Purified graphite: polysilicon manufacturing

graphite heater Mersen
graphite electrode Siemens process Mersen
graphite heater fluidized bed reactor Mersen
graphite cylinder STC converter Mersen

High purity graphite equipment in silicon production process

The polysilicon industry must meet new requirements and reduce its costs.

Mersen's comprehensive offer aims to attain these goals.

  • Guarantee high-purity polysilicon 9N as a benchmark, and reach 10N purity in the near future,
  • Reduce maintenance costs through the use of sustainable equipment,
  • Reduce the process' energy costs.
     

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    Expendables and equipment for polysilicon manufacturing

    We propose expendables and equipment dedicated to the polysilicon manufacturing industry:

    • Ultra-pure graphite electrodes
    • Ultra-pure and composite graphite heaters
    • Large dimension, ultra-pure composite and graphite cylinders
    • Purified rigid carbon and flexible felt insulation.

    The Siemens process deposition reactor

    The quartz reactor chamber contains very thin U-shaped silicon rods mounted on the purified graphite electrodes. The silicon rods heat up due to the electrical current supplied by the graphite electrodes. Gaseous trichlorosilane SiHCl3 (TCS) penetrates the deposition chamber at a high temperature and decomposes, depositing pure silicon on the hot rods. When the deposition process is completed, the silicon rods are removed from the reactor and shattered to recover the polysilicon.

    Mersen supplies ultra-pure graphite electrodes, used as expendables for this process.

    Fluidised bed reactor

    Inside a reactor's quartz chamber, silicon micro-grains are discharged into an opposite flow of silane. The reactor and the gas inlet are heated by a graphite heater and insulated by rigid felt. The silane breaks down into silicon and expands the micro-grains. The pure silicon is recovered in bead form.

    Converter: STC recycling reactor (SiCl4) by high temperature hydrogenation

    During deposition processes, a significant part of the gas is transformed into STC (SiCl4 ). To increase the yield, this STC must be recycled as TCS in a high temperature hydrogenation reactor at 1,500 C.

    Mersen is a recognised leader in this marketowing to its particularly competitive and comprehensive offer:

    • Ultra-pure graphite cylinder up to 1.5 m in diameter.
    • Special coatings to improve service life.
    • Thermal insulation made of high-performance purified rigid carbon.
    • Carbon/Carbon composite heater and plate.