Preparation Of Key Structure Of Ultrahigh Temperature Thin Film Strain Sensor

The ultrahigh temperature film strain gauge is a micro sensor used for strainmeasurement in ultrahigh temperature.This kind of sensor plays an important role in the quality evaluation and improvement of the specimen.NASA has been studying high-temperature thin-film strain gauges since the 1990 s,and domestic research is still lagging behind.In the structure of high temperature film sensor,insulation layer and sensitive layer are the two most important functional layers.In this paper,micro-nano fabrication technology is used to study the insulation layer and sensitive layer of high temperature thin film sensor.First,a stable alumina sol was prepared and physical properties of the sol were tested.In order to avoid the film cracking during heat treatment,alumina nano-particle suspension was added to alumina sol,which were effectively eliminated the cracks.Then,the influence of the deposition height and liquid velocity on the uniformity of the film was investigated,and the optimal deposition parameters of the film were determined.Uniform density crack-free alumina insulation film was prepared on the basis of 100 silicon wafers.In order to reduce the film surface roughness,the film surface was polished and the film surface quality was improved effectively.The high-temperature stable ? alumina thin film was obtained by 1000 ? high temperature sintering.The insulation resistance was tested in the range of 25-1200?.The results showed that the insulation resistance is 100K?at 1000?,which can meet the test requirements of ultrahigh temperature thin film strain sensor.Two different kinds of composite insulation structures were designed,such as alumina film/alumina mixture and silicon nitride/alumina mixture.High temperature tests show that compared with the insulation resistance of alumina mixture film at 1200?,two the insulation resistance value of two kinds of composite structure increased by 34% and41%,respectively,which proved the effectiveness of the composite structure.Finally,tantalum nitride films were prepared by magnetron sputtering on silicon substrate.Under the condition that other magnetron sputtering parameters are invariable,differentcomponents of tantalum nitride film are obtained by adjusting the nitrogen partial pressure.The effects of nitrogen partial pressure on magnetron sputtering rate,film surface roughness,structure and resistivity were investigated.The phase structure of tantalum nitride film was tested by X-ray diffractometer,and the surface morphology and cross section of the film were observed by field emission scanning electron microscope(SEM).The results showed that: under the pressure of 2% nitrogen,the phase structure of the film was Ta N0.1,and the structure of the membrane was Ta2 N under the pressure of 3% nitrogen,while the structure of the film was Ta N when the nitrogen pressure was 4-6%.High temperature heat treatment of tantalum nitride was carried out by High temperature oven.The resistivity of the tantalum nitride film was measured using a semiconductor parameter test system and a 3d manual probe.The results show that the range of film resistivity is from 80 to 433??.cm is increased to 120-647??.cm.The resistance temperature coefficient of the nitride film prepared under 3% nitrogen pressure was tested within 25-600? range.The results showed that the resistance temperature coefficient was 59ppm/ ?.