APPLICATION OF HIGHLY ORIENTED, PLANAR DIAMOND (HOD) FILMS OF HIGH MECHANICAL STRENGTH IN SENSOR TECHNOLOGIES

Diamond possesses many characteristics of an ideal material for micros ensors, and has indeed emerged as a promising candidate. In comparison to its competitors Si and SiC, large area diamond films are still pol ycrystalline and inhomogeneous in grain size and orientation. This sti ll 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 ca n now be fully implemented, allowing one to scale high performance mic romechanical sensor structures into the lower micrometer range. In thi s paper, a novel concept based on selective area epitaxy (SAE), pulse doping, reactive ion etching, multilayer contacts and wet chemical bac kside patterning with micron resolution is presented. The elastic prop erties and the piezoresistive characteristics of boron doped diamond h ave both been investigated from diamond cantilever beam deflection mea surements. For 15 mu m thin HOD-films, a Young's modulus of approximat ely 830 GPa has been extracted From resonance frequency measurements a nd nanoindentation measurements. From this data a Fracture strength of sigma(fr)=2.72 GPa is calculated. To our knowledge, these data repres ent the highest values reported up to now for such thin films. (C) 199 8 Elsevier Science S.A.