HfO 2 films were grown by atomic layer deposition ͑ALD͒ from Hf͓N͑CH 3 )(C 2 H 5 )] 4 and H 2 O on Si͑100͒ substrates. The thickness of 5-45 nm thick films on HF-etched Si was proportional to the number of growth cycles. Crystallization was observed in the 30-45 nm thick films, containing the monoclinic HfO 2 polymorph. Films with thicknesses lower than 10 nm were amorphous. The effective permittivity of the dielectric films varied between 6.5 and 17. The leakage and capacitive characteristics did not show any clear dependence on the HfO 2 growth temperature. HfO 2 is a recognized candidate for high-permittivity dielectric oxide in complementary metal-oxide-semiconductor ͑CMOS͒ devices. 1 The promise for the suitability of HfO 2 for near-term implementation in CMOS transistors stems from its thermal stability in contact with silicon and from its high bandgap ensuring its insulating properties. Uniform growth of ultrathin and dense dielectric layers on complex-shaped, trenched, and large-area substrates common in microelectronic industry can be provided using atomic layer deposition ͑ALD͒ routes to HfO 2 . [2][3][4][5] In ALD, a substrate surface is alternately exposed to highly reactive metal and oxygen precursors and the solid film forms as a result of successive surface reactions between ͑sub͒monolayers of precursor molecules alternately adsorbed. Since the precursors do not meet in the gas phase, they can be chosen to be as reactive as possible to ensure rapid surface reactions and formation of dense structures at as low temperatures as possible. However, monotonously decreasing growth temperature has usually caused a monotonous increase in the residual contamination when common precursors such as metal halides were used, especially at temperatures below 300°C. 6-8 Increase in impurity levels directly results in lower film density and inferior dielectric properties.In recent ALD studies, the use of hafnium alkylamides has been described. 4,9,10 In the case of hafnium tetrakis͑ethylmethylamide͒, Hf͓N͑CH 3 )(C 2 H 5 )] 4 , and H 2 O, 10 it is reported, that crystalline, 100-200 nm thick HfO 2 films can be grown with high rates and uniform compositions at lower temperatures ͑at 200-300°C͒ than found necessary for halide ALD ͑300°C and higher͒. The oxygen to hafnium ratio was found to be 2.0 Ϯ 0.1, with carbon and nitrogen residues of 0.3-0.6 and 0.1-0.2 atom %, respectively. The hydrogen content was, however, rather high, reaching 2-3 atom %.In the present study, thin HfO 2 films were atomic layer deposited from the liquid hafnium precursor Hf͓N͑CH 3 )(C 2 H 5 )] 4 and H 2 O in order to investigate the growth of ultrathin films with this precursor combination. The influence of the number of growth cycles on film thickness and structure was examined. The effect of substrate temperature on the film growth rate, capacitance-voltage, and leakage current characteristics was monitored. ExperimentalThe films were grown in a hot-wall horizontal flow-type F120 ALD reactor 11 onto Si͑100͒ substrates. The substrate temperat...
Polycrystalline monoclinic HfO2 films were atomic layer deposited on Si(100) substrates by a nonhydrous carbon-free process of HfI4 and O2. The oxygen to hafnium ratio corresponded to the stoichiometric dioxide within the limits of accuracy of ion beam analysis. A 1.5–2.0 nm thick SiO2 interface layer formed between the HfO2 films and Si substrates. Hysteresis of the capacitance–voltage curves was observed in Al/HfO2/p-Si(100) structures with oxide grown in the substrate temperature range of 570–755 °C. The hysteresis ceased with an increase in O2 pressure. The effective permittivity of the dielectric layers varied between 12 and 16. The breakdown voltages were found to be lower in the case of higher oxygen doses and higher HfO2 deposition temperatures.
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