Miniature plasma source for in situ extreme ultraviolet lithographic scanner cleaning

Extreme ultraviolet (EUV) lithography is the technology of choice for high-volume manufacturing of sub-10nm lithography. One of the challenges is to enable in situ cleaning of functional surfaces, such as sensors, fiducials and interferometer mirrors, without opening the scanner tool. Thermally created hydrogen radicals have been successfully used for this purpose. These sources have limited cleaning speed and a relatively high thermal load to the surface being cleaned. Here, we present an alternative plasma-based technique to simultaneously create hydrogen radicals and hydrogen ions. This results in significantly improved cleaning speed while simultaneously reducing the overall thermal load. As an additional benefit, this plasma source has a minimized and flexible building volume to allow easy integration into various locations in the EUV lithographic scanner.