Quartzite Mining to Polysilicon

Every silicon wafer starts as quartzite - a high-purity form of silicon dioxide (SiO2) mined from surface deposits worldwide. Quartzite is reduced to metallurgical-grade silicon (MG-Si) in electric arc furnaces, then chemically purified through either the Siemens process or fluidized bed reactor (FBR) technology to produce polysilicon feedstock for semiconductor and solar applications. The supply chain bifurcates at the polysilicon stage: semiconductor-grade production is dominated by Western producers, while solar-grade production is overwhelmingly Chinese.

Stage 1 - Quartzite Mining

High-purity quartzite deposits suitable for semiconductor-grade silicon must contain at least 99.5% SiO2 with tightly controlled trace element limits, particularly for boron, phosphorus, and metals that would carry through to the final polysilicon. Major quartzite-producing regions include the US (South Dakota, Texas, Minnesota, Wisconsin, Utah, Arizona, California), the UK, Canada, and Brazil. Norway's Drag deposit is among the world's highest-purity sources and feeds into European silicon metal production.

Stage 2 - Metallurgical-Grade Silicon (MG-Si)

Quartzite is smelted with carbon reducing agents -- coke, coal, and woodchips -- in submerged electric arc furnaces at temperatures above 1,800°C. The carbothermic reduction reaction (SiO2 + 2C → Si + 2CO2) yields metallurgical-grade silicon at approximately 98-99% purity. MG-Si is the feedstock for both polysilicon production and a range of industrial applications including aluminum alloys and silicone chemistry. Major MG-Si producing countries include China (~65% global share), Norway, Brazil, and the US. China's Yunnan and Sichuan provinces, with access to low-cost hydroelectric power, dominate MG-Si output.

Stage 3 - Polysilicon: Siemens Process vs FBR

MG-Si is chemically purified to polysilicon through one of two primary routes. The Siemens process accounts for over 95% of global polysilicon production by volume. The fluidized bed reactor (FBR) process is a lower-energy alternative gaining share in solar-grade production.

The Siemens process chemistry proceeds in two steps: MG-Si reacts with hydrogen chloride (Si + 3HCl → SiHCl3 + H2) to produce trichlorosilane, which is then purified by distillation and decomposed by CVD at ~1,100°C over silicon seed filaments for 200-300 hours until rods reach 15-20 cm diameter. Silicon tetrachloride (SiCl4) byproduct is recycled via hydrochlorination (SiCl4 + H2 + Si → SiHCl3) to recover TCS, which is critical for process economics and waste reduction.

Polysilicon Purity Grades

Polysilicon Producer Landscape

Geographic Concentration & Supply Chain Risk

The polysilicon supply chain is split by grade. For solar-grade polysilicon, China holds approximately 85% of global production capacity -- led by Tongwei, GCL TECH, Daqo, and Xinte. The top four Chinese producers alone accounted for roughly 65% of global market share in 2024. Xinjiang province is a significant production center, raising forced labor compliance concerns for Western buyers under the US Uyghur Forced Labor Prevention Act (UFLPA).

For semiconductor-grade polysilicon (10N-11N), Western producers remain dominant -- Wacker, Hemlock, Tokuyama, and REC Silicon collectively supply the majority of electronic-grade feedstock to crystal growers globally. China has not yet achieved significant electronic-grade polysilicon production at scale, and China's export controls on 6N-9N polysilicon and crystal-growth equipment do not directly constrain Western semiconductor-grade supply chains in the near term. The longer-term risk is China's intent to move up the purity ladder as part of semiconductor self-sufficiency policy.

Supply Chain Outlook

Western semiconductor-grade polysilicon supply is structurally secure in the near term, supported by Wacker, Hemlock, and Tokuyama's established plants and US policy incentives under the CHIPS Act and IRA. The vulnerability is in solar-grade supply for any Western manufacturer attempting to build a non-Chinese solar module supply chain -- a multi-year project with no near-term substitute for Chinese production volumes.

FBR technology is the most significant process development to watch: GCL TECH's demonstration that granular silicon can meet monocrystalline purity requirements at 40% lower energy consumption narrows the cost advantage of incumbents and positions FBR as the likely dominant process for solar-grade production by 2030. China's 2025 export controls on CVD and crystal-growth equipment represent a new chokepoint targeting the transfer of polysilicon process technology to non-Chinese producers.

Cross-Network: ElectronsX Demand Side

Solar-grade polysilicon demand is visible on the EX side as PV supply chain coverage. The pages below represent the demand-side signal that drives the SX supply chain dynamics described on this page.

EX: Solar Energy & PV Supply Chain | EX: Upstream Materials | EX: Supply Chain Convergence Map

Related Coverage

Raw Materials Overview | Materials & IP Hub | Critical Elements & Geopolitics | Refined & Specialty Materials | Silicon Wafer Production Overview | Crystal Growing | Silicon Ingots | China Bifurcation Spotlight | Bottleneck Atlas