KEYWORDS: Extreme ultraviolet lithography, Etching, Electron beam lithography, Monte Carlo methods, Electron beams, Mercury, Silicon, Molecules, Dry etching
In this paper, we report on a novel metal organic photoresist based on heterometallic rings that was designed for electron beam and extreme ultraviolet lithography. From initial electron beam lithography studies, the resist performance demonstrated excellent resolution of 15 nm half-pitch (HP) and a silicon dry etch selectivity of 100:1 but at the expense of sensitivity. To improve sensitivity, a 3D Monte Carlo simulation was employed that utilizes a secondary electron generation model. The simulation suggested that the sensitivity could be dramatically improved while maintaining high resolution by incorporating HgCl2 species into the resist molecular design. This considerably improved the resist sensitivity without losing the high resolution, where it was determined that the resist sensitivity was increased by a factor of 1.6 and 1.94 while demonstrating a resolution of 15 nm and 16 nm HP when exposed with electrons and EUV radiation respectively. Using x-ray photoelectron spectroscopy measurements, we show that after exposure to the electron beam the resist materials are transformed into a metal oxyfluoride and this is why the resist demonstrates high resistance to silicon dry etch conditions achieving a selectivity of 60:1 at a resolution of 15 nm HP.
KEYWORDS: Extreme ultraviolet lithography, Selenium, Electron beam lithography, Monte Carlo methods, Metals, Mercury, Molecules, Chemical species, Photomicroscopy, Absorption
A new class of negative-tone resist materials has been developed for electron beam and extreme ultraviolet lithography. The resist is based on heterometallic rings. From initial electron beam lithography studies, the resist performance demonstrated a resolution of 40-nm pitch but at the expense of a low sensitivity. To improve the sensitivity, we incorporated HgCl2 and HgI2 into the resist molecular design. This dramatically improved the resist sensitivity while maintaining high resolution. This improvement was demonstrated using electron beam and extreme ultraviolet lithography.
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.
Lithographic control over nanostructures has recently evolved to an accuracy that permits the sub-wavelength manipulation of light within high refractive index semiconductors. We have used this lithographic control to fabricate two-dimensional photonic crystal cavities and micro-ring resonators. Here we will show the fabrication techniques utilized for the construction of High-Q nanocavities and, in particular, focus on the influence of present-day lithographic and etching procedures on the performance of the cavities. Applications of these optical cavities range from communications to chemical sensing and we will describe the effects of geometry on the different applications. We show the use of optical cavities for the miniaturization of optical spectroscopy systems with ultra-high spatial and spectral resolution.
We propose and analyze a new type of resonator in an annular geometry which is based on a single defect surrounded by radial Bragg reflectors on both sides. Unlike conventional, total internal reflection based ring resonators, this structure supports modal fields with very low azimuthal number (large radial k-vector component). We show that the conditions for efficient mode confinement are different from those of conventional Bragg waveguiding in a rectangular geometry. To realize tight confinement of the light in the defect, chirped gratings are required. Compared to a conventional resonator, the new resonator exhibits larger FSR and lower losses making it suitable for both telecom and sensing applications. In addition, the resonance wavelength and Q factor of the device are very sensitive to environmental changes, and thus provide ideal observables for sensing applications. Annular Bragg resonators with several unique geometries have been fabricated in an InGaAsP multi-quantum-well membrane. The spectral properties of the resonators have been investigated through analysis of photoluminescence induced by pulsed optical excitation.
We have described an approach for miniaturizing spectroscopic devices by using the advantages presented by elastomeric based microfluidics and semiconductor detectors/emitters. Elastomers allow for both absorption and fluorescent spectroscopy in the visible range to be conducted on small volumes of solution and allow for easy integration with existing detectors such as CMOS imagers, CCD imagers, and silicon photodiodes. Results of some basic experiments are presented to demonstrate the effectiveness of the system. In addition, several ideas for emission sources are also discussed with their relevance yet to be determined.
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