Burn-In is the application of thermal and electrical stress for the purposes of inducing the failure of "marginal (microelectronic) devices, those with inherent defects or defects resulting from manufacturing aberrations which cause time and stress dependant failures.
Reliability of semiconductors
To evaluate the reliability of an electronic system, reliability Information on the components used in that system is important. Failure rates are often used as an index for reliability. A failure rate indicates how often a failure occurs per unit time, and failure-rate values generally change overtime as shown below
Early failure stage:
During this stage, failures occur at a high rate following
the initial operation of semiconductor devices. They
occur very soon and thus the failure rate declines rapidly
over time. This Is because the potential' failures that
could not be removed through a selective process are
included and surface in a short time if a stress such
as temperature or voltage is applied after use of the
device is started. In the case of semiconductors, these
failures are usually due to defects that could not be
removed during production, such an micro dust collecting
on the wafer, or to material defects.
Random failure stage:
When early failures are eliminated, the failure rate drops
to an extremely low value. However, there is always the
possibility of a potential failure accidentally occurring
after a long time. Consequently the failure rate never
decreases to zero. It is almost constant because failures
occur sporadically,
Wear-out failure stage:
During this stage, failures occur with increasing frequency
over time and are caused by age-related wear and fatigue.
In the case of a semiconductor device, electronic migration
or oxide film destruction (TDDB) may occur.
