Optimization of UV laser scribing process for led sapphire wafers

Billions of LEDs are used today in traffic control, automotive headlights, flat panel display technology, mobile devices, back lighting, projection and general illumination applications. With the dramatic growth in LEDs, manufacturers are looking for technologies to increase production yield and decrease cost. Sapphire wafer singulation into miniature dies is one of the critical steps used in blue/green LED manufacturing. Typical dicing techniques used in wafer singulation process include laser dicing, laser scribing and breaking, mechanical scribing and breaking, and diamond blade sawing. In recent years, laser scribing and breaking has proven to be very efficient for volume LED manufacturing. In this paper we have characterized the effect of 355 nm Q-switched DPSS laser parameters such as fluence, pulse width and repetition rate on laser scribing process by measuring sapphire wafer cutting depth and scribe kerf width. Furthermore we have also explored the techniques to increase process efficiency while maintaining quality of scribes using different laser sources.