{"id":2758,"date":"2011-07-19T15:06:26","date_gmt":"2011-07-19T15:06:26","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/?p=2758"},"modified":"2011-07-19T15:06:26","modified_gmt":"2011-07-19T15:06:26","slug":"a-novel-sublimable-mask-lift-off-method-for-patterning-thin-films-of-organic-semiconductors","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/a-novel-sublimable-mask-lift-off-method-for-patterning-thin-films-of-organic-semiconductors\/","title":{"rendered":"A Novel Sublimable Mask Lift-off Method for Patterning Thin Films of Organic Semiconductors"},"content":{"rendered":"

Photolithography\u2019s accuracy and scalability have made it the method for sub-micron-scale definition of single-crystal semiconductor devices for over half a century. Unfortunately, organic semiconductor devices are chemically incompatible with the types of resists, solvents, and etchants traditionally used. This work investigates the use of an uncommonly used chemically inert resist method [1<\/a>] <\/sup>((A. Han, D. Vlassarev, J. Wang, J. A. Golovchenko, and D. Branton, \u201cIce lithography for nanodevices,\u201d Nano Letters<\/em>, vol. 10, no. 12, pp. 5056-5059, Dec. 2010.))((D. Branton, J. A. Golovchenko, G. M. King, W. J. MoberlyChan, and G. M. Sch\u00fcrmann, \u201cLift-off patterning processing employing energetically-stimulated local removal of solid-condensed-gas layers\u201d U.S. Patent 752443 B1, April 28, 2009.))((G. M. King, G. Sch\u00fcrmann, D. Branton, and J. A. Golovchenko, \u201cNanometer patterning with ice,\u201d Nano Letters<\/em>, vol. 5, no. 6, pp. 1157-1160, June 2005.))((J. Cuomo, C. Guarnieri, K. Saenger, and D. Yee, \u201cSelective deposition with \u2018dry\u2019 vaporizable lift-off mask,\u201d IBM Technical Disclosure Bulletin,<\/em> vol. 35, no. 1, June 1992.)) that relies on physical phase changes for lift-off patterning of thin films of organic semiconductors and metals.<\/p>\n

The resist gas is flowed over a cryogenically cooled substrate, where it freezes solid. This layer can be patterned by thermal excitation in a number of ways to define the areas where the desired thin film is to remain.\u00a0 After the desired thin film or films are deposited, the substrate is brought up above the resist material\u2019s sublimation point, leaving behind only the intended pattern. All the unwanted regions are lifted-off by the subliming resist.<\/p>\n

Creating and defining the shadow mask on the surface of the substrate in this manner allow for patterning it with a stamp or roller with micron-scale features without changing the process conditions.\u00a0 In this work, carbon dioxide is used as the sublimable mask material, and prototype stamps have been fabricated using SU-8 photoresist. A mask and the subsequent organic thin film are shown in Figure 2. This process may provide an alternative to shadow masks and provide a manufacturing solution for large area organic electronics.<\/p>\n\n\t\t