High density plasma flood system for wafer charge neutralisation

The Plasma Flood System, a low energy electron generator, has been widely used as an effective tool to neutralise wafer charging induced by ion implantation. Although it has been successful in achieving the full device yield under high current ion implantation, further advancement in device design imposed a need to minimise the wafer charging down to a few volts due to the use of thin gate oxide of less than 10 nm thickness. The High Density Plasma Flood System (HD PFS) was thus developed for the Applied Materials xR series Ion Implanters to maintain the maximum throughput with high current processes without compromising on device yield. HD PFS is a high efficiency charge neutraliser that supplies very low energy (<3 eV) electrons at high emission (>300 mA). The system has a unique configuration of magnetic circuit and arc discharge profile that enables the effective transport of electrons from the plasma source to the wafer while reducing the power consumption by one order of magnitude. This paper discusses the structure and the performance of the HD PFS in terms of electron transport efficiency and energy distribution. Typical operation window is also shown by using the yield of MOS capacitor devices at different gate oxide thickness (35, 5 and 10 nm). Sir months of filament life has been demonstrated.