Plasma hydrogenated, reactively sputtered aluminium oxide for silicon surface passivation

The intentional addition of hydrogen during reactive sputtering of AlO_x films has led to a dramatic improvement of the surface passivation of crystalline silicon wafers achieved with this technique. The 5 ms effective minority carrier lifetime measured on 1.5 Ω cm n-type CZ silicon wafers is close to the 6 ms of a control wafer coated by atomic layer deposition (ALD) of AlO_x. Hydrogen-sputtered films also provide excellent passivation of 1 Ω cm p-type silicon, as demonstrated by an effective lifetime of 1.1 ms. It is likely that the improved passivation is related to the formation of an interfacial silicon oxide layer, as indicated by FTIR measurements.