Liquid Crystal & FMI
Liquid crystal (LX) and Fluorescent Microthermal Imaging
(FMI) are efficient optical analysis techniques used
to detect and localize certain integrated circuit (IC)
failures. They are non-invasive techniques performed
from either the front or back of devices.
Leakage current in semiconductor devices is likely
to cause local heating along the current path. By coating
the device surface with a material sensitive to temperature
changes, one can detect the location of the hot spot.
Liquid crystals change phase at a given temperature.
By bringing the device very close to this transition
temperature with a hot chuck, one can detect very small
local heating.
FMI relies on the temperature dependence of the fluorescent
yield of an europium compound. It is harder to use
than liquid crystal but it can give very quantitative
results.
LX and FMI are powerful early-stage failure analysis
techniques since they localize failures non-invasively
such as:
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