Application of phase shift focus monitor in EUVL process control

Both 90.9o and 180o phase shifts have been achieved using a new Phase Shift Mask (PSM) structure. This PSM is intended for use as a focus monitor. Both the EUV images of the focus monitor patterns on the new EUV PSM test mask, obtained from the SEMATECH/Berkeley Actinic Inspection Microscope (AIT), and the SEMATECH EUV Micro Exposure Tool (MET), shows that an alternating PSM EUV mask can be effectively used for EUVL focus monitoring.