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wafers are grown using the czochkralski process....
where a seed crystal is used to grow a single large ingot of Si
about 20 cm in dia and even 1m long
hi,
in czochkralski process we can grow crystal of any shape...It actually depends on the pure silicon seed crystal we dip into the melt...it we dip cylindrical seed crystal we get cylindrical ingot...if we dip rectangular seed crystal we get...rectangular bar of crystal...
now commin to ur question about the circularity of wafers...Its simple that for a given crystal shape...circular shape has the easiest steps for processin like..polishing crystal, ingot slicing and others...once the wafers are made..they can be of any shape...dependin upon their usage...i hope this has helped u!!!
since the wafers go thru a lot of processing and com ein caontact with quartz boats,plastic carriers,dump transfers etc
they are prone to damage at the edges....a rectangular wafer is bound to distribute this stress unevenly and may cause the wafer to break
so its almost always a circular wafer to reduce stress and breakage....
as long as it is planar lapping,polishing etc wont fepend much on circular/rectangular
are yaar abishek,
ur basically going away from ur first statement...and telling again the same thing which i have told...u might have not noticed that i have written "polishing crystal, ingot slicing and other processes"...
commin to wafer breakage...poor wafer is just some hundred microns thick...it can maximum have damage to its lattice...how can it break???
damage to the lattice or crystal structure is as good as broken....silicon in fab labs needs to be perfect.....and polishing ,lapping doesnt depend on shape of wafer .....
rounded edge is the best....
give me some links on how rectangular wafers are fabbed....
maybe u r right but i havent sen any so far................
silicon ingots are grown from a single crystal material by a process called CZOCHRALSKI METHOD. in this a seed crystal is lowered into a molten material and a constant rotation is carried out. on the seed crystal silicon ingots are formed, which happened to be in cylindrical shape.The shape of the ingot is determined by a combination of the tendency of the cross section to assume a polygonal shape due to the crystal structure and influence of surface tension which encourages a circular cross section.
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