DLTS Study of RIE-Induced Deep Levels in Si Using p+n Diode Arrays

Deep levels in Si induced by reactive ion etching (RIE) of SiO2 film have been studied by DLTS. In order to detect the RIE-induced damage existing near the surface region, special device structures consisting of p+n diode arrays are used. It is found that the dominant deep levels produced by RIE are four hole traps. One level at E v+0.40 eV exhibits the Poole-Frenkel effect, from which it is identified as an acceptor. Another level at E v+0.46 eV is deduced to be an interstitial iron level from the emission rate. There is a strong decrease in the deep level concentrations upon annealing above 500°C. However, the deep levels do not completely disappear upon annealing at high temperatures. The deep level concentrations correlate well with the current-voltage characteristics of the devices.