Characterization analysis of 532 nm laser drilling of silicon-based glass heterogeneous integration composites

Abstract

Abstract In the era of the Internet of Things, the demand for sensors—including those used in wearable devices, those used in smart machinery, electronic sensors for vehicles, and gas sensors—is steadily increasing. To improve the performance of sensing components, stacking circuits and packaging materials can be used as the heterogeneous chips in manufacturing processes. For example, owing to its composition of multiple materials, a sensing component cannot be returned to a semiconductor production line for a second round of the through-hole process. Because the laser is an excellent tool for via processes, the diffraction limit of a laser-focused spot should be considered. Thus, for holes with large diameters (i.e., 100 µm), composited laser machining should be considered. This study used 532-nm laser milling technology to fabricate holes with large diameters (300 µm) on a silicon-based glass heterogeneous integration composite material used in sensing components. Single-layer and multilayer milling removal rates, depth of focus formula, and experimental analysis results were recorded. The effect parameters were laser power, galvanometric scanning speed, and number of laser milling processes. The fabrication via characteristics were systematically analyzed using a field-emission scanning electron microscope, a confocal laser scanning microscope, and a four-point probe instrument. Moreover, to analyze the via performance after laser milling, a filled metal contact deposition process based on the resistance value measurement was employed. The experimental results revealed that (1) the diameters of the perforated holes increased with the number of laser milling processes, (2) the galvanometer scanning speed increased as the via diameter decreased, (3) the oxygen concentration distribution around the hole decreased farther away from the hole, (4) the inside of the hole contained high concentrations of carbon and oxygen because of the laser processing process, and (5) more laser residues were observed closer to the bottom of the hole, causing more material to adhere to the wall closer to the bottom. Finally, the side view revealed that as the number of laser milling processes increased, the hole could be dug deeper, and the sidewall of the hole became more vertical, resulting in the measurement angle decreasing relatively.