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

在硅技术中，人们认为未来将需要电激活的超浅掺杂层。预计到2014年，源、漏电极下的掺杂扩展层厚度将达到10 nm。硼被广泛用作硅器件技术中的p型掺杂剂。离子注入是一种将杂质可控地引入固体中的有用方法;然而，也引入了缺陷。离子注入后的高温退火恢复了硅的结晶并激活了注入的掺杂剂。然而，在退火期间发生掺杂剂的扩散，并且难以保持超浅掺杂剂分布，因为硼是Si中的快速扩散剂。在本研究中，低于100 eV的超低能量离子注入，这是接近的固体的位移能量，以减少在注入过程中的损伤进行了研究。在室温到1073 K的温度范围内，将能量范围在30和500 eV之间的硼离子注入本征Si衬底（电阻率> 10000 ohm cm）中。在200 eV的能量下注入硼后，随着衬底温度的升高，薄层电阻从100 k欧姆下降到4 k欧姆。当离子能量为300 eV，衬底温度为1073 K时，薄膜的薄层电阻最低，为2.8 k Ω。通过二次离子质谱分析，硼掺杂层的结深度小于8 nm。

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.