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

本研究旨在开发低损伤无掩模三维微结构制作技术。我们首先制造了一个低能聚焦离子束系统，它能产生低能量(&lt；100 eV)、亚微米聚焦离子束。在100pA的电流强度下，根据观察到的金属网图像的分辨率，估计束斑尺寸为&lt；500 nm。这一光斑大小与用Munro程序进行的光学模拟所估计的光斑大小基本一致。光学模拟也被用来估计空间电荷展宽的影响。这预示着，即使在100 eV的能量下，这种影响也几乎可以忽略不计。为了发展加工技术，我们研究了离子束辅助刻蚀(IBAE)、真空光刻和离子束辅助沉积(IBAD)技术。在刻蚀方面，用IBAD刻蚀了砷化镓晶片。我们通过光致发光测量观察到，低能量的IBAE能显著降低损伤。在脉冲辐照下观察到了很高的刻蚀速率(~gt；500个原子/离子)，并用速率方程模型对结果进行了解释。结果表明，采用低能聚焦离子束的真空光刻技术进一步降低了形成图案所需的剂量，并有效地减少了损伤引入。W金属沉积在GaAs面上，并通过制作的W/GaAs接触的肖特基特性来估计其损伤。形成了势垒高度为0.8 eV，理想因子为1.2的接触，所有这些观察结果表明，低能聚焦离子束有望在低损伤、无掩模的三维微结构制造中发挥作用。

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.