Optimum dose for shot noise limited CD uniformity in electron-beam lithography

Kruit, P.; Steenbrink, S. W. H. K.; Jager, R.; Wieland, Marco

doi:10.1116/1.1821577

Cited by 30 publications

(28 citation statements)

References 12 publications

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“…Figure 5 shows that a higher electron dose is needed to write narrower lines. Two factors contributing to this trend are the fact that for narrower lines, thinner resists are needed and the stricter requirements on critical dimension uniformity at higher resolutions [47]. As predicted by Kruit at the International Workshop for Electron Beam Induced Deposition in 2006, EBL and focused electron beam-induced deposition require similar electron doses to achieve similar resolutions.…”

Section: Comparison To Electron Beam Lithographymentioning

confidence: 93%

Sub-10 nm writing: focused electron beam-induced deposition in perspective

Dorp

2014

Appl. Phys. A

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Over the past decade, focused electron beaminduced deposition has become a mature necessary part of the tool box engineers and scientists. This review presents the current state of the art in sub-10 nm focused electron beam deposition and describes the dominant mechanisms that have been found so far for this regime. Several questions regarding patterning at the highest resolution are addressed. What do our findings mean for using sub-10 nm focused electron beam deposition for industrial applications? And which fundamental issues remain to be solved? The overview shows that low-energy secondary electrons dominate the deposition process. As a result, the highest obtainable spatial resolution (averaged over many deposits) is limited by the mean free path of those electrons. Therefore, the only route to improve the resolution beyond the current appears to be using complexes that are sensitive to the high-energy electrons in the incident beam, rather than to the secondaries. Focused electron beam-induced deposition is compared to related techniques. It is on par with resist-based sub-10 nm electron beam lithography, showing similar spatial resolutions at similar electron doses. Regarding ion beam lithography, there are several distinguishing issues. Sub-10 nm writing has yet to be demonstrated for ion deposition, and although the deposition rate is relatively low when writing with electrons, electrons do not induce damage to the sample. The latter is a crucial advantage for focused electron beam-induced deposition. Finally, the main challenges regarding the applicability of sub-10 nm focused electron beam-induced deposition are discussed.

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Section: Comparison To Electron Beam Lithographymentioning

confidence: 93%

Sub-10 nm writing: focused electron beam-induced deposition in perspective

Dorp

2014

Appl. Phys. A

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“…This has long been recognized (Smith 1986(Smith , 1988 and often been discussed (Gallatin 2005, Henke and Torkler 1999, Kotera et al 2002, Leunissen et al 2005, Nakasugi et al 2002, Neureuther 1988, Turner et al 1991. Recently, we developed an analytical model to describe the line-edge position variation (Kruit et al 2004), which we shall illustrate and expand in this paper. The line width is usually measured in an adapted critical dimension scanning electron microscope (CD-SEM).…”

Section: Introductionmentioning

confidence: 90%

Shot noise in electron‐beam lithography and line‐width measurements

Kruit

Steenbrink

2006

Scanning

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Electron-beam lithography is used extensively in nanoscience and technology for making masks for the semiconductor industry and, on a limited scale, for maskless lithography: that is, writing the patterns directly on the chip. We expect the latter application to extend in the years to come. Control of the dimensions of the written structures is essential in the semiconductor industry. For 45 nm generation, which is presently under development and should reach production at the end of the decade, the required control over the line width is between 1.5 and 5 nm, depending on the application. One of the factors of influence on the line-width control is the statistics in the number of electrons illuminating the resist. This effect gives line edge roughness, or in other words a lack of control over the local position of a resist edge. This has long been recognized and often discussed. Recently, we developed an analytic model for the line edge position variation, which we shall illustrate and expand in this paper. The model, supported by Monte Carlo simulations, demonstrates that the line-width variation is inversely proportional to the dose used for the illumination of the resist. This makes it impossible to increase the lithography throughput by developing ultrasensitive resists. For 45 nm features written with a typical resolution of 30 nm, a 30 microC/cm2 resist gives 3 nm line-width variation over line segments of 45 nm long. The line width is usually measured in an adapted critical dimension scanning electron microscope (CD-SEM). This measurement needs to be more precise than the result of the lithography step, so the requirements are typically sub-nm. Apart from all the problems to avoid systematic errors, this measurement also suffers from statistical variations, resulting from the finite number of electrons used for the measurement. In this paper we shall derive an estimate for that variation with a similar model as used for the shot noise effect in the lithography step. One of the conclusions is that for the most precise measurements of the line width it is not advisable to tune the CD-SEM for the best resolution. It is better to allow a larger probe size of the electron beam because that can be accompanied by a much larger current and thus a decrease in the noise level.

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“…However, the development to higher sensitivities might be stopped in the future. CD uniformity considerations under the aspect of line edge roughness [9] show that sensitivities of being considerably higher than 10 lC/ cm 2 become probably (realistic) and the pressure to a high beam current in the target plane increases. Therefore, reducing the beam blur by a low current density is not an option for a new design.…”

Section: Introductionmentioning

confidence: 98%