Study On The Application Of Bonding Technology For Cu/Sn Isothermal Solidification In MEMS Hermetic Package

To protect devices from damage and contamination for longer lifetime, hermetic packaging process has become required characteristics for most MEMS application. Base on the theory of isothermal solidification (IS) which is a process whereby reaction or/and diffusion taking place between a liquid of low melting metal and a solid of high melting one at a constant temperature slightly above the low melting point, to form intermetallic compound or solid solution., this thesis aims at exploiting a new hermetic packaging method in consistence with most common technique used in modem MEMS package at present. For some specific systems, a distinct feature characterized by IS is that the finally formed phases would remelt at a high temperature than that at which they form. This phenomenon makes it possible that a joint be made at a low temperature while capable of withstanding high operation temperature.Cu/Sn was chosen as the bond media in this thesis. With the inspection of shear strength test, x-ray inspection metallographic test and SEM&EDX analysis, The process and materials parameters such as plasma treatment, bonding environment, load and thickness of the Sn layer are evaluated. Plasma treatment is the key of the whole process. After optimization, the power of plasma treatment is set at 500W and the dwell time is fixed to 200 seconds. The bonding environment plays an important role and the results shows under vacuum environment the bonding strength of the sample is larger than those under other environments. The bonding strength is competitive under a small load. The samples with the different thickness show nearly the same performance under the shear test. With the optimized condition, all the bonds can pass the shear strength test specified by MIL STD 883E, Method 2019.5.At last, the hermeticity of the bond structure manufactured by Cu/Sn IS process wasAbstractevaluated. Preliminary results show the bond structure can satisfy the hermetic package criterion of American Military Standards.This thesis has completed the exploitation of the bond method. The feasibility of employing this method to the MEMS hermetic package application has been investigated. The thesis work lays the foundation for the further research.