Electron Irradiation Induced Crystallization of Amorphous Al 2 O 3 Films on Silicon Substrates
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ELECTRON IRRADIATION INDUCED CRYSTALLIZATION OF AMORPHOUS A12 0 3 FILMS ON SILICON SUBSTRATES J. Liu*, C. J. Barbero*, J. W. Corbett*, K. Rajan**, and H. Leary*** Department of Physics, SUNY at Albany, Albany, NY 12222 **Material Engineering Department, NY State Center for Advanced Technology in Automation and Robotics, Rensselaer Polytechnic Institute, Troy, NY 12180 ***IBM Corporation, East Fishkill, NY 12533 ABSTRACT An in situ study of electron beam irradiation induced amorphous-to-crystalline transformation of A12 0 3 films on silicon substrates has been carried out using transmission electron microscopy. Trigonal a-A12 0 3 crystallites can be observed for electron beam dose rates larger than 10 mA/cm 2 . It is found that the nucleation and growth processes dominate near the A12 0 3 -Si interface. The possible effect of the silicon substrate on the growth of A12 0 3 crystallites is considered. INTRODUCTION Aluminum oxide films have several advantages due to the very low mobility of ionic impurities (such as Na+) in it, high radiation resistance, high dielectric constant.[1,2] They can be used as masking layers against diffusion of impurities during device processing, surface passivation, insulation in multi-layer interconnections, fabrication of capacitors, and insulatedgate field-effect transistors (IGFET). Recently, epitaxial aluminum oxide film has been proposed as an insulating layer for silicon on insulator (SOI) structures,[3,4] and the metaloxide semiconductor field effect transistors (MOSFETs) on Si/A1203/Si structures have been realized.[5] Aluminum oxide is known to have various metastable states.[6] There are different routes for phase transformation from its amorphous state to the a--phase depending on both the preparation methods and conditions.[6-15] Although the phase transformations in the bulk materials may be well characterized, the same material in thin film form may have properties substantially different from those of the bulk. One reason is that phase transformation in thin films may strongly influenced by the properties of the underlying substrate, while in the bulk materials this is not the case. Our recent work has shown that the stress can enhance grain growth in an A12 0 3 thin film near the interface region.[16] In the present paper, we summarize the experimental results and give explanations for the observed e-beam-induced abnormal amorphous-to-crystalline (a/c) transformation of the A12 0 3 film near a A12 0 3/Si interface. EXPERiMENTAL PROCEDURES The wafers used in this study ars. oriented p-type, boron doped, resistivity of 11-15 Q cm, dislocation-free silicon covered with a chemical vapor deposited (CVD) amorphous A12 0 3 thin film supplied by the East Fishkill IBM Corporation. A JEM-100CX 100 KeV electron microscope was used for the in situ study. The samples were prepared by standard procedures for transmission-electron-microscopy (TEM). For TEM observations, specimens of cross-sectional geometries were used. Argon-ion-milling was done at 5 KV, 20 mA specimen current with a s
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