Wafer-Level Hermetic Package by Low-Temperature Cu/Sn TLP Bonding with Optimized Sn Thickness

• DOI: 10.1007/s11664-017-5546-1
• Publication Date: 2017-05-10T10:49:11Z
• Authors: Zijian Wu; Jian Cai; Qian Wang; Junqiang Wang; Dejun Wang
• Keywords: Wafer Bonding; Shear Strength; Bonding strength; Anodic bonding

In this paper, a wafer-level package with hermetic sealing by low-temperature Cu/Sn transient liquid phase (TLP) bonding for a micro-electromechanical system was introduced. A Cu bump with a Sn cap and sealing ring were fabricated simultaneously by electroplating. The model of Cu/Sn TLP bonding was established and the thicknesses of Cu and Sn were optimized after a series of bonding experiments. Cu/Sn wafer-level bonding was undertaken at 260°C for 30 min under a vacuum condition. An average shear strength of 50.36 MPa and a fine leak rate of 1.9 × 10−8 atm cc/s were achieved. Scanning electron microscope photos of the Cu/Sn/Cu interlayers were presented, and energy dispersive x-ray analysis was conducted simultaneously. The results showed that the Sn was completely consumed to form the stable intermetallic compound Cu3Sn. An aging test of 200 h at 200°C was conducted to test the performance of the hermetic sealing, while the results of shear strength, fine leak rate and bonding interface were also set out.