Rubbed polyimide layers studied by rotating sample and compensator spectroscopic ellipsometry

Abstract

Rotating compensator spectroscopic ellipsometry was used to study the optical properties of a rubbed polyimide layer. Two operating modes in the transmission configuration were studied. One was a conventional mode of 'polarizer-sample-rotating compensator-analyzer'. The other was a dual rotation mode of 'polarizer-rotating sample-rotating compensator-analyzer'. We found that calibration is not possible in the conventional mode due to the extremely small retardance and non-dichroic nature of the sample. Meanwhile, in dual rotation mode which we developed, a retardance smaller than 0.5 degrees could be measured without calibration. Using this technique, the variation in retardance with rubbing could be easily determined over a range of 320-800 nm. The optical axis could also be determined with high precision for this sample, and this optical axis was found to be parallel to the direction of rubbing.