[sdiy] Static Damage to ICs

[The Old Crow]

On Wed, 13 Mar 2002, Rhen, Kris wrote:

> Have a question.  What is the result of static damage to an IC?  I don't
> think I have any, just a purely informative question.  If I shuffle
> across a carpet and 'zap', say, a TL072 or LM13700 or the like, what
> happens at that electronic level?  What is the mechanism of damage?  
> How does the damage manifest itself when the IC is used?  Curious...  

  'Classic' static damage generally happens to unprotected parts that
incorporate MOS transistors.  What happens is the static spark blows out
the insulated gate region of the transistor, leaving a 'pit' in the
semiconductor material.  I think they used to call this pitting action
"punchthrough."  It is very like a capacitor that is operating above its
rated working voltage: charge on the device blasts through the insulating
dielectric, ruining the cap. The inputs of a xMOS (CMOS/PMOS/NMOS/etc)
part are all essentially MOS transistor gates.

  Modern parts have 'parasitic' diodes fabricated as part of the chip that 
bleed off voltage transients before they encounter the gate region of such 
transistors.  While this is generally effective, it is not foolproof, 
which is why ESD-sensitive device handling precautions still exist.

  One side-effect of these precautions is thqt people tend to get in the 
habit of using ESD precautions on all parts, not just MOS stuff.  Which is 
a good thing.

Crow
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