&lt;title&gt;Thermal stability of Mo/Si multilayers&lt;/title&gt;

Rosen, R.S.; Viliardos, Michael A.; Kassner, M.E.; Stearns, D. G.; Vernon, S. P.

doi:10.1117/12.51281

Cited by 15 publications

(9 citation statements)

References 10 publications

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“…It is known that the EUV reflectance of Mo/Si multilayer structures can degrade at elevated temperatures due to increased inter-diffusion occurring at the layer interfaces [37]. However, during dripping of molten tin with temperatures of ~240 °C onto the MLM sample its surface is affected by high temperatures only for a very short time.…”

Section: Resultsmentioning

confidence: 99%

Induction of tin pest for cleaning tin-drop contaminated optics

Böwering

2017

Materials Chemistry and Physics

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Highlights Tin pest induction leads to embrittlement of tin drops after β → α Sn transformation.  The purity grade influences the transformation speed of tin very strongly.  Tin drops on multilayer-coated optics disintegrate after β → α Sn transformation.  Tin drop contamination of optics is cleaned via phase transformation at -24 °C.  Reflectance of multilayer-coated mirrors is restored after tin drop transformation. Graphical Abstract AbstractTin pest, the allotropic β → α phase transformation of tin, was examined for use in cleaning of tin-contaminated optics. Induction of change in material structure led to disintegration of tin samples into pieces and powder. The transition times were studied for tin drops of different purity grades, using inoculation with α-Sn seed particles, also after prior mechanical deformation and surface oxide removal. For tin of very high purity levels fast nucleation within hours and full transformation within a day could be achieved during cooling at -24 °C, resulting in strong embrittlement of the material. Tin dripped onto samples of multilayer-coated optics as used in extreme ultraviolet lithography machines was made cleanable by phase transition after inoculation and cooling. The reflectance of multilayer-coated mirrors was found to decrease by no more than 1% with this cleaning method.

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Section: Resultsmentioning

confidence: 99%

Induction of tin pest for cleaning tin-drop contaminated optics

Böwering

2017

Materials Chemistry and Physics

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“…The temperature at which the reflectivity of the first order Bragg peaks break down for these mirrors are lower than the baking temperature for our mirrors, which were e--beam deposited and thermally treated during deposition. In the literature activation energies E a for diffusion were deduced by means of an Arrheniusplot of the multilayer d-spacing ln(Ad) 2 versus 1/baking temperature [6,10,11]. The RBS spectra in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The thermal stability of Mo/Si multilayers has been studied earlier in several works [5][6][7][8][9][10][11] but in all of them the multilayers are fabricated by sputtering. In [12] it is shown that thermal treatment during e--beam deposition can considerably enhance the reflectivity of Mo/Si multilayer * Present address: European Synchrotron Radiation Facility, F-38043 Grenoble, France mirrors with a double layer spacing of about 7.5 nm.…”

Section: Pacsmentioning

confidence: 99%

Thermal stability of Mo/Si multilayer soft-X-ray mirrors fabricated by electron-beam evaporation

