Design, Simulation, and Parametric Analysis of an Ultra-High Purity Phosphine Purification Process with Dynamic Control

Phosphine (PH3) is an important functional material that plays a pivotal role in semiconductor fields. As semiconductor technology rapidly advances toward smaller sizes and higher performance, the requirements for the purity of phosphine in chip manufacturing are becoming increasingly stringent. To address this, this study has designed a purification process for ultra-high purity phosphine, capable of achieving a purity level of 6N (99.9999%) for phosphine products. The process was simulated and analyzed using Aspen Plus to investigate the influence of various factors on the purity of phosphine products. In this design, the sensitivity analysis function was used to determine the optimal number of theoretical stages, feed stage, and reflux ratios for each rectifying column in the process. It was also found that an increase in rectifying column pressure is detrimental to the removal of low-boiling-point substances such as N2 and O2 from phosphine. Furthermore, a double-effect distillation process was designed. After adopting the double-effect distillation process, the heat duty on all condensers and reboilers would decrease by 27%, but the purity of the phosphine product would decrease from 99.999943% to 99.999936%. Finally, a control scheme was designed for the distillation column used to extract phosphine products, and the control effect was dynamically simulated and tested using Aspen Plus Dynamics. The test results showed that disturbances caused by a decrease in feed were much more difficult to control than those caused by an increase in feed, and that low-boiling-point impurities had a much greater impact on the purity of phosphine products than high-boiling-point impurities. In addition, the results of steady-state simulation indicate that CO2 in phosphine is difficult to remove through distillation processes. Adding adsorption processes or membrane separation processes after distillation to remove CO2 from phosphine is a research direction for improving the purity of phosphine.