銻離子植入SiO2/Si 基板之擴散特性研究

Abstract

本論文探討以離子佈植法將銻離子植入矽基板及二氧化矽氧化層中，在高溫長時間熱處理下的擴散行為，以及形成n+埋層最佳活化條件。因為離子佈植會破壞矽基板表面結構，所以我們也探討不同溫度和時間的退火熱處理，對矽基板的表面缺陷以及在基板上成長磊晶層的影響。 在減少熱預算的考量下，1220℃/3hours 是形成n+埋層的最佳熱處理條件。但在此熱處理條件下，矽基板仍殘留有表面缺陷 (stacking faults)，造成後續成長的磊晶層表面粗糙。若在磊晶成長前先以HCL去除這些表面缺陷，則可得表面非常平滑的磊晶層。植入二氧化矽內的銻離子，只在靠近表面附近有明顯的擴散現象，但內部的銻離子即使在1220℃/10hours 的熱處理條件下，也未發現有明顯的擴散現象。因此，對厚度6500埃的二氧化矽而言，在1220℃/3hours 熱處理條件下，實質上足以抵擋以能量50KeV、劑量3.8×1015 cm-2植入的銻離子，不致使其穿透二氧化矽。

This thesis studies the diffusion behavior of ion implanted antimony (Sb) in Si as well as SiO2 under prolonged thermal process at high temperatures. The optimal annealing condition for the formation of n+ buried layer for bipolar transistor application was also investigated. Since ion implantation causes damage to Si substrate, we also investigate the residual surface defects on Si substrate resulting from various thermal treatments as well as the influence of the surface defects on the subsequent grown epitaxial layer. From the thermal budget consideration, it is determined that a thermal treatment at 1220℃ for 3 hours is the optimum condition for the n+ buried layer formation. However, residual surface defects (stacking faults) still remained on the Si substrate after such a thermal treatment, and the subsequent grown epitaxial layer was found to fairly rough surface. Removal of the surface defects by HCL etching prior to the epitaxial growth resulted in an epitaxial layer of very smooth surface morphology. Diffusion of implanted antimony species in SiO2 occurred primarily near the surface region, while they were relatively immobile in the bulk of SO2 even after a thermal process at 1220℃ for 10 hours. As a result, we conclude that a 6500A thick thermal SiO2 layer is sufficient to serve as a diffusion mask for Sb+ implantation followed by a thermal drive-in process at 1220℃ for a time period up to 3 hours.