Creation of Deep Gap States in Si During Cl₂Or Hbr Plasma Etch Exposures

We explore the effects of poly crystalline Si overetches on the Si substrate in the SiQ₂/Si materials system. Conventional reactive ion etching (RIE) and magnetically enhanced RIE (MERIE) with Cl₂ or HBr-based chemistries are used. The introduction of electrically active gap states, four hole traps, and an electron trap in the Si substrate during these overetches is revealed by deep level transient spectroscopy. The production rates of these observed defects are found to be unaffected by the magnetic field; however, due to a defect-hydrogen interaction, these rates are observed to become slower in long-duration overetching using hydrogen-rich plasmas in the MERIE mode. Based on their annealing and electronic properties, these traps are tentatively assigned to multivacancy defect structures, and the formation and interaction mechanisms for the suggested defects are discussed in terms of a phenomenological model in which the single vacancy is proposed to play a key role.