Standard MEMS Capacitive Accelerometers for Harsh Environment

Abstract

Many markets have already successfully introduced MEMS based products in a very large panel of applications. When looking carefully at the market implantation, it is very interesting to see that benefits of this technology go well beyond the obvious size advantage. Size and weight but also performance, power consumption, parallel manufacturing capability and cost or reliability are common arguments in favour of this family of products. Nowadays, standard MEMS technologies give access to a broad range of unexpected new applications opportunities by always pushing the products at their limits, mainly in term of environmental constraints. Great potentials have been demonstrated and have engendered development alliance to improve the performances of the products in so called harsh environments: Imagine the utilization of an accelerometer in oil and gas prospecting applications. They must provide precise measurements in a very high or cold temperature environment, in a world of extreme vibrations and must potentially endure very high shocks. The objective of this presentation is to review actual results and current limitations when using MEMS sensors in harsh environments (temperature, shock, vibration, environment, security). The conjunction of material and technologies (standard Si, SiC or SOI), advanced micromachining techniques and advanced assembly techniques are the key to provide robust sensors. Within a large portfolio of examples, the following applications will be presented and developed in more details: • Accelerometers surviving shock levels up to 20’000g with minimum impact on specification. • Very robust MEMS sensors used between −120°C and +180°C. MEMS sensors in harsh environment are already a reality and various products are already available off the shelf and supplied with high volume opportunities.