Laser Releasable Temporary Bonding Film for Fanout Process with Large Panel

One of the largest advantages of wafer level packaging technology and the fanout process is the promise of a dramatic reduction in process costs. Given the semiconductor packaging process, which requires many complex technologies and a large equipment set, it is easy to understand that the more chips that can be worked on at the same time, the lower the process cost. The expansion of the device active area, ever growing in the market, is one of the surest ways to improve throughput. For example, the transition from a 300 mm diameter circular wafer to a 600 mm square panel can produce a more than 4 fold area advantage when compared to the WLP process, and the panel format produces over 5 times more devices when geometry and useable area is considered. However, process yield of the FOPLP process must improve to the levels achieved with FOWLP in order to realize this increase. Process conversion from wafer level to panel level packaging cannot be regarded as only a simple change in shape and size. When considering the bonding of a temporary carrier, problems resulting from change in substrate size and shape are never simple and require significant tuning to the bonding equipment and process. The results of bonding and thermal stability tests carried out on round versus square substrates indicate that a round substrate is the most stable structure in terms of thermal and physical stress, and the square panel is not an easy target. Therefore, the development of temporary bonding and debonding materials with higher levels of adhesion and heat resistance is a primary task for the establishment of mass production capable processes for FOPLP. The semiconductor manufacturing industry requires robust materials with wide process margins to support the price competitiveness and quality required in the final packaged product. The 3M laser releasable temporary bonding film is a fanout process solution targeted at large panel production. Heat resistance of the material allows support for passivation curing processes ranging from 210 to 250C without delamination. Carrier release by laser debonding is shown to remain the same whether carried out before or after high temperature processing. In addition, the top adhesive does not leave residue on the mold compound surface even after a two hour 270C thermal process and does not require a wet chemical process for removal. The laser releasable temporary bonding film has been shown to greatly simplify the process of bonding the device to the transparent glass carrier and does not require additional curing or surface treatments before and after bonding. Results of process performance testing on this material and temporary bonding and debonding approach will demonstrate the suitability of this approach to high volume FOPLP production.