This article presents the results of the experimental and modeling study of a positive tone, chemically amplified photoresist, in application to x-ray lithography. Spectrophotometric titration, Fourier transform infrared spectroscopy (FTIR), and development rate monitor data were acquired and used as inputs for the modeling of the processes and pattern simulations. The exposure model assumes monomolecular decomposition upon radiation and corresponds to Dill’s model for a nonbleaching photoactive compound. The post-exposure bake (PEB) model is based on formal kinetic equations which include a term for photoacid loss (or side reactions) during the post-exposure bake process in a generalized way. The effective kinetic order of the photoacid loss reaction is derived from the FTIR absorbance data obtained for different PEB times and exposure doses. For patterned exposures, a diffusion term for the local photoacid concentration is included. The photoacid and tert-butoxycarbonyloxystyrene concentration profile changes with PEB time have been simulated for a 0.25 μm line and spaces pattern. It is shown that a nonlinear PEB photoacid reaction kinetics, rather than the photoacid diffusion, dominates the linewidth decrease during PEB for the photoresist studied.

We present our effort in developing a complete model of electron energy transfer from fast electrons ͑0.1-100 keV͒ to the photoresist. Our model is based on the direct Monte Carlo method, instead of using continuous slowing down approximation, model and a stopping power curve. We separate the interaction events into four types: Elastic, ionization, excitation, and plasmon. Our results show that: First, secondary electrons are major mechanism of energy distribution; and second, plasmons are very efficient ''friction'' mechanism but do not create molecular changes; and finally, excitations lead to molecular changes.

We report on the results of our effort to extend proximity x-ray lithography (PXL) to 35 nm using a harder energy spectrum, and choosing the appropriate materials for the mask and the resist to match the transmission and absorption at higher energies. Previous studies [M. Kahn et al., J. Vac. Sci. Technol. B 17, 3426 (1999); T. Kitayama, J. Vac. Sci. Technol. B 18, 2950 (2000)] have shown that PXL is capable of printing 50 nm features, and in this study, we extend that work to show that PXL can indeed be used for 35 nm generation. We investigate the use of higher energy radiation, in conjunction with novel resist materials, to deliver the 35 nm node and provide a set of requirements to achieve that goal.

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We present an updated global model for x-ray lithography based on realistic models for image formation, demonstrating how the extendibility of x-ray lithography is well in the nanometer range. We apply these models to define the most convenient spectral range for x-ray lithography manufacturing and the parameters of mirrors and filters to be used in an optimized beam line.

To be competitive with the next-generation lithography technologies, synchrotron-based proximity x-ray lithography (PXRL) must prove to be extendible to produce minimum feature sizes of 70 nm and below. We present here a relatively simple and practical method to improve the PXRL system performance for the replication of features down to 50 nm with reasonable process latitude at large (g≈15μ) mask–wafer gaps. Contrary to previous conclusions indicating λ=1 nm as the best operating region, we find that a significant improvement can be achieved by a modest decrease in the effective wavelength of present PXRL systems, and by the use of non-silicon-based materials in beamline filters and masks. The proposed PXRL system requires a synchrotron storage ring with slightly higher energy than older rings such as Aladdin, but well within the design parameters of the newer generation of synchrotrons, and some beamline modifications. In addition, a diamond mask substrate is also utilized to eliminate the x-ray absorption due to the Si-absorption edge at 1.75 keV.

Articles you may be interested inFast, high bit number pattern generator for electron and ion beam lithographies Rev. Sci. Instrum. 79, 033902 (2008);We present our progress in developing a comprehensive stochastic model that taking into account the energy redistribution from the incoming radiation, the location of the chemical events, the type of chemical changes, and the resist development. A study of line edge roughness extracted from the simulation for 50 nm lines is discussed.

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