Simultaneous distillation-extraction for manufacturing ultra-high-purity electronic-grade octamethylcyclotetrasiloxane (D4)

Ultra-high-purity (UHP) electronic-grade octamethylcyclotetrasiloxane (D4) is the key precursor of low-dielectric constant (low-k) SiCOH films to manufacture integrated circuits (IC), meeting the stringent requirements of the rapidly developing semiconductor industry. Commonly, metallic impurities in D4 were removed by multiple unit operations of adsorption, filtration, and distillation, which could reduce the concentration of a single metallic impurity below 1 ppb. However, D4 with higher purity is required by semiconductor production due to an increase in transistor density. Herein, a novel method based on the integrated simultaneous distillation–extraction (SDE) was developed for manufacturing UHP electronic-grade D4. The lab and pilot scale experiments showed that the purity of water and D4 has a positive correlation. Based on the experimental data, a double-column process, consisting of azeotropic/extractive distillation column and precision distillation column with UNIQUAC method, was established to access the feasibility of scaling up the SDE process. According to the simulation results, D4 with the purity > 99.999 wt.% and total metallic impurities (TMI) content below 1 ppb could be obtained using ultra-pure water.