Field emission devices are promising candidates to replace silicon FinFETs as nextgeneration nanoelectronic components. For these devices to be adopted, nanoscale field emitters with nanoscale gaps between them need to be fabricated, requiring the transfer of e.g. sub-10 nm patterns with sub-20 nm pitch into substrates like silicon and tungsten. New resist materials must therefore be developed that exhibit the properties of sub-10 nm resolution and high dry etch resistance. A negative tone, metal-organic resist is presented here. It can be patterned to produce sub-10 nm features when exposed with helium ion beam lithography at line doses on the order of 10s of pC/cm. The resist was used to create 5 nm wide, continuous, discrete lines spaced on a 16 nm pitch in silicon, and 6 nm wide lines on 18 nm pitch in tungsten, with line edge roughness of 3 nm. After the lithographic exposure, the resist demonstrates high resistance to silicon and tungsten dry etch conditions (SF 6 and C 4 F 8 plasma), allowing the pattern to be transferred into the underlying substrates. The resist's etch selectivity for silicon and tungsten was measured to be 6.2:1 and 5.6:1, respectively; this allowed 3-4 nm thick resist films to yield structures that were 21 and 19 nm tall, respectively, while both maintained sub-10 nm width on sub-20 nm pitch.
A new class of electron bean negative tone resist materials has been developed based on heterometallic rings. The initial resist performance demonstrates a resolution of 15 nm half‐pitch but at the expense of a low sensitivity. To improve sensitivity a 3D Monte Carlo simulation is used that utilizes a secondary and Auger electron generation model. The simulation suggests that the sensitivity can be dramatically improved while maintaining high resolution by incorporating appropriate chemical functionality around the metal–organic core. The new resists designs based on the simulation have the increased sensitivity expected and illustrate the value of the simulation approach.
An
approach is presented for nanoscale patterning of zinc oxide
(ZnO) using electron beam (e-beam) lithography for future nanoelectronic
devices and for hard lithographic masks. Zinc acetate (Zn4O(CH3COO)6) films were exposed using a scanning
electron microscope (SEM), causing decomposition of Zn4O(CH3COO)6 into ZnO. The exposure of Zn4O(CH3COO)6 using an electron beam was
successfully utilized to fabricate 12 nm zinc oxide lines with a 40
nm pitch on silicon. The chemical composition of zinc acetate (film
before e-beam exposure) and ZnO (film after e-beam exposure) was investigated
using X-ray spectroscopy (XPS). The Zn 2p shift peaks and the O 1s
contribution confirmed the decomposition of zinc acetate into zinc
oxide after exposure. To confirm this transformation into ZnO, the
optical band gap of the film was determined and the electrical resistivity
of the film was measured. The electrical resistivity and the optical
band gap results revealed the transformation into a ZnO film with
a band gap of 3.31 eV at room temperature and an electrical resistivity
of 91.5 Ω cm. The ZnO patterns were used as a hard mask to etch
silicon, and it showed a good selectivity of 27:1 for dry etching
silicon using SF6 and C4F8.
A new class of resist materials has been developed that is based on a family of heterometallic rings. The work is founded on a Monte Carlo simulation that utilizes a secondary and Auger electron generation model to design resist materials for high resolution electron beam lithography. The resist reduces the scattering of incident electrons to obtain line structures that have a width of 15 nm on a 40 nm pitch. This comes at the expense of lowering the sensitivity of the resist, which results in the need for large exposure doses. Low sensitivity can be dramatically improved by incorporating appropriate functional alkene groups around the metal-organic core, for example by replacing the pivalate component with a methacrylate molecule. This increases the resist sensitivity by a factor of 22.6 and demonstrates strong agreement between the Monte Carlo simulation and the experimental results. After the exposure and development processes, what remains of the resist material is a metal-oxide that is extremely resistant to silicon dry etch conditions; the etch selectivity has been measured to be 61:1.
A new resist material for electron beam lithography has been created that is based on a supramolecular assembly. Initial studies revealed that with this supramolecular approach, high‐resolution structures can be written that show unprecedented selectivity when exposed to etching conditions involving plasmas.
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