Currently, we are supplying defect-free EUV mask for device development. This was one of the biggest challenges in the implementation of EUV lithography for high volume manufacturing (HVM). It became possible to hide all multi-layer defects by using defect avoidance technique through improvement of blank mask defectivity and development of actinic blank inspection tool. In addition, EUV pellicle is also considered as a requisite to guarantee predictable yield. Both development of mask shop tools and preparation of EUV scanner for pellicle are going well. However, still membrane needs to be much improved in terms of transmittance and robustness for HVM. At the conference, EUV mask readiness for HVM will be discussed including blank defect improvement, preparation of actinic tools and pellicle development.
Extreme ultraviolet (EUV) lithography has received much attention in the semiconductor industry as a promising candidate to extend dimensional scaling beyond 10nm. Recently EUV pellicle introduction is required to improve particle level inside scanner for EUV mass production. We demonstrate that a new pellicle material, nanometer-thick graphite film (NGF), is one of the best candidates of EUV pellicle membrane. A NGF pellicle with excellent thermal (ε≥0.4 @R.T, <100nm), mechanical (415MPa @~100nm), chemical and optical (24hrs durability under exposure of EUV/H2 at 4W/cm2 with pH2~5Pa) properties can be a promising and superb candidate for EUV pellicle membrane compared to Si pellicles with capping layers.
We report the effect of the mesh support for the EUV pellicle on the wafer pattern image. The intensity distribution passing through the meshed pellicle was simulated with a partially coherent EUV beam showing that its non-uniformity and the CD uniformity are increased with the mesh width. In order to reduce a non-uniformity of the intensity distribution and CD uniformity, the mesh width should be narrower and the height becomes smaller as well. Thus, the image deformation on the wafer due to the mesh can be avoided by optimizing the mesh structure and thus the pellicle with the mesh support can be used for the EUV lithography.
The Critical Dimension (CD) uniformity due to the defect on the Extreme-Ultraviolet (EUV) pellicle is reported. Based on computational simulation of the aerial images for different defect size on the wafer, it is found that the size of the defect should be smaller than 2 μm for the CD uniformity of 0.1 nm. The aerial image for the different defect materials, sulfur and ruthenium, are also simulated showing that the CD uniformity does not have a noticeable dependence on the different defect materials. However, the CD uniformity is worsened with the mesh structure due to its shadow and the much smaller defects size, less than 2 μm, can be allowed.
Over the past several years, people have accomplished a great deal of developing the Extreme-ultraviolet lithography
(EUVL) technologies. However, several problems which disturb the mass-production of EUVL still remain. One of the
problems is the defect control. In order to protect the mask from defect, the usage of the pellicle is essential. However the
transmission loss caused by contamination can lead to the pattern error. Therefore it is necessary to find the acceptable
thickness of the contamination layer that would cause the image error. The protection ability of the pellicle in terms of
critical dimension variation is studied. Our study indicated that the process latitude difference is small enough to ignore
whether the pellicle is used or not. In addition the protection ability of pellicle is good against the case of conformal
contamination in terms of CD variation.
38nm half pitch pattern was replicated from Si master pattern to quartz blank template. It is a novel approach different
from typical quartz to quartz replication. This replication concept is expected to alleviate the burden not only in cost but
also resolution for NIL template fabrication. In this study, full field Si master fabricated by ArF immersion lithography,
UV-transparent hard mask for quartz blank template and core-out quartz blank template were applied to prove the
concept. And the replica template was evaluated with NIL and subsequent etching.