氫與氯共存於矽表面上之原子動態研究

Abstract

在矽半導體製程技術中，經常使用SiH4、SiH2Cl2、SiHCl3、SiCl4等氣體來成長Si與SiO2介電質薄膜於Si表面上。在薄膜成長過程中，H2、 HCl與SiCl2等分子為Si表面在不同加熱溫度範圍下的產物，而對於了解H原子與Cl原子共存於Si表面上時的原子擴散、自我組裝與熱反應等研究是重要的。 本論文為探討氫與氯共存於Si(100)-2´1表面上之原子動態研究。我們於樣品表面上先後曝氣H2氣體與Cl2氣體，或以直接曝氣HCl氣體之方式，使得H原子與Cl原子共存於Si(100)-2´1表面上。前者曝氣方式在樣品表面上的H原子與Cl原子覆蓋率為可控制的，並且在樣品表面上產生較多的H-Si-Si-H鍵結與Cl-Si-Si-Cl鍵結。後者曝氣方式在樣品表面上的H原子與Cl原子覆蓋率約各為0.5 ML，室溫下樣品表面上的H原子與Cl原子為隨機分佈，於樣品表面上產生H-Si-Si-H鍵結、Cl-Si-Si-Cl鍵結與H-Si-Si-Cl鍵結。接著我們藉由控制加熱H、Cl/Si(100)與HCl/Si(100)兩種樣品之溫度，以掃描穿隧顯微術 (Scanning Tunneling Microscopy, STM) 來拍攝實空間下，H原子與Cl原子在不同加熱溫度範圍下，同時在樣品表面上的移動、排列演化情形。實驗結果顯示，在我們加熱樣品 (580K至650K) 達到熱平衡後，樣品表面上的H原子與Cl原子產生相互交換移動，傾向各自相聚一起，而不是在樣品表面上均勻擴散分佈。

In the Si-based semiconductor industry, SiH4, SiH2Cl2, SiHCl3 and SiCl4 are frequently used to grow silicon and SiO2 dielectric thin films. During the film growth, the H2, HCl and SiCl2 molecules are all among the desorption products at different temperature range. Therefore, the detailed understanding of atomic diffusion, self organization, and reactions occurred on the silicon surface with the hydrogen and chlorine coexistence are of technological importance. This work investigated dynamics and kinetics of the H, Cl/Si(100) and HCl/Si(100) surfaces. To obtain the H- and Cl-covered surface, hydrogen and chlorine were exposed to the clean Si(100) surface sequentially. In this way, the ratio of the hydrogen and chlorine on the surface can be controlled and produced initially more H-Si-Si-H and Cl-Si-Si-Cl species. Alternatively HCl molecules were directly applied. In this case, the amount of hydrogen and chlorine are both fixed at about 0.5 ML. At room temperature, hydrogen and chlorine appear randomly dispersed on the surface in the forms of H-Si-Si-H, Cl-Si-Si-Cl and H-Si-Si-Cl species. Then, we heated the H, Cl/Si(100) and HCl/Si(100) surfaces to various temperatures and applied scanning tunneling microscopy (STM) to observe in real space the evolution of the morphology and atomic arrangement on the surface. Our measurement showed that hydrogen and chlorine move around on the surface between 580K and 650K and coalesce into small 2D hydrogen and chlorine islands, respectively. That is, the two kinds of atoms do not distribute randomly on the Si(100) surface at near thermal equilibrium conditions.