Polysilicon: Production route
Hot rods versus floating granules: the race to cut power
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.All routes start from metallurgical silicon and end with silicon above nine nines. The modified Siemens process, which grows rods from trichlorosilane in bell-jar reactors, makes about three-quarters of supply and all semiconductor grade. Fluidised-bed reactors (FBR) grow granules from silane or TCS with far less power and now make about a quarter of China's output, led by GCL. Upgraded metallurgical silicon is a cheaper, lower-purity route that faded. Semiconductor grade is a Siemens product with extra purification.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Modified Siemens process (rod polysilicon) | about 76% of China's output (H1 2025, remainder after 24% granular) and nearly all output outside China | about 1.1 t silicon metal (indicative), 48-55 MWh electricity, about 8 t water and 2.3 t steam per t (industry average, 2025) | Tongwei over 900 kt, Xinte 300 kt, Daqo 350 kt capacity (2025) | not published | silicon tetrachloride (recycled), HCl | leading rod makers RMB 30-35/kg cash; Xinte RMB 26/kg; Daqo cash $4.46/kg (Q4 2025) |
| Fluidised-bed reactor (granular polysilicon) | about 24% of China's output (H1 2025), up from under 10% five years earlier; forecast 35% by 2030 | about 11-20 MWh electricity, 3-5 t water, 1.2-1.8 t steam per t | GCL 480 kt in Xuzhou, Leshan and Baotou; produced 269 kt in 2024 | over 97% total yield (H1 2025) | silicon fines, hydrogen | GCL cash cost RMB 25.31/kg (Q2 2025), the lowest reported |
| Semiconductor-grade polysilicon | about 3% by volume (derived); Wacker about 35% of the market | as Siemens, with more purification (indicative) | Wacker 20 kt; Hemlock (Michigan) about 20 kt (2025) | not published | off-spec material sold as solar grade | several times solar grade (indicative) |
| Upgraded metallurgical-grade silicon (UMG) | negligible today (indicative) | silicon metal and power (indicative) | small | not published | slag | low (indicative) |
How each route works
Modified Siemens process (rod polysilicon)Ultra-pure TCS and hydrogen flow into bell-jar reactors where electrically heated silicon rods at about 1,100 C grow as silicon deposits on them over days. Off-gases are recovered and silicon tetrachloride is converted back to TCS. Rods are broken into chunks.
Proven, all purities; energy-intensive, leaders reach under 40 kWh/kg with a ceiling near 35.
China Polysilicon 2026 report Fluidised-bed reactor (granular polysilicon)Small silicon seed particles are suspended in silane (or TCS) and hydrogen in a heated reactor; silicon deposits on them as free-flowing granules. Granules suit continuous Czochralski recharging. GCL switched fully to FBR and exited Siemens in 2025.
About a third to a half the power of Siemens and lowest cost; purity concerns largely solved (over 96% meets n-type grade); REC Silicon exited FBR in late 2024.
China Polysilicon 2026 report; PV Tech (Apr 2025) Semiconductor-grade polysiliconA Siemens process with tighter distillation, cleaner reactors and etching to reach 10-11 nines and very low surface metals. Sold to wafer makers such as Shin-Etsu, SUMCO, Siltronic and GlobalWafers.
High margin, few qualified suppliers outside China; tiny volume.
China Polysilicon 2026 report Upgraded metallurgical-grade silicon (UMG)Silicon metal is refined directly by slag treatment, directional solidification and vacuum refining, skipping the chlorosilane step.
Cheap and low energy; purity too low for modern n-type cells.
Indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.