Polysilicon Production

Siemens · FBR · electricity intensity

Polysilicon is made by heating silicon with electricity until a gas deposits silicon of 9N to 11N purity onto it. Electricity is the largest cash cost, and that is why the industry moved to China's cheapest power.

Top: the process chain from quartz to metallurgical-grade silicon in an arc furnace, to trichlorosilane via reaction with hydrogen chloride, to polysilicon by the Siemens or fluidized bed process, to a Czochralski ingot and a diamond-wire-sawn wafer. Below: electricity per kilogram of silicon - metallurgical-grade silicon in an arc furnace about 11 to 13 kWh; a modern Siemens plant about 40 to 60 kWh including the trichlorosilane loop; fluidized bed granular silicon about 15 to 20 kWh. FROM QUARTZ TO WAFER: EVERY STEP RUNS ON ELECTRICITY Quartz MG-Si TCS Poly Ingot Wafer ELECTRICITY PER KG OF SILICON, KWH MG-Si, arc furnace ~11-13 Siemens, modern plant ~40-60 FBR granular ~15-20 Siemens figures include the trichlorosilane loop; FBR figure is deposition-led.
Siemens rod temperature
~1,100°C
FBR electricity
~one-third of Siemens
Solar grade
9N+
Electronic grade
11N
Hub
Industry

Finding

Polysilicon is an electrified process by design, and electricity per kilogram decides who can make it profitably

A modern Siemens plant uses roughly 40 to 60 kWh of electricity per kilogram, down from more than 100 kWh in the 2000s. Most of the deposition energy is lost as radiation from rods at about 1,100°C to the water-cooled reactor wall. Fluidized bed reactors grow granules at lower temperature in a continuous process and use about one-third of the electricity.

At these intensities, power price sets the cost curve. The large Chinese plants sit on cheap coal power in Xinjiang and Inner Mongolia and on hydropower in Sichuan, Yunnan and Qinghai, and they bought the reactor, hydrogenation and distillation technology at scale. Tongwei, GCL Technology, Daqo, Xinte and East Hope now make most of the world's supply; plants, market share and trade rules are on Polysilicon Plants and the PV Supply Chain.

The Siemens process dominates because it reaches electronic grade (11N) and because the rod-based plants are proven at 100,000-ton scale. FBR, pioneered by REC Silicon on silane and scaled by GCL Technology as granular silicon, trades some purity and surface contamination control for a continuous process and lower electricity. Granular silicon is now widely used in n-type solar ingots, usually blended with rod silicon in the Czochralski crucible.

Siemens and FBR

Siemens process and fluidized bed compared

Siemens and FBR processes
AttributeSiemens (CVD rod)Fluidized bed (FBR)
Feed gasTrichlorosilane (TCS) and hydrogenSilane (SiH4) or TCS and hydrogen
ReactorBell-jar reactor; current heats slim silicon rodsVertical bed of silicon seed particles fluidized by gas
Deposition temperature~1,100°C at the rod surface~650-800°C for silane
OperationBatch: rods grow for days, then the reactor is openedContinuous: granules drawn off while running
ProductRods, crushed into chunksGranules, ready to feed
Electricity~40-60 kWh/kg plant-wide~one-third of Siemens
PuritySolar grade and electronic grade (11N)Solar grade; electronic grade not proven at scale
ProducersTongwei, Daqo, Xinte, East Hope, Wacker, Hemlock, OCIGCL Technology (granular), REC Silicon (Moses Lake, halted)

Process chain

The electrified process chain

Every step from raw quartz to finished polysilicon is driven by electricity.

Electrified polysilicon process chain
StepEquipmentEnergy formNote
Metallurgical siliconSubmerged arc furnace reducing quartz with carbonElectric arc~98-99% silicon; also feeds aluminum alloys and silicones
TCS synthesis and hydrogenationFluidized bed reactor with hydrogen chloride; hydrogenation of silicon tetrachlorideElectric heating, compressorsClosed loop recycles byproduct silicon tetrachloride
PurificationDistillation columnsElectric reboilers, pumpsRemoves boron, phosphorus and metals to parts per billion
DepositionSiemens reactors or FBRDirect resistive heating of rods; heated fluidized bedThe dominant electricity load
FinishingCrushing, sorting, etching, packingElectric drivesContamination control matters more than energy

Downstream

Crystal growth and wafering

After polysilicon, the chain stays electric.

Downstream crystal growth and wafering
StepEquipmentNote
Czochralski growthPullers with graphite resistance heaters melting silicon in quartz cruciblesMakes nearly all solar ingots and most chip wafers; LONGi, TCL Zhonghuan dominate solar ingots
Float zone growthRF induction coil melting a zone along a rodHighest-purity wafers for power devices; small volume
WaferingDiamond wire sawsThin wires cut kerf loss; solar wafers now around 130 microns thick
Wafer finishingEtching and texturing for solar; lapping, polishing and cleaning for chip wafersChip wafers go to SUMCO, Shin-Etsu, GlobalWafers, Siltronic and SK Siltron

Sources

Sources and scope

Scope
Polysilicon Production
Sources
Bernreuter Research; producer annual reports (Wacker, GCL Technology, Tongwei); IEA solar PV supply chain report
Updated
October 2026