Sascha Migura

EUV lithography scanner for sub-8nm resolution

EUV lithography for resolutions below 8 nm half pitch requires the numerical aperture (NA) of the projection lens to be significantly larger than the current state-of-the-art 0.33NA. In order to be economically viable, a throughput in the range of 100 wafers per hour is needed. As a result of the increased NA, the incidence angles of the light rays at the mask increase significantly. Consequently the shadowing deteriorates the aerial image contrast to unacceptably low values at the current 4x magnification. The only solution to reduce the angular range at the mask is to increase the magnification. Simulations show that we have to double the magnification to 8x in order to overcome the shadowing effects. Assuming that the mask infrastructure will not change the mask form factor, this would inevitably lead to a field size that is a quarter of the field size of current 0.33NA step and scan systems. This would reduce the throughput of the high-NA scanner to a value significantly below 100 wafers per hour unless additional measures are taken. This paper presents an anamorphic step and scan system capable to print fields that are half the field size of the current full field. The anamorphic system has the potential to achieve a throughput in excess of 150 wafers per hour by increasing the transmission of the optics as well as increasing the acceleration of the wafer- and mask stage. This makes it an economically viable lithography solution. Furthermore, the simulated imaging behavior of the system is demonstrated and its impact on the rest of the lithographic system is discussed.

EUV lithography optics for sub-9nm resolution

EUV lithography for resolution below 9 nm requires the numerical aperture of the projection optics to be significantly larger than 0.45. A configuration of 4x magnification, full field size and 6’’ reticle is not feasible anymore. The increased chief ray angle and higher NA at reticle lead to non-acceptable shadowing effects, which can only be controlled by increasing the magnification, hence reducing the system productivity. We demonstrate that the best compromise in imaging, productivity and field split is a so-called anamorphic magnification and a half field of 26 x 16.5 mm². We discuss the optical solutions for anamorphic high-NA lithography.

The future of EUV lithography: enabling Moore's Law in the next decade

While EUV systems equipped with a 0.33 Numerical Aperture lenses are readying to start volume manufacturing, ASML and Zeiss are ramping up their development activities on a EUV exposure tool with Numerical Aperture greater than 0.5. The purpose of this scanner, targeting a resolution of 8nm, is to extend Moore’s law throughout the next decade. A novel, anamorphic lens design, has been developed to provide the required Numerical Aperture; this lens will be paired with new, faster stages and more accurate sensors enabling Moore’s law economical requirements, as well as the tight focus and overlay control needed for future process nodes. The tighter focus and overlay control budgets, as well as the anamorphic optics, will drive innovations in the imaging and OPC modelling, and possibly in the metrology concepts. Furthermore, advances in resist and mask technology will be required to image lithography features with less than 10nm resolution. This paper presents an overview of the key technology innovations and infrastructure requirements for the next generation EUV systems.

Imaging performance of EUV lithography optics configuration for sub-9nm resolution

New design solutions are available for high-NA EUV optics, maintaining simultaneously superior imaging performance and productivity below 9nm resolution by means of anamorphic imaging. We investigate the imaging properties of these new optics configurations by rigorous simulations, taking into account mask induced effects as well as characteristics of the new optics. We compare the imaging behavior to other, more traditional optics configurations, and show that the productivity gain of our new configurations is indeed obtained at excellent imaging performance.

Anamorphic high-NA EUV lithography optics

EUV lithography (EUVL) for a limit resolution below 8 nm requires the numerical aperture (NA) of the projection optics to be larger than 0.50. For such a high-NA optics a configuration of 4x magnification, full field size of 26 x 33 mm² and 6’’ mask is not feasible anymore. The increased chief ray angle and higher NA at reticle lead to non-acceptable mask shadowing effects. These shadowing effects can only be controlled by increasing the magnification, hence reducing the system productivity or demanding larger mask sizes. We demonstrate that the best compromise in imaging, productivity and field split is a so-called anamorphic magnification and a half field of 26 x 16.5 mm² but utilizing existing 6’’ mask infrastructure. We discuss the optical solutions for such anamorphic high-NA EUVL.

