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Quality Assurance
- Failure Analysis
RFMD® has a
fully-equipped Failure Analysis Lab onsite in Greensboro North Carolina as well as a Failure Analysis support lab in Beijing, China. Full nondestructive
and destructive physical analysis can be performed on all RFMD
devices. Our highly trained staff of engineers and technicians
perform testing for defect isolation, construction analysis,
and evaluations of new material sets and device types. A careful
methodology is used when performing failure analysis. Often
the defect site can be viewed optically, and root cause determination
can begin. If the defect cannot be viewed optically, Scanning Electron Microscopy (SEM) inspection, Photo Emission Microscopy (PEM) inspection, Fixed Ion Beam (FIB), Reactive Ion Etch (RIE), parallel polishing or other appropriate
approaches, are used to isolate the failure site. All failure
analysis jobs are tracked via QCS - RFMD’s software tracking
system. QCS is a kanban type system that tracks move-ins and
move-outs from each work center. This system allows a structured
approach for tracking, data collection, data analysis, cycle
time monitoring, and capacity analysis.
Accelerated Life Testing Methodology
Accelerated life testing (with
regard to semiconductor device reliability) involves applying
heat and electrical bias to the devices under test in order
to accelerate their time to failure. Once “accelerated”
failure data are obtained, statistical analysis is required
to estimate what the failure time would be for those devices
under normal use conditions. There are several important considerations
when designing an accelerated life test:
› Selecting a representative device,
› Sampling procedures,
› Thermal stress parameters,
› Electrical stress parameters,
› Definition of failure, and
› Degradation mechanisms.
The purpose of performing accelerated
life tests is to either estimate the wearout parameters of
the devices under test (as measured by 3-temperature life
tests), or identify unexpected failure modes (as measured
by operating life tests). From 3-temperature life test data,
lognormal sigma, median time to failure (MTTF), and activation
energy can be calculated (assuming a sufficiently high failure
rate). From operating life test data, it can be determined
whether a product can be qualified by similarity. Using data
from both types of life tests, a FIT calculation can be performed.
Additional information regarding life test methodology is
available
on request.
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Introduction