4-inch sapphire ramp expected at Sumitomo Metal
According to a report from the Japanese news service Nikkei.net, Sumitomo Metal Fine Technology is planning to set itself up as a major supplier of large sapphire substrates suitable for white LED production.
The report suggests that the Osaka-based company, which is a subsidiary of Sumitomo Metal Industries, has developed a fine-polishing technique that uses colloidal silica granules 100 nm in diameter.
This process is said to produce a more uniform wafer finish than is possible with artificial diamonds, and the smoother material that results could help to improve the operating characteristics of the LEDs grown on the wafers.
Most GaN-based blue and green LED chips are produced on sapphire wafers, but the industrial process is still dominated by 2-inch and 3-inch wafer production.
However, recent moves towards more efficient chip manufacturing on larger wafers have been signaled by the US firm Cree, which uses SiC substrate material, and by the Japanese company Showa Denko (see related stories).
Shifting production to the larger format should prove particularly beneficial for the manufacture of high-performance white LEDs based on large chip die, because edge effects that can impact wafer production yields would be reduced.
More efficient production of high-brightness LEDs is recognized to be a critical challenge for chip manufacturers to overcome if the technology is to become cost-competitive in the market for general lighting.
According to Nikkei.net, Sumitomo Metal Fine Technology is already sampling 4-inch material, and has installed a production line that will be able to supply about 5000 wafers per month.
