Improvement in Oxide-Pattern Sizes Controllability on Scanning Probe Nanolithography
Pattern size controllability of SPM-based nano-lithography especially in vertical direction was improved using in-situ height and depth measurements at the processed point. The transient oxide growth was monitored by light transmission (depth of the oxide in sample metal surface) and topographical signals measurements obtained from a scanning near-field optical microscope. First, we investigated oxidizing rate limitation on titanium film. At the voltage rise faster than 10 V/sec, the depth growth didn’t follow the voltage change in spite of immediate upheaval growth. This result suggested the rate determining of reactive chemicals transport in the titanium oxide. Next, we discovered improvement in the process stability on intractable materials (e.g. iron group elements or noble metals; manganese in this paper) by using thin cap layer of titanium. As the result, the oxidization reaction progressed moderately due to the facts that the oxide of the cap layer is electrical insulative and restriction of the permeability of the reactive chemicals (ingredients of the oxide) that were electrochemically generated at apex of the probe tip.
Yunn-Shiuan Liao, Chao-Chang A. Chen, Choung-Lii Chao and Pei-Lum Tso
T. Onuki et al., "Improvement in Oxide-Pattern Sizes Controllability on Scanning Probe Nanolithography", Advanced Materials Research, Vols. 126-128, pp. 701-706, 2010