Ferguson_Mitigating re-entrant etch profile undercut in Au etch_ecs_templated_april27_preprint.pdf (542.71 kB)
Mitigating re-entrant etch profile undercut in Au etch with an aqua regia variant
preprint
posted on 2022-05-03, 01:19 authored by Mark FergusonMark Ferguson, Mohamed Najah, Frederic Banville, Mohamed Boucherit, Naresh Miriyala, Jacques Renaud, Luc Frechette, Francois Boone, Serge Ecoffey, Serge CharleboisSerge CharleboisWe investigate the re-entrant undercut profile resulting from Au wet etching for patterning micron range thick films using an aqua regia-based solution in comparison with an iodine-iodide-based commercial etchant. Our work discriminates between two undercutting mechanisms: galvanic acceleration of etch rate at the Au adhesion or barrier layer, and delamination-based undercutting. We tracked etch outcomes of feature size reduction from photoresist size, undercut Au in cross-section and lift-off of small (5-10 μm) features. Results indicate that galvanic undercutting is well-mitigated by the aqua regia solution compared to commercial etchant results. Good Au adhesion eliminates undercut for 500 nm-thick Au and mitigates it by ~80% for 1 μm-thick Au. We discuss the electrochemical origin of this mitigated galvanic undercut.
Funding
MITACS (Project No. IT17922)
Natural Sciences and Engineering Research Council of Canada (Grant No. RDCPJ 479560 – 15)
Prompt (QuebecInnove) (Grant No. 43_Boone 2015.10)
History
Email Address of Submitting Author
Mark.Ferguson@USherbrooke.caORCID of Submitting Author
0000-0002-5389-9342Submitting Author's Institution
University of SherbrookeSubmitting Author's Country
- Canada