Title : Environmental-Friendly Fluorine Mixture for CVD Cleaning Processes to replace C2F6 and NF3 under industrial Conditions
Abstract:
During the climate conference in Paris (2015) a binding and universal climate target was established. It was agreed to limit the temperature increase to a maximum of 2 C° until 2100 ( ). The most relevant climate gas is CO2, considered as a primary greenhouse gas with a significant impact on global warming. Although the semiconductor industry is only a small contributor to the global warming, several fluorinated gases having a high global warming potential (GWP) ( ), are intensively used. NF3 is the most frequently used gas, having a GWP of 17200, followed by C2F6 and CF4 with GWPs of 1200 and 7390 respectively ( ), as shown in table 1. The main application of these gases is to remove residual films remaining inside deposition chambers after a PECVD process (plasmaenhanced chemical vapor deposition). The most important materials to remove are dielectric layers like silicon dioxides (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 used in 2018 12696 t NF3, 2024 t CF4 and 736 t C2F6 on a global basis. Approximately 72% of all semiconductor industry gaseous emissions are caused from these three gases. This article discusses the replacement of C2F6 and NF3 as cleaning gases thru an environmental-friendly gas mixture named Solvaclean®NO (30% F2, 60%N2 and 10% Ar).
It could be shown at the production site, which the cleaning was done with Solvaclean®NO achieves similar cleaning time with significant lower gas consumption, appr. 60-70% less gas compared to C2F6. The RF-power during cleaning was reduced by 20% and the amount of fluorinated waste water was as well significantly reduced. In addition a Solvaclean®NO supply for a production FAB was installed, based on a bundle delivery system. After a ”craddel to grave” technical check of the gas supply system could be shown, that Solvaclean®NO can be used as a `drop in´ to replace C2F6.