Stress of TiO 2 Thin Films Produced by Different Deposition Techniques
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STRESS OF TiOZ THIN FIuLS PRODUCED BY DIFFERENT DEPOSITION TECHNIQUES C. OTTERMANN, AND K. BANGE
J.
Schott Glaswerke,
OTTO, U. JESCHKOWSKI,
0. ANDERSON,
Research & Development,
M. HEMING
6500 Mainz,
Germany
ABSTRACT Stress in thin films has been measured very precisely (< 10 MPa) by analysing the curvature of quartz glass substrates before and after film deposition by means of a ZYGO Mark IV interferometer system. TiO2 films of approximately 100 nm thickness were prepared by reactive evaporation (RE), reactive ion plating (IP), plasma impulse chemical vapor deposition (PICVD) and spin coating (SC). Large variations in stress are found for different coating techniques and deposition conditions. This can be correlated to differences in optical properties, film density and crystalline structure. Relaxation effects and the influence of thermal treatment are also studied. The crystallization of amorphous TiO2 during heat treatment is accompanied by significant changes in film stress. The crystal size and morphology of Ti0 2 films after heat treatment strongly depend on the deposition technique and process conditions. INTRODUCTION Investigating the relationship between microscopic structure and mechanical properties is one of the primary objectives in thin film technologies. In recent years much attention has been devoted to the development of more and more sophisticated coatings and film production methods. Especially, the complexity of coatings on glass surfaces is widely increased to extend the field of applications of this material or to meet the higher demands of more tougher specifications. Objectives for the development are coatings with specific optical, electronic or magnetic properties and additionally increased durability and stability against temperature treatment and chemically aggressive media in ambient surroundings. Most sophisticated coating systems exhibit a large total thickness because they typically consist of a larger amount of single layers in a stack. Therefore, other basic properties of these films can be extremely important to guarantee the functionality of the final product. For example, the stress of the materials used should be below a certain limit to avoid cracking or detachment of coating causing a catastrophic failure of the coated part. Besides the correct choice of coating material and deposition process, production parameters have to be optimized with respect to film stress. Additionally, it is necessary to understand the influence of basic key properties of the materials which affect their intrinsic stress behaviour, like density, chemical composition or crystalline structure. In this paper we present results of systematic investigations of titania thin films prepared by different techniques, i.e. reactive evaporation, reactive ion plating, plasma impulse Mat. Res. Soc. Symp. Proc. Vol. 308. ©1993 Materials Research Society
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Stress of the chemical vapor deposition and spin coating. coatings has been measured using interferometric methods and analysing the changes in topo
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