Development of ultra shallow doping of semiconductors by ultra low energy ion beams

在硅技术中，人们认为未来需要一种电激活的超浅掺杂层。预计2014年源极和漏极下的掺杂延伸层厚度将达到10nm。硼作为p型掺杂剂广泛应用于硅器件技术中。离子注入是控制杂质进入固体的有效方法；然而，缺陷也被引入。离子注入后的高温退火恢复了硅的结晶，激活了注入的掺杂剂。然而，在退火过程中掺杂物会发生扩散，由于硼在Si中是快速扩散者，所以很难保持超浅掺杂物的轮廓。本研究采用接近固体位移能的100eV以下的超低能离子注入，减少注入过程中的损伤。能量在30 ~ 500 eV之间的硼离子，在RT ~ 1073K的温度范围内注入到本禀硅衬底（电阻率为bbb10 ~ 10000欧姆cm）。随着衬底温度的升高，在200 eV能量下注入硼后的片电阻从100 k ω下降到4 k ω。在离子能量为300 eV、衬底温度为1073K时，薄膜电阻最低为2.8 k欧姆。二次离子质谱分析表明，掺硼层的结深在8 nm以下。

In silicon technology it is thought that an electrically activated, ultra-shallow doping layer will be necessary in the future. The thickness of dopant extension layers under the source and drain electrode is predicted to reach 10nm in the year 2014. Boron is widely used as p-type dopant in silicon-device technology. Ion implantation is a useful method for the controlled introduction of impurities into a solid; however, defects are also introduced. High-temperature annealing after ion implantation recovers the crystallization of silicon and activates the implanted dopant. However, diffusion of the dopant occurs during the annealing, and it is difficult to keep the ultra-shallow dopant profile because boron is the fast diffuser in Si. In this study, ultra-low-energy ion implantation below 100eV, which was close to the displacement energy of the solid, was examined to reduce the damage during implantation process. Boron ion of energy ranging between 30 and 500 eV, was implanted into intrinsic Si substrate (resistivity is > 10000 ohm cm) at temperatures ranging from RT to 1073K. Sheet resistance after boron implantation at the energy of 200 eV decreases from 100 k ohm to 4 k ohm with increasing the substrate temperature. The lowest sheet resistance of 2.8 k ohm was achieved at the ion energy of 300 eV and the substrate temperatures of 1073K. Junction depth of boron-doped layers was below 8 nm by the analysis of secondary ion mass spectroscopy.