November 30, 2011 -- MicroTech has developed a wet process station to etch patterned sapphire substrate (PSS) wafers in a way that increases light-emitting diodes' (LED) light output and efficiency while increasing manufacturing throughput.
In the MicroTech wet etch system, gallium nitride (GaN) or indium gallium nitride (InGaN) coated wafers are submerged in the etch tank with a mixture of etching and buffering agents. Prior to submersion, a silicon dioxide mask is patterned via plasma enhanced chemical vapor deposition (PECVD). A lithography step exposes the pattern to etch. The sapphire etch process takes place between 260°C and 300°C. This ultra high temperature etches the wafers faster than the standard 150-180°C process. Polishing can also occur after etch to further boost efficiencies.
PSS can increase light output power by up to 37% over a standard sapphire wafer. PSS reduces the dislocation density in the GaN layer and enhances the light extraction efficiency (LEE) from the LED chip. Traditional dry PSS etch throughput is too slow to scale up with high-volume LED manufacturing, the company asserts. Independent customer evaluations confirm light-extraction and efficiency improvements, as well as costs savings.
Development work is also being done to improve the dome shapes created on the wafers with a chemical mechanical polishing (CMP) process, and to create new non-cone shapes.
MicroTech Systems provides engineering, manufacturing and applications support for wet process and chemical distribution tools. See www.microtechprocess.com.
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