We have observed net optical gain by current injections to ultra-thin Si embedded in a resonant optical cavity. The cavity consists of a dielectric waveguide fabricated by CMOS and MEMS process. The photoluminescence (PL) spectra show narrow resonances peaked at the designed wavelength, and the electroluminescence (EL) intensity increases super-linearly with currents. The comparisons with first principle calculations suggest that the optical gain is originated from intrinsic material properties of ultra-thin Si due to quantum confinements.

We describe the observation of stimulated emissions by current injections into a silicon quantum well. The device consists of a free standing membrane with a distributed feedback resonant cavity fabricated by state-of-the-art silicon processes. The emission spectra have multimode structures peaked in the near-infrared region above the submilliampere threshold currents at room temperatures. Consequently, electronics and photonics should be able to be converged on chips by using silicon quantum well laser diodes.

Guided by the paper [10] by Polyakov and Rychkov, we compute the second variational derivative of a wavy plane Wilson surface observable, to find that a necessary condition for a proposed surface equation to be satisfied in the large-N limit is that we are in the critical dimension D = 6.

Molecular weight distribution effects of novolak resin-based chemical amplification negative resist systems are investigated for electron-beam lithography. The resist systems investigated consist of onium salts as an acid generator, a methoxymethyl melamine crosslinker, and a conventional/fractionated novolak resin matrix. Delineated patterns of both types of resist systems are compared to evaluate submicron-scale resolution. The conventional novolak resin-based system shows higher contrast than the fractionated one. High aspect ratio patterns are resolved for the conventional novolak-based resist, whereas poor results are obtained for the fractionated resin-based one on the submicron scale. Very thin films (30 nm) of both resist systems are delineated with a finely focused electron beam (diameter: approximately 2 nm at 5 kV) from a scanning electron microscope. Nanometer-scale edge roughness (nanoedge roughness) is observed for the conventional novolak resin-based resist. On the contrary, the degree of nanoedge roughness is greatly reduced for the fractionated one.

A positive chemical amplification resist system has been developed for 50 kV electron-beam direct-writing lithography. This resist consists of a meta-cresol/para-cresol novolak resin, tetrahydropyranyl-protected polyvinylphenol (THP-M) as a polymeric dissolution inhibitor, and tri(methanesulfonyloxy)benzene (MeSB) as an acid generator. Radiation-induced hydrolysis of MeSB in the novolak resin matrix was confirmed to yield methanesulfonic acid and phenol derivatives by using gel-permeation and high-performance liquid chromatography. The catalytic chain length of THP-M deprotection was estimated to be approximately 300 in the matrix. It was found that the compatibility of a polymeric dissolution inhibitor with a novolak matrix relates to their polarity characteristics, and that the increase of para-cresol ratio in the novolak matrix can enhance the compatibility with THP-M and dissolution-inhibition capability of the composition. The optimized composition and process of the resist system achieved high aspect ratio patterns (0.3-μm contact holes/1.6-μm thickness) with high sensitivity (3.5 μC/cm2 at 50 kV).

This paper deals with an acid-catalyzed reaction mechanism of a polymeric dissolution inhibitor of a novolak-resin-based positive chemical amplification resist system. This resist system consists of a novolak matrix resin, tri(methanesulfonyloxy)benzene as an acid generator, and tetrahydropyranyl-protected polyvinylphenol (THP-M) as a polymeric dissolution inhibitor. The acid-catalyzed deprotection products of THP-M in the resist film are detected and their subsequent acid-catalyzed reactivities are evaluated. It is found that tetrahydropyranyl group are exchanged between THP-M and the matrix to yield a strong dissolution inhibitor, causing negative tone behavior at the overexposure dose. High-resolution patterns (0.3-µm contact holes) are achieved with high sensitivity (2.4 µC/cm2 at 50 kV).

A new chemical amplification positive resist system designed for nanofabrication electron-beam lithography is described. The positive resist system consists of an acidgenerator and an acid-breakable (AB) resin that can be converted to polyphenol fragments by an acid-catalyzed reaction. The AB resin is synthesized through a co-condensation reaction between polyphenol and aromatic multi-functional vinylether compounds (bisvinylether and trisvinylether compounds). Molecular weight (MW) of the AB resin increases with an increase in the vinylether feed ratio. A condensation reaction with a polyphenol/vinylether feed ratio of 100/50 results in a high MW (Mw>5000) AB resin which is insoluble in an alkali developer (tetramethylammonium hydroxide: 2.38 wt%). The acid-catalyzed fragmentation of the AB resin in the resist film was confirmed through gel permeation chromatography. The resist with the AB resin showed the high resolution of 80-nm line-and-space patterns with high sensitivity (5.0 µC/cm2 at 30 kV).

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