Research On Fabrication Technology Of Resonant Micromechanical Acceleration Sensor Based On Mask-maskless Etching

The micro machine acceleration sensor is a sensor that measures inertial forces.The advantages are small size,light weight,low cost and easy batch production.The resonant sensors output frequency signal,don't need to add extra A/D converter,reducing the complexity of the design of the test circuit.Therefore,it is of great significance to study the resonant micro accelerometer.In this paper,a new type of resonant micro accelerometer based on mask-maskless etching technology is studied.The sensor is composed of mass,resonant beam and support beam.The main structural features of the sensor is that the resonant beams are located on the surface of silicon wafer,and the center of gravity about the support beams are in the neutral surface of the mass.Support beams and resonant beams are release at the same time.This structure can avoid the effect of the X-axis and the Y-axis accelerations on the Z-axis acceleration measurement,and the sensitivity of the cross-axis is reduced,simplifying the device structure,reducing the difficulty of packaging.This paper focuses on the fabrication process of the resonant micro accelerometer.The diffusion process of polysilicon is studied,and a polysilicon resistors with uniform resistance is fabricated.The resistance of doped polysilicon resistors contacted by the Ti/Pt/Au metallization system or Pt₅Si₂-Ti/Pt/Au metallization system undergone different temperatures and time are measured.The ohmic contacts of Ti/Pt/Au metal lines at different annealing temperatures is compared.By studying the failure temperature of ohmic contacts of Ti/Pt/Au metal lines,the optimum alloying temperature and the constraint temperature of Ti/Pt/Au metal lines are found.The relationship between the lateral recession of the one edge and etching depth during mask-maskless etching in the release process of the support beam is studied,which provides a theoretical basis for device structure design.The possible problems in the release of resonant beams are analyzed and the protection methods are put forward.