利用即時掃瞄穿隧電子顯微技術研究磷在矽(100)表面上的成長

Abstract

發生在phosphine與矽(100)表面作用時所發生的吸附與脫附過程已引起廣泛的注意.然而,我們發現對於此過程的解釋仍存有一些疑點.在此論文中,我們利用即時掃瞄穿隧電子顯微技術來研究溫度介於620 K與 850 K間磷在矽(100)2 X 1表面上的吸附與解離過程,我們同時也以時間與溫度為參數來觀察phosphine連續的沉積過程.實驗資料顯示溫度在表面形態與組成上扮演極重要的角色,因此我們將資料的描述與討論分為三個溫度:620 K以下為低溫,650 K 與730 K之間為中溫,770 K與 850 K之間為高溫.我們計算在這些溫度下磷的涵蓋量並討論表面的形態與組成,我們的研究以原子解析度方式展現了磷在化學氣相沉積過程中表面形態的演化,也因此提供了其於矽(100)表面成長過程中較深入的見解.

The adsorption and desorption processes which occur during the interaction of phosphine with Si(100) surfaces have received extensive attention. However, we found that there were still some ambiguous points remaining for explanation in the process. In this thesis, we apply the real-time STM technique to study the adsorption and decomposition of phosphine on Si(100)2 x 1 surfaces at the substrate temperature between 620 K and 850 K. We also observed the continuing PH$_3$ deposition process as functions of time and temperature. From the data, temperature plays an important role on the surface morphology and surface composition. Thus, we divide the descriptions and discussions of the data into three parts based on three ranges of temperature: the temperature below 620 K as low temperature, that between 650 and 730 K as middle temperature, and that between 770 and 850 K as high temperature. At these temperatures, the P coverages were calculated and the surface morphology and composition were discussed. The main results are summarized as follows. At low temperature (620 K), the surface was covered with Si$_2$H$_2$ and short 1-D islands composed of P-P dimers. At middle temperature (650 K and 700 K), the surface morphology and composition depended on the competition between hydrogen desorption rate and PH$_3$ deposition rate. At high temperature (790 K and 850 K), for initial PH$_3$ exposure, the hydrogens desorbed from the surface upon PH$_3$ adsorption, and the P atoms exchanged with substrate Si atoms to form Si-P dimers, which annihilated the thermally-induced 2 x n structure; at high P coverage ($>$ 0.5 ML), P-P dimers formed on the surface and reapplied the compressive strain to the surface, and thus defect lines reappeared. Our study revealed the evolution of surface morphology during phosphorus CVD in atomic resolution and, thereby providing comprehensive insight into the growth processes which occur on the Si(100) surface.