Chlorosilanes Purification System / “Boron Adsorber”
TCS impurities for example Boron result in inferior polysilicon quality and may even lead to unscheduled downtime. Our Chlorosilanes Purification System incorporates design improvements to increase the robustness and reliability of the existing TCS purification operation in combination with distillation plants. The simplified principle of this purification unit and its results are shown as follows:
The Chlorosilanes Purification System removes dopant impurities e.g. boron from TCS – prior to use as feed gas to CVD reactors during the process of generating electronic grade polysilicon. For example if the boron content in chlorosilanes is up to 1000 ppb then after the chlorosilanes purification by CPS the boron content in silicon is less than 10 ppt. These results by experience show the high efficiency of this technology.
The Chlorosilanes Purification System consists of two adsorber reactors. These two adsorber reactors are operated alternately: that means one adsorber reactor is in operation and the other one is inactive till the reactor in operation is exhausted.
The active adsorber reactor is fed with chlorosilanes from feed tank at ambient temperature. The pressure of the process is adapted to the technological conditions at the existing plant. The impurities are converted during the purification into high-boiling compounds and then removed in the next distillation column and collected in the column sump.
The inactive adsorber reactor is purged with nitrogen at ambient temperature, filled manually with fresh adsorbent material and is ready for the next campaign. The procedure of nitrogen purging for commissioning and maintenance is fully automated. The exchange of the special adsorber material has to be done manually.
Implementation of CPS into an existing plant (example)
Chlorosilanes Purification System can be easily implemented in an existing plant. The place of implementation depends on existing distillation system and target purification level.
Advantages of the CPS Plant:
- Contaminant-free System
- Sophisticated technology
- Successfully used for a long time
- Robust design and simple to handle
- Very easy to implement in existing systems
- Reliable performance at a large range of process parameters (e.g. boron content)
- Simple to scale
- Low operating and power costs
- Modular system capacity: 12,5/25/50 t/h.