Development of optical coatings for 157nm lithography (I:coating materials)

In the basic study to get low loss optics for F2 lithography application, potential of 5 coating materials(AlF3, Na3AlF6, MgF2, LaF3, GdF3) and 3 deposition processes(RH ,EB,IBS) were investigated in VUV region. They were supplied as single layer coating on CaF2 substrate from 4 Japanese coating suppliers by each way of processes. Refractive indices (n) and extinction coefficients (k) at 157nm of these coatings were calculated from transmittance and reflectance by VUV spectrometer and compared. RH thermal evaporation was predominant way from the view of optical loss for AR coating. And we have developed the absorptance measurement system and scatterometer for more work.