Since the beginning of the 1980’s per fluorinated carbons (PFC’s) such as C₂F₆ and CF₄ have been used as cleaning gases in thin film deposition technology and since the 1990’s NF₃ has been used in the same way. PFC’s and NF₃ have long atmospheric lifetimes and therefore high global warming potentials. The main applications of these gases are to remove residual films left behind after a chemical vapor deposition process (CVD). The most important materials to remove are dielectric layers like silicon oxides (SiO₂), carbon-containing silicon oxides, silicon nitrides (Si₃N₄) and, to a certain extent, conducting films like doped poly-silicon and silicide layers. According to the World Semiconductor Council the semiconductor industry in 2013 used 7512 t NF₃, 1133 t CF₄ and 708 t C₂F₆ on a global basis. Approximately 72% of all semiconductor industry gaseous emissions are caused from these three gases (C₂F₆, CF₄ and NF₃). Fraunhofer EMFT and Solvay Special Chem have developed an alternative cleaning process, which can be a replacement for the currently used PFC’s and NF₃in semiconductor CVD tools.

The target of this work was to find viable alternative gas mixtures for the semiconductor industry, which could be used as a “drop in” to avoid additional high investment costs from equipment modification. Our study has demonstrated that these more environment friendly gas mixtures also provide a more efficient and faster cleaning behavior for most applications. A cleaning efficiency gain of a factor 1.3 up to 17 can be expected, relative to the F2-amount required for cleaning; this gain in efficiency depends on the cleaning gas to be replaced and on the reactor type. A shorter cleaning time can lead directly into a higher equipment throughput and more cost effective usage of thin film tools. To generate data on particle and tool attrition, a first “mini marathon” test run has been performed. The test reactor, a 200mm wafer size CVD tool, was equipped with a mass spectrometer, to verify the end point of the chamber cleaning and to gain an overview of the waste gases going into the abatement system.