Solid–Liquid Interdiffusion Bonding of Cu–Sn–Cu Interconnection and Sealing for High-Temperature Pressure Sensor Based on Graphene

Cu–Sn–Cu solid–liquid interdiffusion (SLID) bonding for high-temperature pressure sensors based on graphene has been investigated. Square bumps with a length of
$160~\mu \text{m}$
and an 80-
$\mu \text{m}$
-wide sealing ring were simultaneously fabricated by the evaporation process. The die surface was treated with Ar (5% H
₂
) plasma before bonding. Chip-level bonding was performed at 260 °C for 15 min with a pressure of 9.13 MPa under N
₂
atmosphere. Pure Sn and Cu
₆
Sn
₅
have been exhausted completely, and the as-bonded interface only contains three layers of Cu–Cu
₃
Sn–Cu, with no serious Sn overflow. The average shear strength of 50.6 MPa and an excellent leak rate of around 2.64
$\times 10^{-4}$
Pa
$\cdot $
cm
³
/s are achieved. The resistance measurements are similar to the theoretical estimation. After high-temperature storage (HTS) at 300 °C for 10 h, the average shear strength slightly decreases to 46.7 MPa and the leak rate increases to 1.01
$\times 10^{-3}$
Pa
$\cdot $
cm
³
/s. More importantly, there is no degeneration of the graphene nanofilm during electrical measurement in the bonding process and HTS test. It is concluded that Cu–Sn–Cu SLID bonding is appropriate for high-temperature pressure sensors based on graphene.