Wafer bonding is a process for joining wafers. The process is extensively used in packaging of microsystems, but is also used in building complex structures consisting of several wafers.

At SINTEF MiNaLab, wafer bonding is a key technology in the realization of several of our devices. We offer a wafer bonding foundry service. In addition, we do feasibility studies, process development, and technology evaluation on wafer-to-wafer and chip-to-wafer bonding. We have worked with different types of wafer bonding as listed below.

High-temperature direct wafer bonding (fusion bonding) of silicon to surfaces of silicon, SiO2 and Si3N4. Double-, triple- and quadruple stacks have been realised.
Low-temperature direct wafer bonding (plasma/surface activated bonding) of Si and SiO2 surfaces.
Anodic wafer bonding of glass-Si, glass-SiO2, glass-Si3N4, and glass-Al. The stacks included 2 – 4 wafers.
Thermocompression wafer scale bonding of gold-to-gold.
Adhesive wafer bonding using BCB.
Eutectic wafer scale bonding of AuSn and AuSi.
Chip-to-wafer bonding applying Au stud bump bonding, SnAg microbumps and the Solid-Liquid InterDiffusion technology using SnCu-Sn

Contact person: Maaike M Visser Taklo

Single test chips bonded to a substrate wafer by chip-to-wafer bonding. Three bonding technologies were compared in a feasibility study on 3D-integration of MEMS: Au stud bump bonding, SnAg microbumps and the Solid-Liquid InterDiffusion technology using SnCu-Sn.

Published January 8, 2008

A stack of two plasma activated bonded silicon wafers. The wafers have SINTEF's custom designed mesas, frames and burst structures for bond strength assessment.

A photo-acoustic cell realised by 4-stack anodic bonding. The 4 different wafers are easily discerned in the cut-through sensor.

A capacitive differential pressure sensor made by fusion bonding of 3 silicon wafers. Each wafer is 400 µm thick, resulting in a 1.2 mm thick final sensor.