High Throughput Low Stress Air Jetting Carrier Release for RDL-First Fan-Out Wafer-Level-Packaging

Fan-out wafer level packaging (FOWLP) not only provides simplified supply chain management and lower cost structure, but also enables thinner profile and heterogeneous system integration. FOWLP is becoming increasingly significant and is projected to drive growth in advanced packaging for the foreseeable future. There are many different processing technologies for fabricating FOWLP. One common key practice, which is very different from fan-in wafer level packaging, is the use of a temporary carrier to support wafer-level fabrication. The redistribution-layer (RDL) first approach is one of two mainstream processing technologies for FOWLP at present. One benefit is that the RDL is fabricated with direct support of a flat, rigid carrier prior to the occurrence of molding warpage and die shift. However, the RDL-first approach requires a carrier sacrificial layer that can withstand high-temperature/high-vacuum RDL build-up fabrication. Determined by adhesive chemistry's availability, the present forms of RDL-first FOWLP processing require carrier release by laser ablation, thus further limiting the choice of carrier to glass. At present, laser debonding for RDL-first FOWLP is a very costly and lengthy process. This paper presents a design for optimizing and processing a carrier-sacrificial layer that is compatible not only with current RDL-first FOWLP fabrication, but also enables the carrier's instant release by air jetting at room temperature. This air-assisted mechanical release of the carrier minimizes debonding stress on the wafer surface without localized heating and burning, and provides even more stress relief for larger carriers. A fan-out WLP process flow with air jetting carrier release is presented and evaluated. Key material properties of the current sacrificial-layer design are also analyzed.