China clears its own quartz, but not for the part that counts

Semiconductor supply chains are discussed at the level of the chip and constrained at the level of the mineral. The materials that limit production are rarely the ones that appear in an export control list, because they are too mundane to look strategic until they are missing.

Jiangsu Pacific Quartz, a Chinese producer of high-purity quartz, already supplies its material to leading domestic and overseas makers of chipmaking tools, including Lam Research and Tokyo Electron. Tom's Hardware reported that its components have more recently passed certification by a domestic DRAM manufacturer.

The company has supplied Lam Research and Tokyo Electron with consumables since around 2019 and 2020 — diffusion tubes, wafer boats, quartz ingots, plates and tubes. Quartz for process equipment is typically 4N5 to 5N purity, roughly 99.995% to 99.999% silicon dioxide.

That is a genuine achievement and a limited one, and the limit sits at a specific point in the process. These components are used after the silicon wafer has been made. They are the furniture of the fab, not the vessel the silicon is grown in.

The ingot from which wafers are cut is grown in a crucible made of high-purity fused quartz, typically above 99.999% silicon dioxide, with far tighter limits on individual critical contaminants. It is the same material by name and a different material by specification.

A crucible sits in contact with molten silicon for the length of a growth run. Any contaminant it contributes goes into the ingot, and from the ingot into every wafer cut from it, which is why the tolerance is set where it is.

Quartz of that grade is available in volume from two operators — Sibelco and The Quartz Corp — both working in Spruce Pine, North Carolina, with Russian Quartz LLC producing modest quantities. That is the whole list.

A single town supplying the input for global wafer production is the kind of concentration that would be flagged immediately in any other industry. It persists because the deposit is geologically unusual and because substituting it requires matching a contaminant profile, not just a purity percentage.

The analyst TP Huang, who hosts the China Tech Talk podcast, believes the DRAM maker that granted certification is CXMT. That is an inference rather than a disclosure, and it is worth reading as one.

The strategic reading is straightforward even so. China has reduced its dependence on imported consumables for the equipment layer, which removes a class of leverage that export controls could otherwise reach.

What it has not done is touch the crucible, and the crucible is the input with no second source. A supply chain is diversified only to the level of its least substitutable component, and for wafer production that component is still a mineral from one place.