Surface Passivation by Al₂O₃anda-SiNx: H Films Deposited on Wet-Chemically Conditioned Si Surfaces

The surface passivation of p - and n -type silicon by different chemically grown SiO 2 films (prepared by HNO 3 , H 2 SO 4 /H 2 O 2 and HCl/H 2 O 2 treatments) was investigated after PECVD of a -SiN x :H and ALD of Al 2 O 3 capping films. The wet chemically grown SiO 2 films were compared to thermally grown SiO 2 and the surface passivation was benchmarked against single-layer a -SiN x :H and Al 2 O 3 films deposited on HF-last Si surfaces. Directly after PECVD and ALD the surface passivation was found to be similar for all chemically grown SiO 2 stacks and higher than for the single-layer films. After annealing at 400°C the level of surface passivation improved but remained similar for the chemically grown SiO 2 stacks. Corona charging experiments on the annealed chemically grown SiO 2 /Al 2 O 3 stacks revealed that the fixed charge density, i.e. the field-effect passivation, was lower compared to single-layer Al 2 O 3 films whereas the chemical passivation was found to be higher. The surface passivation was also investigated as a function of the annealing time. Chemically grown SiO 2 stacks achieved the maximum level of surface passivation after annealing for half a minute which is different from the stacks with a -SiN x :H and Al 2 O 3 films deposited on thermally grown SiO 2 or HF-last Si surfaces which required considerably longer annealing times.