Using doubly-clamped silicon (Si) microbeam resonators, we demonstrate sub-attogram per Hertz (ag/Hz) mass sensitivity, which is extremely high sensitivity achieved by micro-scale MEMS mass sensors. We also characterize unusual buckling phenomena of the resonators. The thin-film based resonator is composed of a Si microbeam surrounded by silicon nitride (SiN) anchors, which significantly improve performance by providing fixation on the microbeam and stabilizing oscillating motion. Here, we introduce two fabrication techniques to further improve the mass sensitivity. First, we minimize surface stress by depositing a sacrificial SiN layer, which prevents damage on the Si microbeam. Second, we modify anchor structure to find optimal design that allows the microbeam to oscillate in quasi-one dimensional mode while achieving high quality factor. Mass loading is conducted by depositing Au/Ti thin films on the local area of the microbeam surface. Using sequential mass loading, we test effects of changing beam dimensions, position of mass loading, and distribution of a metal film on the mass sensitivity. In addition, we demonstrate that microbeams suffer local micro-buckling and global buckling by excessive mass loading, which are induced by two different mechanisms. We also find that the critical buckling length is increased by additional support from the anchors.
A material approach to fabricating high-performance nonstick molds for manufacturing ultrahighresolution features (<8 nm) is presented. Low-viscosity liquid blends (4-121 cP) consisting of siliconized silsesquioxane acrylate (Si-SSQA) with low surface energy and difunctional acrylics were used as nonstick replica-mold materials. The cured Si-SSQA-acrylic networks showed a high UV transparency (>92% at 365 nm), high modulus and wide-range modulus tunability (0.757-4.192 GPa), high resistance to organic solvents (<1.2 wt%), low shrinkage (<3%), and high water contact angle (91-103 ). The Si-SSQA-acrylic blends with a nonstick property were easily transferred to high-resolution replica molds with sub-25 nm features, a pitch of 25 nm and a height of 100 nm, even if the release agent was not modified onto the master. In addition, nonstick replica molds with a low concentration of uncross-linked (meth)acrylate showed the ability to duplicate ultrasmall nanostructures with a sub-8 nm parallel line, a pitch of 17 nm and a height of 6-7 nm. Furthermore, the Si-SSQA-based replica mold prevented the formation of bubble defects during imprinting owing to sufficient gas permeability.
A chip-scale optical link system is presented with a transmitter/receiver and optical wire link. The interchip link system consists of a metal optical bench, a printed circuit board module, a driver/receiver integrated circuit, a vertical cavity surface-emitting laser/photodiode array, and an optical wire link composed of plastic optical fibers (POFs). We have developed a downsized POF and an optical wiring method that allows on-site installation with a simple annealing as optical wiring technologies for achieving high-density optical interchip interconnection within such devices. Successful data transfer measurements are presented.
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