Extreme Ultraviolet Light Source: A Feedback Control Primer

The manufacture of the most advanced semiconductor chips requires the capability to produce ever smaller features, of which the EUV source made by ASML is a key enabler. To etch such features, the amount of variation in EUV photons that reaches the wafers must be controlled within stringent bounds. The generation of EUV is a multistage process occurring at extreme conditions, with many stages regulated by individual control systems which generally lack a common reference and have limited communication with one another. How these systems operate together and how they contribute to the final performance in wafer exposure is not trivial. Our goal here is to provide the reader a sense of the objectives, interactions, and relative scale of several critical control systems, which are described in other papers by authors at ASML, in the context of the overall EUV source.