EOS/ESD
Failures and their Attributes (Page 2 of 2)
Conductor / Resistor
Fusing (continued from Page 1)
The high power generated
during the EOS/ESD event is equal to Ie2R,
where Ie is the EOS/ESD current and R is the resistance of
the metal or resistor line. If this power produces enough
localized heat to bring the EOS/ESD site's temperature above the melting
temperature of the conductor or resistor, then the fusing, meltdown, or
burn-out of the conductor/resistor occurs.
Figure 2. Photo of a fused metal
line
Conductor/resistor fusing is
often just a secondary mechanism of another EOS/ESD failure, such as a
dielectric or junction damage that has created a short circuit where
large currents can flow to subsequently cause the conductor/resistor
line to melt down or burn out.
Junction Damage or Burn-out
Junction
damage or burn-out refers to the destruction of a p-n junction due to
joule-heating caused by the EOS/ESD event, resulting either in the
junction's being open- or short-circuited. This type of damage also
involves joule heating, and is more prevalent in bipolar devices.
Hot spots arise in the junction when it undergoes joule heating,
especially in parts where there are non-homogeneities and geometrical
shifts. Silicon where these hot spots arise become intrinsic in
nature, whereby its resistivity goes down as temperature goes up. The
reduction in resistivity further sinks more current, increasing the
temperature further.
This cycle continues,
resulting in a thermal runaway that eventually melts the silicon with
the hot spot when its temperature exceeds the melting point of silicon.
The silicon meltdown often creates a short across the junction, although
high-energy transient EOS/ESD events can also result in open junctions.
Figure 3. Photo of a junction short
The power that heats up the
junction is equal to IeVBD,
where Ie
is the EOS or ESD current and VBD is the breakdown voltage of
the junction.
Reverse-biased junctions are more vulnerable to EOS/ESD damage than
forward-biased ones because its higher breakdown voltage results in a
higher power dissipation in the depletion layer, requiring a smaller
current to cause the damage.
<Back to Page 1>
See also:
What is ESD?;
What is EOS?;
Latch-up;
Die Failures
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