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

摘要

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 gm and below) silicon is explored with Newport / Spectra- Physics? 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.