| 摘要: | 近年來，隨著半導體產業的迅速發展，第一代晶圓材料「矽」逐漸無法滿足現代需求。因此，研究者積極尋找性能更為優越的替代材料。第三代半導體材料「碳化矽」因其卓越的物理特性與化學穩定性，成為矽的有力替代者。碳化矽具備高導熱率與寬能隙，使其在各類半導體元件中展現出極高的應用價值。然而，碳化矽晶圓的製程面臨多重挑戰，其晶體生長耗時且產量有限，製作晶圓需經歷分片、切割、研磨、拋光與蝕刻等多道工序。由於碳化矽的高硬度與化學穩定性，加工過程中常出現瓶頸，並伴隨高耗時與高成本。因此，亟需開發新型加工技術，以提升製造效率並降低成本。
在碳化矽晶圓製程中，分片是至關重要的環節。長晶完成後需將晶錠切割成晶圓，目前主流的分片技術是線鋸切割。然而，由於碳化矽的高硬度與線鋸的線徑和強度限制，該技術不僅耗時，還導致材料損耗率偏高。為解決這些問題，雷射隱形切割技術逐漸成為新興的分片方法。該技術利用雷射對材料內部進行改質，並通過外部拉力使改質層分離，完成晶圓切割。
本研究聚焦於使用波長1030 nm的飛秒雷射對N型4H-SiC晶圓進行內部改質。透過精確聚焦於材料內部，加工後可在試片內部生成改質層。實驗顯示，單次雷射掃描可在不同參數下形成單層或雙層改質層，其中單層結構又可分為「上單層」與「下單層」。為深入理解改質層的形成機制，本研究透過橫切面觀察討論不同改質層形態的生成過程，並進一步分析雷射參數（如脈衝重疊率、能量與掃描間距）對改質層形貌的影響。我們成功實現三種改質層形態的分離，並發現拉開面的表面品質會因改質層類型有所差異。此外，上分片與下分片的表面亦因晶面暴露的不同而存在一定差異。本研究還利用穿透式電子顯微鏡（TEM）對改質前後的碳化矽試片進行晶格繞射與微結構分析，深入探討雷射改質對碳化矽內部結構的影響，為改質技術的優化提供了理論基礎。
;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. |
