Reaearch On Key Technologies Of Vacuum Microelectronic Accelerometer

Accelerometer is an important inertial sensor.High performance accelerometer based on new principle and new technology is the hot research topic in recent years.Vacuum microelectronic accelerometer based on field emission theory has the advantages of solid state devices and vacuum electronic devices in a body,such as high sensitivity,anti radiation,fast response,small size and so on,which is a new exploration of high performance MEMS acceleration sensor.So the research on the key technologies of vacuum microelectronic accelerometer has very important scientific significance and urgent application requirements.Aiming at the science and technology problems in the research of vacuum microelectronic accelerometer,a new structure based on nano-tip array,controllable initial emission space and overload protection was proposed in the paper.The field emission theory was studied and the theoretical model of vacuum microelectronic accelerometer was established.The sensitive structure was designed and optimized.The key technologies of tip array fabrication,low temperature bonding and ICP etching technoogy were break through.The wafer level vacuum packaging was explored and the sample of vacuum microelectronic accelerometer was fabricated.The testing method was studied,and the main performance indexes were tested and analyzed.The main work is listed as follows:?1?The research status and development trend of vacuum microelectronic sensor was analyzed.Aiming at the science and technology problems of vacuum microelectronic accelerometer,the research objectives of this thesis were determinded.?2?Based on field emission theory,the electrical properties both of Eiffel Tower and pyramid shaped field emission cathode were analyzed and the theoretical mode of vacuum microelectronic acclerometer was established.The mechanical and electrical properties was stuied,and the parameters influncing accelerometer performance was analyzed.?3?According to the design goal,a new vacuum microelectronic accelerometer structure based on nano-tip array was put forward.The initial emission space was adjusted by bias voltage;the controlled displacement of sensitive mass with tip array was enlarged by the step between feedback electrode;the tip-protection was achieved by overload protection structure.The fabrication process of vacuum microelectronic accelerometer was simplified,and the electrostatic pull-in failure was effectively restrained.The statics and dynamics performance of sensitive structure was analyzed by ANSYS software,and the structure parameters were optimized.Based on the structural characteristics of vacuum microelectronic acceleration sensor,the wafer level vacuum packaging structure with double bond ring was designed.?4?The Eiffel Tower shaped silicon tip array with good consistency and uniformity were fabricated by optimized HNA isotropic etchant.For good emission properties,the TiW/Au composite metal film was deposited on the surface of silicon tip.The effect of processing parameters both on the anodic bonding and Au/Si eutectic bonding was discussed,and the low temperature bonding process was optimized.The problems of electrode blackening and non-uniformity bonding interface was solved,and the wafer level vacuum packaging process was explored.The micro structure release process was break through,and the sample of vacuum microelectronic accelerometer was fabricated.?5?The test method of the vacuum microelectronic accelerometer was studied and the testing platform was built.The main performance indexes were tested and analyzed.With the bias voltage of 7.6V and the emission voltage of 1.5V,the output current was 52.4?A,the sensitivity was 1.06V/g;the nonlinear was 0.91% and the zero bias stability of 484?g;the resolution was 27?g/Hz^1/2 with the bandwidth of 100¹20Hz,working temperature for-20⁵5?and the anti-Shock function higher than 200g.