Wafer-level Low Temperature Bonding Technology And Performance Characterization Of MEMS

Low temperature bonding technology has attracted amounts of researchers in recent years.Low temperature bonding technology avoids the risks of high temperature to device processing.It has the merite of diverse methods,brief operation,and strong applicability.It has important applications in the new semiconductor materials,high-performance micro/nano devices,three-dimensional integration and packaging,high-density interconnection,integrated photonics and other fields.Gradually,it has become the basic key technology of micro-components in the frontier disciplines.The paper researched the development status of wafer bonding technology both here and abroad.With the view of the science problems in the study of low temperature bonding technology,wafer-level low-temperature bonding technology was conducted between silicon and silicon.Based on combination of spatial domain and morphology,infrared image processing software was designed.It was applied in the detection of bonding voids and bonding rate.Combined with the oxygen plasma activation method,the low-temperature direct bonding experiment was developed.And the activation conditions were optimized.The bonding quality was characterized by various of testing methods and the mechanism was analyzed.The major work accomplished are as follows:(1)The research status of wafer bonding technology was briefly described.The technology problems existing in the bonding process were deeply analyzed.The research value and practical significance of low temperature bonding were clarified,and the overall research programs of this thesis were determinded.(2)Based on combination of spatial domain and morphology,the infrared image processing method was studied.The key parameters of the image processing algorithm were optimized.The software analyzed the proportion of voids in the infrared image.This method needed simpler decomposition and reorganization process compared to wavelet denoising.The normalized high-pass filter avoided image brightness offset,protected sharpening effect,and restored background details.It was inspected the rules of void formation and the impact on bonding rate.The change of the number and diameter of voids was explored in the bonding interface.The criterion of void's causes were established,which has the significance for the analysis of interface mechanism.(3)According to the oxygen plasma surface activation method,the low-temperature direct bonding experiment was developed.The orthogonal experiments were designed and carried out,and the key process parameters affecting bonding quality were determined.With the optimized process parameters of activated power of 150 W,O₂ flow of 100 sccm,and time of 60 s,the bonding rate reached 93.04%and the bonding strength was 18.58 MPa.It was far satisfied with the requirement for tensile strength in the US military standard of MIL-STD-883E.And this method could be applied to the production of high-standard electronic chip products.(4)All sorts of performance characterization methods were applied to test the interface characteristics,such as contact angle,fourier transform infrared spectroscopy,scanning electron microscope and transmission electron microscopy.The test results showed that appropriately increasing the energy and concentration of the oxygen plasma helped to increase the number of hydroxyl groups on the surface and improve hydrophilicity.With the tensile strength of 12.32 MPa,the bonding interface was flat and tight,and the dehydration condensation reaction was thoroughly accomplished.A large number of silicon-oxygen covalent bonds were expressed by the form of SiO_X,and the thickness of the intermediate amorphous layer was about 3.58 nm.