Nanometer-scale processing and creation of novel functional materials using low energy high flux neutral beams

我们已经开发了一个高性能的中性束（NB）系统。首次利用负离子实现了高中和效率和高通量，并建立了50 nm金属氧化物半导体（MOS）栅刻蚀工艺。采用中性束刻蚀技术刻蚀的MOS电容器的漏电流比常规等离子体刻蚀低一个数量级，实现了对多孔甲基倍半硅氧烷（porous MSQ，k-2. 2）薄膜的高选择性、低损伤刻蚀。使用SF_6或CF_4中性束能够以比在常规等离子体中可以获得的更高的对光致抗蚀剂的选择性蚀刻多孔MSQ。这被认为是因为中性束消除了紫外光的曝光，从而增强了抗蚀剂的蚀刻。采用脉冲N_2NB技术，在2nm的SiO_2薄膜中有效地形成了SiO-N键，并获得了更浅、更尖、更高的N浓度分布。所制造的FinFET实现了比使用传统的反应离子蚀刻更高的电子迁移率。原子级平坦的表面很好地解释了迁移率的提高。我们使用低能中性束和铁蛋白铁芯掩模制备了纳米柱结构。铁蛋白中的铁核直径为7 nm，这与蚀刻的纳米柱的直径相同。这表明中性束刻蚀将铁芯的结构和尺寸转移到硅衬底上。这些结果表明，NB可以对无机和有机材料进行原子级无损伤刻蚀和表面改性。该技术是未来纳米器件的实用制造技术的一个有前途的候选者。

We have developed a high-performance neutral beam (NB) system. It achieved high neutralization efficiency and high flux by utilizing negative ions for the first time.A 50-nm-width metal-oxide-semiconductor (MOS) gate etching process was established using the NB system. The oxide leakage current achieved for a MOS capacitor etched by the neutral beam was one order of magnitude lower than that achieved by conventional plasma etching.A highly selective and low-damage damascene process for porous methyl-silsesquioxane (porous MSQ, k-2.2) films has been realized using the NB system. Use of a SF_6 or CF_4 neutral beam enables etching of porous MSQ with higher selectivity to the photoresist than what can be obtained in a conventional plasma. This is considered to be because the neutral beam eliminates exposure to ultraviolet (UV) light which enhances the resist etching.Pulse-time-modulated N_2 NB was used to form ultrathin oxynitride films. SiO-N bonds were effectively formed and a shallower, sharper, and higher density N concentration profile in a thin 2 nm SiO_2 film was produced using a pulsed N_2 NB.Fin-type vertical MOSFETs with damage-less smooth sidewalls were successfully fabricated using the NB system. The fabricated FinFETs realized higher electron mobility than that using a conventional reactive ion etching. The improved mobility is well explained by the atomically-flat surface.We fabricated nanocolumn structure by using a low energy neutral beam and a ferritin iron-core mask. The iron core in the ferritin was 7 nm in diameter, which was identical to that of the etched nanocolumn. This indicates that neutral-beam etching transferred the structure and size of the iron core to the silicon substrate.These results indicate that the NB can perform atomically damage-free etching and surface modification of inorganic and organic materials. This technique is a promising candidate for the practical fabrication technology for future nano-devices.