Study on Image Drift Induced by Charging during Observation by Scanning Electron Microscope

Okai, Nobuhiro; Sohda, Yasunari

doi:10.1143/jjap.51.06fb11

Cited by 17 publications

(9 citation statements)

References 26 publications

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“…This could be due to imperfections in the used mask (i.e., a replica of a mask made by electron beam lithography) which were transferred directly into the PR patterns. Additionally, the loss of focus and drifting of the HR‐SEM images during a slow scan speed could also add to some inaccuracy during image processing and analysis by using ImageJ software. Overall these images indicate a robust fabrication process.…”

Section: Resultsmentioning

confidence: 99%

Shrinkage Control of Photoresist for Large‐Area Fabrication of Sub‐30 nm Periodic Nanocolumns

Le‐The

Berenschot

Tiggelaar

et al. 2016

Adv Materials Technologies

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A method to fabricate large‐area arrays of nanocolumns without a deep‐UV laser source is reported. This method allows high‐yield fabrication of 3 × 3 cm2 arrays of sub‐30 nm nanocolumns made of bottom antireflection layer coating (BARC) by combining displacement Talbot lithography (DTL) using a monochromatic UV beam (365 nm wavelength) with plasma etching techniques. DTL is used to manufacture an initial pattern of periodic photoresist nanocolumns with a diameter of ≈110 nm. N2 plasma can transfer this pattern at a 1:1 ratio to BARC nanocolumns. It is found that reactive O2/N2 plasma etching on the other hand can shrink the BARC nanocolumns to sub‐30 nm dimensions. The shrink‐etching process can be reproducibly controlled by tuning the gas flow ratio and the etching time. It is highly remarkable that the verticality of these BARC nanocolumns remains during O2/N2 plasma shrink etching. Combining the etching of O2/N2 plasma with N2 plasma allows to produce BARC nanocolumns over the entire diameter range from 110 to sub‐30 nm. The fabrication approach enables large‐footprint fabrication of size‐tunable periodic nanostructures that have many potential applications in photonics, electronics, biosensors, smart surfaces, catalysis, and biomedical analysis.

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Section: Resultsmentioning

confidence: 99%

Shrinkage Control of Photoresist for Large‐Area Fabrication of Sub‐30 nm Periodic Nanocolumns

Le‐The

Berenschot

Tiggelaar

et al. 2016

Adv Materials Technologies

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show abstract

“…It was found that the direction of the image drift coincides with the scan‐direction of the electron beam. This is in contrast to previous assumptions stating independence of the two (Okai & Sohda, ). The image drift can in fact be completely eliminated for any image/structure by carefully aligning the objective aperture and the stigmation of the beam, resulting in a still image similar to that of a conductive sample.…”

Section: Resultsmentioning

confidence: 99%

“…The characterization of insulating materials is a well‐known challenge in SEM (Cazaux, ; Joy & Joy, ; Thong et al ., ; Ose et al ., ; Goldstein et al ., ; Okai et al ., ; Okai & Sohda, ). Insulating samples do not provide a path to ground and therefore accumulate charge.…”

Section: Introductionmentioning

confidence: 97%

A systematic investigation of the charging effect in scanning electron microscopy for metal nanostructures on insulating substrates

Flatabø

Coste

Greve

2016

Journal of Microscopy

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Scanning electron microscopy is perhaps the most important method for investigating and characterizing nanostructures. A well-known challenge in scanning electron microscopy is the investigation of insulating materials. As insulating materials do not provide a path to ground they accumulate charge, evident as image drift and image distortions. In previous work, we have seen that sample charging in arrays of metal nanoparticles on glass substrates leads to a shrinkage effect, resulting in a measurement error in the nanoparticle dimension of up to 15% at 10 kV and a probe current of 80 ± 10 pA. In order to investigate this effect in detail, we have fabricated metal nanostructures on insulating borosilicate glass using electron beam lithography. Electron beam lithography allows us to tailor the design of our metal nanostructures and the area coverage. The measurements are carried out using two commonly available secondary electron detectors in scanning electron microscopes, namely, an InLens- and an Everhart-Thornley detector. We identify and discriminate several contributions to the effect by varying microscope settings, including the size of the aperture, the beam current, the working distance and the acceleration voltage. We image metal nanostructures of various sizes and geometries, investigating the influence of scan-direction of the electron beam and secondary electron detector used for imaging. The relative measurement error, which we measure as high as 20% for some settings, is found to depend on the acceleration voltage and the type of secondary electron detector used for imaging. In particular, the Everhart-Thornley detectors lower sensitivity to SE electrons increase the magnitude of the shrinkage of up to 10% relative to the InLens measurements. Finally, a method for estimating charge balance in insulating samples is presented.

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“…Electron beam-based inspection techniques have become a standard where nanometer resolution imaging is required for state of the art semiconductor devices. However, when non-conductive materials are involved, charging occurs and issues are reported such as image distortions due to the primary beam deflections [1]- [5] and image contrast changes due to the changing secondary electron (SE) emission [6], [7, p. 127], [8]. As a consequence measurements of critical dimensions (CD) will be less accurate [9]- [11].…”

Section: Introductionmentioning

confidence: 99%

Model improvements to simulate charging in SEM

Arat

Klimpel

Hagen

2018

Metrology, Inspection, and Process Control for Microlithography XXXII

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Charging of insulators is a complex phenomenon to simulate since the accuracy of the simulations is very sensitive to the interaction of electrons with matter and electric fields. In this study, we report model improvements for a previously developed Monte-Carlo simulator to more accurately simulate samples that charge. The improvements include both modelling of low energy electron scattering and charging of insulators. The new first-principle scattering models provide a more realistic charge distribution cloud in the material, and a better match between non-charging simulations and experimental results. Improvements on charging models mainly focus on redistribution of the charge carriers in the material with an induced conductivity (EBIC) and a breakdown model, leading to a smoother distribution of the charges. Combined with a more accurate tracing of low energy electrons in the electric field, we managed to reproduce the dynamically changing charging contrast due to an induced positive surface potential.

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Study on Image Drift Induced by Charging during Observation by Scanning Electron Microscope

Cited by 17 publications

References 26 publications

Shrinkage Control of Photoresist for Large‐Area Fabrication of Sub‐30 nm Periodic Nanocolumns

Shrinkage Control of Photoresist for Large‐Area Fabrication of Sub‐30 nm Periodic Nanocolumns

A systematic investigation of the charging effect in scanning electron microscopy for metal nanostructures on insulating substrates

Model improvements to simulate charging in SEM

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