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RESEARCH PRODUCT

Influence of plasma chemistry on impurity incorporation in AlN prepared by plasma enhanced atomic layer deposition

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description

Impurities in aluminum nitride films prepared by plasma enhanced atomic layer deposition using NH3-, N2/H2- and N2-based plasmas are investigated by combining time-of-flight elastic recoil detection analysis (ERDA) and Fourier transform infrared spectroscopy. Different atomistic growth mechanisms are found to exist between the plasma chemistries. N2-plasma is shown as not suitable for the low-temperature deposition of AlN. Films deposited by NH3- and N2/H2-based processes are nitrogen rich and heavily hydrogenated. Carbon impurities exist at higher concentrations for the N2/H2-processes. The discovery of nitrile groups in the films indicates that carbon impurities can be partially attributed to an undesirable reaction occurring during the plasma step between nitrogen species and CH groups. Unremoved ligands from the metal precursor are the other source of carbon. A comparison of the hydrogen content within the films as determined by infrared absorption spectroscopy and ERDA suggests the NH3-based films have large quantities of unbonded hydrogen, whereas hydrogen in the N2/H2-based films is mostly in the form NHx. For the N2/H2-based processes, the addition of argon into the plasma mixture is shown to enhance amine formation.