethylmethacrylate (PMMA) have been observed and measured using different measurement techniques. Results from two common‐path baseband optical techniques have been compared with the results of profiling LI using an atomic force probe. These results indicate that 5 A detection limits in optical path length measurements are easily achievable at near video rates using simple optical systems.