Study of silicon/silicon, silicon/silicon dioxide, and metal-oxide-semiconductor (MOS) using positrons.

摘要

A variable-energy positron beam is used to study Si/Si, Si/SiO{dollar}sb2{dollar}, and metal-oxide-semiconductor (MOS) structures. The capability of depth resolution and the remarkable sensitivity to defects have made the positron annihilation technique a unique tool in detecting open-volume defects in the newly innovated low temperature (300{dollar}spcirc{dollar}C) molecular-beam-epitaxy (MBE) Si/Si. These two features of the positron beam have further shown its potential role in the study of the Si/SiO{dollar}sb2{dollar}. Distinct annihilation characteristics has been observed at the interface and has been studied as a function of the sample growth conditions, annealing (in vacuum), and hydrogen exposure. The MOS structure provides an effective way to study the electrical properties of the Si/SiO{dollar}sb2{dollar} interface as a function of applied bias voltage. The annihilation characteristics show a large change as the device condition is changed from accumulation to inversion. The effect of forming gas (FG) anneal is studied using positron annihilation and the result is compared with capacitance-voltage (C-V) measurements. The reduction in the number of interface states is found correlated with the changes in the positron spectra. The present study shows the importance of the positron annihilation technique as a non-contact, non-destructive, and depth-sensitive characterization tool to study the Si-related systems, in particular, the Si/SiO{dollar}sb2{dollar} interface which is of crucial importance in semiconductor technology, and fundamental understanding of the defects responsible for degradation of the electrical properties.