Research On The Design And Preparation Technology Of Thin Film Strain Sensor

Because the size of modern devices are decreasing gradually and they are easier to be integrated,the combination of thin-film technology and sensor technology makes traditional sensors play a more important role.The force signal can be converted to electrical signal by the thin-film sensor and after the subsequent amplification and filtering process to get a useful signal to determine the working status of the toolholder.In modern industry,large machine tools are the key tool in the production of industrial productivity and product quality,so the real-time monitoring of the working condition of machining tools has great significance.In addition,thin-film strain gauges are widely used in weighing and drilling applications because of their high integration,small size,high strain-transfer efficiency and sensitivity.Since the applied devices are usually metallic materials,it is necessary to add an insulating layer to prevent short circuit and structural failure of the strain gage to play the role of insulation and transition,and then prepare a functional layer on that.Moreover,a protective layer can eventually be deposited to form a composite structure for more stable strain measurement.Therefore,it is crucial to investigate the materials and preparation processes of the insulating and functional layers of composite thin-film strain gages.This thesis explores the hard mask patterning and UV lithography patterning processes,summarizes the advantages and disadvantages of both processes,and selects the lithography process to realize the strain gate patterning process according to the demand and obtain suitable lithography process parameters finally and the final exposure time is 8 s and the developing time is 35 s.In this thesis,the radio-frequency magnetron sputtering is used to deposit Al₂O₃ thin films and combine with orthogonal experiments to research the influence of process parameters on the films and optimize the process parameters.Additionally,the ratio of oxygen to argon during the reactive sputtering process is focused on,and the final oxygen-aluminum atomic ratio in Al₂O₃ films prepared at oxygen to argon ratios of 4%to 4.8%is 1.5.In addition,to investigate the effect of thickness and heat treatment of Al₂O₃ films,the I-V characteristic curves of the films are investigated using the capacitive structure.The increasing of thickness and annealing temperature can effectively reduce the film leakage current and improve the insulation performance.But the ideal effect can not be achieved on the metal substrate,so the smoothness of the metal substrate is improved while optimizing the film preparation process.Because the surface of the toolholder will be affected in too high temperature environment,the final heat-treatment process is determined to be annealing at 550℃ for 1 h in O₂ atmosphere.In addition,the effect of sputtering parameters on the preparation of NiCr films is investigated by DC magnetron sputtering technique on sapphire substrates,and strain gates are fabricated to test their mechanical properties.Finally,at room temperature and sputtering power of 98 W and 0.5 Pa working air pressure,the lowest TCR of NiCr film is 188 ppm/℃.