Sapphire-based capacitive pressure sensor for high temperature and harsh environment application

Using sapphire for the sensor chip material, we developed a capacitive pressure sensor for a low-pressure range (0-5 kPa). The features of this sensor are oil-free, the capability of measurement in a highly corrosive medium and at high temperatures. The sensor chip is fabricated through investigations on the improvement in diaphragm size and the anisotropy of sapphire to reduce temperature dependent sensitivity and to make measurement at high temperatures possible. Sapphire etching, direct bonding, and other sapphire processing techniques are developed for the fabrication of the chip. As a result, an extremely low temperature-dependent sensitivity (0.001%F.S./°C at 5-45°C) without any thermal compensation is achieved. This shows the capability of accurate operation at high temperature such as hundreds °C from ambient.