Patterning nickel for extreme ultraviolet lithography mask application I. Atomic layer etch processing

Sang, Xia; Chen, Ernest; Chang, Jane P.

doi:10.1116/6.0000190

Cited by 11 publications

(5 citation statements)

References 24 publications

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“…Subsequently, an exposure to formic acid for 1 h removed the oxidized nickel and produced a Ni etch rate of 6 nm/cycle. 36…”

Section: Introductionmentioning

confidence: 99%

“…The etch rate observed for nickel under the Cl 2 and H 2 plasma conditions was 57 Å/cycle . A hybrid technique involving reactive-ion etching and ALE has also been shown to remove nickel. , The nickel ALE process used oxygen plasma to create an oxidized NiO surface. Subsequently, an exposure to formic acid for 1 h removed the oxidized nickel and produced a Ni etch rate of 6 nm/cycle …”

Section: Introductionmentioning

confidence: 99%

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Thermal Atomic Layer Etching of Nickel Using Sequential Chlorination and Ligand-Addition Reactions

2021

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The thermal atomic layer etching (ALE) of nickel was demonstrated using sequential chlorination and ligand-addition reactions. Nickel chlorination was achieved using SO2Cl2 (sulfuryl chloride) as the chlorine reactant. PMe3 (trimethylphosphine) was employed as the ligand-addition reactant. Sequential exposures of SO2Cl2 and PMe3 led to Ni thermal ALE. This procedure was inspired by the covalent bond classification (CBC) method that categorizes the most common compounds of various metals. Based on the CBC method, the surface reactions during thermal Ni ALE were performed to form NiX2L2 products, where Cl is the X ligand and PMe3 is the L ligand. Using this strategy, thermal Ni ALE was observed at temperatures from 75–200 °C. The etch rates were determined from in situ quartz crystal microbalance (QCM) measurements. The average etch rates determined from the mass changes were 0.14 ± 0.13, 0.57 ± 0.36, 0.67 ± 0.45, 1.30 ± 0.68, and 3.07 ± 1.56 Å/cycle for the temperatures 75, 100, 125, 150, and 175 °C, respectively. The QCM investigations revealed that there was a mass increase on every SO2Cl2 exposure and a mass loss on every PMe3 exposure, resulting in a net mass loss. The amount of chlorination for a given SO2Cl2 exposure increased with increasing temperature. The amount of mass lost on each PMe3 exposure also increased with increasing temperature. The etch rates were also confirmed using ex situ X-ray reflectivity measurements on Ni films on silicon wafers. The etch rates varied from 0.39 ± 0.10 Å/cycle at 125 °C to 2.16 ± 0.47 Å/cycle at 200 °C. Mass spectrometry analysis revealed that the volatile etch product was NiCl2(PMe3)2 as expected from the CBC method. In addition, scanning electron microscopy revealed that the nickel surface morphology had negligible changes after ALE. Atomic force microscopy analysis showed that thin nickel films remained smooth during initial etching and may experience some slight roughening with progressive etching. Using the CBC method to create novel thermal ALE procedures can be generalized for the thermal ALE of many different metals.

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“…Subsequently, an exposure to formic acid for 1 h removed the oxidized nickel and produced a Ni etch rate of 6 nm/cycle. 36…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal Atomic Layer Etching of Nickel Using Sequential Chlorination and Ligand-Addition Reactions

2021

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“…Etching study on Cr has been reported [20], and for the etching of Cr, a precise etching control was performed using ion milling or atomic layer etching (ALE), but Cr also has a low extinction coefficient for the next generation EUV absorber. Recently, a research on the etching of Ni, a material with a higher extinction coefficient than Tabased materials, has been investigated through a plasmathermal ALE method, and a precisely control of Ni etching and anisotropic etching by repeating oxidation and a ligand exchange have been reported [21,22]. However, there are no sufficient studies on the etching of EUV materials with high absorption coefficients applicable to the next generation EUV mask such as precise etching characteristics, the evaluation of etch selectivity with the capping layer, the degree of damage to the capping layer during the etch process, etc.…”

Section: Introductionmentioning

confidence: 99%

Atomic layer etching of Sn by surface modification with H and Cl radicals

Kim¹,

Jang²,

Kim³

et al. 2022

Nanotechnology

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Sn is the one of the materials that can be used for next generation extreme ultraviolet (EUV) mask material having a high absorption coefficient and, for the fabrication of the next generation EUV mask, a precise etching of Sn is required. In this study, the atomic layer etching (ALE) process was performed for the precise etch thickness control and low damage etching of Sn by the formation SnHxCly compounds on the Sn surface using with H and Cl radicals during the adsorption step and by the removal of the compound using Ar+ ions with a controlled energy during the desorption step. Through this process, optimized ALE conditions with different H/Cl radical combinations that can etch Sn at ~2.6 Å/cycle were identified with a high etch selectivity over Ru which can be used as the capping layer of the EUV mask. In addition, it was confirmed that not only the Sn but also Ru showed almost no physical and chemical damage during the Sn ALE process.

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“…Recently, a novel process combining plasma activation and thermal removal was developed and successfully applied to directionally etch Ni 4,5 and Cu. 6 This process is illustrated in with organic etchants that react with the surface oxide to form volatile complexes and water, eliminating the need for an extra energy source and avoiding redeposition.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, a novel process combining plasma activation and thermal removal was developed and successfully applied to directionally etch Ni , and Cu . This process is illustrated in Figure .…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Atomic Layer Etching Chemistry on Copper and Nickel Surfaces from First Principles

Xia

Sautet

2021

Chem. Mater.

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Plasma-thermal atomic layer etching is a promising technique to enable selective and directional etching on metals. It involves a plasma activation step and a thermal step where etchant molecules remove a fraction of the surface. To accelerate process development, a computational model for the thermodynamics of the thermal removal step is highly desirable. An energy expression is developed here to calculate the removal step energy for an activated slab structure. The approach samples the configurations of the activated metal surfaces and determines the thermodynamic balance of the removal step for each obtained configuration. The heterogeneity of the surface terminations is treated by the equilibrium crystal shape method. The models are put to test with combinations of two modifiers (O & N), two substrates (Cu & Ni) and two etchants (formic acid and formamidine). It is found that higher coverages of modifiers leads to more favorable etching. In addition, our results show that removal step energies vary 1 among different terminations, with differences on the order of 0.5 eV. This suggests etching can preferentially occur over certain crystal terminations. Qualitative agreement with the experiment on the Ni/O/formic acid system is obtained with the layer model at high coverages of oxygen atoms.

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Patterning nickel for extreme ultraviolet lithography mask application I. Atomic layer etch processing

Cited by 11 publications

References 24 publications

Thermal Atomic Layer Etching of Nickel Using Sequential Chlorination and Ligand-Addition Reactions

Thermal Atomic Layer Etching of Nickel Using Sequential Chlorination and Ligand-Addition Reactions

Atomic layer etching of Sn by surface modification with H and Cl radicals

Thermodynamics of Atomic Layer Etching Chemistry on Copper and Nickel Surfaces from First Principles

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