Semiconductor manufacturing carbon & embodied compute
From fab process inventory to wafer, die, package and lifetime useful compute.
Abstract. Critical Load's semiconductor programme treats one of carbon accounting's most data-constrained areas as a first-class measurement problem. The working method traces fab electricity, process gases, abatement, chemicals, ultrapure water, yield and advanced packaging through to product-level embodied carbon and, finally, a compute-intensity denominator.
Semiconductor carbon is a measurement problem before it is a reporting problem.
The hardest variables are often inside the fab: process gas use and destruction, cleanroom electricity, chemical and water inventories, node-specific process intensity, equipment allocation, wafer yield and confidential supplier data.
Gas-specific inventory and destruction efficiency can materially change direct process emissions.
Nameplate abatement is not automatically equivalent to realized destruction performance.
The same wafer-level impact is allocated across the number of usable dies that leave the process.
Water and chemical treatment belong inside the manufacturing inventory, not outside the boundary.
Fab inventory is carried through wafer, die and package allocation.
Fab inventory
Electricity, process gases, abatement, chemicals, UPW, equipment and facility allocation.
Wafer basis
Process node, wafer diameter, wafer starts and manufacturing period.
Good die
Die area, gross dies, yield and usable output determine the allocation denominator.
Package
Substrate, advanced packaging, memory/HBM and backend manufacturing are added.
Useful compute
Product carbon is normalized by lifetime utilization and delivered compute.
Yield, allocation rule and data-quality class remain attached to the result.
The dominant driver can move when fab, node, yield and packaging change.
Our semiconductor work is designed around sensitivity rather than a single universal chip factor. The method tests which input actually controls the result under the stated manufacturing configuration.
| Variable | What changes | Expected result effect | Evidence requirement |
|---|---|---|---|
| Fab electricity mix | kgCO₂e / kWh | Operational manufacturing carbon shifts with local electricity | Fab / supplier period |
| Process gas + abatement | Gas use and destruction | Direct process emissions can become a major driver | Gas-specific inventory |
| Good-die yield | Usable dies per wafer | Lower yield raises impact allocated to each good die | Node / product yield |
| Advanced packaging | Substrate, HBM, backend | Packaging can shift the balance after die fabrication | Package bill / process data |
Directional result structure. Proprietary fab-level primary data is not exposed in the public working site.
Published product carbon anchors the downstream system.
A public HGX H100 baseboard PCF reports 1,312 kgCO₂e cradle-to-gate, with 91% attributed to materials and components. Critical Load uses public product-level PCFs as benchmark checks, not as a substitute for upstream semiconductor process research.
Embodied carbon becomes decision-useful only after a compute denominator is attached.
In the existing public reference comparison, embodied compute intensity falls from 0.66 to 0.50 gCO₂e/exaflop — about 24% — illustrating why product carbon alone is not enough for hardware comparison.
Utilization, lifetime and delivered work are first-class parameters.
Semiconductor manufacturing is the upstream component of the broader compute lifecycle model.
CL-SCM ends at an embodied compute intensity. CL-R02 then combines that upstream result with hardware integration, facility, electricity, cooling, shared services and replacement/end-of-life to produce full lifecycle compute carbon.
The semiconductor result never substitutes for the rest of the lifecycle; it feeds it.