Highest-speed dicing of thin silicon wafers with nanosecond-pulse 355nm q-switched laser source using line-focus fluence optimization technique

Abstract

Due to current and future anticipated widespread use of thin silicon wafers in the microelectronics industry, there is a large and growing interest in laser-based wafer dicing solutions. As the wafers become thinner, the laser advantage over saw dicing increases in terms of both the speed and yield of the process. Furthermore, managing the laser heat input during the dicing process becomes more important with increasingly thin wafers and with increasingly narrow saw streets. In this work, shaped-beam laser-cutting of thin (100 µm and below) silicon is explored with Newport / SpectraPhysics® Pulseo® 20-W nanosecond-pulse 355-nm DPSS q-switched laser system. Optimal process conditions for cutting various depths in silicon are determined, with particular emphasis on fluence optimization for a narrow-kerf cutting process. By shaping the laser beam into a line focus, the optimal fluence for machining the silicon can be achieved while at the same time utilizing the full output power of the laser source. In addition, by adjusting the length of the laser line focus, the absolute fastest speed for various cutting depths is realized. Compared to a circular beam, a dramatic improvement in process efficiency is observed.

Dicing of Thin Si Wafers with a Picosecond Laser Ablation Process

“…Thus several laser dicing technologies are currently available on the market: Full cut with ns laser at UV-Wavelength [1] Stealth dicing with ns at IR-Wavelength [2] Full cut with a water-jet guided ns laser at IR --Wavelength [3] Although these developed technologies overcome some of the problems connected with a mechanical sawing process, there is still a lot of optimization potential. For example the kerf loss in a ns laser cutting process is still in the range of 50 μm.…”

Die singulation technologies for advanced packaging: A critical review

“…175,184,185 A line-shaped laser beam allows to sufficiently use high pulse energy to realize laser ablation at low fluence regime around the transition fluence F c (i.e. 175,184,185 A line-shaped laser beam allows to sufficiently use high pulse energy to realize laser ablation at low fluence regime around the transition fluence F c (i.e.…”

Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

“…Existing commercial ablative laser dicing solutions are focused on less than 100 mm thick wafers and also still based on nanosecond pulsed solid state lasers to meet the required throughput and cost targets. 157 Methods to increase productivity and quality of nanosecond lasers by shaping the beam into a line focus, or by using a dual-focus technique have been explored by Bovatsek et al 154 and Venkatakrishnan et al, 156 respectively.…”