Fraunhofer Institute for Electronic Microsystems and Solid State Technologies EMFTCurrently, the semiconductor industry uses process gases that are harmful to the climate and contribute to greenhouse gas potential and global warming. Within its research cleanroom Fraunhofer EMFT employs analytical systems in conjunction with an abatement system, to monitor the emissions of process gases used in semiconductor manufacturing. The measured results are used to optimize the process parameters concerning emissions.
PFAS Reduction in Semiconductor Manufacturing
Lower Greenhouse Gas Emissions from the Semiconductor Industry
Detection of greenhouse gas emissions from harmful PFAS gases in the Fraunhofer EMFT cleanroom
According to a study by McKinsey (2022), approximately 35 percent of greenhouse gas emissions in semiconductor manufacturing arise from direct emissions of production facilities, with 80 percent of this attributed to the process gases used. The semiconductor industry primarily utilizes low-molecular-weight fluorinated gases from the group of per- and polyfluoroalkyl substances (PFAS), as well as nitrogen trifluoride (NF3) and sulfur hexafluoride (SF6). These gases are employed for the deposition and structuring of thin film layers and for chamber cleaning after plasma-assisted chemical vapor deposition (PECVD) processes. All of these gases have a high greenhouse gas potential.
Reduction of Emissions through Abatement Systems
The use of exhaust gas cleaning systems, known as abatement systems, can significantly reduce harmful emissions. As part of the "Green ICT @ FMD" project, Fraunhofer EMFT has established a comprehensive exhaust gas cleaning system, including analytics, in its research cleanroom to accurately capture the emissions of these greenhouse gases from plasma etching and cleaning processes. Process parameters and settings in the abatement system are adjusted based on the measurement results to decrease emissions.
A mass spectrometer has been installed at the outlet of the process chamber of a PECVD system, where thin films are deposited on wafers from plasma-activated reaction gases, to measure residual gas quantities directly after the process. A downstream burner/washer system based on propane reduces the concentration of harmful exhaust gases before they are released into the environment. For precise analysis of the emitted residual gases, a second mass spectrometer and an FTIR spectrometer are integrated at the outlet of the burner.
The innovative gas abatement system for detecting fluorine-containing pollutant emissions from etching and PECVD chambers is available for industry and business partners.
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(Picture in German) A fully functional, environmentally friendly research facility consisting of a 2-chamber PECVD coating system, vacuum pumps with "Green-Mode" functionality, a modern DAS burner/washer system, and two mass spectrometers (MS). One of the mass spectrometers allows for the detection of harmful gases directly at the outlet of the PECVD chamber, while the second, in combination with an FTIR measuring device, quantifies the gas content at the outlet of the burner/washer unit.
(Chart in German)In the mass spectrometer at the outlet of the process chamber, the NF2 signal, generated alongside others through ionization, is most pronounced. Therefore, it is used as an indicator fragment for the NF3 concentration in the gas stream. A comparison of the NF2 measurement signals during chamber cleaning shows that the use of NF3 leads to a significant increase in the concentration of this greenhouse gas at the end of the cleaning step. This is due to the fact that the process chamber is evacuated at the end of the plasma process, pumping out any unconsumed NF3.
Reduction of Emissions through Climate-Friendly Process Gases
Another way to reduce harmful emissions in semiconductor manufacturing is to use gases or gas mixtures with no or minimal greenhouse gas potential. This proactive approach has been pursued by Fraunhofer EMFT in collaboration with industry partners in a project aimed at developing environmentally friendly cleaning gases for semiconductor manufacturing. In this process, the conventional, particularly climate-damaging cleaning PFC and NF₃ gases were replaced by a so-called FAN gas mixture of fluorine, argon, and nitrogen, without compromising the cleaning effectiveness.