Particulate and molecular contamination control in EUV-induced H2-plasma in EUV lithographic scanner

In the past year, EUV lithography scanner systems have entered High-Volume Manufacturing for state-of-the-art Integrated Circuits (IC), with critical dimensions down to 10 nm. This technology uses 13.5 nm EUV radiation, which is shaped and transmitted through a near-vacuum H2 background gas. This gas is excited into a low-density H2 plasma by the energetic EUV and DUV radiation from the Laser-Produced Plasma (LPP) in the EUV Source. In the vicinity of the walls and mirrors within the scanner system, this creates an environment rather similar to that near the surfaces of objects in space, especially when considered in combination with trace species such as N2, O2, H2O and hydrocarbons. This paper will discuss how insights on electrostatics and charging from astrophysics have been used to build understanding of particulate and molecular contamination, and how these were translated into prevention and control schemes to achieve near-zero contamination levels on critical imaging surfaces, compatible with the stringent manufacturing requirements for 10 nm lithography.