Silylating Reagents with High Silicon Contents for Dry-Developed Positive-Tone Resists for Extreme-UV (13.5 nm) and Deep-UV (248 nm) Microlithography

Abstract

Recent results in the use of disilanes as silylating reagents for near-surface imaging with deep-UV (248 nm) and EUV (13.5 nm) lithography are reported. A relatively thin imaging layer of a photo-cross-linking resist is spun over a thicker layer of hard-baked resist that functions as a planarizing layer and antireflective coating. Photoinduced acid generation and subsequent heating crosslinks and renders exposed areas impermeable to an aminodisilane that reacts with the unexposed regions. Subsequent silylation and reactive ion etching afford a positive-tone image. The use of disilanes introduces a higher concentration of silicon into the polymer than is possible with silicon reagents that incorporate only one silicon atom per reactive site. The higher silicon content in the silylated polymer increases etching selectivity between exposed and unexposed regions and thereby increases the contrast. Additional improvements that help to minimize flow during silylation are also discussed, including the addition of bifunctional disilanes. We have resolved high aspect ratio, very high quality 0.20 μm line and space patterns at 248 nm with a stepper having a numerical aperture (NA)= 0.53, and have resolved ≤ 0.15 μm line and spaces at 13.5 nm.Design rules for microlithography are moving into the sub 0.35 μm regime. This generates more stringent requirements for the entire lithographic process. Deep UV (248 nm) lithography has demonstrated the ability to print sub 0.35 μm features. However, deep UV lithography at 248 nm will probably be unable to meet the design rules that are expected to be needed at the turn of the century. To meet these needs, exposure tools will probably employ shorter wavelength radiations. Extreme ultraviolet lithography, EUVL, at 13.5 nm has demonstrated the capability to print very fine features, and it is predicted that the trend to shorter wavelengths will eventually employ 13.5 nm radiation about the year 2010. Unfortunately, radiation at 0097-6156/96/062O-O399$12.00/0