Dr. Nicolae Maxim Profile

Dr. Nicolae Maxim

at ASML Netherlands BV

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Publications (2)

Proceedings Article | 27 May 2009 Paper

Contamination control for ArF photo masks

Joseph Gordon, Marianna Silova, Brid Connolly, Jeroen Huijbregtse, Nicolae Maxim, Larry Frisa, Christian Chovino, Colleen Weins

Proceedings Volume 7470, 74700C (2009) https://doi.org/10.1117/12.835174

KEYWORDS: Air contamination, Reticles, Photomasks, Pellicles, Humidity, Lithography, Contamination, Manufacturing, Contamination control, Optical lithography

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Advanced photolithography tools use 193 nanometer wavelength light for conventional and immersion printing. The increased energy of 193 nm (ArF) light coupled with the higher absorption cross section of most materials has lead to a dramatic increase in the rate of haze formation as compared to previously used lithographic wavelengths (248 KrF and 365 nm i-line systems). It is well known that at this short wavelength photochemical reactions are enhanced leading to progressive defect formation, or haze, on optical surfaces within microlithography tools. Therefore, strict contamination control of the optics environment is needed to avoid cumulative effects. Such measures have been implemented in lithography tools both for the optics and for the reticle during exposure. However, the patterned side of the photomask is the most sensitive element in the litho optical path for haze growth, because it is in focus and small defects will show up as printing defects. Moreover, the reticle life time depends both on rigorous contamination control for expose and transport/storage conditions (both inside and outside of the lithography tool). The litho operating cost depends directly on reticle life time. It is imperative that the industry takes the required measures to improve the airborne molecular contamination levels both in the storage part of the photolithography tool and in devices used to transport reticles outside of the tool to slow down reticle haze Past studies have shown the large effects of humidity and AMC on haze growth during storage and exposure. Therefore, significant improvements in storage and exposure environment have been implemented by many fabs to reduce the frequency of haze failures. It has also been shown that outgassing from materials surrounding the mask can influence or cause haze. It is clear that the reticle must be adequately protected from contamination sources throughout the life cycle of the reticle (both inside and outside of the lithography tool). In this paper we examine improvements in the storage conditions of reticles inside the lithography tool as well as improvements in commercial SMIF pods used in fab storage and automated handling of reticles.

Proceedings Article | 1 April 2009 Paper

Quantitative measurement of resist outgassing during exposure

Nicolae Maxim, Frances Houle, Jeroen Huijbregtse, Vaughn Deline, Hoa Truong, Willem van Schaik

Proceedings Volume 7273, 72733Z (2009) https://doi.org/10.1117/12.813726

KEYWORDS: Silicon, Polymers, Nitrogen, Carbon, Semiconducting wafers, Calibration, Ultraviolet radiation, Sensors, Lithography, Photoresist materials

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Determination of both the identity and quantity of species desorbing from photoresists during exposure at any wavelength - 248nm, 193nm and EUV - has proved to be very challenging, adding considerable uncertainty to the evaluation of risks posed by specific photoresists to exposure tool optics. Measurements using a variety of techniques for gas detection and solid film analysis have been reported but analytical results have not in general been easy to compare or even in apparent agreement, in part due to difficulties in establishing absolute calibrations. In this work we describe two measurement methods that can be used for any exposure wavelength, and show that they provide self-consistent quantitative outgassing data for 2 all-organic and 2 Si-containing 193 nm resists. The first method, based upon gas collection, uses two primary chromatographic techniques. Organic products containing C, S and Si are determined by collection of vapors emitted during exposure in a cold trap and analysis by Gas Chromatography-Flame Ionization Detector-Pulsed Flame Photometric Detector-Mass Spectrometry (GC-FID-PFPD-MS). Inorganic products such as SO2 are identified by adsorbent bed with analysis by Gas Particle-Ion Chromatography (GP-IC). The calibration procedure used provides reasonable accuracy without exhaustive effort. The second method analyzes the elemental concentrations in resist films before and after exposure by secondary ion mass spectrometry technique (SIMS), which requires only knowledge of the resist compositions to be quantitative. The extent of outgassing of C and S determined by the two methods is in good agreement for all 4 resists, especially when taking their fundamentally different characters into account. Overall, the gas collection techniques yielded systematically lower outgassing numbers than did SIMS, and the origins of the spread in values, which likely bracket the true values, as well as detection limits will be discussed. The data for Si were found to differ significantly, however, and we show that the discrepancy is due to photo-induced reactions at the polymer surface with the gas atmosphere present above the resist during exposure. For example, photolytic oxidation of the C-Si bonds in air causes volatile Si-containing products to be formed from an otherwise stable polymer, showing it is important to take the gas environment during exposure into account when designing resist polymers for low Si outgassing.

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