AVS 49th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeA

Paper TF-WeA4
Temperature Effects during Quartz-crystal Microbalance Measurements of Thin Film Growth during Atomic Layer Deposition

Wednesday, November 6, 2002, 3:00 pm, Room C-101

Session: Atomic Layer Deposition - Applications of ALD
Presenter: M.N. Rocklein, University of Colorado, Boulder
Authors: M.N. Rocklein, University of Colorado, Boulder
S.M. George, University of Colorado, Boulder
Correspondent: Click to Email
The quartz-crystal microbalance (QCM) has become a very useful, in situ tool for monitoring atomic layer deposition (ALD) in viscous flow reactors. Mass changes can be measured for individual reactant pulses and for the entire ALD reaction cycle. These mass changes reveal information about the ALD reaction stoichiometry and the ALD film growth rate. Unfortunately, serious error in the QCM mass measurement can occur because of temperature effects. We will show that instantaneous apparent mass changes may be caused by differences in temperature between the reactant gas pulse and the QCM and that slow apparent mass drift may be caused by the integrated effect of many individual reactant gas pulses. These effects are clearly demonstrated by modifying the temperature profile along the length of the reactor tube and by using an exposure sequence of inert gases. These temperature effects are also illustrated using Al@sub 2@O@sub 3@ ALD as a model system. The primary factors influencing the magnitude and sign of the temperature-induced apparent mass change are determined to be the QCM temperature, the temperature profile of the reactor before the QCM, the type of gas, the gas flux, the ALD timing sequence and adiabatic cooling of the reactant gas. The results of this study also suggest methods to minimize these temperature-induced apparent mass changes for reliable QCM measurements of ALD in a viscous flow reactor.