UV Air & Surface
for Electronics
& Semiconductor

Molecular bases are the most yield-critical AMC category in DUV and EUV lithography. Ammonia (NH₃) and organic amines originate from multiple sources inside the cleanroom — human metabolic products exhaled in breath, cleanroom glove outgassing (particularly latex and some nitrile formulations), construction materials, HEPA filter binders and process chemicals. In photolithography bays processing chemically amplified resist (CAR), these molecular bases diffuse into the exposed resist film between the DUV/EUV exposure and the post-exposure bake (PEB) step.

Inside the resist, molecular bases neutralise the photo-acid generated by the exposure event, preventing the acid-catalyzed deprotection reaction that defines the pattern in the resist. The result is a T-shaped resist profile — T-topping — where the top of the resist feature is insoluble (the neutralised layer) while the bulk develops normally, creating a T-shaped cross section that fails pattern transfer. Critical dimension shifts of 10–20 nm have been documented at total molecular base exposures above 18 ppb over 10 minutes. UV photo-oxidation decomposes NH₃ and amines before they reach the wafer, protecting the photoresist chemistry without any chemical treatment of the cleanroom air.

Molecular acid AMC originates from process chemical outgassing, semiconductor equipment exhaust, and combustion products from facility operations. HCl and SO₂ are particularly problematic in semiconductor facilities because they attack chromium-coated photomask surfaces and reticle pellicle materials, forming corrosion products that cause pattern defects when the mask is used repeatedly. Acid AMC also accelerates corrosion of copper and aluminium interconnect metals exposed at the wafer surface between process steps.

UV photo-oxidation at 254 nm and ozone generated at 185 nm both contribute to the oxidative decomposition of acid AMC compounds. Ozone reacts with SO₂ to form SO₃ and then sulphuric acid aerosol — which is then collected by downstream HEPA filtration rather than remaining as a gas. The combined UV + ozone mechanism addresses both gas-phase and particle-forming acid contaminants. Acid AMC monitoring using ion mobility spectroscopy downstream of UV treatment systems allows confirmation of real-time photolysis performance.

Organic AMC in semiconductor cleanrooms originates from polymer outgassing — FOUP liners, cleanroom furniture, tool enclosure materials, HEPA filter binders, sealants and adhesives — as well as from process chemical vapours, solvent-based cleaning agents and human metabolic products. Organic compounds accumulate in cleanroom recirculating air because their molecular size allows them to pass through HEPA filtration, and their vapour pressure is sufficient to maintain them in the gas phase at cleanroom temperature.

UV photo-oxidation at 185 nm (with accompanying ozone) is the most effective treatment for the full spectrum of organic AMC. The 185 nm photon has sufficient energy to break C–C and C–H bonds directly through photolysis, initiating oxidative decomposition chains. The ozone generated simultaneously continues the oxidation process downstream of the UV lamp. For photoresist coating and develop areas, controlling organic AMC is important for preventing contamination of resist chemistry and for maintaining the precise surface energy properties of wafer surfaces required for uniform resist adhesion.

Condensable AMC compounds have low vapour pressure and deposit preferentially on cold surfaces and on surfaces with favourable surface energy — including fused silica projection lens elements in DUV lithography tools, photomask substrates and reticle pellicle membranes. Siloxanes (silicon-containing organic compounds outgassed from polydimethylsiloxane sealants, silicone rubber components and cleanroom materials) are particularly destructive on optical surfaces because they form hard, transparent silicon oxide films upon UV photo-oxidation — a film that cannot be removed without physical cleaning of the lens surface.

UV surface treatment directly on equipment enclosures and mini-environments prevents condensable AMC from depositing on internal surfaces by continuously photo-oxidizing the condensable compounds before they can accumulate. UV-LED fixtures at 254–265 nm are preferred for this application because they enable precise, localised UV treatment inside equipment enclosures without the ozone generation that can degrade precision polymer and elastomer components nearby. For reticle storage and pod environments, UV surface treatment prevents the siloxane deposition on photomask surfaces that causes pattern transfer defects in subsequent lithography exposures.