Development of Low-Damage, Maskless 3-Dimensional microstructure Fabrication Technology

本研究旨在发展低损伤无掩模三维微结构制造技术。我们首先制造了一种低能量聚焦离子束系统，可以产生低能量（<100eV）的亚微米聚焦离子束。根据观察到的金属网图像分辨率，在电流强度为100pA时，估计光束光斑尺寸小于500nm。该光斑大小与使用Munro PROGRAM进行的光学模拟估计的光斑大小几乎一致。通过光学模拟来估计空间电荷展宽的影响。这表明，即使在100eV的能量下，这种效应几乎可以忽略不计。对于加工技术的发展，我们研究了离子束辅助蚀刻（IBAE），真空光刻和离子束辅助沉积（IBAD）技术。蚀刻采用IBAD蚀刻GaAs晶片。通过光致发光测量，我们观察到低能IBAE明显减轻了损伤。通过脉冲辐照观察到很高的蚀刻速率（bbb500原子/离子），并用速率方程模型解释了这一结果。结果表明，利用低能量聚焦离子束的真空光刻技术进一步降低了砷化镓图像化所需的剂量，有效地减少了损伤的引入。在GaAs表面进行了W金属沉积，并利用制备的W/GaAs触点的肖特基特性估计了GaAs中的损伤。实验结果表明，低能量聚焦离子束在低损伤、无掩膜的三维微结构制备中具有良好的应用前景。

The present research aims to develop low damage maskless 3-dimensional microstructure fabrication technology. We first fabricated a low energy focused ion beam system which produces low energy (<100eV), submicron focused ion beams. The beam spot size was estimated to be <500nm from the resolution of observed metal mesh images at a current intensity of 100pA. This spot size is nearly in agreement with that estimated by optics simulation performed using Munro PROGRAM. Optics simulation was also performed to estimate the effect of space charge broadening. This predicts that the effect is almost negligible even at an energy of 100eV. FOr the development of processing technology, we investigated ion beam assisted etching(IBAE), vacuum lithography and ion beam assisted deposition(IBAD) techniques. For the etching, GaAs wafers were etched by IBAD. We observed by photoluminescence measurement that damage is significantly reduced by low energy IBAE. Very high etching rate(>500atoms/ion) was observed by pulse irradiation and the results was explained by a rate equation model. It was shown that vacuum lithography technique using low energy focused ion beams reduced required dose for patterning GaAs further and effective to reduce damage introduction. W metal deposition was performed on GaAs surface and damage in GaAs was estimated by Schottky characteristics of fabricated W/GaAs contacts. Contacts with a barrier height of 0.8eV and ideality factor of 1.2 was formed, All the observed results suggest that low energy focused ion beams are promising for low damage, maskless 3-dimensional microstructure fabrication.