Microsensor applications based on doped diamond thin films

The development of simple diamond based sensors for mass production is reported. To make a diamond film based sensor in micron dimensions a success as an industrial product, it has to be shown, that such sensors can technically and economically be produced in large numbers. For a number of different applications such as mass flow meters, pressure transducers, thermistors, IR-windows and sensing devices, free standing membranes of diamond are required either as support and/or as sensing element. In all these cases the deposition of diamond and p-doped diamond is performed by thermal filament CVD (TF-CVD) or by μ-wave/electron cyclotron resonance-CVD (μ W/ECR-CVD) on wafers of 4" diameter with a coating uniformity of ±5% of the average film thickness. The substrate temperature is kept at all times at 800°C, the filament temperature at 2300°C±100°C when using TF-CVD. These deposition conditions provided a constant and reproducible diamond quality of low impurity (originating from the filament material) as well as of graphite, sp². The coatings are fairly smooth, with an average roughness, R_a, of 0.1 μm. An integrated gas-flow transducer has been fabricated to demonstrate the feasibility