Etching Gas Filtration

    Etch gas filtration refers to a multi-stage purification process that removes impurities (particles, moisture, metal ions, and organics) from high-purity etch gases such as CF₄, SF₆, Cl₂, and NF₃ in semiconductor dry etching processes. This ensures etch precision, yield, and equipment safety.

   Purpose: To prevent pattern defects caused by micron/submicron particles, gate contamination from metal deposition, and changes in etch rate or selectivity due to moisture/oxygen impurities, ensuring consistency in nanoscale feature fabrication.

   Mechanism: It employs physical interception (e.g., sintered metal or PTFE membrane filters to capture ≥0.003 μm particles), chemical adsorption (activated carbon or impregnated packing to trap acidic/organic impurities), catalytic decomposition (for pre-treatment of greenhouse gases like NF₃), and material compatibility design (316L stainless steel or Hastelloy for fluorine corrosion resistance).

   Location: It is deployed at the end of the piping between the specialty gas cabinet (SMIF) and the process chamber, typically as a two-stage filter (pre-filter + terminal high-efficiency filter). Some are integrated into the gas distribution unit (GDU).

   Challenges: Etch gases are often corrosive/reactive, requiring filter media to balance high filtration efficiency with chemical resistance (e.g., avoiding intergranular corrosion). Additionally, filters must support high-temperature baking (≥500°C) to desorb adsorbed contaminants and maintain low outgassing rates.