Stealth dicing of SiC using femtosecond laser Bessel beam

• Main Authors: Li, Shaowei, Chen, Pei, Qin, Fei, Tu, Senyu, Wu, Kunzhou
• Format: Conference Proceeding
• Language: English
• Subjects: Bessel beam; Diamonds; Particle beams; Power lasers; Scanning electron microscopy; Semiconductor lasers; SiC; Silicon carbide; Stealth dicing; Wires
• ISSN: 2836-9823
• DOI: 10.1109/ICEPT59018.2023.10492365

Nowadays, the mainstream way of dicing SiC is diamond or wire saw dicing, which has low dicing efficiency and high dicing loss. The edges of the cuts all have different degrees of chipping and incompleteness. Thus, the existing diamond mechanical cutting process is one of the factors limiting the development of SiC semiconductor process. Femtosecond laser is considered as an alternative to mechanical cutting because of its non-contact, high precision and how heat-affected zone processing characteristics.In this paper, we take advantage of the high penetration of the infrared laser to focus the femtosecond laser beam to form a modified layer inside the SiC. Then the separation of the wafers is achieved with the help of mechanical means. Scanning electron microscopy (SEM) was used to observe the microstructure of the modified layer. Raman spectrograms are used to characterize mechanical features such as component changes and residual stresses in the modified layer. Different laser parameters such as laser power and pulse width have an important influence on the modified layer. It further affects the ease of separating the wafers and the quality of the cross section. The increase in pulse width facilitates the formation of modified layers inside the SiC by ranging from 250fs to 5ps. This is because when the pulse width is small, the self-defocusing effect from too high plasma density cannot produce a stable modified layer inside the SiC. Different energy densities form a large difference in the size of the internal modification zone of SiC.