Development of Chip Separation Technique for InGaN-Based Light Emitting Diodes

We compare the chip separation techniques for InGaN-based light emitting diode (LED), which are prepared by conventional diamond tip scribing and short pulse laser scribing with pulse width of nanosecond or femtosecond. Differently from the diamond tip scribing, the laser scribing does not suffer from the shallow scribing depth, which usually results in a failure in cleaving the wafer along the scribed line. Furthermore, the LED scribed by using a femtosecond pulse laser exhibits an 11% enhancement in the output power at 20 mA, compared to that by using a nanosecond pulse laser. This is because the femtosecond laser scribing not only eliminates particle generation, but also minimizes the effect of thermal damage on the sapphire substrate. The femtosecond laser also offers a high speed, high yield, and hence low cost scribing process due to its extremely short pulse width and deep focal length.