Effects of CO2 critical point drying on nanostructured SiO2 thin films after liquid exposure

• Published in: Thin solid films 2013-01, Vol.527, p.344-348
• Main Authors: Shah, Piyush J., Wu, Zhi, Sarangan, Andrew M.
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Compounding; Compounds; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Drying; Ethyl alcohol; Exact sciences and technology; Glancing angle deposition; Liquids; Lithography; Materials science; Nanorods; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Oblique angle deposition; Other topics in nanoscale materials and structures; Physics; Silicon dioxide; Structure and morphology; thickness; Supercritical carbon dioxide; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Thin films
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2012.10.057

It is known that structured thin films (STF) grown using oblique angle deposition exhibit permanent structural deformation when exposed to liquids. This is a major limitation because these films cannot be patterned using conventional wet lithographic processes. In this work, CO2 critical point drying (CPD) is demonstrated as a viable technique to maintain the film structure even after prolonged liquid exposure. Evaporative room temperature drying and CPD of SiO2 STF samples for two commonly used solvents in lithographic processing viz. acetone and ethanol have been compared. We find that the physical structure of the unexposed STF is similar to STF samples after liquid exposure and CPD technique. ► Exposure to liquids changes the physical structure of nanorod thin films. ► This effect prevents lithographic processing of such thin films. ► CO2 critical point drying technique (CPD) prevents the structure of such films. ► Results would enable wet lithographic processing of these films. ► CO2 CPD minimizes the surface tension effects of the liquids on such thin films.