A Novel Single-Layer High-Temperature-Resistant Adhesive Layer Applied in Advanced Wafer-Level Packaging

Recently, advanced packaging technology has continued to develop towards the miniaturization and heterogeneous integration of devices in the post-Moore era [1]. In order to be suitable for requirement of ultrathin packaging, smaller form factor, more comprehensive functions and lower cost, temporary bonding and debonding (TBDB) as a significant technology for handling ultrathin wafers has been contributed in many sections of the semiconductor industry. Several researchers have shown solutions in TBDB technology which focus on various design materials, including releasing layer, bonding layer, and adhesion promotion layer [2], [3]. However, the implementation of multi-layer coating and baking and cleaning process greatly increases the cost and construction difficulty, reduces the throughput, and is not disproportionate with the performance of final devices.In order to coinage more cost-effective way with lower risk to handle ultrathin packaging, the single-layer thermoplastic adhesive with organic flexible moieties has been developed [4], [5]. We found that temporary bond adhesive based on thermoplastic polyimide could not only function as a releasing layer but also as a bonding layer which is not like other multi-layer TBDB solutions shows. Wafer bonding evaluation shows the single-layer bonds the wafer on glass carrier for 120s at 230~250ºC with 100% yield. Meanwhile, low modulus of thermoplastic based adhesive weakens warpage of highly stressed substrates and increases the yield of the temporary bonding process. The results of ultrasonic scanning microscope shows there is no outgassing and defect can be found between the interfaces of the bonding pair and low TTV and warpage bonding pair has been observed. Excellent thermal stability, robust mechanical stability, laser response performance and simple material cleaning making it suitable for wafer level assembly with a carrier.