et al. 1994

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Abstract. Mo/Si multilayers are fabricated by electronbeam evaporation in UHV at different temperatures (30 ° C, 150 ° C, 200 ° C) during deposition. After completion their thermal stability is tested by baking them at temperatures (Tbak) between 200°C and 800°C in steps of 50°C or 100 ° C. After each baking step the multilayers are characterized by small angle CuK -X-ray diffraction. Additionally, the normal incidence soft-X-ray reflectivity for wavelengths between 11 nm and 19 nm is determined after baking at 500 ° C. Furthermore, the layer structure of the multilayers is investigated by means of Rutherford Backscattering Spectroscopy (RBS) and sputter/Auger Electron Spectroscopy (AES) technique. While the reflectivity turns out to be highest for a deposition temperature of 150 ° C, the thermal stability of the multilayer increases with deposition temperature. The multilayer deposited at 200 ° C stands even a 20 min 500 ° C baking without considerable changes in the reflectivity behaviour. 68.55, 68.65, 78.65 In the wavelength range between 13 nm and 30 nm the combination of Mo and Si is most widely used for normalincidence multilayer mirrors. Reflectivities around 60% have been achieved with both sputtering [1] and e -beam evaporation in combination with thermal treatments during deposition [2,3]. Besides a high value for the reflectivity, the stability of the multilayer stack is also an important property, since applications include for example synchrotron radiation optics, where the multilayer can be heated to a few hundred degrees Celsius [4]. The long-term stability is also important for a number of applications. PACS:The thermal stability of Mo/Si multilayers has been studied earlier in several works [5][6][7][8][9][10][11] but in all of them the multilayers are fabricated by sputtering. In [12] it is shown that thermal treatment during e--beam deposition can considerably enhance the reflectivity of Mo/Si multilayer * Present address: European Synchrotron Radiation Facility, F-38043 Grenoble, France mirrors with a double layer spacing of about 7.5 nm. For a deposition temperature (Tdep) of 150°C the reflectivity is about a factor of two larger than the reflectivity of the 30 ° C and 200 ° C sample [12,13]. In other previous works [14,15] the influence of the deposition temperature on the microstructure of Mo/Si-multilayer systems fabricated by e--beam evaporation was studied. They have shown that Mo/Si muttilayers have interlayers of a mixture of Mo and Si at the Mo-Si interfaces and that the thickness of Mo-on-Si interlayers increases with increasing deposition temperature, while the thickness of the Si-on-Mo interlayers keeps constant. In our work the influence of the different microstructure for the multilayers which were deposited at different temperatures on the thermal stability is also investigated.

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“…Ruthenium has a high transmission in the EUV, thus does not severely compromise the EUV reflectivity and offers significant chemical and mechanical protection during mask processing and exposure. [12][13][14][15][16] Hence we have also explored additive ruthenium repair strategies using focused electron beam induced deposition. 17 …”

Section: Introductionmentioning

confidence: 99%

Evaluation of mask repair strategies via focused electron, helium, and neon beam induced processing for EUV applications

et al. 2014

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One critical area for EUV lithography is the development of appropriate mask repair strategies. To this end, we have explored etching repair strategies for nickel absorber layers and focused electron beam induced deposition of ruthenium capping layers. Nickel has higher EUV absorption than the standard TaN absorber layer and thus thinner films and improved optical quality can be realized. A thin (2.5 nm) ruthenium film is commonly used as a protective capping layer on the Mo-Si EUV multi-layer mirror which mechanically and chemically protects the multi-layers during standard mask-making procedures. The gas field ion (GFIS) microscope was used to investigate helium and neon ion beam induced etching (IBIE) of nickel as a candidate technique for EUV lithography mask editing. No discernable nickel etching was observed for helium, however transmission electron microscopy (TEM) revealed subsurface damage to the underlying Mo-Si multilayers. Subsequently, neon beam induced etching at 30 keV was investigated and successfully removed the 50 nm nickel absorber film. TEM imaging also revealed subsurface damage in the underlying Mo-Si multilayer. Two damage regimes were apparent, namely: 1) beam induced mixing of the Mo-Si layers and 2) nanobubble formation. Monte Carlo simulations were performed and the observed damage regimes were correlated to: 1) the nuclear energy loss and 2) a critical implant concentration. Electron beam induced deposition (EBID) was explored to deposit ruthenium capping/protective layers. Several ruthenium precursors were screened and so far liquid bis(ethylcyclopentyldienyl)ruthenium(II) was successful. The purity of the as-deposited nanodeposits was estimated to be 10% Ru and 90% C. We demonstrate a new chemically assisted electron beam purification process to remove carbon by-products and show that high-fidelity nanoscale ruthenium repairs can be realized.

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<title>Thermal stability of Mo/Si multilayers</title>

Cited by 15 publications

References 10 publications

Induction of tin pest for cleaning tin-drop contaminated optics

Induction of tin pest for cleaning tin-drop contaminated optics

Thermal stability of Mo/Si multilayer soft-X-ray mirrors fabricated by electron-beam evaporation

Evaluation of mask repair strategies via focused electron, helium, and neon beam induced processing for EUV applications

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