《外延抑制自掺杂技术简介.docVIP

毕业论文简介 外延抑制自掺杂技术研究 应用物理2班伏瑜 指导老师：王青 ( 教授) 杜金生 (工程师) 摘 要 外延层杂质浓度是影响电学性能的重要参数，外延掺杂存在有意识掺杂和无意识掺杂（即自掺杂），自掺杂影响外延生长。自掺杂降低了衬底/外延界面过渡区的陡峭程度，同时也增加了外延淀积过程中的本底浓度。不但对外延层的电阻率控制带来相当大的困难，使外延层界面处杂质分布梯度变缓，外延层有效厚度减薄，PN结击穿电压的显著降低，晶体管的大电流特性变坏，特别不利于要求薄而界面处杂质分布陡的外延层的微波器件的制造。而且一些有害杂质的存在，还会使噪声增加等。 本文对外延淀积过程中自掺杂的产生进行了分析，提出了在外延淀积过程中可以通过改变压力、温度、及采用HCl腐蚀抛光技术、背封技术、H2烘烤赶气技术、二步外延技术等方法来解决外延自掺杂，从而改善器件的特性参数。 关键词：外延 淀积 自掺杂 Abstract The impurity concentration is a key parameter which has an effect on the electrical performance of the device in the epitaxy, the doping of epitaxy exists conscious and unconscious doping (i.e, self-doping), the growth of epitaxy is influenced by self-doping. Since the self-doping reduced the steep degree of substrate and the epitaxy interface of transition region, also increased background concentration in the process of the extension. It makes the control of the epitaxy,s resistivity difficult, the epitaxy of the interface between layer impurities distribution gradient slow, the epitaxy of effective thickness thin, the breakdown voltage of PN junction significantly reduce, and the current characteristics of transistor change bad, especially to the disadvantage of manufacturing microwave devices ,which were required thin and the distribution of the impurities were steep in the interface. And the existence of some harmful impurities, still can make noise up, etc. This paper analised the generation of self-doping during the epitaxial deposition , some techniques such as altering press, temperature，HCl rot, back-seal, H2 expel，and two-step epitaxy, are proposed to improve the electrical charateristics of the device by reducing self-doping effect during epitaxial deposition. Key words: Epitaxy; Deposition;Self-doping; 第一章 外延技术概述 1、概念 所谓外延就是在一定的条件下，在单晶衬底上，沿原来的结晶方向生长一层导电类型、电阻率、厚度和晶格结构、完整性等都符合要求的新单晶层的工艺过程。生长的单晶层称为外延层（如图1-1）。 图1-1 硅外延层 2、工艺知识 目前制备半导体单晶外延层的最主要方法是化学气相淀积法(Chemical Vapor Deposition，CVD)。所谓化学气相淀积，就是利用气态物质在固体表面上进行化学反应，生成固态淀积物的过程。其主要的反应式为： SiHxCl