temperature storage, we introduced a thin buffer layer into the A low temperature hermetic wafer bonding using In/Sn under bump metallization (UBM). The buffer layer plays two interlayer and Cu/Ti/Au metallization was investigated for roles. Firstly it is used to prevent diffusion during materials MEMS and sensor packaging application. Bonding was evaporation, room temperature storage, and at the initial stage performed in a vacuum wafer bonder at 1800C and 1500C for of bonding between SnIn and Cu, which will allow the solder 20min under 5.5MPa. It is found that bonding at 1800C, voids materials on each die has chance to wet the metallization and free joints composed of high temperature intermetallic to form a good seal. Then, since buffer layer is thinner, it can compounds (IMCs) were obtained with good hermeticity and be dissolved or broken out, which allow the diffusion reliability. However, bonding at 1500C, voids were generated happened between solder and high temperature component to along the seal joint which caused poor hermeticity comparing form IMCs. with that bonded at 1800C. After four kinds of reliability tests, By introducing thin Ni buffer layer, we have successfully i. e., Pressure cooker test, high humidity storage, high achieved high yield hermetic wafer level bonding using In/Sn temperature storage, temperature cycling test, dies bonded at with respect to Cu metallization system at 1800C. In this case, 1800C showed good reliability properties by hermeticity test Ni was resolved into solder alloy and was incorporated into and shear tests. Present results proved that high yield and low CuSnIn high temperature compounds [9-10]. From the point temperature hermetic bonding can be achieved by using of view of reliability, we would like to get a thinner IMC Sn/In/Cu metallization with thin Ti as a buffer layer.layers. Then a more effective buffer layer is preferred. In Introduction addition, since thin Au layer is employed upon the solder surface to prevent oxidation, AuIn phase is formed inside Low temperature fluxless solder bonding process is a CuSnIn IMCs during bonding. We hope the buffer layer can promising MEMS packaging technology demanded by promisng MES pacagingtechnlogy emandd by mprove the adhesion between different IMCs. It iS known that industrial users because it offers comparative advantages such imrvthadeonbwenifrntIC.tiskwnht Ti has a good wetting property with various solders and at the as low residual stress [1-2]. Wafer level bonding is a cost-same time, it is a more effective barrier layer comparing with effective method for MEMS packaging. Low-cost vacuum Ni to these solders [11]. Further, it is difficult to be resolved packaging of MEMS has become one of the most important into liquid Sn-In solder. The effect of such kind of buffer layer challenges [1][2]. For eutectic wafer bonding, researchers have '~~~on the wafer level bonding needs to be studied and investigated several systems of low temperature solders and understood. In present research, we try to use Ti as a buffer hig...
