This Phase I SBIR proposal addresses the development of a standards quality, solid state detector technology for measurement of deep ultraviolet (DUV) irradiance. There is a particular need among manufacturers of DUV photolithography equipment for an accurate and stable detector technology to measure excimer laser (248, 193, 157nm) pulse energy and total ultraviolet (UV) exposure for wafer plane dose uniformity. The current industry standard is the KrF 248 nm excimer laser. Systems utilizing the 193 nm ArF laser are ready now and 157 nm F2 laser systems will soon become the industry standard. The requirements for DUV detection products are high durability under intense UV exposure, uniformity of response over large areas, low noise, linear response, and a high power saturation point. The ultraviolet degradation of existing UV detection technologies, i.e. silicon or GaAsP, restricts the utilization of these materials for the new generation (F2 excimer laser) of DUV lithography tools. A single detection/power measurement technology that can be used for all UV wavelengths would minimize the new engineering work necessary for each new generation of photolithography systems. The wide band gap semiconductor gallium nitride (GaN) is proposed as the ideal material system to meet the current and future needs for DUV photolithography. P-I-N and Schottky barrier photodiode detectors made from GaN, and its ternary compounds with aluminum (AlGaN), have high quantum efficiency responsivity for wavelengths shorter than 365 nm. They have low noise, linear response over several decades of incident power, and high bandwidth. Most importantly for DUV irradiance measurements, the material system has the potential to resist degradation under prolonged exposure to high intensity UV radiation. In this proposal, plans are presented to evaluate the robustness and long term stability of GaN and AlGaN UV detectors under intense, prolonged DUV exposure, and also to develop one of the most important, and currently unavailable, detection products for this industry, a large area, multi-element photodiode array for power and dose uniformity measurements at the wafer plane.
In addition to DUV lithography, there are many other industrial and scientific applications for group III-nitride technology including UV curing and drying, printed circuit board fabrication, sterilization control, phototherapy, combustion monitoring, and solar irradiance measurement.
