Correction to “Evaluation of H2 Plasma-Induced Damage in Materials for EUV Lithography”

Abstract

Adv. Mater. Interfaces 2024, 11, 2300867

DOI: 10.1002/admi.202300867

We found that the damages of material we had seen in the published paper were greatly influenced by the base material rather than damage to the EUV material itself. Therefore, the content related to the material evaluation results in the paper should be excluded. The following contents should be corrected.

The last sentence in the abstract section, “The damage to Mo₂C …,” should be removed.

In paragraph 3 of the “Introduction” section, the last 2 sentences “To observe the effect of the …,” should be removed. This should have been written as “In addition, the radical density which can represent the value in an actual mass production process environment, was measured using a quadrupole mass spectrometer (QMS).”

The content in Section 2.2 “Surface damage analysis” is incorrect and should be excluded. It should have been written in the “Discussion” section below.

: ″Inside EUV lithography equipment, the EUV beam is reflected off (or passes through) various EUV optical components such as multilayer mirrors, reticles, and pellicles before reaching the photoresist (see Figure 9). As the process cycle is repeated, surface of the components can be damaged by EUV-induced H₂ plasma, potentially reducing the overall process reliability. This suggests that H₂ plasma durability evaluations are needed for all EUV components within the EUV lithography equipment. Nevertheless, several factors make it challenging to conduct such damage evaluation:

1. It is difficult to use actual mass-production equipment for damage evaluation,

2. The cost of using high power EUV sources comparable to mass-production equipment for setting up evaluation systems is very high,

3. Using low-power EUV sources cannot generate a suitable density of H₂ plasma for evaluation.

The evaluation system in this study uses ICP to generate a H₂ plasma environment similar to EUV lithography at relatively low cost. Additionally, it enables accelerated life testing (ALT) with electron density control, making it a valuable option for addressing the previously mentioned issues.

Damage to samples can be examined using various methods. For relatively large surface damages such as blisters, identification with a microscope or even with the naked eye may be sufficient. The extent of surface etching on EUV components caused by H₂ plasma can be measured by a change in weight using a calibrated scale. However, the weight differences before and after H₂ plasma exposure are often smaller than the measurement uncertainty of the scale. Therefore, field-emission scanning electron microscopy (FE-SEM) is generally more suitable for damage analysis. Vertical imaging can quantify layer thickness changes or pore area fractions in porous structures. Surface deformation can also be a significant cause of changes in material characteristics. It can be analyzed using X-ray photoelectron spectroscopy (XPS).″

Figure 9. Materials and components employed in EUV processes that necessitate evaluation of damage caused by H₂ plasma.^[55,56]

Where the references 55, 56 are:

[55] S. Wurm, SPIE Newsroom 2006, DOI 10.1117/2.1200602.0079.

[56] K. Ko, G, Kim, M, Yeung, E, Barouch, M. Kim, S. Kim, H. Oh, Proceedings of SPIE - The International Society for Optical Engineering 2014, 9048, DOI 10.1117/12.2046202.

The last 3 sentences in the conclusion section, “As an example of …,” should be removed. This should have been written as follows:

“The hydrogen radical density measured using QMS in this environment increased as the gas pressure and electron density increased. Based on these plasma parameter measurements, it was confirmed that a H₂ plasma environment similar to that inside current and next-generation EUV lithography equipment could be predicted and generated using the developed system. Therefore the developed system can be effectively used for quantitative evaluation of damages induced by H₂ plasma to EUV lithography tools and materials.”

The last 4 sentences in the experimental section, “The sample used for damage …,” should be removed.

We apologize for these errors.