Synchrotron lithography - the way to sub-micron features with single layer resist
Soft x-ray radiation is affected neither by scattering in the resist nor by reflection from the substrate surface, so that a one-layer resist system can be maintained even in the sub-micron range. This holds primarily for the parallel synchroton radiation avoiding all the geometrical distortions connected with x-ray tubes and even plasma sources. It has been shown that a minimum feature size of 0.2 micrometers can be achieved in this case. Different resist systems applicable in x-ray lithography have been tested regarding resolution, sensitivity, and etch stability. The optical resists "HPR 204" shows very high process stability, good resolution but low sensitivity. It is, therefore, suitable for an x-ray pilot process but not for high throughout production. The high sensitive x-ray resist "FBM 120" which shows originally a very poor etch stability can be stabilized by post exposure with synchrotron radiation.