Particle contamination control by application of plasma

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

Particle contamination control by application of plasma

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.\u3cbr/\u3eIn 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.\u3cbr/\u3eA 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

The charge of micro-particles in a low pressure spatial plasma afterglow

In this letter, we present charge measurements of micro-particles in the spatial afterglow (remote plasma) of an inductively coupled low pressure radiofrequency plasma. The particle afterglow charge of (-30 ± 7) e, being deducted from their acceleration in an externally applied electric field, is about three orders of magnitude lower compared to the typical charge expected in the bulk of such plasmas. This difference is explained by a relatively simplistic analytical model applying orbital motion limited theory in the afterglow region. From an application perspective, our results enable further understanding and development of in situ plasma-based particle contamination control for ultra-clean low pressure environments

Charge control of micro-particles in a shielded plasma afterglow

In this work, charge control of micro-particles from ~ -40 to +10 elementary charges is presented. This is achieved at 0.9 mbar argon in the spatial afterglow of an inductively coupled plasma by solely changing the strength of an externally applied electric field. Crucial in the presented experiments is the use of a grounded mesh grid in the cross section of the setup, separating the active plasma region from the "shielded" spatial afterglow. While in the regions above the mesh grid all particles reached a constant negative equilibrium charge, the actual control achieved in the shielded spatial afterglow can most probably be explained by variations of the local ion density. The achieved charge control not only opens up possibilities to study nano-scale surface charging physics on micro-meter length scales, it also contributes to the further development of plasma-based contamination control for ultra-clean low-pressure systems

The charge of micro-particles in a low pressure spatial plasma afterglow

\u3cp\u3eIn this letter, we present charge measurements of micro-particles in the spatial afterglow (remote plasma) of an inductively coupled low pressure radiofrequency plasma. The particle afterglow charge of (-30 ± 7) e, being deducted from their acceleration in an externally applied electric field, is about three orders of magnitude lower compared to the typical charge expected in the bulk of such plasmas. This difference is explained by a relatively simplistic analytical model applying orbital motion limited theory in the afterglow region. From an application perspective, our results enable further understanding and development of in situ plasma-based particle contamination control for ultra-clean low pressure environments.\u3c/p\u3