AVS 51st International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session DI+PS-TuM

Paper DI+PS-TuM6
Plasma-Enhanced Atomic Layer Deposition for Compositionally Controlled Metal Oxide Thin Films

Tuesday, November 16, 2004, 10:00 am, Room 304C

Session: High-k Dielectrics: Growth and Processing
Presenter: S.X. Lao, University of California, Los Angeles
Authors: S.X. Lao, University of California, Los Angeles
R.M. Martin, University of California, Los Angeles
J.P. Chang, University of California, Los Angeles
Correspondent: Click to Email
The need to replace SiO@sub 2@ by a higher dielectric constant material in fabricating smaller and faster metal-oxide-semiconductor (MOS) transistors is well recognized by the National Technology Roadmap for Semiconductors. Atomic layer deposition emerges as a viable chemical processing technique to enable the deposition of ultra-thin and highly conformal thin films, and the use of plasma allows greater flexibility and higher processing yield. In this work, ZrO@sub 2@ and HfO@sub 2@ films were deposited using zirconium and hafnium tetra-tert butoxides as the metal precursors and oxygen radicals generated from oxygen plasma as the oxidant, introduced in alternating, cyclical sequence. The thicknesses of the films scaled linearly with the number of deposition cycles as determined by both ellipsometry and x-ray photoelectron spectroscopy (XPS) measurements. Optical emission spectroscopy (OES) was utilized to identify and quantify the gas phase atomic radicals. It was found that the OES intensity of oxygen radicals varies inversely with that of hydrogen radicals originating from the precursor. The presence of oxygen and hydrogen radicals in the gas phase resulted in the formation of surface hydroxyl groups, an important surface functional group for the chemisorption of precursors. As measured by the Fourier transform infrared spectroscopy (FTIR), the -OH integrated absorption intensities increased linearly with the number of deposition cycles and decreased upon annealing. Atomic force microscopy (AFM) analysis showed fairly smooth films with an RMS roughness of 1.7 Å after 5 deposition cycles. MOS capacitors were fabricated with the PEALD deposited films. The capacitance-voltage (C-V) and current-voltage (I-V) measurements showed that the PEALD HfO@sub 2@ films had the highest dielectric constant of 25 with an equivalent oxide thickness (EOT) of 12.5-15 Å. The leakage currents were several orders of magnitude less than that of SiO@sub 2@ films at the same EOT.