【作者】 吴贵斌；

【导师】 叶志镇；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2006， 博士

【摘要】 锗硅(Si_1-xGe_x)是硅和锗组成的半导体合金材料。除具有硅材料的优点外,还具有能带可调以及应力调整等自身的特性,同时它还与目前先进的硅集成电路工艺相兼容,因此锗硅材料在如今的集成电路领域有着重要的应用。当然,随着技术进步,锗硅材料在应用中又会不断面临新问题的挑战,从下面的论述中可以看到,这些问题的解决毫无疑问将会对拓展硅基材料的应用范围以及提高器件性能的重要性起着推动的作用。 涉及到本论文中,锗硅材料所面临的问题主要有以下两个方面:第一,随着器件向着深亚微米级发展,单纯的外延生长已无法满足锗硅材料的应用,一系列新器件、新结构的出现,对锗硅材料的生长提出了更高的要求。例如在抬高源/漏极MOSFET中,要求选择性生长单品锗硅材料,而目前采用的选择性生长方法普遍具有较高的生长温度,这会导致锗硅材料的应力弛豫,产生缺陷,影响器件性能,因此很有必要研究适合锗硅材料低温选择性生长的方法。第二,就多晶SiGe材料而言,我们知道,多品锗硅材料具有广阔的应用前景,但采用目前方法生长的多晶锗硅薄膜并不象理论预期一样,具有较高的载流子迁移率,这主要是由于生长的多晶锗硅薄膜内的缺陷较多以及锗偏析等原因造成的,从而限制了锗硅薄膜作为器件有源区的应用,因此开发先进的多晶锗硅薄膜生长技术是当务之急。本文的研究正是围绕上述两方面问题展开的。 本文采用一种先进的薄膜制备技术—超高真空化学气相沉积（UHVCVD）对锗硅薄膜的生长进行了研究,该技术不仅具有超净的生长环境,而且能够在低温、低压下生长锗硅薄膜,可以精确控制薄膜的生长速度等,这些特性对生长高质量的薄膜是必不可少的,因此我们利用该技术,对单晶锗硅薄膜、多品锗硅薄膜的生长进行了研究,主要取得以下成果: （1） 研究了不同的生长气氛对超高真空化学气相沉积选择性生长锗硅薄膜的影响,指出当温度高于550℃时,气氛中锗含量对超高真空选择性生长锗硅有明显的影响,低于550℃时,氢气以及锗烷相互作用共同对锗碓选择性生长产生影响。通过对比不同的生长条件,并结合锗硅材料的生长特性,更多还原

【Abstract】 Silicon Germanium is an alloy of semiconductor material, which is formed through the covalent bonding between element Si and Ge atoms. SiGe is superior to Si because of band gap adjustment and strain engineering etc. SiGe is compatible with the state-of-art advanced CMOS technology. So SiGe plays an important role in today’s IC. With the technology developing, SiGe is exposed to the continuous problems, once these problems are resolved, SiGe would be the driving force of extending Si-based applications and improving the performance of devices.In this dissertation, we discussed two issues about SiGe. Firstly, as the devices is scaling down, merely epitaxy of SiGe is not sufficient for the application, for example the raised S/D MOSFET, Selective growth is the key step, but the existing methods which realize the selective growth need relatively high temperature, so it’s necessary to bring out the solution that can realize selectively growth of SiGe at low temperature. Secondly, as far as poly-SiGe is concerned, poly-SiGe has a promising future in application, but the present growth method can’t prepare the films with high carrier mobility, due to possible defects in the materials and Ge segregation, so poly-SiGe has poor performance as active region of device. The priority is to develop the feasible growth method.Based on the above analysis, we adopt an advanced technology called UHVCVD to grow single crystalline or polycrystalline SiGe films; this technology is characterized with ultraclean environment and growth of SiGe thin films at low temperature and low pressure. These factors guarantee to obtain high quality films. Therefore, we use this technology to investigate the growth of SiGe thin films, and achieve the following results:（1） The effect of growth atmosphere on selective growth of SiGe thin films by UHVCVD was investigated, and it is shown that when the temperature is above 550℃, Ge content has an apparent effect on the selective growth. And the interaction between H₂ and GeH₄ became important at temperature below 550°C. In comparison with various growth parameters, the optimum growth atmosphere is determined: the substrate temperature of 580°C, the flow ratio of SiH4 to GeH4 （90%H2） is 5:5sccm. Under such environment, the incubation time can reach up to 40min.（2） Based on the above conclusion, the prototype of SBD has been fabricated. The result shows that not only the SBD with selective growth of SiGe simplify the fabrication process, but also the reverse saturation current is lowered by two or three orders compared with the regular SiGe SBD.（3） It’s firstly reported that poly-SiGe thin films was prepared by a novel method called MIG that is a combination of MIC and CVD. The key point is poly-SiGe heteroepitaxial grow on metal silicide, the advantage of this method is that films grow accompanied by crystallization without annealing, and the growth temperature is below 600 °C, so glass can be used as the substrate, and compared with other CVD methods, there is no incubation time;（4） The effect of thickness of Ni on the grain size of SiGe thin films was also investigated, and pointed that it has crest at certain thickness, when the thickness of Ni is 60nm, the cluster size can reach 500⁶00nm.（5） In the heterostructure of SiGe/Ni, strain relaxation is the driving force for the morphology formation of Poly-SiGe. At lOPa, a continuous film can be formed, with uniform grain size, while at pressure from O.lPa to lOPa, densely packed SiGe whiskers were formed.（6） Using this method, it’s very convenient to utilize the Ni silicide as self-aligned ohmic contact of SBD, the experiments have proven that the SBD based on this method has better rectification characteristic and the rectification ratio can reach up to 8000.更多还原