HVAC Duct Machinery for Semiconductor Fabrication Facilities

Lithography areas in modern fabs typically require ISO 14644-1 ISO Class 1-3 (the old Federal Standard 209E Class 1 to Class 1,000) — the most stringent cleanroom classifications available. ISO Class 1 allows only 10 particles per cubic metre at 0.1 µm and effectively zero at 0.5 µm. Lithography sub-fabs and stepper rooms generally specify ISO Class 1-2; etch and deposition tool bays ISO 3-4; chemical mechanical planarization and metrology ISO 5-6; service chases and gowning ISO 7-8.

ISO Class 1 cleanrooms typically require 500-700 air changes per hour (ACH) — driven primarily by FFU (Fan Filter Unit) ceiling coverage rather than discrete duct supply. ISO 2 = 250-500 ACH, ISO 3 = 60-300 ACH, ISO 4-5 = 60-180 ACH, ISO 6 = 60-90 ACH, ISO 7 = 30-60 ACH, ISO 8 = 10-25 ACH. The implication for ductwork: stainless welded round duct from SBTF tubeformers is the standard supply path; sub-fab plenum return is typically high-velocity galvanized rectangular duct from SBAL-V.

Three reasons: (1) sub-micron particle release — galvanized zinc surface generates particulate as it ages, stainless 304L/316L electropolished to Ra ≤ 0.4 µm does not, (2) AMC (airborne molecular contamination) outgassing — stainless does not outgas, galvanized and many sealants do, (3) process chemical resistance — etch tool exhaust contains HF, HCl, H2SO4, ammonia and other corrosives that destroy galvanized coating. Taokron supplies SBTF spiral tubeformers and SBAL-V auto duct lines configured for 304L and 316L stainless work.

ULPA (Ultra Low Penetration Air) filters per EN 1822 are classified U15 to U17 — efficiencies 99.9995% to 99.999995% at the Most Penetrating Particle Size (typically 0.12-0.25 µm). Semiconductor fab ceilings are typically 100% FFU coverage with U15-U17 modules; the ductwork above the FFUs is the supply plenum that pressurises the FFU array. Stainless welded round duct from SBTF feeds the plenum; rectangular sub-plenums distribute. Leakage class for the supply plenum must be SMACNA Class A (essentially zero leakage) — TDF flange with closed-cell EPDM gasket and orbital TIG welded longitudinal seam are the typical specifications.

Acid exhaust (HF, HCl, H2SO4, HNO3 — from etch and CMP tools): 316L stainless or PVDF-lined duct, separate scrubber. Base exhaust (NH3, NaOH — from clean tools and CMP): 316L or PP duct. Organic/VOC exhaust (IPA, photoresist solvents): 316L stainless to oxidiser/scrubber. Pyrophoric/flammable (silane SiH4, hydrogen, GeH4): special silane-rated duct with detection, often jacketed double-wall design with N2 purge. Toxic (arsine AsH3, phosphine PH3, BCl3): dedicated isolated exhaust to scrubber. Taokron supplies SBTF stainless tubeformers and SBAL-V stainless rectangular auto duct lines for all the above except specialty PVDF/PP composite ducts.

AMC refers to gaseous molecular contaminants in the cleanroom air that affect lithography exposure, photomask cleanliness and wafer surface quality at sub-100nm process nodes. The four main categories: acid (sulfur as ppb-level SO2, NOx), base (ammonia at ppb), organic (VOCs, condensable organics), dopant (boron, phosphorus). Modern fabs use chemical filter banks (carbon for organics, ion-exchange resin for acids/bases) integrated into the supply ductwork. The duct material itself must be low-AMC: stainless steel passes; galvanized fails (zinc oxide outgases). Sealants must be silicone-free and low-VOC: EPDM, PTFE, FKM are typical.

Top-of-cycle hyperscale fabs (TSMC Arizona, Intel Ohio, Samsung Texas, TSMC Kumamoto) carry duct packages in the USD 50-200 million range covering supply HVAC, sub-fab return, process exhaust, scrubber pre-treatment and chemical filter integration. The duct is typically 60-70% stainless steel (304L for non-process areas, 316L for acid exhaust), with 30,000-80,000 metres of welded round and rectangular duct per fab. Smaller specialty foundries and OSAT facilities run USD 5-25 million packages. Taokron supplies the auto duct lines and tubeformers — the local fabrication contractor manufactures and installs.

SBTF spiral tubeformer in stainless configuration (304L and 316L tooling, reduced cutting speed, mandrel-formed seam, optional orbital TIG longitudinal seam welder) — the workhorse for ULPA supply duct. SBAL-V auto duct line in stainless variant (upgraded forming rollers, stainless-compatible lubrication, 316L corner clip integration) — for sub-fab return and chemical exhaust ducts. Orbital welding stations for full-penetration TIG seam welds. Pickle-and-passivate or electropolish surface finishing equipment available as add-on. Fab stainless duct normally requires mill-certificate traceability (EN 10204 3.1) and welder qualification records (WPS/PQR/WPQ per ASME IX or AWS D18.1); these come from the coil supplier and the fabricator's welding procedures.