Molecular layer deposition using cyclic azasilanes, maleic anhydride, trimethylaluminum, and water

Abstract

Molecular layer deposition (MLD) is used to grow hybrid organic–inorganic films based on two or more self-limiting surface chemical reactions. A four-step ABCD sequence using N-(2-aminoethyl)-2,2,4-trimethyl-1-aza-2-silacyclopentane (AZ), maleic anhydride (MA), trimethylaluminum, and H2O and a three-step ABC sequence consisting of AZ, MA, and H2O are reported for growing hybrid organic–inorganic thin films. The ABCD sequence exhibited self-limiting growth behavior with a constant growth rate of 3.5 Å/cycle at 100 °C, while the growth rate of the ABC sequence increased to 90 Å/cycle after approximately 50 cycles. The growth rate using the ABC chemistry is much larger than for MLD/ALD chemistries that involve exclusively surface reactions, and displayed a strong dependence on the substrate temperature. Fourier transform infrared measurements of the as-deposited films indicated -COOH functionalities in the ABC film, and provided evidence for the reaction mechanisms. These results indicate that precursor diffusion into the ABC MLD film plays a key role in the large growth rate. The density, roughness, and dielectric constant (κ) of the films are reported in the as-deposited state and after treatment in air at temperatures up to 400 °C. The as-prepared and thermally treated ABC films with densities <1 g/cm3 and κ < 3 may be useful in applications requiring porous and low-κ films.