The blur caused by the nonzero mean free path of electrons in photoresist during extreme ultraviolet lithography has detrimental consequence on patterning resolution, but its effect is difficult to measure experimentally. In this work, a modified substrate-overlayer technique was used to evaluate the attenuation of the photoemission spectra produced in thin chemically amplified photoresist films. The inelastic mean free path of electrons was found to be between 1 to 2 nm in the entire range of interest for EUV lithography (20 to 100 eV kinetic energy). At higher kinetic energy, the mean free path increased consistently with well-known behavior. The presence of photoacid generator and quencher did not change the mean free path significantly (within experimental error).
In an effort to improve on the sensitivity of commercial nonchemically amplified e-beam resists, four polyacrylates functionalized with -CF3 and/or CH2CF3 alkoxy substituents were studied. The -CF3 substituent is known to increase backbone-scission efficiency while simultaneously eliminating acidic outgassing and cross-linking known to occur in -halogen substituted polyacrylates. Contrast curves for the polymeric -CF3 acrylates, generated through e-beam exposure, showed that the resists required an order of magnitude less dose than the current industry standards, poly(methyl methacrylate) (PMMA) and ZEP. The fundamental sensitivity of these materials to backbone scissioning was determined via 60Co -ray irradiation. The chain scissioning, G(s), and cross-linking, G(x), values calculated from the resulting change in molecular weight demonstrated that all fluorinated resists possess higher G(s) values than either PMMA or ZEP and have no detectable G(x) values. Utilizing e-beam and EUV interference lithographies, the photospeed of poly(methyl -trifluoromethacrylate) (PMTFMA) was found to be 2.8× and 4.0× faster, respectively, than PMMA.
In an effort to improve upon the sensitivity of commercial non-chemically amplified e-beam resists, four polyacrylates
functionalized with α-CF3 and/or CH2CF3 alkoxy substituents were studied. The α-CF3 substituent is known to increase
backbone-scission efficiency while simultaneously eliminating acidic out-gassing and cross-linking known to occur in α-
halogen substituted polyacrylates. Contrast curves for the polymeric α-CF3 acrylates, generated through e-beam
exposure, showed the resists required an order of magnitude less dose than the current industry-standards, PMMA and
ZEP. The fundamental sensitivity of these materials to backbone scissioning was determined via 60Co γ-ray irradiation. The chain scissioning, G(s), and cross-linking, G(x), values calculated from the resulting change in molecular weight
demonstrated that all fluorinated resists possess higher G(s) values than either PMMA or ZEP and have no detectable
G(x) values. Utilizing e-beam and EUV interference lithographies, the photospeed of PMTFMA was found to be 2.8x
and 4.0x faster, respectively, than PMMA.
Double patterning has become one of the candidates to bring us to the next node of the ITRS-roadmap. As an alternative
to immersion lithography with higher index fluids and EUV lithography which both require considerable changes in
infrastructure, double patterning makes use of the existing infrastructure. Because of this, double patterning has gained
considerable attention during the past few years. It has become a serious candidate to reach the 45 nm node and even the
32 nm node.
Most of the currently known double patterning techniques have relatively complex process flows, which may prevent
them from being used in production. One of the complicating factors is the use of an etch step in between the two
lithography steps. This etch step is necessary to transfer the pattern of the first resist layer into an underlying hard mask
before a second exposure can be done. Another complicating element, arising in several known double patterning
techniques, is the translation of overlay error in CD-error. This translation occurs when a feature is printed in two
exposures, i.e. not features but the spaces between them are patterned, patterning the left and right edge of a feature in
different exposures.
In this paper, we examine and evaluate a novel double patterning method that does not include transfer etch in between
the lithography steps. This method would simplify the double patterning process. Furthermore, each feature is patterned
completely in one exposure, for which CD-value is not affected by overlay error. This paper discusses the feasibility of
the new double patterning method and compares it to conventional double patterning schemes. Furthermore, an
assessment will be made whether the proposed technique has the potential to be used in production.
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