NEWS ANALYSIS
Rubicon reveals sapphire plans
Rubicon Technology plans to ease LED manufacture by ramping patterned sapphire substrate production.
While industry players debate whether silicon or sapphire is the best foundation for the GaN LED, US sapphire substrate manufacturer, Rubicon Technology, has sold $28.2 million of common stock to fund expansion.
Developing sapphire substrate fabrication for LEDs is high on the company’s investment list, chief financial officer, Bill Weissman, tells Compound Semiconductor. And plans are underway to do this soon.
The company will first extend sapphire substrate patterning facilities. Etching a nano-pattern onto the sapphire wafer eases epitaxial growth and reduces the light reflected back into the LED from the polished surface, boosting light output. But according to Weissman, LED chip manufacturers are becoming more and more interested in outsourcing this production step. “We’re seeing a real trend here,” he says. “So a lot of the money we are raising is going into the expansion of our LED patterning operation.”
The company started supplying 4- and 6-inch patterned sapphire substrates last year − Weissman reckons only Rubicon offers 6-inch wafers − and will now triple capacity in its existing cleanroom at its fabrication facility in Penang, Malaysia. Then, if demand for patterned sapphire substrates continues, construction of additional polishing and patterning facilities to this plant could follow by the end of the year.
“We don’t think chip manufacturers are going to shut down their internal patterning operations, but we do think they will stop investing and expanding those capabilities, and so will outsource more and more,” he says.
At the same time, Rubicon is eyeing other LED opportunities, including aluminium nitride on sapphire templates. Here the company would deposit an AlN layer onto its patterned 4- and 6-inch sapphire substrates, onto which chip manufacturers could then directly grow GaN layers. Kyma, for one, has demonstrated 10-inch diameter AlN on sapphire templates for LED growth and alongside the likes of Azzuro Semiconductors and Translucent, is also working on 300 mm (12-inch) AlN on silicon templates.
“Templates could be a next potential step downstream for us,” says Weissman. “The jury is still out on whether chip manufacturers are interested in this product − issues include contamination for example − but this is something we’re looking at as an additional product within the LED market.”
Silicon rivals
But while Rubicon executives grow their LED materials empire aren’t they concerned about a potential industry transition from sapphire to silicon substrates?
Only late last year, business analyst IHS forecast that come 2020, GaN-on-silicon
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www.compoundsemiconductor.net March 2014
Patterned substrates: Rubicon is ramping up sapphire substrate patterning at its Malaysia plant
LEDs will increase market share from today’s 1 percent to 40 percent, mostly at the expense of GaN-on-sapphire devices. This forecast lies at the extreme end of the predictions for silicon success, but nonetheless indicates a rising interest in processing LED structures in depreciated CMOS facilities.
But Weissman says the company isn’t worried and he doesn’t expect GaN-on- sapphire LEDs to lose market share to silicon-based alternatives in the near future. Many organisations have been developing methods to circumvent the
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