| MEMS sensors are characterized by small size,low energy consumption,high degree of integration,and great development potential.However,the high temperature oxidation problem of MEMS sensor sensitive materials limits their further development in the fields of aerospace,nuclear power generation,and civil production.Therefore,the protection technology of sensitive materials is crucial for MEMS high-temperature sensors.Aiming at the protection of MEMS high-temperature sensors in high-temperature measurement,this paper proposes a Pt–Pt flip chip bonding method for high-temperature packaging,and uses this method to fabricate an oxygen insulated sealing chamber to achieve high-temperature oxidation resistance protection for sensitive materials.First,the structure of Pt–Pt hot-press bonding chip and substrate is designed,Each group of bonding chips is composed of 16 sealing cavity structures.The size of bonding bump and sealing ring is designed in detail,the total bonding area is determined,and the high temperature resistance experiment of Pt wiring is designed.The optimal thickness of bonding substrate is determined by combining the heat transfer principle and finite element analysis method simulation.Then the process flow design and lithographic mask design of the chip and substrate are carried out,The photolithography process,metal sputtering process and metal stripping process are described in detail.The key point is to explore the process parameters of Pt–Pt hot pressing bonding.Combined with the Ar（5%H2）plasma pretreatment method,the control variable method is adopted,and the bonding pressure is used as the reference variable to keep the bonding time（350℃）and the bonding time（1200 s）unchanged,and the influence of the bonding pressure on the quality of Pt–Pt bonding is explored.Finally,the samples successfully bonding were tested and characterized.It mainly completed the characterization and analysis of the bonding interface of Pt–Pt bonding samples,the test and analysis of the shear resistance of the bonding samples,the test of the gas tightness of the samples and the analysis of the bonding failure efficiency,and carried out the high-temperature resistance test on the Pt wiring samples.The results show that there is no obvious crack on the bonding interface,the overall surface tends to be smooth,the metal thickness and element distribution after bonding are the same as expected,and the Cr element has a tendency to diffuse into the Pt layer,indicating that the interconnection effect is good.The shear force and air tightness are positively correlated with the bonding pressure.When the bonding pressure is 100 MPa and the bonding time is 20 min,the maximum shear resistance reaches 30MPa.The thrust test shows that the fracture interface is mostly on the silicon-metal layer,which indicates that the bonding interface is stable and not easy to fracture.The hermeticity of the sample meets the relevant standards,and the minimum leakage rate is only 1.29×10-5 Pa·cm3/s.By comparing the bonding failure rates under different bonding temperatures and pressures,the process parameters with higher Pt-Pt bonding success rates were obtained:temperature above627 K,pressure above 50 MPa.The Pt wiring was tested for temperature resistance at 1500℃.The 500 nm thick Pt wiring was completely damaged after 2 hours of high temperature test,while the 1000 nm thick Pt wiring was not completely damaged,which can withstand high temperature for a long time,indicating the development potential of Pt in the field of MEMS high temperature sensors and packaging. |
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