Photoresists

Successful measurement of photoresist requires overcoming several unique challenges, all of which can be dealt with automatically by Filmetrics measurement systems. These challenges include not exposing the resist with the measurement light source, having access to a refractive index library that covers the extensive range of photoresists, and having the ability to deal with photoresist’s tendency to change refractive index with the degree of baking and exposure.

Measurement of SU-8 and other thick photoresists is a particularly important application, since spin coating, though quick and easy, can be an inaccurate method for yielding a desired thickness. Since exposure time is dependent on resist thickness, an accurate measurement should be taken. Moreover, since positive and negative photoresists can be used together to create complex multilayer MEMS structures, knowing the thicknesses of each layer becomes extremely important.

Filmetrics offers a range of tabletop and mapping solutions for measuring the thickness of single layer, multilayer, and even freestanding photoresist films from 3 nm to 1 mm. All Filmetrics models measure thickness (and index) by accurately modeling spectral reflectance. Special proprietary algorithms allow robust "one-click" analysis, with results typically available in less than a second.