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Davydova N.,ASML Netherlands BV | De Kruif R.,ASML Netherlands BV | Rolff H.,AMTC GmbH and Co. KG | Connolly B.,Toppan Photomasks Inc. | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering

EUV lithography performance is improved significantly by optimizing and fine-tuning of the EUV mask. The EUV mask is an active element of the scanner optical system influencing main lithographic figure of merits such as image contrast, critical dimension uniformity (CDU), focus and overlay. The mask stack consists of Mo/Si multilayer acting as a bright field and a patterned absorber stack. In this work we will concentrate on investigation of EUV absorber. Absorber topography that is pronounced compared to the imaging wavelength of 13.5 nm, will give rise to various mask 3d effects such as shadowing or dependence of CD on feature orientation, best focus shift of different resolution structures, etc.[1][2]. Light interference in the absorber layer results in swinging behavior of various lithography metrics as function of the absorber height[5]. Optimization of the mask absorber allows mitigating mask 3d effects and improving imaging performance. In particular, reduction of the absorber height mitigates the shadowing effect and relaxes requirements on Optical Proximity Correction (OPC), but can result in smaller Process Window due to lower imaging contrast and larger best focus shifts. In this work we will show results of an experimental approach to absorber height optimization. A special mask with 27 different absorber heights in the range 40-70 nm is manufactured by Toppan Photomasks. EUV reflectivity spectra are measured for the different absorber heights and an experimental swing curve is constructed. For each absorber height various resolution features are present on the mask. Lines of 27 nm and 22 nm are imaged on the wafer using the ASML EUV scanner NXE:3300B with an NA of 0.33. The experimental CD swing curve is constructed as well as HV change as a function of absorber height. The impact of the absorber height on Exposure Latitude (EL) and Dose to Size (D2S) is investigated. EL improves with increasing absorber height in some cases, however there is no clear EL gain for a 70 nm absorber compared to for example 52 nm absorber. D2S does show a clear trend through absorber height. In particular, D2S can be reduced by absorber height reduction: e.g. for 52 nm absorber D2S is 5% or 1 mJ/cm2 smaller compared to 70 nm. The experimental results are used for calibration and verification of rigorous mask 3d simulations. This knowledge is crucial for accurate OPC of production masks and allows for accurate litho simulations of EUV user cases as a basis for lithography roadmaps towards High Volume Manufacturing and High NA EUV. © 2013 SPIE. Source

Badger K.D.,IBM | Seki K.,Toppan Photomasks Inc.
Proceedings of SPIE - The International Society for Optical Engineering

As part of 20 nm/22 nm process development, an evaluation was performed to determined the impact of Thin OMOG on mask inspection. Despite significant improvements in mask inspectability and reduced database modeling errors, thin OMOG demonstrated lower defect sensitivity as compared to Standard OMOG at the same inspection conditions (calibration, sensitivity). Stack height aside, the primary difference between standard and thin OMOG is attenuator reflectivity. It is surmised that the reduction in sensitivity is due to a lower reflected light contrast on thin-OMOG. This characteristic was noted for both 257 nm and 193 nm inspection wavelengths. In addition to the reduction in defect sensitivity, an unexpected phase interference was noted at the image edge with a 193 nm inspection wavelength, for Standard OMOG, but not for Thin OMOG. This interference, or undershoot is due in part to the low difference in reflectivity and phase between the quartz and the attenuator on the Standard OMOG substrate. This difference is more than five times greater for the Thin OMOG attenuator. The primary focus of this paper is on the characterization of thin OMOG relative to the interaction between attenuator reflectivity, image quality, database modeling and tool calibrations as they relate to mask inspectability and defect sensitivity. This paper will also address the changes required to compensate for the loss of sensitivity induced by the introduction of the thin OMOG absorber. © 2011 SPIE. Source

Kalk F.,Toppan Photomasks Inc.
Semiconductor International

The litho cell cost per circuit function has decreased by a factor of 3000, even while lithography exposure tool unit prices have increased 24 times. The business model for mask manufacturing and associated infrastructure is distinct and different than the business model for the rest of the litho cell. Designs are increasingly complicated and their costs are rising because design automation is not keeping pace with the products' function requirements. The cost of technology migration favors high-volume manufacturing, yet few chips are produced in high volume. Mask costs are especially affected by the technology migration to EUV. The change in the semiconductor business model presents several opportunities to reduce mask cost, but often at the expense of wafer scanner throughput. Lithography cell efficiency is the key enabler of continuing cost reduction in semiconductor manufacturing. Source

Toppan Photomasks Inc. | Date: 2011-09-23

An apparatus for transporting equipment and a method for the manufacture of the apparatus are disclosed. A damping assembly configured to dampen movement of a first item relative to a second item may include an arm and a shock absorber. The arm may be configured to be located between the first item and the second item and may be configured to pivotally couple to the first item and configured to slidably couple to the second item. The shock absorber may be configured to couple between the first item and the arm, such that the shock absorber dampens rotation of the arm to dampen movement of the first item relative to the second item.

Badger K.,IBM | Gallagher E.,IBM | Seki K.,Toppan Photomasks Inc. | McIntyre G.,IBM | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering

EUV wavelength inspection tools are several years away from product release. Until then, the EUV Lithography (EUVL) community faces the challenge of inspecting EUV masks at non-actinic wavelengths. It is critical to understand how to improve mask inspectability and defect sensitivity. The absorber stack is one contributor, since changing the film stack modifies image contrast. To study the effect, masks were fabricated from three different film stacks on which the thickness of the low reflective and absorber layers vary. These three absorbers are identified in this paper as Type A, Type B and Type C. All blanks had the same Ru-capped multi-layer substrate beneath the absorber stack. Inspection contrast, defect sensitivity and inspectability were measured on a 193nm wavelength inspection tool. The focus of this paper will be on inspection at the 193nm wavelength; however, simulated wafer results at the 13.5 nm EUV exposure wavelength will be included to anchor the relevance of the mask inspection results. A comparison of the different absorber stacks, the ability to detect defects on the various masks, and how defects on these substrates prints on wafer will be provided. This work addresses the gap between EUVL mask inspection and wafer defect printability and how the two views differ relative to various absorber stacks. © 2013 SPIE. Source

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