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

我们研制了一套高性能的中性束系统。首次利用负离子实现了高中和效率和高通量。利用Nb系统建立了50 nm宽的金属氧化物半导体(MOS)栅刻蚀工艺。中性束刻蚀MOS电容器的氧化物漏电流比传统的等离子体刻蚀低一个数量级。利用Nb系统实现了一种高选择性、低损伤的多孔甲基倍半硅氧烷(多孔MSQ，k-2.2)薄膜的大马士革工艺。使用SF_6或CF_4中性束可以刻蚀多孔MSQ，其对光致抗蚀剂的选择性比在常规等离子体中获得的选择性更高。这被认为是因为中性光束消除了紫外光的照射，从而增强了抗蚀剂的刻蚀。脉冲时间调制的N2Nb被用来形成超薄的氧氮化物膜。利用脉冲N2Nb，有效地形成了SiO-N键，并在2 nm薄的SiO_2薄膜中形成了更浅、更锐利、更高密度的N浓度分布。利用Nb系统成功地制作了侧壁无损伤的鳍片型垂直MOSFET。与传统的反应离子刻蚀相比，制备的FinFET实现了更高的电子迁移率。迁移率的提高很好地解释了原子平坦的表面。我们使用低能量的中性束和铁蛋白铁核掩模制备了纳米柱结构。铁蛋白中的铁核直径为7 nm，与蚀刻的纳米柱相同。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无损刻蚀和表面改性。这项技术是未来纳米器件实用化制造技术的一个很有前途的候选者。

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.