Raman spectra of n-type gallium nitride with different carrier concentrations have been measured. The LO phonon band shifted towards the high-frequency side and broadened with an increase in carrier concentration. Results showed that the LO phonon was coupled to the overdamped plasmon in gallium nitride. The carrier concentrations and damping constants were determined by line-shape fitting of the coupled modes and compared to values obtained from Hall measurements. The carrier concentrations obtained from the two methods agree well. As a result, the dominant scattering mechanisms in gallium nitride are deformation-potential and electro-optic mechanisms.

The radiation-induced reactions of onium salts in some kinds of solutions and model compound solutions of chemically amplified electron beam (EB) and X-ray resists have been studied by means of picosecond and nanosecond pulse radiolysis. The following reaction mechanisms of the chemically amplified EB and X-ray resists have been elucidated. The radiation-induced reaction mechanisms are complicated due to the presence of several proton donors. The onium salts directly produce small amounts of Brønsted acids by EB and X-ray exposure and most of the Brønsted acids are formed from proton adducts of the base polymer. The onium salts are strong electron scavengers and promote the generation of the proton adducts in the chemically amplified resists.

The proton dynamics of poly(4-hydroxystyrene) (PHS) films were investigated using Coumarin 6 (C6). The acid density was 0.022 nm À3 at the exposure dose of 10 mC cm À2 (75 keV electron beam). The absorption intensity of C6 proton adducts was saturated at a certain concentration of C6, indicating an almost complete addition of protons at this C6 concentration. Protons can move in PHS films near C6 molecules even at room temperature. Also, the absorbed dose was estimated using 60 Corays. The acid yield can be well explained by an acid generation model involving the ionization of a base polymer.

Extreme ultraviolet (EUV) lithography is promising for the high-volume production of semiconductor devices for the 16 nm node and below. However, the stochastic effect is a significant concern in lithography using high-energy (92.5 eV) photons and highly sensitive resists. In this study, we report a technique for evaluating the stochastic effect on line edge roughness (LER). Resist patterns were analyzed using a Monte Carlo simulation on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. The contribution of protected unit fluctuation to LER was estimated to be ±0.31 to ±0.37σ.