Three-dimensional vector accelerometer using SOI structure for high-temperature use

In order to improve the high-temperature reliability of a silicon accelerometer, an accelerometer was fabricated using an SOI substrate and its temperature dependence was compared with that of conventional silicon accelerometers. In addition, the authors attempted to detect the three-dimensional components of the acceleration vector using a new theoretical principle. The new theoretical principle was validated, and accelerometer design was carried out using a program for structure analysis, ANSYS, which is based on the finite element method (FEM). It was found that, in the accelerometer fabricated using an SOI substrate, the offset voltage and sensitivity at temperatures higher than 200 °C were superior to those in the conventional pn junction device. It was also found that the new device could detect acceleration even at 410°C. Using the new device, the acceleration components in the three directions were accurately measured and the sensitivity for the other axis was suppressed to less than 5.7 percent. The frequency characteristic of the new sensor was in agreement with the theoretical results. Because of high-temperature operation and detectability of the three directional components of acceleration, this new accelerometer will be much more widely used.