Design And Preparation Of Multi-spring Cantilever Structure Micro-Acceleration Sensor

Acceleration sensor is the core component of inertial measurement system and have a wide range of application in geological exploration such as minerals and oil and gas field exploration.With the increasing accuracy requirements for geological structure exploration,the traditional accelerometers used for geological exploration have been unable to meet the increasingly high detection requirements for microseismic detection.Micro Electro Mechanical System(MEMS)accelerometers provide new impetus for the development of seismic exploration.The MEMS accelerometer uses monocrystalline silicon as the mechanical structure body,and has the advantages of structural stability,high elastic modulus,and high Q value.However,the current MEMS accelerometers are pursuing miniaturization,structural design is limited,and there are disadvantages such as low detection accuracy for microseismic detection.In this study,Designed and prepared a multi-spring and large-mass cantilever structure acceleration sensor with a resonant frequency of about 10 Hz and a small seismic signal detection.The main research contents are as follows:1.Designed the sensitive components of the capacitive multi-spring mass acceleration sensorThe sensitive component of the capacitive multi-spring mass accelerometer is made of silicon,on which six pairs of spring-mass cantilever structures including inner and outer frames are processed.The COMSOL simulation analysis of the structure shows that the natural frequency of the silicon structure of the sensitive component is 10.56 Hz.The mass of the sensitive component sinks under the action of gravity is 70 microns.The upper surface of the silicon structure of the sensitive component comprises two metal layers,two insulating layers and one ohmic contact layer.The metal layer II comprises an array capacitor plate,a feedback coil,and an electrical signal derivation line.The array capacitor plate and the feedback coil are designed on the upper surface of the mass.2.Design magnetic feedback control structureA feedback coil having a size of 14 mm×8 mm and a total length of about 1.5 m is designed on the mass of the sensitive component,and the coil is placed in a uniform magnetic field to realize magnetic field force feedback control of the mass.The single feedback magnet unit is composed of two lengths and widths.The neodymium iron boron magnet with a height of 20×9×4 mm and a pure iron with a length,width and height of 20×20×5 mm are simulated by MAXWELL.The feedback magnet can generate magnetic field strength in a rectangular region of 6.4 mm×18 mm.A uniform magnetic field of 0.68 T with a magnetic field uniformity of 10-2 covers the feedback coil on the sensitive component.3.Preparation of sensitive components of MEMS accelerometerThe preparation of sensitive components of MEMS accelerometers is realized by multi-step processes such as cleaning,photolithography,sputtering,stripping,photolithography and etching.A special mask mask is designed to reduce the accumulation error caused by photolithographic alignment marks.By reducing the thickness of the silicon oxide and the annealing of the silicon oxide and the metal layer,the stress mismatch between the silicon oxide and the metal layer of the insulating layer is eliminated.Preparation of three inner frame six spring-mass sensing elements using DRIE etching process.4.Design and preparation package structure of MEMS accelerometerThe upper end cover-sensitive element-lower end cover sandwich packaging structure is used,and the upper end cover and the sensitive component are bonded by metal bonding,and the lower end cover and the sensitive component are bonded by anodic bonding to realize packaging of the sensitive component of the acceleration sensor.A feedback magnet is symmetrically mounted on the outside of the upper and lower end caps in a direction perpendicular to the plane of the sensitive component to establish a stable and uniform feedback magnetic field.