Aerial image based mask defect detection in dense array structures

Köhle, Roderick; Hennig, Mario; Pforr, Rainer; Bubke, Karsten; Sczyrba, Martin; Dürr, Arndt C.

doi:10.1117/12.617303

Cited by 2 publications

(1 citation statement)

References 8 publications

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“…3(a)] only the 0 th order falls in the NA and thus the pattern will not be resolved on the wafer or in the AIMS TM -tool. [17][18][19] Still using a point-source, however, from an off-axis position [see Fig. 3(b)] the refraction pattern is simply moved and two orders fall into the NA enabling pattern imaging.…”

Section: Imaging Of Patternsmentioning

confidence: 99%

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: Imaging Of Patternsmentioning

confidence: 99%

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

et al. 2005

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An advanced study for defect disposition through 193-nm aerial imaging

2006

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With decreasing structure sizes on masks also the acceptable CD variation corridor for printing on the wafer and therefore, the maximum allowed defect size is decreasing. This has not only implications to the accuracy and repeatability of front-end processes such as writers, etchers, etc. but also challenges defect inspection and qualification. Defect qualification is usually done by an AIMS TM tool which optically simulates the aerial image of the structures by applying the same illumination conditions as the wafer fabs' scanners. As lithographers continue to produce smaller and smaller structures, the as well decreasing acceptable design variation pushes the AIMS TM evaluation step by step towards a metrology method. Thus, an advanced measurement capability of the AIMS TM tool is mandatory to reliably disposition defects within these small margins. It is influenced by the performance of illumination, imaging homogeneity, and stability. A possible measure for the tool's capability is the (long term) repeatability, i.e. the 3σ-variance of the tool by evaluating the same defect with a certain frequency over several weeks. The AIMS TM fab 193i platform takes into account the tightened requirements with respect to homogeneity and stability by improved optics such as a new beam homogenizer module, new energy monitoring and vibration isolation concept. In this paper we show data on the long term repeatability compared between the first generation AIMS TM fab 193SE and the new AIMS TM fab 193i platform and discuss the implications on the measurement capabilities of the two platforms.

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Aerial image based mask defect detection in dense array structures

Cited by 2 publications

References 8 publications

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

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

An advanced study for defect disposition through 193-nm aerial imaging

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