EUV lithography (EUVL) is a leading candidate for printing sub-32 nm hp patterns. In order for EUVL to be
commercially viable at these dimensions, a continuous evolution of the photoresist material set is required to
simultaneously meet the aggressive specifications for resolution, resist sensitivity, LWR, and outgassing rate.
Alternative PAG designs, especially if tailored for EUVL, may aid in the formation of a material set that helps
achieve these aggressive targets. We describe the preparation, characterization, and lithographic evaluation of
aryl sulfonates as non-ionic or neutral photoacid generators (PAGs) for EUVL. Full lithographic
characterization is reported for our first generation resist formulation using compound H, MAP-1H-2.5. It is
benchmarked against MAP-1P-5.0, which contains the well-known sulfonium PAG, triphenylsulfonium
triflate (compound P). Z-factor analysis indicates nZ32 = 81.4 and 16.8 respectively, indicating that our first
generation aryl sulfonate formulations require about 4.8x improvement to match the results achieved with a
model onium PAG. Improving the acid generation efficiency and use of the generated byproducts is key to
the continued optimization of this class of PAGs. To that end, we believe EI-MS fragmentation patterns and
molecular simulations can be used to understand and optimize the nature and efficiency of electron-induced
PAG fragmentation.
The introduction of 157nm lithography has raised many issues, not the least of which is the requirement of a new material for soft pellicle. At 157nm, the incident energy of 7.9 eV is enough to break any single organic bond. This makes the design of a soft pellicle material quite a challenge. Additionally, previous work in the industry has shown that improving transparency does not necessarily translate into longer pellicle lifetimes. Based on extensive investigation of how existing materials are degrading in the VUV, these new polymer systems have been produced. This study shares detailed structural information about several novel materials developed for use as soft pellicles. Additionally, data is shown for material properties including transmission and lifetime of films under 157 nm and 193 nm exposures.
The design of 157 nm photoresists is a daunting task since air, water, and most organic compounds are opaque at this wavelength. Spectroscopic studies1 led to the observation that fluorinated hydrocarbons offer the best hope for the transparency that is necessary for the design of an effective 157nm photoresist, and these classes of materials have quickly become the prominent platforms for a variety of research activities in this field. Our approach to the design of the resist polymer requires identification of a backbone that tethers the functional substituents and provides basic mechanical properties, an etch barrier that provides RIE resistance, an acidic group that permits solubility in tetramethylammonium hydroxide (TMAH) developer. Fluorocarbon polymers have been identified as promising resist candidates for 157nm material design because of their relatively high transparency at this wavelength. Numerous authors have discussed negative photoresists over the years. There are many uses for such materials at various levels in a semiconductor device. One such use is with complementary phase shift mask thus eliminating the need for a second exposure step. This paper reports our recent progress toward developing a negative 157nm resist materials based on fluoropolymers with crosslinkers that are transparent at 157nm. The authors will report on the synthesis of the polymers used in this work along with the crosslinkers and other additives used in the formulation of the photoresist. Imaging experiments at practical film thicknesses at 157nm with binary and strong phase shifting masks will be shown demonstrating imaging capabilities. Spectroscopic data demonstrating chemical mechanisms and material absorbance will be shown along with other process related information
Conference Committee Involvement (10)
Advances in Patterning Materials and Processes XLII
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