Over the past years, ASML has taken the NXE pellicle concept (2015) from the concept level to pilot production (2016) and subsequently to a final product (2017 and onwards). In this paper we will show the progress in pellicle development that was made over the past year. After ASML started volume production of pellicles with the previous film generation, a new film generation was introduced end 2018. This new generation of pellicles shows considerable improvements in imaging performance, stability, EUV power capability and EUV reflectivity. The current generation of pellicle films show an EUV power capability of 250 Watts; improvements were also made in the imaging performance, where the EUV reflectivity of the pellicle reduced to below 0.04%. The EUV transmission of the latest pellicles increased to 83%.
ASML introduced the NXE pellicle concept, a removable pellicle solution that is compatible with current and
future patterned mask inspection methods. We will present results of how we have taken the idea from
concept to a demonstrated solution enabling the use of EUV pellicle by the industry for high volume
manufacturing. We will update on the development of the next generation of pellicle films with higher power
Further, we will provide an update on top level requirements for pellicles and external interface requirements
needed to support NXE pellicle adoption at a mask shop.
Finally, we will present ASML’s pellicle handling equipment to enable pellicle use at mask shops and our
NXE pellicle roadmap outlining future improvements.
Towards the end of 2014, ASML committed to provide a EUV pellicle solution to the industry. Last year, during SPIE Microlithography 2015, we introduced the NXE pellicle concept, a removable pellicle solution that is compatible with current and future patterned mask inspection methods. This paper shows results of how we took this concept to a complete EUV pellicle solution for the industry. We will highlight some technical design challenges we faced developing the NXE pellicle and how we solved them. We will also present imaging results of pellicle exposures on a 0.33 NA NXE scanner system. In conjunction with the NXE pellicle, we will also present the supporting tooling we have developed to enable pellicle use.
EUV pellicle membranes are being pursued to protect scanner images from repeating defects caused by reticle fall-on particle defects. Because most materials highly absorb EUV, pellicle membranes must be ultrathin. In an attempt to increase the strength of the ultrathin membranes, grid-supported pellicle membranes have been proposed. In this study we compare grid-supported pellicles (GSP) over free-standing pellicles (FSP). We considered imaging, thermal, mechanical, and thermo-mechanical characteristics. Finite Element Methods (FEM) was used to investigate the thermal, and (thermo-)mechanical behavior of pellicles. The maximum temperature reached under operational conditions by the pellicle film was determined. Using a thermo-mechanical analysis wrinkling behavior was quantified. The mechanical analysis considered the influence of grid structures on the sagging behavior, on crack propagation, on the pellicle film resistance to collision with solid particles, and on the resistance to shocks on the pellicle frame. The analysis shows that GSP that meets imaging requirements will not bring any advantages over FSP.
As EUV approaches high volume manufacturing, reticle defectivity becomes an even more relevant topic for further investigation. Current baseline strategy for EUV defectivity management is to design, build and maintain a clean system without pellicle. In order to secure reticle front side particle adders to an acceptable level for high volume manufacturing, EUV pellicle is being actively investigated. Last year ASML reported on our initial EUV pellicle feasibility. In this paper, we will update on our progress since then. We will also provide an update to pellicle requirements published last year. Further, we present experimental results showing the viability and challenges of potential EUV pellicle materials, including, material properties, imaging capability, scalability and manufacturability.