EOS/ESD Failures: Dielectric Punchthrough; Metal Burn-out; Junction Damage

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 I_e²R, where I_e 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 I_eV_BD, where I_e is the EOS or ESD current and V_BD 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.

See also: What is ESD?; What is EOS?; Latch-up; Die Failures

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