Dry lithography of chemically amplified acid-catalyzed deep-UV and e-beam resist

The process, chemistry, and characterization of the silylation and dry-development of acid catalyzed resist is described. The resist is sensitive to deep-UV, x ray, and e-beam exposure and its sensitivity can be tailored by the relative concentration of its components. The resist is positive or negative for dry or wet development, respectively. Two silylation agents were studied: Hexamethyldisilazane (HMDS) and N,N-Dimethylaminotrimethylsilane (DMATMS). The silylation was characterized by Fourier-transform-infrared (FTIR) transmission spectroscopy and Rutherford-backscattering spectrometry (RBS). FTIR revealed the total number of OH and SiO bonds, while RBS revealed the composition profile in various regions of the resist. The silylation by HMDS was not well controlled and was characterized by a large incubation period followed by fast penetration. The DMATMS silylation process, however, was well controlled and reproducible. The penetration of the silicon atoms monotonically increased with time until it reached saturation. Films patterned by deep-UV (254 nm) exposure were silylated with DMATMS and were etched by an oxygen plasma in a magnetron ion etcher (MIE). The etch rate of the oxygen plasma was characterized for the unexposed, silylated regions, as well as for the exposed, unsilylated regions. The optimized dry-development process is described and SEM cross sections of lines as narrow as 0.4 micrometers wide are presented.