The effect of diaphragm on performance of MEMS pressure sensor packaging

MEMS (Micro Electro-Mechanical System) is a technology that offers significant advantages over various microscopic elecromechanical devices. In the field of MEMS products, pressure sensor represents a considerably mature technology and has been extensively used in a variety of applications. Nevertheless, packaging is a key issue among the processes of MEMS manufacture due to the specialty and complexity of MEMS devices. For isolated packaged MEMS pressure sensor, design and fabrication of insulated diaphragm structure is a key factor as it directly affects the accuracy and reliability of packaged pressure sensor. Thermal expansion will emerge among the parts of pressure sensor when working temperature is extremely high. In this paper, finite element method is applied to study the issue on thermal expansion of silicon oil under using flat diaphragm and corrugated diaphragm, respectively. Simultaneously, the volume expansion of silicon oil under using the two diaphragms is calculated. Through comparison, it can be found that the volume expansion of silicon oil under using corrugated diaphragm is less than that when using flat diaphragm along different path. Therefore, conclusion can be achieved that optimization of insulated diaphragm structure will be superior in realization of transmission of pressure almost without loss and relief of additional pressure to the sensor chip induced by thermal expansion of silicon oil.