Float-zone silicon

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Float-zone silicon is a high-purity alternative to silicon grown by the Czochralski process. The concentrations of impurities, such as carbon and oxygen are extremely low. Impurities such as nitrogen, which are thought to bring about an improvement in mechanical strength of the wafers, are now being intentionally added during the growth stages.

Float-zone silicon is typically used for power devices and detector applications. The dimensions of float-zone wafers are generally less than 150mm due to the surface tension limitations during growth. An RF field is used to produce a local melted zone on the polycrystalline rod that is dragged from one end to the other. seed crystal is used at one end in order to start the growth. This molten zone carries the impurities away with it and hence reduces impurity concentration.