IN-SITU CONDUCTIVITY CHARACTERIZATION OF OXIDE THIN-FILM GROWTH PHENOMENA ON MICROHOTPLATES

Through the use of silicon micromachining, we have developed a microho tplate structure capable of reaching temperatures in excess of 500 deg rees C, onto which thin films have been selectively grown via metalorg anic chemical vapor deposition. The microhotplate structure contains s urface electrical contacts which permit conductance measurements to be made on films during and after deposition, and therefore presents som e unique opportunities for the in situ characterization of growing fil ms as well as for novel gas sensing approaches. We have investigated t he deposition of conducting oxides such as SnO2 and ZnO on these micro hotplate platforms for gas sensing applications. The conductance of th e deposited films has been measured in situ as a function of time, and used in combination with postdeposition thickness measurements to pro vide insights into the growth rate of the oxide films. Results indicat e that our conductance measurements are sensitive, in certain cases, t o changes in the film thickness on the order of an angstrom. Conductan ce oscillations observed during the growth of ZnO thin films have been attributed to variations in the precursor concentration, and were det ected as a gas sensor response by the growing films. (C) 1998 American Vacuum Society.