CVD-Siemens Monosilane Reactor Process with Complete Utilization of Feed Gases and Total Recycle
AssigneeSavi Research, Inc.
InventorsVithal Revankar, Sanjeev Lahoti
Life of this patent
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Abstract
The present invention relates to a monosilane (SiH4) and hydrogen recycle process/system for chemical vapor deposition (CVD) of monosilane-based CVD polysilicon. In particular, the present invention relates to the substantially complete silane utilization and unconverted (from the reactor) contamination-free complete silane and hydrogen recycle process of producing polysilicon chunk materials via the decomposition of gaseous silane precursors.
Claims12
An improved CVD-Siemens reactor system, said improvement comprising a monosilane and hydrogen recovery and recycle system, wherein:
- i) hot reactor gas, comprising unreacted monosilane, hydrogen and impurities, from a CVD Siemens reactor is cooled and purified by filtration, absorption and fractional distillation to produce purified monosilane, a separate hydrogen stream and separate impurities;
- ii) said separate hydrogen stream is further cooled and purified to produce a cooled, purified hydrogen stream;
- iii) wherein a countercurrent heat exchanger between said cooled, purified hydrogen stream and said hot reactor gas cools the hot reactor gas from the CVD Siemens reactor;
- iv) said purified monosilane is compressed with a first compressor and fed back into said CVD-Siemens reactor;
- v) wherein said purified hydrogen stream is compressed with a second compressor and fed back into said CVD reactor after being used in said countercurrent heat exchanger.
A monosilane and hydrogen recycle system for a CVD Siemens reactor, wherein:
- a) hot reactor gas from a CVD Siemens reactor is cooled and filtered, said hot reactor gas comprising unreacted monosilane, hydrogen and impurities;
- b) wherein hydrogen is removed one or more convenient points, purified and further cooled to create a cooled purified hydrogen stream;
- c) said hot reactor gas from step a) is further cooled to −170° C. to −180° C. to condense the monosilane and impurities;
- d) wherein said condensed silane and impurities are passed through a degasser column to remove the light weight impurities and then through a heavy component purification column to remove heavy weight impurities and produce monosilane vapor;
- e) wherein said monosilane vapor is passed through absorber columns containing 4 Å molecular sieves to remove ethylene;
- f) wherein monosilane emerging from said adsorption columns is optionally filtered, and passed to a finishing column to distill ethylsilane away from purified monosilane silane;
- g) wherein purified monosilane is optionally stored as liquid and then heated before use;
- h) wherein a countercurrent heat exchanger between said cooled, purified hydrogen stream and said hot reactor gas cools the hot reactor gas from the CVD Siemens reactor;
- i) said purified monosilane is optionally compressed with a first compressor and fed back into said CVD-Siemens reactor;
- j) wherein said purified hydrogen stream is optionally compressed with a second compressor and fed back into said CVD reactor after being used in said countercurrent heat exchanger.
Dependencies are inferred from the claim text.