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why aluminium is used instead of copper in ic fabrication

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rakesh1234

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can anybody tell me why aluminimium is used until now in ic fabrication for metal layers insted of copper in spite copper has low resistance and now they have move back toward to copper
 

Re: why aluminium is used instead of copper in ic fabricatio

hello rakesh


your ans is that cu has less res than al now a days cu introduce in fabs b'coz to kept delay low now a days the capacitance becomes increases so we have to reduces the resistance.

ok.
 

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    rakesh1234

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the idea is that Cu diffuse into Si and oxide , so u need some barrier to use Cu, also Cu is easily oxidized also u have to use additive technique to use Cu interconnects like single or double damascence "cause u cannot RIE the Cu"

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however i think modern echnology tends to use Cu and try to use some techniques to overcome the difficulties in using it
 

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Re: why aluminium is used instead of copper in ic fabricatio

copper diffuses into Si, so you have to put a barrier layer to prevent that (usually TiN)
and after polishing for the surface of copper, another layer is put to totally encapsulate the copper
this technique is called Damascene (taken from the name of the city of damas, the capital of Syria, since they do many metal carvings there)

for aluminium,it also has the diffusion problem for temperatures more than 450° (spiking) and another problem:electromigration
for the first problem, Al can be replaced by AlSi
for the second problem, AlCu can be used and to prevent diffusion then a barrier layer of TiN is used
 

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Re: why aluminium is used instead of copper in ic fabricatio

Electro migration is the major disadvantage of Aluminum

yash
 

what is the differance between lattice diffusion and grain boundary diffusion in metals, while undergoing electromigration.another question,can electromigration take place in semiconductorsb also?
 

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