Al 2 O 3 thin films were deposited on Si substrates by atomic layer deposition ͑ALD͒ using Al(CH 3 ) 3 ͑trimethylaluminum, TMA͒ as a metal source and (CH 3 ) 2 CHOH ͑isopropyl alcohol, IPA͒ as an oxygen source at 250°C. The film growth rate is saturated at 0.8 Å/cycle, and it is slightly lower than that for the procedure which uses water vapor instead of IPA. The as-deposited film has a stoichiometry close to Al 2 O 3 ͑Al/O ratio ϳ2:3.1͒ and the residual carbon content of the films is below the detection limit of secondary ion mass spectroscopy. An interface oxide between the Al 2 O 3 film and Si-substrate was not detectable on the asdeposited film by transmission electron microscopy. However, after annealing at 800°C for 5 min, an interface oxide is newly formed even under the neutral ambient of Ar, and it grows thicker under the oxidizing ambient of O 2 . That is, oxygen, which is needed for forming the interface oxide during the annealing process is supplied from both of the ambient oxygen and the excess oxygen in the films. Thus, although the loss of dielectric constant is inevitable during the annealing process, it can be minimized by using IPA in Al 2 O 3 ALD.As the size of microelectronic devices is scaled down, oxide films with high dielectric constants are required for gate and capacitor dielectrics. Even though SiO 2 is an excellent dielectric material in many features, the preparation of reliable SiO 2 films thinner than 30 Å is difficult, because of the quantum mechanical tunneling of electrons, which generates a large leakage current across the films. 1 Thus, an alternative oxide film with higher dielectric constant than SiO 2 is needed. 2 In this respect, Al 2 O 3 has been considered as a possible candidate for gate oxides as well as Ta 2 O 5 , HfO 2 , and ZrO 2 . 3-5 Also, Al 2 O 3 is considered as a promising capacitor dielectric, which can replace silicon oxynitride ͑SiON͒ in future dynamic random access memories ͑DRAM͒. 6 In addition, Al 2 O 3 has been recently regarded as a good passivation layer, which can prevent hydrogen penetration into the active region of semiconductor devices. 7 In preparing high-dielectric metal oxides with a thickness in the subhundred angstrom range, atomic layer deposition ͑ALD͒ attracts considerable interest owing to its inherent merits in thin film depositions, such as a digital controllability of film thickness on an atomic scale, a superior conformal deposition on three-dimensional structures, and no particle generation, etc. 8-10 In typical ALD of metal oxide thin films, H 2 O has been most widely used as the oxygen source. [11][12][13][14][15][16] However, by using H 2 O an unwanted interface oxide may be formed between the metal oxides and Si substrates, and it is thought that the interface oxide is composed mainly of SiO x , as the result of the reaction between H 2 O and the Si substrates during the initial stage of the ALD. Hence, the interfusion of the interface oxide would be expected to reduce the dielectric constant of the deposited thin films. 17-19 Th...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.