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

纳米结构光学器件的发展近年来在光电子应用领域引起了广泛的关注。这是由于量子点的基本物理研究，量子点在某种意义上是人造原子。这些活动的其他因素将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及其集成，用于光学并行互连和并行光学信息处理。在本计画中，我们将原子力显微镜（AFM）与扫描电子显微镜（SEM）结合，提出一种新的微影技术。原子力显微镜（AFM）的探测范围为mn tpm，而扫描电镜（SEM）的探测范围为μm ~ mm。由于AFM和SEM都具有探测表面的能力，因此，这两种方法的图形对准将是容易的，并且将覆盖宽的动态范围。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，可以直接用AFM光刻法进行图形化。这种无光致抗蚀剂工艺可以在空气中以及在真空中应用。通过对影响空间分辨率的因素进行理论建模，可以将空间分辨率提高到~ 25 nm。使用最新的锐利的摄像头，分辨率可以进一步提高。提出了一种基于碳质掩模的选择性生长方法，利用该方法可以实现CdS/ZbMgCdS量子点的高密度有序阵列<10><-2>。

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.