Zone Refining Unit |
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Zone melting is a family of techniques, variation of which are applied in semiconductor industry viz. Zone refining for purification of semiconductor elements, zone leveling for uniform addition of dopants to the semiconductors and Bridgman’s or float zone technique for crystal growth. It is being widely used in the semiconductor industry for refining of germanium and silicon to purity levels of 9N and above (i.e. >=99.9999999%). An automatic zone refining unit has been indigenously designed and developed using indigenous available components. The unit is capable of variable forward and reverse traverse. The unit is mounted with a digital man- machine interface (MMI) for easy indication/ operation of parameters such as temperature, speeds, count, etc. Both resistance heaters and induction heating coils can be mounted with little customization depending on the requirement of the process. With use of induction heating the time required for achieving the melting point is faster as compared to a resistance heater. Another advantage is minimized heat loss as compared to the conventional resistance heater which involves heat transfer from the heating coil to the actual charge through various barriers like ambient air, the container wall and inert gas used or vacuum through convection. An induction heater heats only the charge / material or the container carrying the charge. A wide range of temperature (RT to 2800°C) not achievable by conventional resistance heater (RT to 800°C) is achievable. The machine is capable of handling 678 cm3 (maximum) (calculated considering a tube of 6.5cm diameter with 60 cm working length, and suitable materials container usually a semicircular boat) of material in a single batch. For e.g. purification of 5 kg (approx) of germanium (99.99%) having density of 7.435 gm/cm3 in a single batch will yield 3.5 kg of pure material (99.9999%) in 15 passes. The duration of one batch may vary depending on number of passes, speed selected (depends on cross section of charge) and desired purity level. The end portions of the processed material where the concentration of impurity builds up while purifying the central portion can be further reprocessed. Application area
Salient Features
Specifications The zone refining unit is fully fabricated with SS304 grade stainless steel and houses the following components
Infrastructural facilities/equipment for a typical zone refining setup
Manpower for operation
For details contact : BHABHA ATOMIC RESEARCH CENTRE, TROMBAY, MUMBAI - 400 085 Fax : 091-022-25505151 Email : technology@barc.gov.in |