High Rep Rate High Performance Plasma Focus as a Powerful Radiation Source

Abstract—Basic operational characteristics of the plasma focus are considered from design perspectives to develop powerful radiation sources. Using these ideas we have developed two compact plasma focus (CPF) devices operating in neon with high performance and high repetition rate capacity for use as an intense soft X-ray (SXR) source for microelectronics lithography. The NX1 is a four-module system with a peak current of 320 kA when the capacitor bank (7.8 F 4) is charged to 14 kV. It produces 100 J of SXR per shot (4 % wall plug efficiency) giving at 3 Hz, 300 W of average SXR power into 4. The NX2 is also a four-module system. Each module uses a rail gap switching 12 capacitors each with a capacity of 0.6 F. The NX2 operates with peak currents of 400 kA at 11.5 kV into water-cooled electrodes at repetition rates up to 16 Hz to produce 300 W SXR in burst durations of several minutes. SXR lithographs are taken from both machines to demonstrate that sufficient SXR flux is generated for an exposure with only 300 shots. In addition, flash electron lithographs are also obtained requiring only ten shots per exposure. Such high performance compact machines may be improved to yield over 1 kW of SXR, enabling sufficient exposure throughput to be of interest to the wafer industry. In deuterium the neutron yield could be over 1010 neutrons per second over prolonged bursts of minutes. Index Terms—Lithography, plasma focus, X ray. I