With the introduction of EUV lithography, the control of contamination in advanced semiconductor processes has become increasingly critical. Our work is a joint effort (TU/e and VDL-ETG) and is aimed at the development of plasma-assisted contamination control strategies mainly focusing on airborne particles in a low pressure gas. We present experiments comparing the charge-to-mass ratio of single spherical micron-sized particles with that of non-spherical agglomerates thereof in the spatial plasma afterglow. It is shown that the charge-to-mass ratio of two-particle clusters deviates only 6% from that of singlets. This means that for the proposed mitigation strategy, of which the efficiency is based on the charge-to-mass ratio, it is acceptable to study the charging of spherical particles and to extrapolate the results towards non-spherical particles within a reasonable range.
With the introduction of Extreme Ultraviolet (EUV) lithography, the control of contamination has become crucial. Sources for contamination in EUV lithography scanners are not limited to only particle generation and release inside the scanner environment but may be introduced from outside as well, e.g. through translational and/or rotational (robotic) feedthroughs.
In this contribution we highlight our joint (TU/e and VDL ETG) research efforts aimed at the development of plasma-enabled contamination control strategies. The focus in this research is on airborne particles immersed in a low pressure gas flow that interact with both the afterglow of a plasma and an externally applied electric field.
A flexible experimental setup has been developed and will be introduced which is able to study the interaction between contaminants, plasmas and externally applied electric fields. Our results show that the designed configuration allows to carefully control the residual charges of the particles as well as their positions and trajectories with respect to the gas flow in which they are immersed. These results, together with the understanding of the underlying principle processes, open-up various possibilities to achieve improved cleanliness of the mentioned systems.
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