Graphene Pressure Sensor Based on Flip-Chip Bonding and Porous Silicon Nitride Membrane for Negative Pressure Measurement

Graphene is regarded as a highly promising material for Micro/Nano Electro-Mechanical Systems (M/NEMS) pressure sensors due to its exceptional mechanical and electrical properties. However, graphene pressure sensors often exhibit poor stability and sensitivity because the graphene sensitive layer is prone to oxidation, damage, and contamination in harsh environments, which further limits their practical applications. We designed and fabricated a novel graphene pressure sensor based on flip-chip bonding and a porous silicon nitride membrane. The sensor utilizes a hexagonal boron nitride/graphene/hexagonal boron nitride (h-BN/Graphene/h-BN) sandwich heterostructure and a Cu-Sn flip-chip bonded inert gas sealing cavity to protect the graphene. The porous silicon nitride membrane is placed above the heterostructure to achieve high sensitivity of the pressure sensor. Finite element simulations revealed that the maximum strain in the porous Si₃N₄ membrane is approximately 2.5 times higher than that in the non-porous membrane. Static testing of the sensor showed a sensitivity of 3.54 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> kPa<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> within the range of -80 to 0 kPa, representing an improvement of nearly 22% compared to graphene pressure sensors with non-porous silicon nitride membranes. Stability tests demonstrated that the sensor maintains relatively stable resistance even under high-temperature and high-humidity conditions. This work provides a reference solution for enhancing the stability and sensitivity of graphene pressure sensors.