Effect of radiation on the defectivity and stability of Ru-capped MoSi multilayer blanks

Abbas Rastegar; Göksel Durkaya; Aron Cepler; Matt House; Steve Novak

doi:10.1117/12.916631

22 March 2012 Effect of radiation on the defectivity and stability of Ru-capped MoSi multilayer blanks

Abbas Rastegar, Göksel Durkaya, Aron Cepler, Matt House, Steve Novak

Proceedings Volume 8322, Extreme Ultraviolet (EUV) Lithography III; 832211 (2012) https://doi.org/10.1117/12.916631
Event: SPIE Advanced Lithography, 2012, San Jose, California, United States

Abstract

During their usage and fabrication, EUV masks are exposed to light radiation from λ=13.5 nm up to infrared wavelengths. During EUV exposure, masks are not only exposed to 13.5 nm radiation but also to out-of-band radiation which expands from λ=140 to 600 nm for a long period of time. The mask surface is also exposed to different chemicals during cleaning processes, depending on the usage of the mask. During its effective life, an EUV mask should undergo many cycles of cleaning and radiation. Consequently, the Ru surface is modified by photon energy (wavelength) as well as number of photons (intensity and energy). This modified Ru surface will react with chemicals in different ways. Exposure to 172 nm light followed by Ammonium Hydroxide/ Hydrogen peroxide/ water mixture (APM) will result in 0.5% loss of EUV light while 172nm light exposure followed by Sulfuric acid /Hydrogen peroxide mixture (SPM) will reduce EUV reflectivity by 3%. Higher radiation energy on the order of 200 Joules will damage the Ru surface and cause increased defectivity at the mask surface. In addition, higher radiation energies will result in thermal effects such as formation of Ru silicide and Mo silicide. Ru oxidation valence also depends on the radiation power and radiation wavelength. In the absence of radiation or low energy radiation, RuO3 is preferred oxidation state but RuO is preferred in the higher radiation energies. Comparison between 532 nm and 1064 nm radiation showed that RuO2 is the preferred oxidation state at a wavelength of 532 nm, despite much lower radiation power.

Citation Download Citation

Abbas Rastegar, Göksel Durkaya, Aron Cepler, Matt House, and Steve Novak "Effect of radiation on the defectivity and stability of Ru-capped MoSi multilayer blanks", Proc. SPIE 8322, Extreme Ultraviolet (EUV) Lithography III, 832211 (22 March 2012); https://doi.org/10.1117/12.916631

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KEYWORDS

Ruthenium

Silicon

Extreme ultraviolet

Extreme ultraviolet lithography

Oxidation

Reflectivity

Oxides

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