Application of highly oriented, planar diamond (HOD) films of high mechanical strength in sensor technologies

Abstract

Abstract Diamond possesses many characteristics of an ideal material for microsensors, and has indeed emerged as a promising candidate. In comparison to its competitors Si and SiC, large area diamond films are still polycrystalline and inhomogeneous in grain size and orientation. This still determines the material properties, and thus the sensor technology and device performance. However, highly oriented diamond films of high quality have been developed recently, using a modified bias enhanced nucleation method [1]. These films can be described by highly planar, textured surfaces, mirror like backsides, low internal stress and high mechanical strength. Conventional semiconductor processing schemes can now be fully implemented, allowing one to scale high performance micromechanical sensor structures into th lower micrometer range. In this paper, a novel concept based on selective area epitaxy (SAE), pulse doping, reactive ion etching, multilayer contacts and wet chemical backside patterning with micron resolution is presented. The elastic properties and the piezoresistive characteristics of boron doped diamond have both been investigated from diamond cantilever beam deflection measurements. For 15 μm thin HOD-films, a Young's modulus of approximately 830 GPa has been extracted from resonance frequency measurements and nanoindentation measurements. From this data a fracture strength of σfr=2.72 GPa is calculated. To our knowledge, these data represent the highest values reported up to now for such thin films.