August 11, 2011 — In these 2 video interviews from SEMICON West 2011, ESI technologists John Sabol and Vernon Cooke discuss what LED chips require on the back-end manufacturing line, starting at wafer scribing and moving on through test. LEDs differ from semiconductor chips — high light extraction is a major goal, for example — though some goals — high yields and low costs — remain universal.
Wafer scribing for brighter LEDs
John Sabol of ESI talks about wafer scribing for LEDs. The LED industry is working on increasing quantum well efficiencies and light extraction. ESI focused on the latter in developing tools for scribing patterned sapphire wafers and distributed Bragg and metal mirrors.
LED scribing cuts LED wafers into die, going through layers of gold, sapphire, GaN, and other materials. By paying attention to sidewall construction during this cut, ESI was able to integrate a laser cutting technology that keeps light output high.
Handling LED packages for better throughput and yields
Vernon Cooke, ESI, covers the company’s new light emitting diode (LED) manufacturing technologies, focusing on advanced packaging test tools and handling systems. "The back-end process of packaged LEDs equates to about 60% of the total cost of LED manufacturing," Cooke notes.
ESI sees lowering the cost of handling, testing, and binning LEDs as a major goal. Multi-track handling doubles throughput for LED testing. Handling without device damage is also important. Ceramic packages with delicate lenses require different handling methods than standard chips. A nested carrier brings the LED through processes in a protected manner. Equipment toolsets for LEDs must be flexible, Cooke adds, seeing many package sizes and designs for LEDs.
Standardization should occur in the end-product luminaire, Cooke believes, which he says will push standardization back up the manufacturing and interconnect chain.