Development of molding process to reproduce micro-structures of 100 nm pitch at a wide area of 100 mm - side square

本研究的目的是为一种新型光学元件开发一种新的成型工艺，在100mm边长的正方形上再现100nm间距的微结构。为了实现这一目标，本研究实施了三个项目：(a)局部控制成型过程，(b)精确制造模具表面的微观结构，以及(c)光学元件的原型制作。(a)在注塑或热压等成型过程中控制模具表面的温度和热流密度以及腔内再生材料的压力。结果表明，当表面温度保持在玻璃化转化温度（Tg）以上时，在模具与再生材料第一次接触后的一秒钟内，微观结构可以再生，而再生材料的压力即使在几个MPa下也可能很低。(b)在玻璃热压陶瓷模具的SiC材料上采用电子束光刻和快速原子束（FAB）蚀刻，在塑料注塑或热压金属模具的镀镍材料上采用聚焦离子束（FIB）弯曲制备微结构。而闲置的方槽在陶瓷模具上经FAB刻蚀后形成梯形槽，在金属模具上经FIB弯曲后形成圆底槽。(c)像线和空间光栅这样的光学元件被原型化：一个槽上有金属线的偏振光板，或者一个只有特殊光线透明的彩色滤光片，因为每个间距都是为特殊光线设计的。他们可以用麦克斯韦方程模拟光学性能。

The purpose of this research is to develop a new molding process to reproduce micro-structures of 100nm pitch on a wide area of 100mm-side square for a new optical element. To realize the purpose, the research executed the three projects : (a)locally controlling the molding process, (b)precisely fabricating the micro-structures on the mold surface, and (c)prototyping the optical element. (a)The surface temperature and heat flux on the mold surface and the pressure of the reproduced material in a cavity ware controlled in the molding process like injection molding or hot pressing. In result, we revealed that the micro-structures could be reproduced when the surface temperature should be hold at the glass transformed temperature (Tg)and more during only one second just after the first contact between the mold and the reproduced material, while the pressure of the reproduced material might be low even at several MPa. (b)The micro-structures were fabricated using electron beam lithography and fast atom beam (FAB)etching on the SiC material of a ceramics mold for glass hot pressing, and focus ion beam (FIB)curving on the Ni plated material of a metal mold for plastic injection molding or hot pressing. The idle square groove, however, was made as a trapezoid groove on the ceramics mold after FAB etching, or a round bottom groove on the metal mold after FIB curving. (c)The optical elements like a line ＆ space grating were prototyped : a polarized plate with metal lines on the groove, or a color filter where only special lights are transparent because the each pitch is designed for the special light. They could realize the optical performance as simulated using the Maxwell equation.