Quantifying the Impact of Al Deposition Method on Underlying Al2O3/Si Interface Quality

Oxide-semiconductor interface quality has often a direct impact on the electrical properties of devices and on their performance. Traditionally, the properties are characterised through metal-oxide-semiconductor (MOS) structures by depositing a metal layer and measuring the capacitance-voltage (C-V) characteristics. However, metal deposition process itself may have an impact on the oxide and the oxide-semiconductor interface. The impact of magnetron sputtering, e-beam evaporation, and thermal evaporation on an Al2O3/Si interface was studied, where
atomic layer deposited (ALD) Al2O3 was used, by MOS C-V and Corona Oxide Characterization of Semiconductors (COCOS) measurements. The latter allows characterisation of the interface also in its original state before metallisation. The results show that sputtering induces significant damage at the underlaying Al2O3/Si interface as the measured interface defect density Dit increases from 1011 cm−2eV to 1013 cm−2eV. Interestingly, sputtering also generates a high density of positive charges Qtot at the interface as the charge changes from –2 · 1012 cm−2 to +7 · 1012 cm−2. Thermal evaporation is found to be a softer method, with modest impact on Dit and Qtot. Finally, we show that Alnealing heals the damage but has also a significant impact on the charge of the film recovering the characteristic negative charge of Al2O3 (∼ –4 · 1012 cm−2).