Electrical studies on annealed d2 plasma-exposed silicon

Defects introduced by annealing in D2 plasma-exposed, boron-doped silicon have been studied by means of deep level transient spectroscopy (DLTS) and capacitance-voltage measurements. A hole trap at Ev = 0.48 eV (Ev being the edge of the valence band) seen after annealing at 175°C, is tentatively assigned to a defect containing a vacancy. This hole trap anneals out following heat-treatment at 225°C. Other hole traps at Ev + 0.30 eV and Ev + 0.50 eV are observed in the samples following annealing at temperatures higher than 475°C. In the annealing temperature range 325-425°C, an observed broad DLTS band is attributed to complex defect structures in which deuterium atoms are bonded to an as-yet unidentified defect core. These structures are suggested to differ in the number of deuterium atoms bonded to the core. Each of these structures gives rise to a hole trap(s) in the energy range Ev + 0.4 eV to Ev + 0.6 eV within the forbidden gap. A nonzero residual DLTS signal seen in all the samples annealed at 525°C or below is proposed to be due to extended defects or platelets, confined to the first few microns region close to the plasma-exposed surface.