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Surface analysis of photolithographic patterns using ToF‐SIMS and PCA
Author(s) -
Dubey, Manish,
Emoto, Kazunori,
Cheng, Fang,
Gamble, Lara J.,
Takahashi Hironobu,
Grainger David W.,
Castner David G.
Publication year - 2009
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.3056
Subject(s) - photoresist , photolithography , secondary ion mass spectrometry , characterization (materials science) , analytical chemistry (journal) , principal component analysis , chemistry , materials science , nanotechnology , mass spectrometry , chromatography , layer (electronics) , computer science , artificial intelligence
Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is a surface analysis technique well suited to detect and identify trace surface species. With the latest analyzers, ion sources and data analysis methods, imaging ToF‐SIMS provides detailed 2‐D and 3‐D surface reactivity maps. Coupling multivariate analysis methods such as principal component analysis (PCA) with ToF‐SIMS provide a powerful method for differentiating spatial regions with different chemistries. ToF‐SIMS and PCA are used in this study to image and analyze a two‐component photolithograph‐patterned surface chemistry currently published and commercialized for bioassays, bio‐chips and cell‐based biosensors. A widely used reactive surface coupling chemistry, N‐hydroxysuccinimide (NHS), and 2‐methoxyethylamine (MeO) were co‐patterned into adjacent regions on a commercial microarray polymer coating using standard photolithography methods involving deposition, patterning and removal of a routinely used photoresist material. After routine processing, ToF‐SIMS and PCA of the patterned surface revealed significant residual photoresist material remaining at the interface of the NHS/MeO patterns, as well as lower concentrations of residual photoresist material remaining within the MeO‐containing regions, providing spatial mapping and residue analysis not evident from other characterization techniques. As detection of surface photoresist residue remains an inherent challenge in photolithographic processing of a wide array of materials, the use of ToF‐SIMS coupled with PCA is shown to be a high‐resolution characterization tool with the high sensitivity and specificity required for surface quality control measurements following photolithography and pattern development relevant to many current processes. Copyright © 2009 John Wiley & Sons, Ltd.