Degradation of Perfluorododecyl-Iodide Self-Assembled Monolayers upon Exposure to Ambient Light

• Published in: Nanomaterials (Basel, Switzerland) Switzerland), 2024-06, Vol.14 (11), p.982
• Main Authors: Colbeck Kirby, Lauren, Lodha, Jayant K, Astley, Simon, Skelton, Dave, Armini, Silvia, Evans, Andrew, Brady-Boyd, Anita
• Format: Article
• Language: English
• Subjects: area selective deposition; Chemical properties; Contact angle; Defluorination; Degradation; Exposure; Fluorine; Fluorocarbons; Iodides; Iodine; Iodine compounds; Light; Materials research; Metal oxides; Monolayers; Monomolecular films; perfluorododecyl iodide; Photocatalysis; Photodegradation; Photoelectron spectroscopy; Photoelectrons; Photolithography; self-assembled monolayer; Self-assembled monolayers; Self-assembly; Silicon dioxide; Silicon wafers; Substrates; Surface energy; Surface properties; Temperature; Titanium dioxide; Vapor deposition; X ray photoelectron spectroscopy
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano14110982

Perfluorododecyl iodide (I-PFC12) is of interest for area-selective deposition (ASD) applications as it exhibits intriguing properties such as ultralow surface energy, the ability to modify silicon's band gap, low surface friction, and suitability for micro-contact patterning. Traditional photolithography is struggling to reach the required critical dimensions. This study investigates the potential of using I-PFC12 as a way to produce contrast between the growth area and non-growth areas of a surface subsequent to extreme ultraviolet (EUV) exposure. Once exposed to EUV, the I-PFC12 molecule should degrade with the help of the photocatalytic substrate, allowing for the subsequent selective deposition of the hard mask. The stability of a vapor-deposited I-PFC12 self-assembled monolayer (SAM) was examined when exposed to ambient light for extended periods of time by using X-ray photoelectron spectroscopy (XPS). Two substrates, SiO and TiO , are investigated to ascertain the suitability of using TiO as a photocatalytic active substrate. Following one month of exposure to light, the atomic concentrations showed a more substantial fluorine loss of 10.2% on the TiO in comparison to a 6.2% loss on the SiO substrate. This more pronounced defluorination seen on the TiO is attributed to its photocatalytic nature. Interestingly, different routes to degradation were observed for each substrate. Reference samples preserved in dark conditions with no light exposure for up to three months show little degradation on the SiO substrate, while no change is observed on the TiO substrate. The results reveal that the I-PFC12 SAM is an ideal candidate for resistless EUV lithography.