Fourier analysis of AIMS images for mask characterization

Koehle, Roderick; Dettmann, Wolfgang; Verbeek, Martin

doi:10.1117/12.504216

Cited by 4 publications

(4 citation statements)

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“…The still existing difference between the measured data and the simulated data for the same orientation can be attributed to the above mentioned effects such as flare, crosstalk, aberrations, etc. 15,16 which are characteristic for the hardware of any tool and are yet neither strongly reduced (as for e.g. in steppers) nor included in the simulations.…”

Section: Measurement and Simulation Of The Contrast Of Horizontal Andmentioning

confidence: 99%

“…These are aside the pupil inhomogeneity, e.g., flare, cross-talk or lens aberrations, where the former two are considered to be the major effects. 15,16 To distinguish between these effects from those originating from the pupil inhomogeneity, AIMS TM -images of the same structure were acquired in both vertical and horizontal direction. As flare and crosstalk should be less direction dependent, a comparison between both images gives a good indication of the influence of pupil illumination inhomogeneity.…”

Section: Masks and Illumination Settingsmentioning

confidence: 99%

“…[11][12][13][14] However, the matching between AIMS TM results and simulations is often unsatisfactory since the imperfections of the AIMS TM optics are normally not included in simulations (e.g., flare, aberrations, cross-talk, inhomogeneous illumination). 15,16 This discrepancy between simulation and measurement is exemplified in the upper part of Figure 1 on a lines and spaces (referred to as l&s hereafter) pattern for annular illumination † . In addition, the lower part of Figure 1 shows the orientation dependence of the measured contrast of the same lines and spaces pattern, which can be attributed to the inhomogeneous illumination.…”

Section: Introductionmentioning

confidence: 99%

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The importance of being homogeneous: on the influence of illumination inhomogeneity on AIMS images

et al. 2005

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Defect disposition and qualification with stepper simulating AIMS TM tools on advanced masks of the 90 nm node and below is key to match the customer's expectations for "defect free" masks, i.e. masks containing only nonprinting design variations. For defect dispositioning usually printability studies are carried out using the same illumination settings at the AIMS TM tool as later on at the steppers in the wafer fab. These studies then establish an AIMS TM criterion (e.g., CD variation or transmission deviation) a structure deviation must not exceed. For ever more advanced technologies the accessible process window gets smaller and thus more and more complex apertures have to be used to allow for a still suitable contrast and reliable printing of the patterns. This results in more time-consuming printability studies and tighter AIMS TM specs. Simulations of the printing of mask defects could potentially help to decrease the amount of time for printability studies and also the time for defect disposition in the production. However, usually simulations in their first approximation do not account for effects such as flare, aberrations or illumination inhomogeneities of the AIMS TM tool. This makes it difficult to derive the AIMS TM criterion by simulations. In this paper we show that a homogeneous aperture illumination is crucial for the image contrast and the defect disposition. We present a method to characterize the pupil illumination and investigate the impact of illumination inhomogeneities on various structures and their orientation employing two different aperture types. The experimental results are compared to simulations with both homogeneous illumination and the real illumination distribution. It turns out that for correct simulation predictions on experimental results it is important to provide the correct illumination distribution to the simulations.

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Section: Measurement and Simulation Of The Contrast Of Horizontal Andmentioning

confidence: 99%

Section: Masks and Illumination Settingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The importance of being homogeneous: on the influence of illumination inhomogeneity on AIMS images

et al. 2005

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“…This is currently the main application for an AIMS tool. On the other hand, the tool provides the opportunity of an optical performance evaluation for advanced phase shift masks, where the phase and transmission signatures can be determined via Fourier analysis [3]. Additionally, it can be used for CD measurements (critical dimension) on the photomask avoiding disadvantages like carbon contamination when using a photomask SEM [4].…”

Section: Introductionmentioning

confidence: 99%

First results from AIMS beta tool for 157-nm lithography

Teuber

Higashikawa²,

Urbach³

et al. 2004

SPIE Proceedings

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In modern mask manufacturing, a successful defect mitigation strategy has been become crucial to achieve defect free masks for high-end lithography. The basic steps of such a strategy include inspection, repair, and subsequent post-repair qualification of repair sites. For the latter task, actinic aerial image measurements have been proven to be the technique of choice to assess the printability of a repaired site. In the last three years, International SEMATECH in cooperation with Infineon/AMTC-Dresden and SELETE, funded a joint development project at Carl Zeiss to develop an AIMS  tool operating at the 157nm wavelength. The three beta tools were shipped in 2003 to the three beta customer sites. In this paper are presented the first results obtained with these beta tools, including measurements on binary as well as alternating phase shift masks. The technical properties of the tool were discussed with regards to the capability of the tool for defect qualification on photomasks. Additionally, preliminary results of the evaluation of alternating phase shift masks will be discussed, including measurements performed on dense lines-and-spaces structures with various pitch sizes.

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