1364 Chem. Mater. zyxwvu 1992,4, 1364-1368 A Positive Tone Plasma-DevelopableResist Obtained by Gas-Phase Image Reversal Scott A. MacDonald,* Hubert Schlosser,t Nicholas J. Clecak, and C. Grant Willson IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120-6099 Jean M. J. Frechet Department of Chemistry, Cornell University, Ithaca, New York 14853-1301 Received July 7, 1992. Revised Manuscript Received September 15, 1992 This paper describes a gas-phase image reversal process that generates a positive tone, plasma-developable image from a chemically amplified photoresist system. This system is based on the catalytic photogeneration of phenolic hydroxyl groups within the resist zyxwvu film that react, in subsequent steps, with either a silylating agent or an isocyanate that is delivered in the gas phase. This forms silyl ethers and carbamates within the polymeric fii. The regions of the fii containing the organosilicon species are not etched in an oxygen plasma environment. Correspondingly,the carbamate regions of the film are rapidly etched in an oxygen plasma. The overall process results in a positive tone image after development in an oxygen plasma. Introduction Plasma-developable resist systems have been an active area of research for several years. While there are a variety of schemes used to obtain plasma-developable resists, the predominant approach involves a hydrocarbon polymer film containing an inorganic component.' When placed into an oxygen plasma environment, the hydrocarbon re- gions etch to substrate while the inorganic component (such as silicon,*tin,3 germanium: or titanium5) is con- verted into a nonvolatile oxide. This nonvolatile oxide significantly retards the oxygen etch rate, and hence the resist regions containing the inorganic component remain after oxygen plasma development. For this approach to work, it is necessary to define within the polymer film regions containing the inorganic component and, correspondingly, regions lacking the in- organic species. A very attractive way to accomplish this is to expose the polymeric film to UV light and, in a sub- sequent step, treat the f i with an inorganic reagent (such as diborane: tin(1V) chloride: hexamethyldisilazane,8 or bis(triethylgermyl)amineg) to selectively incorporate the inorganic species into the zyxwvuts fii. While this general process can be applied to a variety of polymers and inorganic reagents, most of the published work deals with phenolic hydroxyl-containing films that react with a silylatingagent to yield the corresponding silylether. A key feature in these systems is the way in which the UV exposure alters film reactivity toward the silylating reagent. For example, we have described a positive tone system consisting of a phenolic polymer, photoacid generator, and acid-activated cross-linking agent.'O In this system, UV exposure and heating cross-link the exposed regions, re- ducing the rate at which hexamethyldilsilazane (HMDS) zyxwvu can diffuse into these areas. Hence, when the exposed f i is treated with HMDS vapor, the silylating agent diffuses more rapidly into the un-cross-linked region of the film, reacts with the phenolic hydroxyl group to form a silyl ether, and yields a positive tone image when developed in an oxygen plasma. Workers at Philips Research," Shipley Co.,12 Lincoln Lab~ratories,'~ and IBM14 have also de- scribed positive tone systems derived from radiation-in- duced cross-linking of phenolic films. * To whom correspondence should be addressed. 'Current address: Hoechst AG Corporate h e a r c h , Frankfurt am Main, Germany. Scheme I. Negative Tone Dry Develop Process 1 Expose 2 Bake 3 Silyate 4 02RIE Ph3SAsF6 - H+AsF~ + others OH O-SiR3 Poly-s~R~ + Si02 Poly-H 4 CO,, H20 One can also obtain negative tone, dry-developable systems based on altering the diffusion rate of a phenolic (1) Taylor, G. N.; Wolf, T. M.; Stillwagon, L. E. Solid State Technol. (2) MacDonald, S. A.: Ito, H.; Willson. C. G. Microelectron. E m . 1983. 1984, Feb, 145-155. I 1, 269-293. (3) Labadie, J. W.; MacDonald, S. A.; Willson, C. G. zyx J. Img. Sci. 1986, 30, 169-173. (4) Fujioka, H.; Nakajima, H.; Kishimura, S.; Nagata, H. Advances in Resist Technology and Processing VII. Proc. SPIE 1990,1262, 554-563. (5) Nalamaau, 0.; Baiocchi, F. A.; Taylor, G. N. In Polymers in Mi- crolithography: Materials and Processes; ACS Symposium Series, No. 412; Reichmanis, E., MacDonald, S. A., Iwayanagi, T., Eds.; American Chemical Society: Washington, DC, 1989 pp 189-209. (6) Taylor, G. N.; Stillwagon, L. E.; Venkatesan, T. J. Electrochem. SOC. 1984,131, 1658-1664. (7) Wolf, T. M.; Taylor, G. N.; Venkatesan, T.; Kraetach, R. T. J. Electrochem. SOC. 1984, 131, 1664-1670. (8) MacDonald, S. A.; Ito, H.; Hiraoka, H.; Willson, C. G. Proceedings of SPE Regionul Technical Conference; Mid-Hudson Section, Society of Plastic Engineers: Ellenville, NY, 1985; pp 177-196. (9) Yoshida, Y.; Fujioka, H.; Nakajima, H.; Kishimura, S.; Nagata, H. J. Photopolym. Sci. Technol. 1991, 4, 497-507. (10) FrBchet, J. M. J.; Fahey, J.; Lee, S. M.; Matuszczak, S.; Shac- ham-Diamand, Y.; MacDonald, S. A.; Willson, C. G. J. Photopolym. zy Sci. Technol. 1992,5, 17-30. (11) Schellekens, J. P. W.; Visser, R.-J. Advances in Resist Technology and Processing VI. Proc. SPIE 1989, 1086, 220-228. (12) Thackeray, J. W.; Bohland, J. F.; Pavelechek, E. K.; Orsula, G. W.; McCullough, A. W.; Jones, S. K.; Bobbio, S. M. Dry Processing for Submicrometer Lithography. Proc. SPIE 1989, 1185, 2-11. (13) Hartney, M. A.; Johnson, D. W.; Spencer, A. C. Advances in Resist Technology and Processing VIII. Roc. SPIE 1991,1466, 238-247. 0897-4756/92/2804-1364$03.00/0 0 1992 American Chemical Society