Chemically amplified resist CDSEM metrology exploration for high NA EUV lithography

Severi, Joren; Lorusso, Gian; Simone, Danilo De; Moussa, Alain; Saib, Mohamed; Duflou, Rutger; Gendt, Stefan De

doi:10.1117/1.jmm.21.2.021207

Cited by 14 publications

(22 citation statements)

References 9 publications

(15 reference statements)

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“…As previously reported [2,5], we observe that the SNR decreases as the target FT gets thinner also in the case of dry MOR. However, for all pitches and target FT, we observe that the SNR is larger than 2 in the case of dry MOR, thus ensuring the accurate metrology [2,5].…”

Section: Cdsem Metrologysupporting

confidence: 89%

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Dry resist metrology readiness for high-NA EUVL

Lorusso

Heuvel

Zidan

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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As High Numerical Aperture Extreme Ultraviolet Lithography (High NA EUVL) gets ready to step in the integrated circuit manufacturing (ICM) world, more and more work is being devoted to ensuring that all the elements involved in the process, from materials to equipment, will be ready to meet the required specifications when the time comes. One of the most critical pieces in such an ecosystem is the photoresist (PR), the material used to accurately transfer the design to the wafer. In the last years we have observed the introduction of various effective alternative approaches, such as dry metal oxide photoresist. PR always had to meet daunting specifications in terms of resolution, roughness, and sensitivity. However, in the brave new world of High NA EUVL, this is not enough. In fact, as the size of the printed features shrink, it is essential to limit the aspect ratio to avoid pattern collapse. Furthermore, the larger NA will reduce the Depth of Focus (DOF), thus requiring the use of ultra-thin resist films. The direct consequence of that is that the resist thicknesses used nowadays will not be suitable for High NA EUVL, where target thickness is expected to drop down to 20nm or less. Such a dramatic reduction in thickness has the potential to negatively impact, beside printing performances, the quality of the metrology and inspection as well, as discussed in our previous work. In the present work, we study the effects of reducing thickness in the case dry resist using various metrology and inspection techniques, such as Critical Dimension Scanning Electron Microscope (CDSEM), Atomic Force Microscopy (AFM), and e-beam defect inspection. As resist thickness decreases, noise level and image contrast are expected to be reduced, with a potential negative impact on the quality of the CD measurements both in terms of accuracy and precision.

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Section: Cdsem Metrologysupporting

confidence: 89%

“…5, we show the trend of estimated uLWR versus SNR for different target FT for dry resist at P32. As reported previously [2,5], the uLWR estimate is accurate when the SNR is larger, becoming artificially low and unreliable when the SNR drops below 2. In each curve in Fig.…”

Section: Cdsem Metrologysupporting

confidence: 78%

Dry resist metrology readiness for high-NA EUVL

Lorusso

Heuvel

Zidan

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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“…As a result, lesser secondary electrons are produced to generate signals thus a poorer image quality for the thinner resist. The positive impact of OUL has been explained in reference [4]. Predominantly, the bonds in OUL are carbon-carbon.…”

Section: Programmed Defect (Pd) Inspectionmentioning

confidence: 98%

Influence of photoresist thinning and underlayer film on e-beam using eP5 for high-NA patterning

Hasan

Béral²,

Lorusso³

et al. 2022

International Conference on Extreme Ultraviolet Lithography 2022

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The introduction of Extreme Ultraviolet Lithography (EUVL) has been an extraordinary achievement in keeping Moore's law alive, as it minimizes the cost, time, and number of patterning steps required for device fabrication. However, as the advanced technology nodes require further scale down of the semiconductor devices, the current state-of-art EUVL tool, equipped with 0.33 Numerical Aperture (NA) and 13.5nm wavelength cannot print the features of interest with an acceptable yield. As a solution, a new generation of EUVL tool has been proposed (High-NA EUVL), having 0.55 NA and 8nm resolution. As a result of the increased NA, the depth of focus is reduced, thus thinner resist is required. Moreover, we need to restrict the aspect ratio of the features to avoid pattern collapse. For instance, resist thickness of approximately 30nm, which is typically used to print a 16nm half-pitch feature, cannot be applied to print an 8nm half-pitch feature, resist thickness must be lowered significantly to circumvent pattern collapse. However, the use of thin resist may have several negative effects on metrology and defect inspection. In this paper, we will discuss the influence of resist thickness and underlayer films on Scanning Electron Microscope (SEM) using ASML's eP5. For this study, we prepared a set of wafers with 16nm line-space (LS) patterns at different resist thicknesses using either Metal-Oxide Resist (MOR) or Chemically Amplified Resist (CAR). The case study compares both resist platforms on Spin on Glass (SoG) and Organic Underlayer (OUL).To conduct this study our BKM ADI eP5 SEM condition has been used.We observed that thinning down film thickness leads to deterioration of SEM image quality as well as loss of defect sensitivity during the inspection. In addition, varying the underlayers greatly affects both image quality and sensitivity. By decreasing the resist thickness, MOR and CAR were observed to behave in the same way, in terms of both image degradation and loss of sensitivity, although image quality did not degrade in the same way in the two cases.

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“…[8,9] Not only that, the underlayer choice also affects the metrology introducing optical contrast variations depending on the underlayer used. [10] Finally, the film thickness of the photoresist and underlayers used in high-NA tools will have to scale to accommodate the reduced depth of focus of the new tools. This will only amplify the metrology issues and increase the need for underlayer/photo-resist customization and optimization.…”

Section: Introductionmentioning

confidence: 99%

EUV lithography patterning using multi-trigger resist

Popescu¹,

O'Callaghan²,

McClelland³

et al. 2023

Advances in Patterning Materials and Processes XL

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Research and development of EUV photoresists capable of supporting future requirements such as high-NA EUV continues. It is foreseen that, to contend with much higher photon-shot noise, resists will require high EUV absorbance to offset the need for thin films in high-NA, where depth of focus may be less than 20nm. We are developing a photoresist based on the multi-trigger concept, which seeks to suppress roughness using a new photoresist mechanism, and which is based on molecular rather than polymeric materials to maximize resolution. MTR Resist absorbance of greater than 18 μm-1 has been measured. Here we present recent NXE3400 results where, by modifying the PAG to optimize the reactions rates in the MTR mechanism, we have reduced the dose requirement compared to the orthodox high opacity MTR resists previously presented. Lines of 14 nm width at p28 nm can be patterned at a dose between 21 mJ/cm2 and 48 mJ/cm2 dependent on formulation ratio, with optimum LWR (3.9 nm, biased) occurring at 43 mJ/cm2 with a film thickness of 20.7 nm. Similarly, we present p34 pillars patterned between 21 mJ/cm2 and 59 mJ/cm2 doses for 17 nm diameter pillars, with a minimum LCDU for 19 nm diameter pillars of 3.05 nm occurring with a 21.7 nm FT at 58 mJ/cm2. The same resist can pattern p36 pillars at 52 mJ/cm2 with an LCDU of 3.44 nm at 18 nm diameter with no measured defects between 15.9 nm and 18.1 nm diameter. The impact of the substrate (such as use of various organic underlayers or SOG layers) on defectivity issues such as bridging or falling pillars will be presented here.

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Chemically amplified resist CDSEM metrology exploration for high NA EUV lithography

Cited by 14 publications

References 9 publications

Dry resist metrology readiness for high-NA EUVL

Dry resist metrology readiness for high-NA EUVL

Influence of photoresist thinning and underlayer film on e-beam using eP5 for high-NA patterning

EUV lithography patterning using multi-trigger resist

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