Thermal Slide Off Debonding
Thermoplastic adhesives have the characteristic properties that they are rigid at room temperature, but the viscosity of the adhesive is reduced at elevated temperature. This drop in viscosity enables a unique debonding mechanism - thermal slide off debonding. Figure 1 shows the principle process flow for slide off debonding. The wafer stack is loaded to the debonding module and heated to the debonding temperature. At the debonding temperature the viscosity of the adhesive is reduced, which enables to slide off the thin device wafer from the carrier. During the slide off process the thin device wafer is mounted on a full area chuck on the backside. After debonding the thin wafer is cleaned and then mounted on dicing tape on film frame.
Thermoplastic adhesives offer the advantage of having the option to perform solvent cleaning after debonding to remove adhesive residues. In comparison crosslinking adhesives do not offer such wet chemical cleaning capability and will have to be mechanically peeled either during the debonding operation or after debonding in order to remove the adhesive from the product wafer. Such peeling operation requires the adhesives to exhibit some degree of softness at room temperature in order to enable a reliable peeling process for removing the adhesive residue from product wafers that have topography such as solder bumps or copper studs. This softness can have a negative impact on the device wafer thickness uniformity as it impacts wafer grinding and polishing operations adversely. For this reason, thermoplastic adhesives offer advantages in terms of cleanliness of the product wafer post debond and quality of wafer thinning due to the rigid support they can provide at room temperature.
Thermal slide off debonding was first introduced in high volume production for compound semiconductor wafers  and has recently been introduced into high volume manufacturing for 300mm CMOS wafers.
 Dave Kharas, Nagul Sooriar, Cycle Time and Cost Reduction Benefits of an Automated Bonder and Debonder System for a High Volume 150 mm GaAs HBT Back-end Process Flow, Proceedings of CS MANTECH Conference, May 18th-21st, 2009, Tampa, Florida, USA
Figure 1: Process flow for thermal slide off debonding