Coherent scattering microscopy as an effective inspection tool for analyzing performance of phase shift mask

Woo, Dong Gon; Lee, Jae Uk; Hong, Seong Chul; Kim, Jung-Sik; Ahn, Jinho

doi:10.1364/oe.24.012055

Cited by 5 publications

(3 citation statements)

References 28 publications

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“…The EUV transmittance was derived by comparing the number of photons reflected by the Mo/Si multilayers with and without the pellicle. The EUV reflectivity was calculated by comparing the number of photons reflected by the EUV pellicle when it was mounted on an absorber material where the EUV reflectivity converges to zero, with the number of photons reflected by the Mo/Si multilayers [ 22 , 23 , 24 ].…”

Section: Methodsmentioning

confidence: 99%

Study on ZrSi2 as a Candidate Material for Extreme Ultraviolet Pellicles

Kim

et al. 2023

Membranes

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An extreme ultraviolet (EUV) pellicle is an ultrathin membrane at a stand-off distance from the reticle surface that protects the EUV mask from contamination during the exposure process. EUV pellicles must exhibit high EUV transmittance, low EUV reflectivity, and superior thermomechanical durability that can withstand the gradually increasing EUV source power. This study proposes an optimal range of optical constants to satisfy the EUV pellicle requirements based on the optical simulation results. Based on this, zirconium disilicide (ZrSi2), which is expected to satisfy the optical and thermomechanical requirements, was selected as the EUV pellicle candidate material. An EUV pellicle composite comprising a ZrSi2 thin film deposited via co-sputtering was fabricated, and its thermal, optical, and mechanical properties were evaluated. The emissivity increased with an increase in the thickness of the ZrSi2 thin film. The measured EUV transmittance (92.7%) and reflectivity (0.033%) of the fabricated pellicle satisfied the EUV pellicle requirements. The ultimate tensile strength of the pellicle was 3.5 GPa. Thus, the applicability of the ZrSi2 thin film as an EUV pellicle material was verified.

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Section: Methodsmentioning

confidence: 99%

Study on ZrSi2 as a Candidate Material for Extreme Ultraviolet Pellicles

Kim

et al. 2023

Membranes

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“…The EUV transmittance (EUVT) of the pellicle composite as a function of the pulsed heating time was measured using coherent scattering microscopy (CSM) with an EUV source. The EUVT was calculated by comparing the number of photons reflected from an EUV mirror composed of 40 pairs of Mo/Si multilayers with and without pellicles [ 15 , 16 ]. The EUV transmittance was determined from the average value by repeating the measurements 10 times at each of the three points in the membrane area to obtain reliable results.…”

Section: Methodsmentioning

confidence: 99%

Investigating the Degradation of EUV Transmittance of an EUV Pellicle Membrane

Jang

Lee

et al. 2022

Membranes

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The extreme ultraviolet (EUV) pellicle is a freestanding membrane that protects EUV masks from particle contamination during EUV exposure. Although a high EUV transmittance of the pellicle is required to minimize the loss of throughput, the degradation of EUV transmittance during the extended exposure of the pellicle has been recently reported. This may adversely affect the throughput of the lithography process. However, the cause of this phenomenon has not yet been clarified. Therefore, we investigated the cause of the degradation in the EUV transmittance by observing the compositional change when the Ru/SiNx pellicle composite was heated in an emulated EUV scanner environment. The Ru thin film that was deposited at high pressure had more void networks but was not oxidized, whereas the SiNx thin film was oxidized after heating. This was because the void network in the Ru thin film served as a preferential diffusion path for oxygen and caused oxidation of the SiNx thin film. It was confirmed that the degradation of the EUV transmittance was due to the oxidation of SiNx. The results verified the effect of diffusivity in the thin film due to the void network on oxidation and EUV transmittance.

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“…We have already reported quantitative analysis of the phase shift effect of EUV phase shift mask using single-shot CDI engines, such as error reduction algorithm (ERA) and hybrid input-output (HIO) algorithm. [13][14][15][16][17] However, in the case of single-shot CDI, the field-of-view is limited by the size of the inspection beam at the mask plane (3 μm diameter). Also, the information of light source and object cannot be deconvolved, and this makes an accurate analysis of the object difficult.…”

Section: Introductionmentioning

confidence: 99%

Through-pellicle imaging of extreme ultraviolet mask with extreme ultraviolet ptychography microscope

Woo

Kim

Jang

et al. 2019

J. Micro/Nanolith. MEMS MOEMS

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Background: An extreme ultraviolet (EUV) pellicle is necessary to increase the process yield even though the declining throughput is a big concern. However, an EUV metrology/inspection tool for this pellicle has not been commercialized yet. Aim: The goal of this study is to verify the pellicle/mask inspection feasibility of EUV scanning lensless imaging (ESLI) and verify the impact of contaminants on pellicles depending on their size. Approach: Through-pellicle imaging was implemented by using ESLI, which uses a high-order harmonic generation EUV source and ptychography. Optical characteristics of various sizes of Fe-contaminated EUV pellicles were evaluated to verify their impact on wafer images. Results: Large size (∼10 μm) contaminants on the pellicle were found to contribute to the final wafer pattern loss. However, small size (2 to 3 μm) contaminants on the pellicle do not have substantial impact on the wafer image. Conclusions: The defect detection capability of ESLI for pellicle and mask was confirmed. Therefore, ESLI is useful in applications like pellicle qualification and EUV mask inspection metrology.

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Coherent scattering microscopy as an effective inspection tool for analyzing performance of phase shift mask

Cited by 5 publications

References 28 publications

Study on ZrSi2 as a Candidate Material for Extreme Ultraviolet Pellicles

Study on ZrSi2 as a Candidate Material for Extreme Ultraviolet Pellicles

Investigating the Degradation of EUV Transmittance of an EUV Pellicle Membrane

Through-pellicle imaging of extreme ultraviolet mask with extreme ultraviolet ptychography microscope

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