Influence of single and double deposition temperatures on the interface quality of atomic layer deposited Al_2O_3 dielectric thin films on silicon

摘要

An electrical characterization of Al_2O_3 based metal-insulator-semiconductor structures has been carried out by using capacitance-voltage, deep level transient spectroscopy, and conductance-transient (G-t) techniques. Dielectric films were atomic layer deposited (ALD) at temperatures ranging from 300 to 800℃ directly on silicon substrates and on an Al_2O_3 buffer layer that was grown in the same process by using 15 ALD cycles at 300℃. As for single growth temperatures, 300℃ leads to the lowest density of states distributed away from the interface to the insulator [disorder-induced gap states (DIGS)], but to the highest interfacial state density (D_(it)). However, by using 300/500℃ double growth temperatures it is possible to maintain low DIGS values and to improve the interface quality in terms of D_(it). The very first ALD cycles define the dielectric properties very near to the dielectric-semiconductor interface, and growing an upper layer at higher ALD temperature produces some annealing of interfacial states, thus improving the interface quality. Also, samples in which the only layer or the upper one was grown at the highest temperature (800℃) show the poorest results both in terms of D_(it) and DIGS, so using very high temperatures yield defective dielectric films.