Analysis of surface adsorption kinetics of SiH_4 and Si_2H_6 for deposition of a hydrogenated silicon thin film using intermediate pressure SiH_4 plasmas

摘要

For the future mass production of silicon-based devices, the deposition process of hydrogenated silicon (Si:H) thin films must not only satisfy several important material properties, it must also be highly productive. Therefore, a deep understanding of the reactivities of silicon precursors such as SiH4 and Si2H6 on substrate surfaces is required to obtain a rapid growth rate for the Si:H thin film. Thus, we performed first-principles density functional theory calculations to investigate the reactivities of the silicon precursors in detail. Our results show that the exposure of the Si(001) surface to Si2H6 is the most efficient method for depositing Si:H thin films among the different cases tested, including SiH4 on Si(001), Si2H6 on Si(001), SiH4 on Si(111), and Si2H6 on Si(111). The dissociative reactions of Si2H6 on the Si(001) surface were energetically the most favorable. The energy difference between the initial adsorbate (Si2H6) and the most stable adsorbate (Si2H2) on the Si(001) surface was 1.45 eV, which was the highest value among the four cases tested. In addition, it was numerically demonstrated that although Si2H6 is not added to a source mixture, Si2H6 can be observed to a non-negligible degree during the deposition process using an intermediate pressure SiH4/He plasma.