Low-impact resist metrology: the use of ultralow voltage for high-accuracy performance

Sundaram, Ganesh; Sullivan, Neal T.; Mai, Tung; Ke, Chih-Ming

doi:10.1117/12.539221

Cited by 17 publications

(17 citation statements)

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“…Continued work on ultra-low voltage microscopy may become more critical. [8,10,15] This CD dependence has many other implications. Isolated trenches and contact holes in ArF resist have always appeared to shrink more; this is nothing other than the big line behavior shown above.…”

Section: Discussionmentioning

confidence: 96%

“…A reference site, which must never be exposed to the ebeam, must be used to offset any tip differences between the two runs of AFM measurements. Examples of this technique can be found in the literature [8,10]. This CD-AFM technique will be used with dry ArF features to experimentally prove a curve-fitting method to solve the 0 th shrink later in this work.…”

Section: Basic Methodology For Resist Shrinkage Testingmentioning

confidence: 97%

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Characterization of CD-SEM metrology for iArF photoresist materials

Bunday¹,

Cordes²,

Orji³

et al. 2008

SPIE Proceedings

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For many years, lithographic resolution has been the main obstacle for keeping the pace of transistor densification to meet Moore's Law. For the 45 nm node and beyond, new lithography techniques are being considered, including immersion ArF lithography (iArF) and extreme ultraviolet (EUV) lithography. As in the past, these techniques will use new types of photoresists with the capability to print 45 nm node (and beyond) feature widths and pitches.In a previous paper ("SEM Metrology for Advanced Lithographies," Proc SPIE, v6518, 65182B, 2007), we compared the effects of several types of resists, ranging from deep ultraviolet (DUV) (248 nm) through ArF (193 nm) and iArF to extreme UV (EUV, 13.5 nm). iArF resists were examined, and the results from the available resist sample showed a tendency to shrink in the same manner as the ArF resist but at a lower magnitude.This paper focuses on variations of iArF resists (different chemical formulations and different lithographic sensitivities) and examine new developments in iArF resists during the last year. We characterize the resist electron beam induced shrinkage behavior under scanning electron microscopy (SEM) and evaluate the shrinkage magnitude on mature resists as well as R&D resists. We conclude with findings on the readiness of SEM metrology for these challenges.

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Section: Discussionmentioning

confidence: 96%

Section: Basic Methodology For Resist Shrinkage Testingmentioning

confidence: 97%

Characterization of CD-SEM metrology for iArF photoresist materials

Bunday¹,

Cordes²,

Orji³

et al. 2008

SPIE Proceedings

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“…A reference site, which must never be exposed to the e-beam, must be used to offset any tip differences between the two runs of AFM measurements. An example of this technique can be found in the literature [7]. However, in the EUV and iArF experiments in this paper, the pitches, and thus the spaces between lines, are too small for proper tip penetration to the feature bottoms, so this analysis technique was not possible here.…”

Section: Basic Methodology For Resist Shrinkage Testingmentioning

confidence: 94%

SEM metrology for advanced lithographies

Bunday¹,

Allgair²,

Rice³

et al. 2007

SPIE Proceedings

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For many years, lithographic resolution has been the main obstacle for keeping the pace of transistor densification to meet Moore's Law. The industry standard lithographic wavelength has evolved many times, from G-line to I-line, deep ultraviolet (DUV) based on KrF, and 193nm based on ArF. At each of these steps, new photoresist materials have been used. For the 45nm node and beyond, new lithography techniques are being considered, including immersion ArF lithography and extreme ultraviolet (EUV) lithography. As in the past, these techniques will use new types of photoresists with the capability of printing 45nm node (and beyond) feature widths and pitches. This paper will show results of an evaluation of the critical dimension-scanning electron microscopy (CD-SEM)-based metrology capabilities and limitations for the 193nm immersion and EUV lithography techniques that are suggested in the International Technology Roadmap for Semiconductors. In this study, we will print wafers with these emerging technologies and evaluate the performance of SEM-based metrology on these features. We will conclude with preliminary findings on the readiness of SEM metrology for these new challenges.

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“…A reference site, which must never be exposed to the e-beam, must be used to offset any tip differences between the two runs of AFM measurements. Examples of this technique can be found in the literature [1,9,10]. This CD-AFM technique was used with dry ArF features to solve the 0 th shrink.…”

Section: The Ismi Unified Advanced Critical Dimension Scanning Electrmentioning

confidence: 99%

Phenomenology of electron-beam-induced photoresist shrinkage trends

Bunday¹,

Cordes²,

Allgair³

et al. 2009

Metrology, Inspection, and Process Control for Microlithography XXIII

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For many years, lithographic resolution has been the main obstacle in keeping the pace of transistor densification to meet Moore's Law. For the 45 nm node and beyond, new lithography techniques are being considered, including immersion ArF (iArF) lithography and extreme ultraviolet lithography (EUVL). As in the past, these techniques will use new types of photoresists with the capability to print 45 nm node (and beyond) feature widths and pitches.In a previous paper [1], we focused on ArF and iArF photoresist shrinkage. We evaluated the magnitude of shrinkage for both R&D and mature resists as a function of chemical formulation, lithographic sensitivity, scanning electron microscope (SEM) beam condition, and feature size. Shrinkage results were determined by the well accepted methodology described in ISMI's CD-SEM Unified Specification [2].A model for resist shrinkage, while derived elsewhere [3], was presented, that can be used to curve-fit to the shrinkage data resulting from multiple repeated measurements of resist features. Parameters in the curve-fit allow for metrics quantifying total shrinkage, shrinkage rate, and initial critical dimension (CD) from before e-beam exposure. The ability to know this original CD is the most desirable result; in this work, the ability to use extrapolation to solve for a given original CD value was also experimentally validated by CD-atomic force microscope (AFM) reference metrology.Historically, many different conflicting shrinkage results have been obtained among the many works generated through the litho-metrology community. This work, backed up by an exhaustive dataset, will present an explanation that makes sense of these apparent discrepancies. Past models for resist shrinkage inherently assumed that the photoresist line is wider than the region of the photoresist to be shrunk [3], or, in other words, the e-beam never penetrates enough to reach all material in the interior of a feature; consequently, not all photoresist is affected by the shrinkage process. In actuality, there are two shrinkage regimes, which are dependent on resist feature CD or thickness. Past shrinkage models are true for larger features. However, our results show that when linewidth becomes less than the eventual penetration depth of the e-beam after full shrinkage, the apparent shrinkage magnitude decreases while shrinkage speed accelerates. Thus, for small features, most shrinkage occurs within the first measurement. This is crucial when considering the small features to be fabricated by immersion lithography.In this work, the results from the previous paper [1] will be shown to be consistent with numerically simulated results, thus lending credibility to the postulations in [1].With these findings, we can conclude with observations about the readiness of SEM metrology for the challenges of both dry and immersion ArF lithographies as well as estimate the errors involved in calculating the original CD from the shrinkage trend.

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Low-impact resist metrology: the use of ultralow voltage for high-accuracy performance

Cited by 17 publications

References 0 publications

Characterization of CD-SEM metrology for iArF photoresist materials

Characterization of CD-SEM metrology for iArF photoresist materials

SEM metrology for advanced lithographies

Phenomenology of electron-beam-induced photoresist shrinkage trends

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