Design, Fabrication And Measurement Of LTCC Capacitive High-temperature Pressure Sensor

In recent years, there has been a growing demand for both military and civil use industryabout pressure signal obtainment under high temperature environment, in which traditionalpressure sensors show great limitation. This dissertation presented a capacitivehigh-temperature pressure sensor based on LTCC(low temperature co-fired ceramic) whichwould not only solve the problem of pressure signal obtainment under400°C-600°C hightemperature environment, but also start new method and ideas for sensors structure design, itwould be of great guidance and reference for future MEMS structure design and fabrication.Summing up the research status of both home and abroad，this paper focused on thedesign, fabrication and key processes, and measurement of LTCC capacitive high-temperaturepressure sensor.In the design chapter：the electromagnetism model and Planar spiral inductor model ofLTCC capacitive high-temperature pressure sensor was introduced; the capacitance variationof the senor was analyzed based on the electro-mechanical principal; the LTCC capacitivehigh-temperature pressure sensor structure model was designed, simulated and verified; thefrequency-pressure function of the model was discussed and theoretical sensitivity isobtained.In the fabrication and key process chapter: The LTCC material and technology wasintroduced; the key processes: pressure sensitive membrane process and air-hole sealingprocess were elaborated, especially with the novel bringing in of carbon film as sacrifice layerin the pressure sensitive membrane process, more favorable flatness of sensitive membranewas realized and higher sensitivity was achieved; the fabrication flow of LTCC capacitivehigh-temperature pressure sensor is presented and related process for improvement wasdiscussed. In the measurement chapter; the subatmospheric pressure measurement platform wasbuilt, where the surface topography of the sensor and deformation of the sensitive membranewere scanned and analyzed; the room-temperature uniform pressure measurement platformwas built; where batches of sensors were tested and experimental results were comparedwith theoretical ones, world-widely advanced sensitivity of the sensor was demonstrated;high-temperature measurement platform was built, where sensor behavior under hightemperature was tested and temperature parasitic parameters were analyzed.