Femtosecond laser single step, full depth cutting of thick silicon sheets with low surface roughness
Femtosecond laser single step, full depth cutting of thick silicon sheets with low surface roughness
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DOI：
10.1016/j.optlastec.2020.106899
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发表时间：
2021-06
影响因子：
5
通讯作者：
Zhaoqing Li;O. Allègre;Qianliang Li;Wei-rong Guo;Lin Li
中科院分区：
文献类型：
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作者：
Zhaoqing Li;O. Allègre;Qianliang Li;Wei-rong Guo;Lin Li
硅晶片的分离是半导体器件制造中不可或缺的一部分。广泛使用的机械分离方法产生大的切口宽度和微裂纹。现有的激光分离、分割和切割方法可以减小切割切口宽度，但通常涉及多个步骤。虽然以前已经报道了通过烧蚀的单步激光穿透切割，但表面粗糙度通常很差。本文介绍了一种在环境条件下用800 nm波长的飞秒脉冲激光通过显微镜物镜透镜聚焦对200 µm厚的硅片进行单步全深度切割的方法。通过引入平行扫描线，实现了具有191 nm Ra的优异侧壁全面积粗糙度的贯穿切割，这比以前报道的类似厚度的厚硅片的激光贯穿切割要好得多。研究发现，通过增加过扫描次数、脉冲能量或平行扫描线数，侧壁表面粗糙度降低，底部表面切口边缘直线度提高。比较了p极化和s极化对切削质量的影响。通过选择合适的光束偏振方向和切割速度，可以提高侧壁质量。讨论了相关机制。
Separation of silicon wafers is an integral part of semiconductor device manufacture. The widely used mechanical separation methods produce large kerf widths and micro-cracks. Existing laser separation, singulation and dicing methods can reduce cutting kerf widths, but usually involve multiple steps. Although single step laser through cutting by ablation has been reported before, surface roughness is usually poor. This paper presents a method for single step, full-depth cutting of silicon wafer sheets of 200 µm in thickness with an 800 nm wavelength femtosecond-pulse laser focused using a microscope objective lens under ambient condition. By introducing parallel scan lines, through cut is realized with an excellent sidewall full area roughness of 191 nm Ra, which is much better than that of reported previously in laser through-cutting of thick silicon sheets of similar thickness. It is found that by increasing the number of overscan, pulse energy, or number of parallel scan lines, the sidewall surface roughness reduces and the kerf edge straightness at the bottom surface is improved. The effects of p- and s-polarization on cutting quality are compared. Sidewall quality can be improved by appropriate selection of beam polarization and cutting speed. The mechanisms involved are discussed.