June 19, 2008 – Researchers at Kobe U. and Yumex have prototyped a UV light source made without mercury and twice as efficient as existing mercury lamps, with a commercial product possibly ready in two years, according to the Nikkei Business Daily.
The source uses a proprietary thin-film method starting with aluminum nitride, using a 10% gadolinium additive instead of mercury. A standard mercury lamp requires a filter to remove unwanted light wavelengths except UV light, with the end result that only ~1% of light from the lamp is utilized, the paper notes. The new UV light source only emits short-wavelength UV light (311nm-312nm), with double the operating efficiency to produce 1mW/A. The palm-sized prototype emits light from a ~1cm-dia. opening.
Next step is to increase the surface area of the light-generating portion of the device, and design a 1W source for semiconductor lithography. (Extreme ultraviolet lithography [EUV], a candidate for use at the 22nm node, is expected to require 100W of average power; source supplier Cymer recently said it achieved 25W of average power continuously for 1 1/2 hours.) The goal is to commercialize the lights in two years, for use in other industries as well, such as medical (e.g., sterilization, therapy for atopic dermatitis).