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学领域引起了极大的关注。这归功于对量子点的基本物理研究，量子点在某种意义上是人造原子。这些活动的另一个因素是实现极低阈值的半导体激光器和量子化的亚微米光学器件，以及它们用于光学并行互连和并行光学信息处理的集成。在本项目中，我们提出了原子力显微镜(AFM)和扫描电子显微镜(SEM)相结合的新的光刻技术。原子力显微镜覆盖了MnTPM的范围，扫描电子显微镜覆盖了μm到mm的范围。由于两种方法都具有探测表面的能力，两种方法的图形对准容易，覆盖的动态范围很大。本项目的主要成果如下：开发了扫描电子束直接写入碳质掩模的方法，可以用AFM光刻直接形成图形。这种无光刻胶工艺既可以在空气中应用，也可以在真空中应用。通过理论模型对限制空间分辨率的因素进行研究，可以将分辨率提高到~25 nm。使用最新的尖锐悬臂尖端，分辨率可以进一步提高。基于碳素掩膜的选择性生长方法是最新发展起来的，用这种方法可以实现密度为1z10^&lt；10&gt；cm^&lt；-2&gt；的有序的CdS/ZbMgCdS量子点阵列。

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.