Wafer Level Package with Y shaped TSV and Vacuum Sealing by Cu-Sn Isothermal Solidification for MEMS Resonator Open Access

A novel WL- CSP structure for MEMS device is proposed. Key features are: “Y-shaped” TSV is fabricated to reduce cost; Cu-Sn isothermal solidification is used to achieve lower temperature bonding; I/O interconnection and vacuum sealing are achieved simultaneously simplifying the whole process. Average shear strength of 25.5 MPa and excellent leak rate of around 1.9×10⁻⁹atm cc/s have been achieved, which meet the requirements of MIL-STD-883E. Four point probe setup is used to measure the resistance of the “Y shaped”-TSV and the contact resistance of the Cu/Sn IMC bond joint. “Q factor extraction method” is used to monitor the vacuum property of the packaging structure by integrating a MEMS resonator with a resonant frequency of 1.3 KHz. Reliability tests such as long-term and accelerated life testing are also performed both achieving good results.