Current lithographic resists depend on large polymeric materials, which are starting to limit further improvements in line-width roughness and feature size. Fullerene molecular resists use much smaller molecules to avoid this problem. However, such resists have poor radiation sensitivity. Chemical amplification of a fullerene derivative using an epoxy crosslinker and a photoacid generator is demonstrated. The sensitivity of the material is increased by two orders of magnitude, and 20-nm line widths are patterned.

Current resist materials cannot simultaneously meet the sensitivity, resolution and line width roughness (LWR) requirements set out by the International Technology Roadmap for Semiconductors (ITRS) for the 32nm node and beyond. Here we present a fullerene‐based, chemically amplified resist system, which demonstrates the potential to fulfill these requirements for next generation lithography. A chemically amplified fullerene resist was prepared, consisting of the derivative MF07‐01, an epoxide crosslinker, and a photoacid generator, such as triarylsulfonium hexafluoroantimonate. The sensitivity of this resist was shown to be between 5 and 10 µC cm−2 at 20 keV for various combinations of post‐application bake and post‐exposure bake conditions. Using 30 keV electron beam exposure, sparse patterns with 15 nm resolution were demonstrated, whilst for dense patterns a half‐pitch of 25 nm could be achieved. The LWR for the densely patterned features is ∼4 nm. The etch durability of the fullerene CA system was shown to be comparable to that of SAL601, a common novolac‐based commercial resist, at almost four times that of silicon.

Since the discovery of C 60 , [1] attempts to utilize the unique properties of fullerene molecules have been widespread. [2] One field of particular interest is the potential use of novel fullerene-based materials within the semiconductor industry, [3] where the interplay between new materials and new technologies is always of vital importance. Two such emerging technologies proposed for next-generation lithography are arrayed microcolumns [4] and multiple electron-beam (ebeam) systems, [5] both of which have recently shown promise. [6] In the former, multiple electron guns are used to create an array of individually controlled beams, while the latter uses a single large beam split by an aperture plate into many concurrently controlled beams. In each case a massive parallelization of the system should allow greatly enhanced patterning speeds. As these technologies will most likely operate in the low ebeam energy regime (below 5 keV), the requirement for high-resolution resists suitable for low energies is becoming increasingly important. Significantly, because low-energy electrons have a dramatically reduced penetration depth, re-sists with ultrahigh etch durability become vital due to the fact that only thin films of resist can be used.C 60 itself can be used as a negative-tone e-beam resist with extremely high etch resistance. [7] However, pure C 60 films require preparation via vacuum sublimation and also need an extremely high electron dose, in the region of 12 mC cm À2 , to change the dissolution rate in organic solvents. Previous studies by Robinson and co-workers showed that films of C 60 derivatives could be cast by the more conventional spin-coating technique, while achieving an order of magnitude increase in sensitivity. [8,9] It was also shown that 20-nm features could be patterned in the resist, while maintaining an etch durability six times that of silicon (in electron cyclotron resonance (ECR) microwave plasma etching with SF 6 ). [9] Electron-beam energies of 20 to 30 keV were employed in all of this prior work. Herein, we report the performance of the multiaddend methanofullerenes MF02-01A and MF03-01 (Scheme 1) when the e-beam energy is reduced to the low-energy regime, specifically 0.2 to 5 keV. The synthesis of these derivatives will be presented elsewhere. [10] Samples of the methanofullerenes were dissolved in chloroform and deposited by spin coating on hydrogen-terminated silicon < 100 > samples, approximately 4 cm 2 in size. Sample concentrations ranged from 1 to 20 g L À1 , which resulted in film thicknesses of between 10 and 120 nm. Anisole was also found to be an effective casting solvent. The sensitivity of these resist films to e-beam irradiation at energies below 5 keV was investigated using a FEI XL30SFEG scanning electron microscope equipped with a pattern generator for lithography (Raith Elphy Quantum). The samples were exposed to various electron doses between 5 and 5000 mC cm À2 , and were then developed in a suitable solvent such as monochlorobenzene (MCB) before rinsing in i...

No abstract

This work demonstrates the patterning of thin films (approximately 25 nm) of a newly synthesized fullerene derivative by direct-write electron-beam lithography to produce highly conducting carbon microstructures. Scanning electron microscopy and atomic force microscopy are used to characterize the resulting microstructure morphology, whilst the resistivities of the structures are probed using four-point probe electrodes deposited on the microstructures by lift-off. The microstructures have a resistivity of approximately 9.5 x 10(-3) Omega cm after exposure to an electron dose of 0.1 C cm(-2). The method may have applications in the generation and electrical contacting of organic electronics, organic photovoltaics, and lab-on-a-chip devices.