| dc.description.abstract | In recent years, the rapid development of the semiconductor industry has rendered the first-generation wafer material, silicon, increasingly unable to meet modern demands. Consequently, researchers have been actively seeking superior alternative materials. Third-generation semiconductor material silicon carbide (SiC), with its exceptional physical properties and chemical stability, has emerged as a strong candidate to replace silicon. SiC′s high thermal conductivity and wide bandgap make it highly valuable for various semiconductor applications. However, the manufacturing of SiC wafers faces multiple challenges, including the lengthy crystal growth process and low production yield. The fabrication of SiC wafers involves multiple steps such as slicing, cutting, grinding, polishing, and etching. Due to SiC’s high hardness and excellent chemical stability, these processes encounter significant bottlenecks and are time-intensive and costly. As a result, the development of novel pro-cessing technologies is critical to improving manufacturing efficiency and reducing costs.
Slicing is a crucial step in SiC wafer manufacturing. After crystal growth, the ingot must be cut into wafers. Currently, wire sawing is the predominant slicing technology. However, SiC′s high hard-ness, combined with the limitations of wire diameter and strength, results in prolonged processing times and high material wastage rates. To address these issues, laser stealth dicing has gradually become a promising alternative. This technology uses a laser to modify the internal structure of the material and applies external tensile force to separate the modified layer, completing the wafer slicing process.
This study focuses on using a 1030 nm femtosecond laser to perform internal modification on N-type 4H-SiC wafers. By precisely focusing the laser within the material, a modified layer is formed inside the wafer. Experimental results show that single-pass laser scanning under various parameters can produce single-layer or double-layer modified structures. The single-layer structure can be further categorized into ＂upper single-layer＂ and ＂lower single-layer.＂ The formation of these structures is primarily influenced by the pulse overlap rate: a lower overlap rate generates a lower single-layer, while increasing the overlap rate can result in double-layer or upper single-layer structures. Additionally, laser parameters such as energy and scanning spacing significantly impact the morphology of the mod-ified layers.
To better understand the formation mechanisms of these modified layers, this study examines cross-sections to analyze different structural morphologies and investigates how various laser parame-ters influence the modifications. The successful separation of three types of modified layers revealed that the surface quality of the separated layers varies with the type of modification. Furthermore, the upper and lower wafer surfaces differ slightly due to the distinct exposed crystal planes. This research also employs transmission electron microscopy (TEM) to analyze the lattice diffraction and micro-structure of SiC samples before and after laser modification, providing an in-depth understanding of how laser-induced modifications affect the internal structure of SiC and offering a theoretical basis for optimizing modification techniques. | en_US |