Study of the airborne SO2 and NH3 contamination on Cr, MoSi, and quartz surfaces of photomasks

H. Fontaine; G. Demenet; V. Enyedi; S. Cetre

doi:10.1117/12.864268

24 September 2010 Study of the airborne SO₂ and NH₃ contamination on Cr, MoSi, and quartz surfaces of photomasks

H. Fontaine, G. Demenet, V. Enyedi, S. Cetre

Proceedings Volume 7823, Photomask Technology 2010; 782328 (2010) https://doi.org/10.1117/12.864268
Event: SPIE Photomask Technology, 2010, Monterey, California, United States

Abstract

The study of the airborne SO₂ and NH₃ contamination on Cr, MoSi and Quartz photomask surfaces was addressed by the intentional exposure to controlled contaminated air. Experimentally, mask-like layers (representative Cr, MoSi and SiO₂ layers) deposited on wafers were used and then characterized by LPE-IC. Results showed that Cr surfaces clearly present a higher ability to be contaminated than MoSi and even more than Quartz, both for SO₂ and NH₃ (Cr >> MoSi > Quartz). For each mask surface, the NH3 contamination occurred more rapidly than the SO₂ deposition. The contamination of Cr and MoSi surfaces respectively for the 2 contaminants and for SO₂, are governed by Langmuir-type adsorption models allowing then the forecasting of the deposited contaminant amounts depending on the time and the airborne concentration. A very slow and low adsorption process of SO₂ on Quartz is observed whereas the NH3 deposition on MoSi and quartz appear very rapid at ambient concentrations such as a way saturation levels are likely reached in few minutes. Furthermore, a significant enhancement of the SO₂ and NH3 deposition is characterized in clean room humidity versus drier conditions, this effect being extremely drastic for SO₂ on Cr. The knowledge of the contamination behavior of the SO₂ and NH₃ on photomask surfaces is very relevant for the control of the crystal growth /haze occurrence on reticles. Their application led to recommend SO₂ and NH₃ threshold levels lower than 10 pptv in the mask environment to avoid haze beyond one year.

Citation Download Citation

H. Fontaine, G. Demenet, V. Enyedi, and S. Cetre "Study of the airborne SO₂ and NH₃ contamination on Cr, MoSi, and quartz surfaces of photomasks", Proc. SPIE 7823, Photomask Technology 2010, 782328 (24 September 2010); https://doi.org/10.1117/12.864268

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