Sub-20 nm laser ablation for lithographic dry development

Pattern collapse of small or high aspect ratio lines during traditional wet development is a major challenge for miniaturization in nanolithography. Here we report on a new dry process which combines high resolution resist exposure with selective laser ablation to achieve high resolution with high aspect ratios. Using a low power 532 nm laser, we dry develop a normally negative tone methyl acetoxy calix(6)arene in positive tone to reveal sub-20 nm half-pitch features in a ∼100 nm film at aspect ratios unattainable with conventional development with ablation time of 1-2 s per laser pixel (∼600 nm diameter spot). We also demonstrate superior negative tone wet development by combining electron beam exposure with subsequent laser exposure at a non-ablative threshold that requires far less electron beam exposure doses than traditional wet development.

Label-free in situ imaging of lignification in the cell wall of low lignin transgenic Populus trichocarpa

Chemical imaging by confocal Raman microscopy has been used for the visualization of the cellulose and lignin distribution in wood cell walls. Lignin reduction in wood can be achieved by, for example, transgenic suppression of a monolignol biosynthesis gene encoding 4-coumarate-CoA ligase (4CL). Here, we use confocal Raman microscopy to compare lignification in wild type and lignin-reduced 4CL transgenic Populus trichocarpa stem wood with spatial resolution that is sub-microm. Analyzing the lignin Raman bands in the spectral region between 1,600 and 1,700 cm(-1), differences in lignin signal intensity and localization are mapped in situ. Transgenic reduction of lignin is particularly pronounced in the S2 wall layer of fibers, suggesting that such transgenic approach may help overcome cell wall recalcitrance to wood saccharification. Spatial heterogeneity in the lignin composition, in particular with regard to ethylenic residues, is observed in both samples.