Atomic-scale Etching and Deposition using adsorbed Halogen gases on Semiconductor surfaces.

随着器件规模的缩小，最终有必要在原子水平上了解表面反应，如蚀刻和沉积过程。本研究项目旨在利用扫描隧道显微镜(STM)，在考虑反应物种的化学性质的情况下，阐明此类表面反应。取得了以下研究成果：1.阐明了Si(001)表面的电子结构。由于再成键的性质，S_B型台阶带正电荷。AlCl3和BCl3分子立即在硅表面分解，提供硅吸附原子上的氯原子。研究发现，在热处理过程中，氯原子从表面解吸，金属沉积并在表面形成超结构。在扫描隧道显微镜针尖和样品表面之间施加电压脉冲来操纵吸附在硅原子上的氯原子。通过积累数据，提出了一种可能的刻蚀机理，并与理论结果进行了比较。其机理包括近场效应修正的场蒸发。同时考虑了电子注入效应。还实现了对吸附的未破裂分子的操纵。脉冲引起分子的解离、置换和脱附。利用NH3气体分子成功地在硅表面沉积了N原子。结果形成了一层完美的SiN薄膜。硅层的刻蚀是在原子氢的帮助下完成的。提出了刻蚀机理。

With the down-scaling of devices, it would be ultimately necessary to understand surface reactions at an atomic level, such as etching and deposition processes. The present research project aims to clarify such surface reactions, taking into consideration the chemical properties of the reaction species, by use of scanning tunneling microscopy (STM). The following research results have been obtained.1. The electronic structures of the Si (001) surface have been clarified. The S_B-type step is positively charged due to the rebonding nature.2. Both AlCl_3 and BCl_3 molecules immediately break down on the silicon surface, supplying the Cl atoms on the Si adatoms. It is found that, upon annealing, Cl atoms desorb from the surface and the metal is deposited and formed a supestructure on the surface.3. The Cl atom adsorbed on the Si adatom was manipulated by voltage pulses applied between the STM tip and the sample surface. By accumulating data, a possible etching mechanism was proposed in comparison with the theoretical results. The mechanism includes field evaporation modified by near-field effect. Electron injection effect is also considered.4. Manipulation of adsorbed non-broken molecules is also realized. The pulse causes the dissociation, displacement and desorption of molecules.5. The deposition of N atoms on the silicon surface was successfully achieved using NH_3 gas molecules. As a result, a perfect SiN thin film was formed.6. The etching of the Si layr was accomplished by help of atomic hydrogen. The etching mechanism was proposed.