Environmental Analysis of RF Substrates

In order to incorporate environmental considerations into the decision criteria used to select substrates for radio-frequency integrated circuits (RF IC) technologies, we report here a comparative cradle-to-gate life cycle assessment (LCA) for Si and III-V state-of-the-art RF technologies. It appears that the global warming potential (GWP) of GaN-on-SiC is penalized by the high manufacturing energy of SiC wafers. Although less impactful than SiC, GaAs substrates show a higher GWP than Si-based technologies, which is also linked to an energy-intensive wafer fabrication. For GaN-on-Si, the epitaxy of the ~2.5 um-thick III-N layers represents an important part of the emissions making it ~30% more impactful than TR SOI substrates. In terms of abiotic depletion potential (ADP), the relatively large amount of Ga and As required to fabricate GaAs wafers leads to the highest ADP of all substrates. SiC also shows a high ADP due to the energy-intensive wafer fabrication. A significantly lower ADP is obtained for Si-based technologies.