This Small Business Innovation Research Phase I project proposes to design and build a liquid metal droplet generator that will enable high power Extreme Ultra Violet (EUV) sources for photolithography. The methods for EUV generation currently being developed do not satisfy the projected power requirement, generate too much debris, have short collector mirror lifetime and have thermal management issues. The droplet generator uses tin for higher conversion efficiency and higher power output, respectively. The discrete droplets presented to the laser have the size selected so they can be entirely converted into plasma (mass-limited) and significantly reduce the debris generation. The droplet generator design will optimize the geometrical dimensions using numerical simulations and models based on the continuous jet theory. The material and processes will be also defined together with the placement of the heating elements and thermocouples for a uniform temperature distribution. Two droplet generators will be fabricated. Functionality of the fabricated generators will be verified using water and then tin for which the evaluation will be performed in an inert environment. The range of operational parameters (drop size, velocity, frequency range, and distance between droplets) will be measured and compared to the model predictions. Drop stability will be also measured.
Laser Produced Plasma EUV lithography is considered as the only viable alternative that will supply the required power output for the next generation photolithographic sources. The tin droplet generator that will be fabricated by MicroFab is the enabling technology for this new generation EUV sources. Commercial EUV sources will lead to increased processor power, operational speed and memory capacity for integrated circuit devices for a lower cost. Other spin-off opportunities could be to enable metal freeform fabrication, X-ray microscopy sources, precision deposition of materials and means for presenting the bio-molecules for mass spectrometry. The droplet generator will also enable basic research in plasma emissions.
