The flows above are this dataset's own records. What follows are the scope rules set once for the whole database in the methodology report, repeated here so every dataset page carries them.

Boundary declared by this dataset

Gate-to-gate CF4 synthesis from carbon tetrachloride (CCl4) + HF

Database-wide boundary policy — applies to every REEL dataset

These boundaries are set once for the whole database, in Chapter 2 of the methodology report, and apply to this dataset wherever they are relevant to it. The excluded flows listed above are specific to this dataset.

Use phase

Product operation is outside the cradle-to-gate scope.

End-of-life treatment

Recycling and disposal are outside the cradle-to-gate scope.

Distribution and retail

The gate is a finished component ready for integration into a higher-level assembly.

Inbound transport of raw materials

Transport of purchased raw materials to the manufacturing facility is already inside the upstream "market for" datasets that users link to a background database, so it is not modelled a second time here. This does not cover freight between REEL production stages, which is modelled where a dataset authors it.

Returnable shipping containers

Where freight between production stages is modelled, the mass moved is the product itself. The shipping container (FOSB, SEMI M31) is returnable capital equipment whose per-trip share is unsourced, so its tare is excluded from the transport effort.

Photomask fabrication

A mask set's embodied burden is amortised across a high-volume production run and is not attributed per wafer. Users assessing low-volume production should add mask fabrication separately; the methodology report gives the basis for the exclusion.

Employee transport, administration and R&D overhead

Employee transportation, facility administration and R&D/pilot-production overhead are outside scope.

Capital goods

Manufacturing equipment, cleanroom construction and facility infrastructure are excluded, on the grounds of absent public data on equipment embodied energy, uncertainty in equipment lifetime and allocation, common practice in electronics LCA, and a focus on the operational inventory. Future versions may include capital goods when sufficient public data becomes available.

Precious metal recovery credits

Scrap recovery credits for precious metals are excluded pending data availability.

Wafer reclaim

Test wafers and scrap are outside the system boundary.

Inside the boundary, linked rather than modelled

Silicon ingot growth and wafer slicing

Inside the cradle-to-gate scope, but treated as upstream material inputs linked to background databases rather than modelled as REEL processes.

Freight between production stages

Where a dataset's product moves between REEL production stages - wafer fabrication to the packaging site, for example - that leg is authored as a transport service and linked to an ecoinvent freight activity. It is measured as a transport effort in tonne-kilometres, not as a mass. Route distances are authored per route class with a stated band; a lower bound of zero is a modelling statement that the two sites can be co-located, not a missing value.

Cut-off criteria

A flow is excluded from a process inventory when it contributes less than 1 % of the total mass of inputs to that unit process, or less than 1 % of its total energy input. The denominator is total process inputs, not product mass. That distinction matters in semiconductor manufacturing, where the input mass of water, chemicals and gases greatly exceeds the product mass, so the threshold removes only genuinely minor flows.

Included regardless of the cut-off

• Perfluorocarbons (CF4, C2F6, SF6, NF3) - high GWP, EPA regulated
• Heavy metals (Pb, Cd, Hg, Cr(VI)) - RoHS regulated, high toxicity
• Volatile organics (photoresist solvents, PGMEA) - air quality
• Precious metals (Au, Ag, Pd, Pt) - high embodied impacts
• Ozone-depleting substances (legacy CFCs, HCFCs) - Montreal Protocol