Optimization of UV laser scribing process for light emitting diode sapphire wafers

Billions of light emitting diodes (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 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 diode-pumped solid-state (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.