Thermal Atomic Layer Deposition of Device-Quality SiO2 Thin Films under 100 degrees C Using an Aminodisilane Precursor

Abstract

SiO2 is one of the most important dielectric materials that is widely used in the microelectronics industry, but its growth or deposition requires high thermal budgets. Herein, we report a low-temperature thermal atomic layer deposition (ALD) process to fabricate SiO2 thin films using a novel aminodisilane precursor with a Si-Si bond, 1,2-bis-(diisopropylamino)disilane (BDIPADS), together with ozone. To compare the film quality, ALD SiO2 films grown at various temperatures from 250 down to 50 degrees C were systematically investigated. Our data suggest that even without the aid of plasma-enhanced or catalyzed surface reactions, high-quality SiO2 films with relatively high growth rates, high film densities, and low impurity contents compared to conventional Si precursors can be attained through our process at a low growth temperature (similar to 50 degrees C). Chemical analyses via Auger electron spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy confirm the formation of stoichiometric SiO2 films without noticeable impurity contents of nitrogen and carbon, regardless of the growth temperature. However, low-temperature growth of the SiO2 film (<= 80 degrees C) results in a slight ingress of SiH-related moieties during the ALD processes that is not observed at temperatures over 80 degrees C. Density functional theory calculations show that the Si-Si bond present in the BDIPADS precursor is easier to be oxidized compared to the Si-H bonds. Through electrical characterization of the SiO2 films grown at different temperatures, we confirm only slight degradation in the dielectric constants, leakage currents, and breakdown fields with decreasing growth temperature, which may be due to the slightly decreased film density and the increased defect density of SiH-related bonds.