AVS 53rd International Symposium
    Thin Film Monday Sessions
       Session TF-MoM

Paper TF-MoM5
Mechanism of Al@sub 2@O@sub 3@ Atomic Layer Deposition Using Trimethylaluminum and Ozone

Monday, November 13, 2006, 9:20 am, Room 2022

Session: ALD and Applications I
Presenter: D.N. Goldstein, University of Colorado at Boulder
Authors: D.N. Goldstein, University of Colorado at Boulder
S.M. George, University of Colorado at Boulder
Correspondent: Click to Email
Al@sub 2@O@sub 3@ atomic layer deposition (ALD) is typically performed using trimethylaluminum (TMA) and H@sub 2@O. However, ozone can be used as the oxidant instead of H@sub 2@O. Ozone may lead to reduced Al@sub 2@O@sub 3@ leakage current for dielectric applications. Ozone may also purge faster than H@sub 2@O and lead to faster Al@sub 2@O@sub 3@ ALD. The mechanism of Al@sub 2@O@sub 3@ ALD using TMA and ozone is still under debate. To study the chemical species on the growing Al@sub 2@O@sub 3@ ALD surface, we have performed transmission FTIR vibrational spectroscopy investigations. High surface area ZrO@sub 2@ nanoparticles were utilized to obtain high surface sensitivities. The vibrational spectrum was recorded after each TMA or ozone reaction. The ozone generator produces 3.7 wt.% ozone in a 300 sccm O@sub 2@ flow in a viscous flow ALD reactor. Argon is utilized as the carrier gas to reduce reactive NO@sub x@ species. At the growth temperatures of 175 and 275°C, the FTIR results reveal that O@sub 3@ reacts with Al-CH@sub 3@ surface species produced by the TMA reaction and forms primarily formate groups and a mixture of methoxy and hydroxyl species on the surface. Production of formate groups may involve oxygen insertion into the Al-CH@sub 3@ bond to form methoxy species that are known to condense into formate groups at the reaction temperatures. The TMA then displaces the formate and methoxy groups and reforms Al-CH@sub 3@ surface species. FTIR difference spectra after TMA and O@sub 3@ reactions at 275°C are shown in the accompanying figure. These spectra are consistent with the loss and gain of formate and methoxy groups. The surface features are temperature dependent. At temperatures greater than 375°C, the FTIR vibrational spectrum reveals only formate groups on the surface.