DAMAGE TO THE SILICON SUBSTRATE BY REACTIVE ION ETCHING DETECTED BY A SLOW POSITRON BEAM

Defects in reactive ion-etched Si have been investigated by means of a slow positron beam. A thin carbon-containing film (<30 angstrom) was formed on the Si surface after reactive ion etching (RIE). Vacancy-type defects, which were estimated to distribute over 1200 angstrom in depth by numerical fitting using the positron trapping model, were observed in the damaged subsurface region of Si. Aside from ion bombardment, ultraviolet radiation is also presumed to affect the formation of vacancies, interstitials in oxide and the formation of vacancies in Si substrate. The ionization-enhanced diffusion (IED) mechanism is expected to promote the diffusion of vacancies and interstitials into Si substrate.