Deposition of aluminum Oxynitride Films by Magnetron Sputtering: Effect of Bombardment and Substrate Heating on Structur
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ABSTRACT Aluminum oxynitride films, 1pim thick, are deposited onto glass substrates by planar magnetron sputtering from an alumina target in a mixture of nitrogen and argon. One set of films is deposited onto glass substrates that are heat sunk to a holder, whose temperature is held below I 00°C. A second set of films is deposited onto glass substrates that are mechanically clamped to a holder, whose temperature is allowed to rise up to 250'C. Characterization by continuous indentation testing, secondary electron microscopy, and x-ray diffraction reveals significant differences in mechanical properties and surface structure between the two sets of films. Films deposited with holder cooling have a smooth surface and no evidence of crystallinity; films deposited without holder cooling have etch pits on their surface that vary with position across the substrate. The later films show crystallinity and have twice the hardness and a 60% greater elastic modulus.
INTRODUCTION Alumina is a hard, inert, transparent ceramic. These properties are often desirable in a protective coating. Alumina films with bulk-like properties can be deposited by chemical vapor deposition (CVD) but high (>800'C) deposition temperatures are required [1]. Alumina films can also be produced at lower temperatures by physical vapor deposition (PVD) techniques such as sputtering. In general the properties of alumina films deposited by PVD techniques are inferior [1]. Many properties of films, such as hardness, adhesion to substrate and crystallinity depend critically on deposition conditions. One of the most difficult conditions to control is substrate temperature, especially when the substrate is a relatively poor conductor, such as glass. In this study we examine the mechanical and structural properties of sputter-deposited aluminum oxynitride films subjected to two commonly used methods of thermal management: simple clamping of substrates to an uncooled holder and pasting down substrates to an intentionally cooled holder. Indentation testing is used to determine hardness, elastic modulus (defined as E/(1-u 2), where E is Young's modulus and u is Poisson's ratio) and indentation fracture toughness. Secondary electron microscopy (SEM) and x-ray diffraction (XRD) are used to characterize film morphology and crystallinity. Changes in the properties of the films are discussed in terms of bombardment and thermal effects.
FILM PREPARATION AND CHARACTERIZATION Films are prepared by the technique of planar magnetron sputtering. The sputtering system is built around a stainless steel chamber approximately 15 liters in volume pumped by a 50 I/s turbomolecular pump backed by a mechanical pump. It achieves a base pressure of 4x10-5 Pa (3x1 0-7 torr). Nitrogen and argon gas are introduced into the chamber through leak valves. The gas pressure is monitored by either a pirani gauge or a capacitance manometer. 311 Mat. Res. Soc. Symp. Proc. Vol. 388 01995 Materials Research Society
A 2" diameter planar magnetron source is mounted in the chamber with the target
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