Thermal stabilities of ALD-HfO₂ films on HF- and (NH ₄)₂S-cleaned InP

The thermal stabilities of the atomic layer deposited HfO₂ films were investigated on HF-cleaned InP substrates with and without additional (NH₄)₂S cleaning. An abrupt interface without any interfacial layer between the HfO₂ film and InP substrate was maintained during annealing at up to 600C for both samples. The S-passivation resulting from the (NH₄)₂S cleaning reduced the interface defect density, thereby decreasing the frequency dispersion and low-field leakage current. The increase of the capacitance equivalent SiO₂ thickness after the thermal annealing was also delayed by the S-passivation, which was possibly attributed to the retardation of substrate materials diffusion into the HfO₂ film.