AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP2
Quartz Crystal Microbalance and Quadruple Mass Spectrometry Studies of Surface Reactions of @beta@-diketonate Precursors and O Radicals

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: T.T. Van, University of California, Los Angeles
Authors: T.T. Van, University of California, Los Angeles
J.P. Chang, University of California, Los Angeles
Correspondent: Click to Email
Pure and Er-doped Y@sub 2@O@sub 3@ thin films are of interest for next generation of microelectronic and optoelectronic devices. In this work, a radical-enhanced atomic layer deposition (ALD) process was developed for synthesizing these materials. Specifically, quartz crystal microbalance (QCM) and quadruple mass spectrometry (QMS) were used to study the surface reaction kinetics of @beta@-diketonate precursors with O radicals. The @beta@-diketonate complexes chosen for this study are Tris(2,2,6,6-tetramethyl-3,5-heptanedionato) M(III), or M(TMHD)@sub 3@, where M = Y or Er. The temperature-controlled QCM was used to measure the real time mass changes, since each reaction steps in ALD cycles causes a specific mass increase or decrease. The evolution of surface species during the deposition was identified and analyzed by QMS. Similar adsorption and desorption kinetics were observed for both Y(TMHD)@sub 3@ and Er(TMHD)@sub 3@. The surface coverage increased with increasing substrate temperature then saturated. The adsorption isotherms were fitted with the simple Langmuir model and the adsorption rate coefficients were found to decrease with increasing temperature. Conversely, the desorption rate coefficients increased with increasing temperature. The apparent activation energies are ~0.25 eV. The desorption of volatile by-products during the O radical pulse resulted in a rapid mass decrease followed by saturation. The critical O radical dose needed to reach this saturation increased with increasing coverage and approached 2 minutes at high coverage. The O radicals, besides effectively remove the @beta@-diketonate ligands, were found to create reactive site for precursor adsorption. Specifically, the mass increase during a subsequent precursor pulse depended linearly on the preceding O radical pulse time. Finally, well-controlled atomic layer deposition of Er@sub 2@O@sub 3@ and Y@sub 2@O@sub 3@ was demonstrated.