Phame: a novel phase metrology tool of Carl Zeiss for in-die phase measurements under scanner relevant optical settings

Perlitz, Sascha; Buttgereit, Ute; Scherübl, Thomas

doi:10.1117/12.712813

Cited by 5 publications

(3 citation statements)

References 3 publications

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“…Furthermore the tool is fully SMIF compatible and in combination with the optionally available SECS/GEM capabilities the system is suited to match the automation and cleanliness requirements of high-end photomask production. Phame ® tool performance was reported earlier and shows excellent performance in terms of accuracy and repeatability [6]. The phase shift accuracy is well below 1°, the static phase reproducibility for large reference features is below < 0.2° (3sigma) and for small production features below 0.4° (3sigma).…”

Section: Phame ® -Phase Metrology Systemmentioning

confidence: 80%

Laterally resolved off-axis phase measurements on 45-nm node production features using Phame

et al. 2007

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As lithography mask process moves toward 45nm and 32nm node, phase control is becoming more important than ever. To ensure an accurate printing both attenuated and alternating PSMs (Phase Shift Masks) need precise control of phase as a function of both pitch and target sizes. However critical target CDs fall much below conventional phase metrology tools capabilities. Interferometer-based phase shift measurements are limited to large CD targets and require custom designed features in order to function properly, which limits phase measurement. AFM (Atomic Force Microscopy) methods are able to capture small feature sizes but do not consider any diffraction effects which are caused by the topography of the features itself when getting close to the used wavelength.Imaging simulations, both, in a rigorous and a Kirchhoff regime, show the dependency of the phase in the image plane of a microlithography exposure tool on numerical aperture and pitch due to the loss of phase information in the imaging pupil. Additionally, for small features the phase is strongly impacted by polarization and 3D mask effects. For these feature sizes, the image phase does not coincide with the etch depth equivalent phase calculated from the nominal depth and optical constants of the shifter material. Deviations up to 20° have been observed leading to strong variations in the imaging quality and process window variations during scanner printing. Considerations of CD variation between 0 and pi features by simulation show lowest 0/pi CD variation and therefore largest process window if the scanner relevant phase is at 180°. The simulation results illustrate the importance to measure the scanner relevant phase, effective in the image plane of the scanner.Consequently Zeiss, in collaboration with Intel, has developed a laterally resolving Phase Metrology Tool -Phame ® -for in-die phase measurements. The optical metrology tool is able to perform in-die phase measurement on alternating PSM, attenuated PSM and CPL masks down to 120nm half pitch at mask. On-axis measurement results have already been published.In this paper we elaborate on off-axis phase measurement theory and procedure. Furthermore we present first off-axis measurement results over varying features sizes using different illumination conditions.

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Section: Phame ® -Phase Metrology Systemmentioning

confidence: 80%

Laterally resolved off-axis phase measurements on 45-nm node production features using Phame

et al. 2007

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“…As briefly discussed in the introduction with the newly developed phase metrology system Phame® it has now for the very first time become possible to retrieve the phase behaviour of a small structure on a phaseshifting mask. [4] The initial intention for the development of the phase metrology system Phame® has come from a number of different requirements, for instance because proximity effects due to the finite extension of the phase grating can significantly influence the phase value of individual lines, or as a means to improve OPC (optical proximity correction) strategies or other reticle enhancement technologies. Nevertheless, this capability is also of great interest for the mask repair process development and repair success assessment.…”

Section: Repair Resultsmentioning

confidence: 99%

Phase-shifting photomask repair and repair validation procedure for transparent and opaque defects relevant for the 45nm node and beyond

et al. 2008

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“…[1] On-and off-axis illumination including polarization can be applied using a mask side NA going up to 0.4 which is 1.6 NA scanner equivalent. This enables full compatibility to current and future 193nm immersion scanners down to the 32nm node.…”

Section: Basic Working Principle Of the Toolsmentioning

confidence: 99%

MeRiT repair verification using in-die phase metrology Phame

Buttgereit

Birkner

Stelzner

2009

25th European Mask and Lithography Conference

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With the transition of lithography into 45nm node and beyond the industry faces the challenge that mask complexity increases steadily, mask specifications tighten and process control becomes extremely important. The use of Phase Shifting Masks (PSM), combined with off-axis illumination schemes, is essential to print feature sizes going beyond the lithographic wavelength. In conjunction with the shrinking feature size the tolerable defect size shrinks as well. This goes along with rising mask costs and therefore a high first pass yield becomes more important than ever. Repair strategies are required which have the potential to support the trend of decreasing tolerable defect sizes for both clear and opaque defects. In case of PSM it is not only important to remove material, of special interest is the capability to repair phase defects. This requires material deposition and etching accounting for transmission and phase as well.The ebeam repair system MeRiT ® MG 45 is based on the GEMINI ® column and allows etching and deposition to repair both clear and opaque defects with high resolution and edge placement precision.In this paper we focus on repair of phase defects on 6% att. PSM. We concentrate on 45nm lines/spaces looking into different defect dimensions. At feature sizes of 45nm CD, corresponding to 180nm CD at mask, feature topography already impacts the phase shift. Therefore a base line investigation is performed evaluating the correlation between deposited PSM layer height and phase shift covering also the impact of 3D mask effects on phase shift.The deposited layer height is measured using AFM. For phase evaluation the newly developed phase metrology system Phame ® was used. Phame ® enables optical phase shift measurement with high spatial resolution down to 120nm half pitch on mask. On-axis and off-axis illumination can be applied according to the required scanner settings during wafer printing. Phame ® captures imaging effects as well as 3D mask effects which are of special importance for further shrinking feature sizes.

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Phame: a novel phase metrology tool of Carl Zeiss for in-die phase measurements under scanner relevant optical settings

Cited by 5 publications

References 3 publications

Laterally resolved off-axis phase measurements on 45-nm node production features using Phame

Laterally resolved off-axis phase measurements on 45-nm node production features using Phame

Phase-shifting photomask repair and repair validation procedure for transparent and opaque defects relevant for the 45nm node and beyond

MeRiT repair verification using in-die phase metrology Phame

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