An approach to reduce greenhouse gases in the semiconductor industry using F2 for CVD chamber cleaning

 

Jamila Boudaden1, S. Altmannshofer1, R. Wieland1, M. Pittroff 2 and I. Eisele1

 

1 Fraunhofer EMFT, Hansastraße 27d, 80686 Munich, Germany

2 Solvay Fluor GmbH, Hans-Böckler-Allee 20, 30173 Hannover, Germany

 

ABSTRACT:

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Semiconductor chip manufacturers use in their processes a variety of gases to pattern silicon wafers and to reach a rapid cleaning of chemical vapor deposition (CVD) tool chambers. Most of the gases employed by the semiconductor industry are such as CF4, C2F6 and C3F8 named perfluorocarbons, nitrogen trifluoride NF3 and sulfur hexafluoride SF6. Under industrial process conditions, non-negligible amounts of unreacted fluorinated gases, ranging between 10 to 80 %, are released into the atmosphere. Unfortunately, the perfluorinated gases, NF3 and SF6 are considered as greenhouse gases and have a high global warming potential. Greenhouse gases in the upper atmosphere avoid releasing the infrared radiation to the universe, by reflecting it backwards to the earth. The global warming potential (GWP) of a gas is generally measured in 100-year time horizon and expressed in CO2 equivalents. The GWP value depends on the lifetime of the gas in the atmosphere and its ability, to absorb radiation.

Both Fraunhofer EMFT and Solvay were joining their efforts in a research program to find save alternative gases to be used in the manufacturing processes for ensuring climate safety. Our goal is focused on finding an adequate gas for semiconductor industry, which could be easily integrated to the existing CVD equipment so that buying any new systems or including important modifications to the onsite hardware are avoided. This means the proposed approach has to be, on the one hand, a cost effective solution for industrial companies, on the other hand, to reduce the amount of the used greenhouse gases. Here, we propose a fluorine gas mixture as an environmental friendly gas for CVD cleaning processes to replace in the near future C2F6 and NF3 gases.

In this paper, we will report a comparison study between cleaning processes using NF3 and using fluorine gas mixture performed in a 200 mm wafer size CVD tool for SiO2 thin layer deposition. . The process chamber ran with the new cleaning chemistry and inspected on a regular basis during the period of this study, in order to detect any equipment’s degradation related to using the new gas mixture. As the molecular fluorine has no global warming potential, the F2 gas represents a beneficial cleaning gas alternative for the CVD equipment.

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BIOGRAPHIE:

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Dr. Jamila Boudaden received her PhD in Physics from the University of Basel in Switzerland. Since 2011 she has been working as a scientific member of the Silicon Technologies and Devices team. She has experience in MEMS devices realization, like microphones, micro-pumps. She is also in charge of designing sensitive materials for highly selective gas detection, developing and analyzing chemical sensors.

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