View in EDS

3D-structures with arbitrary shapes created in negative resists by grayscale proton beam writing

Saved in:
Bibliographic Details
Title: 3D-structures with arbitrary shapes created in negative resists by grayscale proton beam writing
Authors: Menzel, F. fmenzel@physik.uni-leipzig.de, Spemann, D.1, Koal, T.1, Butz, T.1
Source: Nuclear Instruments & Methods in Physics Research Section B. Oct2011, Vol. 269 Issue 20, p2427-2430. 4p.
Subjects: Proton beams, Microlithography, Microstructure, Three-manifolds (Topology), Irradiation, Simulation methods & models, Microphotometry
Abstract: Abstract: The direct and maskless technique of proton beam writing (PBW) was used for grayscale lithography which allows to create 3D microstructures with arbitrary surface topographies. For this purpose, several micrometer thick layers of the negative resists ma-N and SU-8 were irradiated with 2.25MeV H+ and 1.125MeV in arbitrary shapes using different fluences on different areas with values smaller than the threshold fluence for complete exposure. These irradiations result in multilevel microstructures, whose heights increase with increasing fluence. However, the comparison of the measured structure height with calculated predictions from SRIM simulations disproves the assumption that the structure height is proportional to the linear energy transfer (LET). In fact, the fluence reduction below the threshold for sufficient exposure is responsible for grayscale structuring due to reduced etching of the insufficiently exposed regions. The artifacts obtained with the first grayscale structures created by PBW in ma-N and strongly affecting the structure quality could be reduced by optimizing the scanning procedure, e.g. reducing the pixel distance. Therewith, a micro-Fresnel-lens could be fabricated in ma-N. The first PBW grayscale structures in SU-8 exhibited very strong mechanical instabilities which could be reduced by the use of a post exposure bake step, normally omitted for PBW with SU-8. [Copyright &y& Elsevier]
Copyright of Nuclear Instruments & Methods in Physics Research Section B is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
Description
Abstract:Abstract: The direct and maskless technique of proton beam writing (PBW) was used for grayscale lithography which allows to create 3D microstructures with arbitrary surface topographies. For this purpose, several micrometer thick layers of the negative resists ma-N and SU-8 were irradiated with 2.25MeV H+ and 1.125MeV in arbitrary shapes using different fluences on different areas with values smaller than the threshold fluence for complete exposure. These irradiations result in multilevel microstructures, whose heights increase with increasing fluence. However, the comparison of the measured structure height with calculated predictions from SRIM simulations disproves the assumption that the structure height is proportional to the linear energy transfer (LET). In fact, the fluence reduction below the threshold for sufficient exposure is responsible for grayscale structuring due to reduced etching of the insufficiently exposed regions. The artifacts obtained with the first grayscale structures created by PBW in ma-N and strongly affecting the structure quality could be reduced by optimizing the scanning procedure, e.g. reducing the pixel distance. Therewith, a micro-Fresnel-lens could be fabricated in ma-N. The first PBW grayscale structures in SU-8 exhibited very strong mechanical instabilities which could be reduced by the use of a post exposure bake step, normally omitted for PBW with SU-8. [Copyright &y& Elsevier]
ISSN:0168583X
DOI:10.1016/j.nimb.2011.02.060