Application of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Imaging for Photolithographic Structuring

Abstract

The aim of this contribution is the application of matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) in the area of photolithographic structuring. As proof of concept, this method was used to image an UV exposed negative photoresist layer, which is generally used to manufacture printed circuit boards (PCB) for electronic components. The negative photoresist layer consisting of the main component novolac, benzophenone as the active component, and the solvent tetrahydrofuran was mixed with the matrix dithranol and the salt additive LiTFA and spin-coated onto an ITO-conductive glass slide. To imprint an image on the created surface, a transparency with a printed wiring diagram was placed on top of it and irradiated by UV light for 15 min. The inspection of the efficient imprinting of the microstructure onto the photoresist layer was performed by MALDI-MSI. This unique application represents a further step toward the surface analysis of polymer films by this emerging life science imaging technique.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric imaging of synthetic polymer sample spots prepared using ionic liquid matrices

“…utilized MALDI imaging for the analysis of polymer surfaces after UV treatment, e.g. in photolithography . In a recent paper, Krueger et al .…”

“…in photolithography. [27,28] In a recent paper, Krueger et al analyzed different polymeric membranes regarding their chemical structure and compound distribution by MALDI-MSI. [29] In 2001, the use of room-temperature ionic liquids (RTILs) as matrices was reported by Armstrong et al [30] RTILs are non-flammable salts with a melting point below 100°C, which are stable up to 250°C, are non-explosive and have a negligible vapor pressure.…”

Visualizing molecular distributions for biomaterials applications with mass spectrometry imaging: a review

“…The ability to monitor surface modification upon light irradiation opens up the possibility of studying the chemical changes occurring on photoresists and performance coatings. 151 Here a negative photoresist (Novolac) containing benzophenone photo-activator (10% w/w) was used and a wiring diagram imprinted onto the surface with UV light. The substrate was imaged with a resolution of 100 mm, and polymer signals characteristic of the Novolac resin monitored.…”

A mass spectrometry imaging method for visualizing synthetic polymers by using average molecular weight and dispersity as indices

“…It is also considered to be a powerful tool for synthetic polymers; however, MALDI-MSI in polymer applications is still limited, although the number of reports is increasing. [18][19][20][21][22][23][24][25][26][27] Conventional MALDI-MSI visualizes the spatial distribution of target compounds, which have specified m/z values, by extracting their mass images from the MSI raw data. This method is not suitable for synthetic polymers because they have a mass distribution.…”