Fabrication of 4H–SiC microvias using a femtosecond laser assisted by a protective layer

SiC is the core material of the third generation of semiconductors, and the fabrication of SiC microvias is of great significance for the integrated packaging of the new generation of microelectromechanical systems. However, due to its hard nature and brittle properties, cracking and shedding of the surface can easily occur when SiC is processed directly using femtosecond lasers. In this study, the protective-layer-assisted femtosecond laser drilling method was adopted to overcome the above issues during the drilling process. The influence of the type and thickness of the protective layer material on the quality of the microvias was studied. The results show that selecting an adequate protective layer material and a suitable thickness can improve the entrance morphology. On the other hand, the exit morphology remains poor, and a recast layer and ablative debris are present on the inner wall, which need to be removed via ultrasonic cleaning and chemical corrosion. Therefore, based on our previous work on water-assisted laser drilling, a protective layer and water were simultaneously used to assist the drilling process. In this manner, high-quality microvias with no cracks at the entrance and exit and smooth inner walls were obtained. At the same time, a group of hole arrays were processed, and their consistency in size and roundness was verified. The findings of this study will be of great importance for the development of SiC-based electronic devices as well as for high-quality micromachining of other hard and brittle materials.