Viability of HFO-1234ze(E) (trans-1,3,3,3-tetrafluoropropene) as a low global warming potential silicon dioxide etch gas

The American Innovation and Manufacturing Act, enacted by Congress in 2020, grants the U.S. Environmental Protection Agency the authority to phase down the production and consumption of hydrofluorocarbons (HFCs), thereby reducing carbon emissions and addressing the negative environmental impact of HFCs. To comply, the semiconductor industry, which uses a variety of processing gases that contain HFCs, must transition to alternative gases in chip manufacturing, particularly in etching processes. Many of the HFC etch gases in current use have high global warming potentials (GWPs). One potential alternative to the high-GWP gases are hydrofluoroolefins (HFOs), which were developed by the refrigerant industry as fourth generation, low-GWP alternatives to legacy refrigerants and foam expansion agents. The present work will investigate the viability of the environmentally friendly HFO, trans-1,3,3,3-tetrafluoropropene [C3H2F4 or HFO-1234ze(E)], as a replacement gas for reactive ion etching of silicon dioxide (SiO2). Initial etch tests demonstrated that HFO-1234ze(E) has higher etch rates and better selectivity than the saturated alkane legacy gases trifluoromethane (CHF3) and difluoromethane (CH2F2). Repeated SiO2 etching with HFO-1234ze(E) appears to not affect the etch chamber or future etch processes. Thus, the present work suggests that the low-GWP HFO-1234ze(E) could be an effective etch gas for the semiconductor industry as an alternative to HFC gases.