Shorted FET

Electrical continuity tests suggested that the gate was shorted to the drain and the source was intact. SEM analysis revealed a suspected damage site at the end of a gate finger (see below).

shorted-fet-1

An elemental dot map at the breakdown site showed some slight disturbance of the aluminum metallization at the site.

shorted-fet-2

Voltage contrast imaging confirmed that the suspect damage site was indeed the location of the short.

shorted-fet-3

These results suggested that the device failed due to a voltage transient on the gate signal. The small dimensions of the damage site suggest that the transient was very fast (rough estimate 1E-9 to 1E-6 seconds). The damage could potentially be related to an ESD event. It could also potentially be caused by accumulated damage at the tips of the gate contacts due to excessive turn-on or turn-off dV/dt.

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