Effect of ALD window on thermal ALD deposited HfOx/Si interface for silicon surface passivation

Abstract

The quality of oxide-silicon interface plays a crucial role in reducing the surface recombination losses. In the present study, we demonstrate the importance of ALD temperature window and its impact on the quality of HfOx/Si interface using X-ray photoelectron spectroscopy (XPS), Variable angle spectroscopy ellipsometry (VASE) and Capacitance-voltage (C-V) measurements. VASE results confirm that for films grown within the ALD window the film growth is uniform across the wafer. XPS results show that performing a post deposition anneal restructures the interfacial layer and oxidizes the interface. C-V results conclude that positive fixed charges are present in the pristine films, however negative charges are activated after performing post deposition annealing. Further, it is observed that to investigate the true properties of the deposited layer, the films should be annealed before metallization. It is thus concluded that uniform films would be grown for films deposited at temperature lying within the ALD window and would effectively passivate silicon surface owing to their low interface defect density and moderate fixed oxide charges.