Accent Unveils New Etch Process

BEND, Ore., Sept. 1 -- Accent Optical Technologies, a supplier of process control tools for optoelectronic, wireless and silicon semiconductor manufacturers worldwide, has released a novel etch process for electrochemical CV (ECV) carrier concentration profiling of p-doped gallium nitride (GaN). The process will be described in a presentation by Accent's Akihiko Majima at the Japanese Applied Physics conference in Tokushima on Sept. 7.
Achieving a high concentration of holes in p-type GaN is a critical step in the manufacture of high-brightness LEDs or ultraviolet lasers for next-generation DVD players. Conventional metrology methods, such as SIMS (secondary ion mass spectrometry), measure the chemical concentration of the dopant species but not the electrically active carrier concentration. The chemical and electrically active concentrations can differ in p-GaN by more than an order of magnitude. In contrast, ECV profiling measures the electrically active carrier concentration, which has a direct influence on performance parameters such as forward voltage and contact resistance.
According to Tom Ryan, product manager for compound semiconductor products at Accent, "We have been able to etch and profile n-GaN for some time now, but p-GaN has been a challenge because of the behavior of magnesium as a deep-level acceptor and the high-defect density of GaN materials. Our new method produces a flat and consistent etch profile that enables ECV profiling of complete device structures."

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