Researching new EUV pellicle films for source powers beyond 250 watts

In order to deploy EUV lithography as a high volume manufacturing technology an extreme control of reticle defectivity is required. Systematic defect printing is unaffordable. A potential solution being investigated for meeting the EUV reticle contamination control requirements is to utilize a suspended thin membrane (pellicle) mounted at a fixed distance in front of the reticle as a physical barrier against particles. Pellicles of the aspect ratios relevant for the scanner (similar to 11x14cm(2), similar to 50 nm) that are based on polycrystalline silicon were produced and successful imaging runs were carried out. Investigations of pellicles using different materials continue to ensure having membranes capable of withstanding future high EUV source powers and to ensure larger EUV transmission values. The ideal requirements of the pellicle are: (i) maximum EUV transmission ideally above 90% single pass, (ii) chemical stability and (iii) thermo-mechanical resistance under EUV/H-2. Since fulfilling all the requirements in one single layer is a challenge, different layer film architectures are proposed. This paper discusses such architectures, both silicon-and carbon-based. The base materials are complemented by nanometre thin coatings that increase IR absorption and thus enhance emissivity and that prevents oxidation of the base material occurring in high power EUV systems.