Sub-20 nm laser ablation for lithographic dry development

Abstract

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.

Selective laser ablation of radiation exposed methyl acetoxy calix(6)arene

“…Surprisingly, while MAC6 acts in negative tone with the wet development method, in SLAD, MAC6 acts in a) Electronic mail: DLOlynick@lbl.gov positive tone. Using FTIR, previously, 6 we have found that laser-only exposed films, prior to ablation, showed a reduction of the C¼O band in the e-beam exposed samples while showing a development of O-H stretching peak around 3500 cm À1 in the exposed films. More importantly, we found that both pristine and e-beam exposed MAC6 ablate, however, the ablation onset is significantly accelerated by e-beam exposure as monitored by in situ fluorescence and Raman spectroscopy.…”

“…6 SLAD is schematically shown and compared to conventional wet development in Fig. 6 SLAD is schematically shown and compared to conventional wet development in Fig.…”

Selectively accessing the hotspots of optical nanoantennas by self-aligned dry laser ablation

“…49 Recently, a dry development method demonstrating selective laser ablation of MAC that has been exposed with an electron beam was demonstrated by the authors, turning it into a positive tone process. 50,51 In the present work, the resist around the tip apex is removed by dry laser ablation as well, but here the laser illumination itself is employed as the required energy source for local patterning. Two basic mechanisms come into play: Strong local electric fields are created at the nanocone tips (and/or the base edge, depending on the polarization -see discussion in Experimental: Laser ablation) under laser illumination.…”

“…It was shown previously by the authors that the onset of MAC ablation following an electron beam exposure is likewise based on a two-photon process, from which the process was deduced to be predominantly photochemical, since photothermal ablation would be a one-photon process. 50 While calixarenes are known for their relatively high thermal stability up to few 100 °C, they can be removed by thermal treatment at higher temperatures. 58 It has been shown that the threshold temperature for thermal ablation may be locally reduced by previous treatment, e.g.…”

Selective Laser Ablation in Resists and Block Copolymers for High Resolution Lithographic Patterning

“…[16,17] In our selective ablation process, we expose the calixarene using electron beam lithography and replace the wet development step with laser ablation. We found there is a difference in absorption between the exposed and unexposed regions allowing selective development of the exposed region.…”