Update on the EUVL mask blank activity at Schott Lithotec

Sobel, Frank; Aschke, Lutz; Becker, Hans; Renno, Markus; Ruggeberg, Frauke; Kirchner, Steffen; Leutbecher, Thomas; Olschewski, Nathalie; Schiffler, Mario; Walter, K.; Hess, Guenter; Buttgereit, Ute; Knapp, Konrad; Lebert, R.; Juschkin, Larissa; Wies, Christian; Jagle, Bernhard

doi:10.1117/12.518061

Cited by 5 publications

(2 citation statements)

References 4 publications

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“…Despite the fact that defect reduction remains the most important issue for the multilayer, the other layers of an EUV mask blank represent also some technical goals for the past and next months. We already presented some new studies that were performed at Schott Lithotec about a new material absorber stack [10] and this system is still under evaluation. Firstly, we evidence some new techniques to lower down the surface roughness of the SiO 2 buffer layer and the new alternative absorber material (AAM) was mainly investigated in terms of defect level and inspection reflectivity.…”

Section: Absorber Stack and Backside Coating Improvementsmentioning

confidence: 98%

Production of low-thermal-expansion EUVL mask blanks with low-defect multilayer, buffer, and absorber

et al. 2004

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Schott Lithotec has introduced all relevant technology steps to manufacture EUV mask blanks -ranging from Low Thermal Expansion Material (LTEM) via high quality substrate polishing to low defect blank manufacturing. New polishing and cleaning technologies, improved sputter technology and updated metrology enable us to routinely produce EUVL mask blanks meeting already many of the roadmap requirements. The goal is pilot production of EUV blanks for the 45 nm node end of 2005. There are several technology options for achieving the mechanical, optical and chemical specs for substrates and coatings. Some of them are already integrated in our processes. An important focus of this paper is the understanding of defect sources starting from the LTEM bulk material to the fully coated blanks with multilayer, buffer and absorber. We present details on some production steps controlling defect detection sensitivity dedicated to various layers and report on new results on defect reduction research after the different process steps.

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Section: Absorber Stack and Backside Coating Improvementsmentioning

confidence: 98%

Production of low-thermal-expansion EUVL mask blanks with low-defect multilayer, buffer, and absorber

et al. 2004

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“…The lowest level of freestanding flatness of low thermal expansion material mask substrates had been about 250 nm p-v.2 However, now several suppliers have been able to produce substrates that nearly meet the specification. 3 One of the key issues in EUVL is the flatness of the mask as chucked in the e-beam and exposure tools. The tight flatness requirements are a result of the extremely small overlay error allowed for EUVL since current EUV imaging systems utilize nontelecentric illumination of the mask.4 As a result, image placement error occurs at the wafer due to the nonflatness of the chucked mask.…”

Section: Introductionmentioning

confidence: 99%

Effect of electrostatic chucking on EUVL mask flatness

et al. 2004

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The International Technology Roadmap for Semiconductors for Extreme Ultraviolet Lithography (EUVL) places strict requirements on the quality and flatness of the substrate and patterned mask. The SEMI EUVL Mask Substrate Standard (SEMI P37) specifies that the substrate frontside and backside nonflatness be no more than 50nm peak-tovalley (p-v). Recent technological advances in polishing and finishing techniques have placed the 50 nm p-v specification within reach. A key ingredient in the development of EUVL is understanding and characterizing the clamping ability of the electrostatic chuck and the resulting effect on the flatness of the chucked mask. By implementing the shape of a representative EUVL mask surface into a numerical model, the effect of electrostatic chucking on the shape of the mask was determined. Legendre polynomials have been identified as an effective and efficient means of representing EUVL mask surface shapes. Finite element (FE) models have been developed to utilize the Legendre coefficients as input data to define the surfaces of an EUVL mask. The FE models were then used to determine the clamping response of the mask. In particular, the maximum mask-to-chuck gap within the Flatness Quality Area and over the entire mask has been tracked as a function of clamping pressure for representative EUVL surfaces. One ofthe important parameters in this study was the chuck's mechanical stiffness (comprised of the thickness and modulus). The flatness of the EUVL mask also depends on the intrinsic stress and thickness of the multilayer and backside layers. The results in this paper show that the recent advances in EUVL substrate polishing have resulted in masks that can be chucked relatively flat.

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Effect of electrostatic chucking and substrate thickness uniformity on extreme ultraviolet lithography mask flatness

Mikkelson

Engelstad

Sohn

et al. 2004

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Thermal modeling of extreme ultraviolet and step and flash imprint lithography substrates during dry etch Extreme ultraviolet lithography (EUVL) is one of the leading candidates for next-generation lithography in the sub-45 nm regime. Successful implementation of this technology will depend upon advancements in many areas, including the quality of the mask system to control image placement errors. Such errors will occur at the wafer as a result of height variations of the patterned (frontside) mask surface (i.e., its nonflatness). The Semiconductor Equipment and Materials International EUVL Mask Standard (SEMI P37) specifies that the mask frontside and backside nonflatness be no more than 50 nm peak-to-valley (P-V). Currently, the lowest level of freestanding flatness of EUVL mask substrates from production-level polishing and finishing techniques is about 200 nm P-V. The frontside and backside of typical (and representative) EUVL substrates were measured for flatness and these surfaces were represented mathematically using Legendre polynomials. The Legendre coefficients were then utilized in a finite element model to predict the effect of chucking on the flatness of these substrates. One of the significant conclusions of this research is that the substrate thickness nonuniformity has a dominant effect on the flatness of the patterned surface after chucking.

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Update on the EUVL mask blank activity at Schott Lithotec

Cited by 5 publications

References 4 publications

Production of low-thermal-expansion EUVL mask blanks with low-defect multilayer, buffer, and absorber

Production of low-thermal-expansion EUVL mask blanks with low-defect multilayer, buffer, and absorber

Effect of electrostatic chucking on EUVL mask flatness

Effect of electrostatic chucking and substrate thickness uniformity on extreme ultraviolet lithography mask flatness

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