Dicing of gallium arsenide (GaAs) wafers with the laser MicroJet® challenges, improvements and safety issues

Abstract

GaAs wafers are fragile and brittle and, therefore, the well-developed dicing saw technique, which is widely used in the silicon industry, faces serious problems when used for dicing GaAs wafers. GaAs wafers are very sensitive to changes in the dicing tools and to drifts in the dicing machinery, which makes the dicing difficult and causes some throughput issues. At the moment, the most commonly used dicing saw process is dicing with a 30 µm thick resinoid blade. Although, these blades provide high-quality kerf, they are also very fragile and, thus, have a very short life. Dicing of GaAs wafers with the Synova Laser MicroJet®, which implements a YAG- Nd laser beam confined in a water jet, gives exciting and promising results for a general solution of the problem. By means of the Laser MicroJet®, wafers as thin as 25 µm can be diced in streets of 30 – 50 µm width, providing kerf quality comparable to the dicing saw cut and in some cases even better than the dicing saw. The Synova MicroJet® increases the wafer throughput and under certain conditions yields 100% throughput. As far as we are aware, the presented results are the first for laser dicing of GaAs wafers, and, therefore, provoke a detailed discussion about the safety of the new technique. In this paper, we address the advantages and optimization, as well as safety issues of the laser water-jet dicing process for GaAs wafers.