We reported that we were successful in our 45nm technology node device demonstration in February 2008 and 22nm
node technology node device patterning in February 2009 using ASML's Alpha Demo Tool (ADT).1, 2, 3 In order to
insert extreme ultraviolet (EUV) lithography at the 15nm technology node and beyond, we have thoroughly
characterized one EUV mask, a so-called NOVACD mask.
In this paper, we report on three topics. The first topic is an analysis of line edge roughness (LER) using a mask
Scanning Electron Microscope (SEM), an Atomic Force Microscope (AFM) and the Actinic Inspection Tool (AIT) to
compare resist images printed with the ASML ADT. The results of the analysis show a good correlation between the
mask AFM and the mask SEM measurements. However, the resist printing results for the isolated space patterns are
slightly different. The cause of this discrepancy may be resist blur, image log slope and SEM image quality and so on.
The second topic is an analysis of mask topography using an AFM and relative reflectivity of mirror and absorber
surface using the AIT. The AFM data show 6 and 7 angstrom rms roughness for mirror and absorber, respectively. The
reflectivity measurements show that the mirror reflects EUV light about 20 times higher than absorber.
The last topic is an analysis of a 32nm technology node SRAM cell which includes a comparison of mask SEM image,
AIT image, resist image and simulation results. The ADT images of the SRAM pattern were of high quality even though
the mask patters were not corrected for OPC or any EUV-specific effects. Image simulation results were in good
agreement with the printing results.