EUV High-NA scanner and mask optimization for sub 8 nm resolution

EUV lithography for resolution below 8 nm half pitch requires the numerical aperture (NA) of the projection lens to be significantly larger than the current state-of-the-art 0.33NA. In order to be economically viable, a throughput in the range of 100 wafers per hour is needed. As a result of the increased NA, the incidence angles of the light rays at the mask increase significantly. Consequently the shadowing and the variation of the multi-layer reflectivity deteriorate the aerial image contrast to unacceptably low values at the current 4x magnification. The only solution to reduce the angular range at the mask is to increase the magnification. Simulations show that we have to double the magnification to 8x in order to overcome the shadowing effects. Assuming that the mask infrastructure will not change the mask form factor, this would inevitably lead to a field size that is a quarter of the field size of current 0.33NA step and scan systems. This would reduce the throughput of the high-NA scanner to a value significantly below 100 wafers per hour unless additional measures are taken. This paper presents an anamorphic step and scan system capable to print fields that are half the field size of the current full field. The anamorphic system has the potential to achieve a throughput in excess of 150 wafers per hour by increasing the transmission of the optics as well as increasing the acceleration of the wafer stage and mask stage. This makes it an economically viable lithography solution. The proposed 4x/8x magnification is not the only logical solution. There are potentially other magnifications to increase the scanner performance while at the same time reducing the mask requirements.

The future of EUV lithography: continuing Moore's Law into the next decade

While 0.33NA EUV systems are readying to start volume manufacturing, ASML and Zeiss are ramping up development activities on a 0.55NA EUV exposure tool, extending Moore’s law throughout the next decade. A novel, anamorphic lens design, has been developed to provide the NA; this lens will be paired with new, faster stages and more accurate sensors and the tight focus and overlay control needed for future process nodes. This paper presents an overview of the target specifications, key technology innovations and imaging simulations demonstrating the advantages as compared to 0.33NA and showing the capabilities of ASML’s next generation EUV systems.

High-numerical aperture extreme ultraviolet scanner for 8-nm lithography and beyond

Abstract. Current extreme ultraviolet (EUV) projection lithography systems exploit a projection lens with a numerical aperture (NA) of 0.33. It is expected that these will be used in mass production in the 2018/2019 timeframe. By then, the most difficult layers at the 7-nm logic and the mid-10-nm DRAM nodes will be exposed. These systems are a more economical alternative to multiple-exposure by 193 argon fluoride immersion scanners. To enable cost-effective shrink by EUV lithography down to 8-nm half pitch, a considerably larger NA is needed. As a result of the increased NA, the incidence angles of the light rays at the mask increase significantly. Consequently, the shadowing and the variation of the multilayer reflectivity deteriorate the aerial image contrast to unacceptably low values at the current 4× magnification. The only solution to reduce the angular range at the mask is to increase the magnification. Simulations show that the magnification has to be doubled to 8× to overcome the shadowing effects. Assuming that the mask infrastructure will not change the mask form factor, this would inevitably lead to a field size that is a quarter of the field size of the current 0.33-NA step and scan systems and reduce the throughput (TPT) of the high-NA scanner to a value below 100 wafers per hour unless additional measures are taken. This paper presents an anamorphic step and scan system capable of printing fields that are half the field size of the current full field. The anamorphic system has the potential to achieve a TPT in excess of 150 wafers per hour by increasing the transmission of the optics, as well as increasing the acceleration of the wafer stage and mask stage. This makes it an economically viable lithography solution.

High-NA EUV lithography exposure tool progress (Conference Presentation)

While EUV systems equipped with a 0.33 Numerical Aperture (NA) lens are readying to start high volume manufacturing, ASML and Zeiss are in parallel ramping up their activities on an EUV exposure tool with an NA of 0.55. The purpose of this high-NA scanner, targeting an ultimate resolution of 8nm, is to extend Moore’s law throughout the next decade. A novel lens design, capable of providing the required Numerical Aperture, has been identified; this lens will be paired with new, faster stages and more accurate sensors enabling the tight focus and overlay control needed for future process nodes. In this paper an update will be given on the status of the developments at Carl Zeiss and ASML. Next to this, we will address several topics inherent in the new design and smaller target resolution: M3D effects, polarization, focus control and stitching.

High-NA EUV lithography enabling Moore’s law in the next decade

While EUV systems equipped with a 0.33 Numerical Aperture lenses are readying to start volume manufacturing, ASML and Zeiss are ramping up their activities on a EUV exposure tool with Numerical Aperture of 0.55. The purpose of this scanner, targeting an ultimate resolution of 8nm, is to extend Moore’s law throughout the next decade. A novel, anamorphic lens design, capable of providing the required Numerical Aperture has been investigated; This lens will be paired with new, faster stages and more accurate sensors enabling Moore’s law economical requirements, as well as the tight focus and overlay control needed for future process nodes. The tighter focus and overlay control budgets, as well as the anamorphic optics, will drive innovations in the imaging and OPC modelling. Furthermore, advances in resist and mask technology will be required to image lithography features with less than 10nm resolution. This paper presents an overview of the target specifications, key technology innovations and imaging simulations demonstrating the advantages as compared to 0.33NA and showing the capabilities of the next generation EUV systems.