Proc. SPIE. 9425, Advances in Patterning Materials and Processes XXXII
KEYWORDS: Lithography, Electron beam lithography, Electron beams, Calibration, Chemistry, Atomic force microscopy, Scanning electron microscopy, Scanning probe microscopy, Line edge roughness, Line scan image sensors
One of the key challenges to high resolution resist patterning is probing the resist properties at length scales commensurate with the pattern size. Using a new scanning probe microscopy (SPM), Peak Force™ tapping, we map exposure dependent nanoscale modulus of the exposed/developed resist patterns with sub-10 nm resolution. By innovative electron beam exposure pattern design, the SPM technique reveals that resist modulus follows the height contrast profile, but with a shift to higher exposure doses. SEM image analysis of patterned resist structures confirm that the best line-space patterns are achieved at exposure dose where modulus reaches its maximum and shows how modulus can be used to probe patternability of resist systems.
EUV lithography is needed by the semiconductor industry for both its resolution and for the process simplification it provides compared to multiple patterning. However it needs innovations to make it a success. One area where innovation is needed is resist performance. Resists that are commercially available for EUV use are typically based on conventional chemically amplified resist chemistry. So far, this has not provided the required performance at fast enough photo speed. Many innovative resist systems have been introduced in the last few years that have novel mechanisms and/or incorporate novel chemical elements with high EUV absorbance. These new systems are promising enough for EUV use that work on many of them now needs to shift to characterizing their functional parameters and optimizing their performance. For the future, new systems beyond these will have to focus on reducing the inherent noise in resist imaging. The concept of pixelated resists is introduced and it is suggested pixelated resists are one possible avenue for imaging sub 10nm features with sufficient feature size and profile control.
One of the key challenges to high resolution resist patterning is pattern collapse. Using a new scanning probe microscopy (SPM), Peak ForceTM tapping, we map nano-mechanical properties-- modulus, adhesion, and dissipation-- of the exposed/developed resist structures with sub-10 nm resolution. Properties are compared across a carbon based negative resist with and without cross-linking. The SPM technique reveals that cross-linking significantly enhances the mechanical properties to give a champion resolution of sub 20 nm half-pitch in a chemically amplified negative resist system. Beyond mechanical properties, surface morphology and redistribution kinetics were examined using complementary techniques and reveal additional benefits with cross-linking.
Here, we report the highest recorded resolution for a negative-tone, carbon-based, chemically amplified (CA) resist of 20 nm half-pitch (HP) using both E-beam and EUV exposure systems. The new chemistry incorporates variable amounts of oxetane (0, 5, 10 and 20%) cross-linker into a base of Noria-MAd (methyl-admantane) molecular resist. Cross-linkable resists showed simultaneous improvements in surface energy, structural integrity, and swelling to ensure collapse free 20nm HP patterns and line-edge roughness (LER) down to 2.3 nm. EUV exposed Noria-Ox (5%) cross-linked resist patterns demonstrated 5 times improvement in Z-factor (for 24 nm HP) over Noria-MAd alone.