Pupil-fill imperfections and their effect on lithography

Renwick, Stephen P.; Slonaker, Steven D.

doi:10.1117/12.485444

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…Several valuable tools are now available to the lithographic tool builder or user wishing to characterize a tool: measurement of lens aberrations via interferometry, measurement of the illuminator pupil fill using a pinhole method 1, , 2 and even measurement of the lens NA. At the same time, in recent years, the coherence behavior of a tool has increased in importance, primarily due to increased use of OPC.…”

Section: Introductionmentioning

confidence: 99%

What makes a coherence curve change?

Renwick

2005

Optical Microlithography XVIII

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With use of OPC on the rise, lithographers have now added coherence behavior to their list of important concerns about an imaging tool. Previously, parameters like nested-to-isolated bias were important. Now, we need to think about the behavior of an entire coherence curve, which is a plot of printed linewidth versus pitch for a set of features at constant reticle linewidth. While the precise shape of a curve may not be especially important, the lithographer will want to know the tool-to-tool variation and whether the curve will change with time. That variation is affected by at least both lens aberrations and illuminator pupil fill, and potentially by other factors as well, like flare or optics contamination. We have made a systematic study of coherence sensitivity to a host of potential factors, and we will present a sensitivity analysis, identifying the big and the small drivers of coherence-curve behavior.

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Section: Introductionmentioning

confidence: 99%

What makes a coherence curve change?

Renwick

2005

Optical Microlithography XVIII

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“…Partially coherent illumination sources such as circular, annular, c-quad, r-quad, and quasar, have continuous pupil illumination functions unlike the so called top-hat approximation, [1][2][3][4][5] which is piecewise constant and discontinuous. Previously reported techniques 5-10 of measuring the pupil illumination function require specialized hardware that is sometimes not readily available.…”

Section: Introductionmentioning

confidence: 99%

Metrology for stepper illumination pupil profile

Perçin¹

2006

J. Micro/Nanolith. MEMS MOEMS

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A technique for measuring the profile of the illumination in the pupil of a lithography projector is presented. The technique is based on exposing pinhole patterns on a wafer at different dose and defocus settings, and processing the scanning electron microscopy ͑SEM͒ images of the printed pinholes. The latent image intensity at the edges of the resist patterns equals the dose-to-clear. This establishes a multitude of equations, each of which states that the latent image intensity at a particular field location, dose, and defocus is known. The intensity distribution in the pupil of the illuminator is obtained by solving a large system of such equations, subject to the constraint that the intensity distribution is non-negative. An image processing algorithm based on nonlinear diffusion is used for finding coordinates of points on the edges of resist in SEM images. The results of the inversion for 193-nm stepper with 0.55/ 0.85 annular illumination and numerical aperture of 0.75 at five exposure field locations are presented.

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