Specifications

17
Dec. 20
Mitsubishi IPM-series Application Note
7-5. Failure Analysis
Failure analysis is one of the sources of information used
in maintaining, and making improvements in standards of
quality and reliability. Failure analysis procedures are
performed on failed devices at all stages of their life cycle,
ranging from the development state to failure while in use.
Failure analysis procedures are generally divided into area
of external inspections, electrical testing, internal inspections,
and chip analysis. The flow chart for these procedures is
shown in Fig.7.8, while Table 7.4 lists the nature of the tests.
The results of the various reliability and failure analysis tests
reveal the failure mode and mechanism, and this information
is fed back to the process technology and manufacturing
personnel so that they can take the appropriate measures to
improve the final product.
7-6. Derating and Reliability Projections
The degree of reliability for a semiconductor device varies
considerably depending on usage and environmental
conditions. Design standards, the method of manufacture,
and quality-control procedures also play a role in
establishing the intrinsic reliability for semiconductors.
Correlating device derating with reliability is also not an easy
task. Please refer to Mitsubishi device reliability handbook
for more information in detail.
http://www.semicon.melco.co.jp/confidence/index.html
Fig.7.8 Failure Analysis Procedure
Table7.4. Failure analysis inspections and equipment used
Category Inspection Items Equipment
External Inspection ٤ Condition of leads, plating, soldering, and welds
٤ Packaging defect
٤ Solderability
Stereoscopic microscope
Metallurgy microscope
Electrical Characteristics
Testing
٤ Static electrical characteristics, voltage and temperature
margins, checking for broken bond wire, wire
٤ Internal wiring
Oscilloscope
Curve tracer
Characteristics tester
X-ray equipment
Internal Inspection ٤ Device removed from package and chip surface observed
for defects
٤ Electrical characteristic check using microprobe
٤ Check for hot spots and other abnormalities
Chip Analysis ٤ Analysis techniques used to supplement chip surface
observation in internal inspection
٤ Cross-section of chip observed for analyzing oxide film,
diffusion and metallizing
Metallurgy microscope
microprobe
Scanning electron microscope
X-ray micro-analyzer
Infrared micro-scanner
Spectrum analyzer
7-7. Conclusion
The above is a simple introduction to general ideas about reliability, reliability tests, and derating and forcasting of reliability of
high power semiconductor, which are semiconductor devices for electric power. As explained above, it is vital for higher
reliability in practical use of semiconductor devices to understand their features and select those, which are suitable for
equipment and sets. It is also important to design semiconductor devices with some allowance to improve reliability, fully taking
their derating into consideration in relation to operating and environmental conditions.
Other essential things to do are to “debug” equipment and sets, and to analyze data obtained in fabrication process and
actual operation to feed them back to design and fabrication stages. To improve the reliability by design of high power
semiconductor requires considerations on many issues as described above. Utilize the semiconductor devices successfully
with the utmost care with comprehensive understanding of their quality, reliability, and economy.
Reliability