Development of AFM-SEM Coupled Lithography for Fabricating Nano Optical Devices

近年来，纳米结构光学器件的发展在光电子领域受到广泛关注。这是由于量子点的基本物理研究，它在某种意义上是人造原子。实现极低阈值半导体激光器和量子化亚微米光器件及其用于光并行互连和并行光信息处理的集成将是这些活动的另一个因素。本课题提出了原子力显微镜（AFM）与扫描电子显微镜（SEM）相结合的光刻新技术。AFM覆盖的范围为mn - tpm，而SEM覆盖的范围为μm - mm。由于两者都具有探测表面的能力，因此两种方法的图案对齐将很容易，并且将覆盖较宽的动态范围。本课题的主要成果是：开发了扫描电子束直接刻写碳膜的方法，该方法可以直接用原子力显微镜刻印。这种无光刻胶的工艺可以在空气中也可以在真空中应用。通过理论建模研究限制空间分辨率的因素，可以将分辨率提高到~ 25nm。随着使用最新的尖锐悬臂尖，分辨率可以进一步提高。本文提出了基于碳膜的选择性生长方法，可以实现密度为1z10^<10> cm^<-2>的CdS/ZbMgCdS量子点的有序排列。

The development of nano-structure optical devices has attractedmuch attentionrecently in optoelectronic applications. This is due to the basic physical studies of quantum dots, which are in a sense artificial atoms. The other factors for these activities will be the realization of semiconductor lasers with extremely low threshold and the quantized sub-micron optical devices and their integrations for optical parallel interconnects and parallel optical information processings. in this project, we have proposed the new lithography technique by the combination of atomic force microscope(AFM)and scanning electron microscope(SEM). AFM covers the range of mn tpm, while SEM covers the range of μm to mm. Since both have the capability to probe the surface, the alignment of the patterning with the two method will be easy and will cover the wide dynamic range.The main outcome of this project is as follows : The direct writing of carbonaceous masks with scanning electron beams was developed, which could be directly pattern with the AFM lithography. This photoresist free process can be applied in air as well as in vacuum. By the studies of the factors which limit the spatial resolution with a theoretical modeling, the resolution could be improved up to〜25nm. With the use of the up-to date sharp cantilevertips, the resolution can be further improved. The selective growth method based on the carbonaceous masks was newly developed and ordered array of CdS/ZbMgCdS quantum dots with the very high density of 1z10^<10> cm^<-2> could be realized with this new method.