Miniature Heterogeneous Fan-Out Packages for High-Performance, Large-Format Systems

High-throughput assembly of miniature wafer-fabricated packages onto panel substrates provides a manufacturing framework for high-performance multi-functional displays and other large-format systems. Control circuits, light emitters, sensors, and other micro-components formed in high-density arrays on wafers use a variety of processes and materials that do not easily translate to large-format panel processing. Systems assembled from some or all of those components can therefore exhibit combinations of properties and performance characteristics that are difficult to achieve by panel processes only. Here, we demonstrate hierarchical assembly strategies for fabricating high-performance systems using elastomer stamp micro-transfer-printing. In this work, red, green and blue microscale inorganic LEDs (μILEDs) are fabricated on their respective native wafer substrates and then assembled onto non-native intermediate silicon wafers. The intermediate silicon wafer, populated with heterogeneous μILEDs, then undergoes conventional wafer-level processes, such a dielectric depositions and thin-film metallization, to form miniature fan-out packages. Here, we will demonstrate three heterogeneous μILEDs integrated within a 75 μm × 35 μm fan-out package. We will present how this microscale package can be undercut and then micro-transfer-printed directly onto large-format application substrates. The print-compatible packages also include sharp pressure-concentrating conductor structures which allow the heterogeneous fan-out packages to be electrically interconnected to large-format substrates during the printing operation. We will present functional μILED displays that have been fabricated using these assembly techniques. We will report on the benefits of using intermediate packaging substrates for manufacturing of high-performance large-format systems, such as displays. We will also demonstrate strategies for repairing large multi-functional systems.