Hydrogen recycling in CVD processes using electrochemical hydrogen compression

Hydrogen usage is increasing, especially in photovoltaics and semiconductor industry. A large share is accounted for by chemical vapor deposition (CVD) plants, where high purity hydrogen is needed as reaction and carrier gas. The waste gas still consists largely of hydrogen, but also of gaseous dopants and reaction products. After cleaning from toxic and harmful substances, the off gas is either burned or vented to atmosphere. Reuse of the H2 could reduce operating costs and mitigate the effects of global warming from H2 production and H2 increase in the atmosphere. We have integrated an electrochemical hydrogen compression (EHC) system into our atmospheric pressure CVD lab environment for SiC growth and tested this system for possible limitations and influences during operation. Hydrogen recycling with stable recycling rates of more than 50 % could be demonstrated. The grown SiC films were characterized in terms of their growth parameters and impurities. Additionally, we integrated the EHC system into an industrial scale MOVPE reactor and tested the performance and recovery of hydrogen on larger and relevant input flows. Based on these results, we determined that the EHC technique is suitable for H2-recycling from CVD waste gas mixtures. We also think that using the recycled hydrogen as burn gas in CVD waste-gas abatement systems or in other sectors instead of direct reuse as process gas is a preferable intermediate step until quality controls with in-situ trace-measurements are ready to be implemented.