High reflectivity and long-term stability in multilayer mirrors (MLMs) are crucial for extreme ultraviolet (EUV) photolithography. The conventional base stack to reflect 13.5 nm light is a Mo/Si... Show moreHigh reflectivity and long-term stability in multilayer mirrors (MLMs) are crucial for extreme ultraviolet (EUV) photolithography. The conventional base stack to reflect 13.5 nm light is a Mo/Si multilayer, which offers a maximum theoretical reflectivity of 75%. In practice, however, the efficiency of the mirror is strongly affected by intermixing between Mo and Si. Diffusion barriers have therefore been adopted, which nevertheless do not provide a perfect solution. In this work, we propose to suppress intermixing in Mo/Si MLMs by substituting the pure Si with a Si compound that can ensure higher thermodynamic stability, while simultaneously providing comparably high EUV theoretical reflectivity, with the net effect of increasing both reflectivity and lifetime. Our theoretical calculations show that rubidium silicide is the most promising material for this purpose. We estimate the optical and thermodynamic properties for each phase of rubidium silicide, and we show that Mo/Rb12Si17 provides the highest theoretical reflectivity, while Mo/RbSi is the most thermodynamically stable. The suppression of intermixing in Mo/RbSi MLMs should lead to a maximum reflectivity at least 2% higher than the best Mo/Si MLMs, integrated with diffusion barriers. The proposed Mo/RbSi MLM solution has the potential to increase the total EUV lithography throughput by similar to 50%. Show less
The European Union's REACH regulation has introduced Socio-Economic Analyses as a new decision support tool in the domain of chemical policy-making. This paper presents a pragmatic method to review... Show moreThe European Union's REACH regulation has introduced Socio-Economic Analyses as a new decision support tool in the domain of chemical policy-making. This paper presents a pragmatic method to review the replacement of chemicals in processes or products in terms of the environmental impact. The aim of this work is to develop a broadly accepted method for environmental impact assessment as part of Socio-Economic Analyses. The method consists of a stepwise and tiered approach for Environmental Impact Assessment whereby the expected impact of the replacement of chemicals is assessed via Risk Characterization Ratios and toxic pressure quantification (expressed as a Potentially Affection Fraction ofspecies), and e if relevant e via a Persistency, Bioaccumulation potential and Toxicity score. The working of the method is demonstrated by the replacement of chemical substances in detergents, gutters and Expanded Polystyrene. Of the three replacements, for gutters, the reduction of the toxic pressure on the aquatic compartment was highest. Based on 50% effect concentrations the Potentially Affection Fraction of species due to the use of zinc gutters was relatively high (15%), while it was 0.6% after replacement by PVC gutters. This indicates that PVC gutters have a lower direct impact on aquatic biodiversity than zinc gutters. This paper demonstrates that even with limited data the proposed method can be used to move from risk indicators to impact indicators. The tiered approach allows finding the most appropriate level of analysis in a cost and resource efficient way. The method allows comparison of results of different scenarios and as such allows selecting the most preferable alternative from an environmental perspective. This is useful in the context of socio-economic analysis and as such, this method is available as a decision-support tool under REACH and other chemical policy frames such as the United Nations Environment Program. Show less
