Automated Platform for Wafer Sizes up to 300 mm
SUSS MicroTec’s wafer bonding platforms combine over seventy years of microstructuring experience with solid product quality and a broad range of productivity features. Partnering with research, academia and material suppliers we develop intelligent bond solutions which offer leading-edge technology for our customers. Our wafer bonding platforms cover many different applications in 2.5D and 3D integration, MEMS, LED and power devices as well as other areas of research and development.
Wafer bonding refers to attaching two or more substrates or wafers, of materials such as glass or silicon, to each other by means of various chemical and physical effects. Wafer bonding is mainly used in MEMS, where sensor components are encapsulated in the application. Other markets for this technology include advanced packaging, 3D integrationand CIS manufacturing. Temporary wafer bonding is a specialized technology within wafer bonding that is regarded as a key technology for 3D integration.
A variety of materials are available for adhesive wafer bonding techniques utilizing polymers and adhesives, including epoxies, dry films, BCB, polyimides, and UV curable compounds.
Anodic wafer bonding involves encapsulating components on the wafer by means of ionic glass. In triple-stack bonding, three layers (i.e. glass-silicon-glass) are simultaneously bonded, enhancing both functionality and yield.
Eutectic wafer bonding takes advantage of the special properties of eutectic metals. Similar to soldering alloys, such metals melt already at low temperatures. This property allows planar surfaces to be achieved.
In order to control reflow of the eutectic material, eutectic bonding requires precise dosing of the bonding force and even temperature distribution.
Fusion bonding refers to spontaneous adhesion of two planar substrates with a dielectric material (typically silicon oxide) as the bonding layer. The process usually involves a proper surface activation that renders the substrates to be largely hydrophilic. Subsequently the substrates are aligned, brought into contact and finally tempered at elevated temperature.
Glass Frit Bonding
A glass frit bonding process involves screen-printing glass frits onto the bonding surfaces. This results in structures that are subsequently heated and fused when the two substrate surfaces are placed in contact. On cooling, a mechanically stable bond results.
Hybrid bonding is an extension of fusion bonding, so that in addition to the dielectric material also metallic structures can be found in the bonding interface, which are bonded by diffusion during the annealing process. Successful bonding requires very careful control of the metal structure topography.
Various combinations of adhesive and release layers are available on the market that enable mechanical separation of the carrier wafer from the wafer before further processing. It is consequently essential to be able to vary parameters such as debonding speed and the debonding force applied in order to support the method applied in the particular case. The process needs to be controlled and monitored. During debonding, the thin wafer remains attached to dicing tape in order to facilitate further processing after being released from the carrier wafer.
The mechanical debonding processes supplied by SUSS MicroTec run at room temperature and are suitable for all common adhesives and techniques for temporary bonding. After debonding, the wafers require cleaning in order to remove any adhesive or release layer residues. Certain types of dicing tapes for mounting wafers have only limited resistance to cleaning media. Such tapes require protection during wafer cleaning.
Metal Diffusion Bonding
Metal diffusion bonding is based on Cu-Cu, Al-Al, Au-Au and other metallic bonds. In addition, the use of metal diffusion allows two wafers to be bonded both mechanically and electrically in a single step. The technique is required for bonding in 3D applications such as 3D stacking.
SLID bonding (solid-liquid inter-diffusion) is based on diffusion and the mixture of different metals. The melting temperature of the alloy after bonding is very much higher than the bonding temperature, which clearly widens the range of possible applications.