Laser Releasable Temporary Bonding Film with High Thermal Stability

Abstract

A temporary bonding film using a unique, laser releasable pressure sensitive adhesive construction has been formulated to advance wafer level fan-out process technology development. The film format and excellent thermal and dimensional stability of the temporary bonding film are particularly well suited to address the developing needs of panel level fan-out processes. The development of wafer level packaging process technology provides many benefits, including increased density and performance, greater design flexibility, simplification of the supply chain and process, and improved yield and overall cost of the semiconductor package. Specifically, in the case of fan-out, technology advances allowing wafer thinning to as little as 30 microns, backside patterning, and handling of the wafer or panel during copper RDL processing have become possible. The thinning and handling processes on the molded wafer or panel are accompanied by large thermal, physical and chemical stresses. These external stimuli, which are difficult to overcome with non-rigid semiconductor materials such as poly-silicone or organic encapsulants, can significantly reduce the yield of these processes. The most effective approach to protecting the semiconductor package substrate from these process stresses is the use of a support carrier. The combination of a rigid carrier and a semiconductor device reduces or eliminates physical stresses in the process and can control the warping and expansion or contraction of the substrate during thermal exposures. Various carrier materials can be used, including thick silicon wafers, glass, ceramics, metals and others, with the choice of carrier dependent on a multitude of factors such as suitability for the carrier release process to be used, carrier CTE, reusability, and cost. 3M's laser releasable temporary bonding film supports bonding between semiconductor device and carrier with excellent adhesion. The benefits of process simplicity and the high level of material heat tolerance achieved with the 3M technology are well aligned with the current direction of packaging technology, with the film format allowing for processing of either wafers or large panels. 3M's laser releasable temporary bonding film employs a glass carrier. Laser scanning through the glass carrier enables separation of the carrier without physical stress, allowing thin materials to be easily removed from the carrier without physical damage. The heat resistance of the 3M temporary bonding film of up to 250C for an extended period allows precise passivation layer curing and sputtering processes. With the 3M temporary bonding film, process designers will be able to implement package production processes with a wide process margin and superior quality.