Radical bonding attracts LED makers
A low-temperature radical activation wafer bonding technique is challenging direct bonding, and proving itself particularly useful for HB-LED heat sinks and reflectors.
Applied Microengineering Limited extracts radicals from argon, oxygen or nitrogen gas plasmas onto the wafer, activating the surface for bonding at room temperature to 300 deg C.
The complexities involved in LED manufacture have been attracting III-V chip makers to the radical activation (RAD) service AML offers at its Bondcentre facility in Harwell, UK.
“All HB-LEDs are different in their construction - they typically comprise a variety of III-V materials that need to be bonded to each other or to glass, sapphire or silicon,” said Rob Santilli, managing director of AML.
“Thermal coefficient of expansion (TCE) mismatch is a big problem, along with wanting to bond materials to each other that have not been bonded before.”
Direct bonding involves a high-temperature processing step, typically performed at 1000 deg C.
But, if the attached wafers used have sufficiently different TCEs, they will break when they subsequently cool.
“We use the RAD tool in our bonding service for people who are developing new processes in the HB-LED area - mainly from Asia,” explained Santilli.
The company s Bondcentre service is a centre of excellence recognized by the UK government, receiving funds since 2005 to make its expertise available globally.
AML also supplies wafer bonding tools, having sold RAD systems to Qinetiq, the Fraunhofer Institute for Mechanics and Materials, Halle, and Scottish MEMs maker Semefab.
As the new processes are increasingly taken up by different chip makers, AML expects to benefit from the production bonding and equipment orders that will follow.
“AML wafer bonders are at home in a production environment as well as research,” Santilli said.
“From a routine commercial bonding service to process development, we have an unbeatable, world class capability.”
