A research team at the Korea Advanced Institute of Science and Technology (KAIST), working in collaboration with Samsung Electronics, has developed a breakthrough catalytic technology that efficiently breaks down tetrafluoromethane (CF4) while significantly extending operating lifetime under demanding industrial conditions.
CF4 is an indispensable specialty fluorinated gas used extensively in semiconductor front-end manufacturing, primarily for dry plasma etching to pattern ultra-fine circuits on silicon wafers and for cleaning deposition chambers. However, because the covalent bond between carbon and fluorine is exceptionally strong, the gas resists natural degradation, remaining in the atmosphere for roughly 50,000 years with a global warming potential more than 6,000 times greater than carbon dioxide (CO2).
To prevent direct atmospheric release, semiconductor fabrication facilities deploy point-of-use (POU) thermal and catalytic abatement systems that decompose CF4 at high temperatures using steam. Conventional catalysts primarily standard alumina (Al2O3) suffer from rapid structural degradation. As CF4 breaks down, it generates hydrogen fluoride byproducts that, in the presence of high-temperature steam, create an aggressive corrosive environment. This causes fine catalytic particles to aggregate and undergo phase transformations, shrinking the active surface area and sharply decreasing gas abatement efficiency over time.
To overcome this durability bottleneck, the researchers harnessed the thermodynamic principle of entropy stabilization. By introducing multiple distinct metal cations into a single aluminate crystal framework, the team created a disordered atomic structure that resists phase changes and suppresses particle sintering.
The resulting “entropy-stabilized aluminate” (ESA) catalyst evenly incorporates five metals—aluminum, zinc, gallium, nickel, and cobalt into its matrix. This multi-element configuration prevents structural deformation even under concurrent exposure to extreme thermal stress, moisture, and corrosive fluorine.
In performance assessments, the ESA catalyst demonstrated an intrinsic CF4 decomposition activity roughly 2.3 times higher than conventional alumina. Crucially, during an accelerated industrial endurance test at approximately 800°C for 150 hours, CF4 conversion rate of conventional alumina dropped from 93% down to 48%. In contrast, the entropy-stabilized catalyst maintained near-peak abatement, declining only slightly from 98% to 92%.
Using oxygen isotope tracking, the researchers also experimentally proved the underlying reaction mechanism for the first time. The catalyst initially utilizes lattice oxygen from its own crystal structure to cleave CF4, while ambient steam continuously replenishes depleted oxygen sites, functioning as a self-sustaining regenerative cycle.
Beyond addressing CF4 emissions, this entropy-driven synthesis strategy provides semiconductor equipment and fab infrastructure manufacturers with a flexible materials framework. By tailoring the combination of constituent transition metals, engineers can design resilient abatement catalysts for a wide array of persistent perfluorocarbon (PFC) and fluorinated greenhouse gases utilized in modern fab environments.
Source: KAIST News Center / Angewandte Chemie International Edition (Study led by Dr. Seunghyuck Chi and Prof. Minkee Choi, KAIST Department of Chemical and Biomolecular Engineering, in collaboration with Samsung Electronics).
