A Study of 355 Nm UV Laser Ablation Process for Singulation of Silicon Wafers

This work presents the results of the development of a 355 nm nano-second UV laser ablation process for silicon wafer singulation. The study focuses on the two most prevalent crystal orientations in semiconductor manufacturing: Si (100) and Si (111). The developed laser ablation process is purely dry, doesn't require any liquid, vapor phase or plasma and minimizes particles generation in the close vicinity of the dicing street. This process is specifically suitable for applications involving wafers sensitive to liquid exposure and particles contamination. Notable examples include MEMS devices and metal-oxide (MOX) micro-hotplate gas analyzers, where conventional blade dicing with constant water flow may cause irreversible damage to delicate structures and functionalized layers, as well as introduce contamination. The proposed alternative - UV laser ablation singulation technique achieved a narrow <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$36 \mu \mathrm{m}$</tex> kerf width on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$525 \pm 25 \mu \mathrm{m}$</tex> thick Si (100) and Si (111) wafers. The process achieved an aspect ratio (cutting depth to kerf width) of approximately <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15: 1$</tex>. Notably, no chipping on the face and backside of the wafer were observed. Furthermore, despite inherent variations in laser-ablated groove depth, cutting performance showed no statistically significant difference between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Si}(100)$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Si}(111)$</tex> wafers.