Thin Film Inhomogeneity: An Overlooked Physical and Chemical Manifestation in Aqueous, Solution-Deposited Films [a collaboration with the D. C. Johnson (UO), D. W. Johnson (UO), G. S. Herman (OSU), and E. L. Garfunkel (RUT) groups]
Aqueous, solution-deposited thin films are often assumed to be homogenous. However, we have shown that solution-deposited hafnium sulfate (“HafSOx”) thin film photoresists are, in fact, inhomogeneous. A detailed physical and chemical analysis of the films shows a denser surface ‘crust’ forms over a less dense bulk layer. Additionally, it was shown that the surface crust has a greater Hf content that the film bulk.
These observations raise important questions about the effects of inhomogeneity in aqueous solution-deposited functional films. We are finding that the presence of a thin surface layer of different density is a general feature of these solution-cast films, and are actively studying their evolution using in-situ XRR studies, as well as the studying the presence of these inhomogeneities in multiple-coat films and their effects on dielectric and other properties.
Relevant Publications
Mitchson, G.; Ditto, J.; Woods, K. N.; Westover, R.; Page, C. J.; Johnson, D. C. Application of HAADF STEM image analysis to structure determination in rotationally disordered and amorphous multilayered films. Semicond. Sci. Technol. 2016, 31, 084003. DOI: 10.1088/0268-1242/31/8/084003
Fairley, K. C.; Merrill, D. R.; Woods, K. N.; Ditto, J.; Xu, C.; Oleksak, R. P.; Gustafsson, T.; Johnson, D. W.; Garfunkel, E. L.; Herman, G. S.; Johnson, D. C.; Page, C. J. “Non-uniform Composition Profiles in Inorganic Thin Films from Aqueous Solutions.” ACS Appl. Mater. Interfaces. 2016, 8, 667-672. DOI: 10.1021/acsami.5b09692.