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ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUES. Walt Willing Mike Cascio Jonathan Fleisher. Agenda. Importance of effective Failure Analysis Basic Failure Analysis Process Failure Analysis Techniques Electrical Testing / Characterization Non-Invasive Tests Invasive Tests - PowerPoint PPT Presentation
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ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUES
Walt WillingMike CascioJonathan Fleisher
2010 RAMS –Tutorial 11B – Cassady
Importance of effective Failure Analysis Basic Failure Analysis Process Failure Analysis Techniques
Electrical Testing / Characterization Non-Invasive Tests Invasive Tests
Suggestions for your own failure analysis capabilities Understanding Electronic Part Failure Mechanisms
Excerpts from the 1997 Alan O. Plait Award for Tutorial Excellence
Agenda
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2010 RAMS –Tutorial 11B – Cassady
Importance of Effective Failure Analysis
Effective root cause analysis helps assure proper corrective action can be implemented
When electronic parts fail, it’s important to understand why - the Root Cause Accurate root cause assessment important for High Reliability systems where failures
are very critical: Implantable medical devices Space satellite systems Deep well drilling systems
As well commercial high production products, where the cost of a single failure mode is replicated multiple times
Common term for process of root cause determination and applying corrective action FRACAS (Failure Reporting, Analysis and Corrective Action System)
Failure Analysis is the crucial “Analysis” part of the FRACAS process
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2010 RAMS –Tutorial 11B – Cassady
Failure Analysis - Caution“Preserve the Failure” / Prevent “RTOKs”
Failure Analysis has to be handled carefully Assure the failure mechanism is preserved, not “Lost” due to
Carelessness Bypassing important tests / measurements Performing destructive analyses in an incorrect sequence.
Example: Once wirebonds are removed, the part may not be able to be electrically tested
Many parts removed for failure analysis may “Re-Test OK” (RTOK) Possibly the wrong part was removed Part level testing performed did not properly capture the failure mode
Subtle parameter shifts, etc. Peculiar failure sensitivity (e.g. gain vs temperature) exists
Important to assure board level fault isolation / troubleshooting performed correctly
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2010 RAMS –Tutorial 11B – Cassady
Top Reasons for Component Failures (1 of 3)
1) Electrical Overstress Transients related to test setups. Rapid switching to full amplitude voltage / lead to inrush or high transient Human body electrical static discharge (ESD)
2) Solder joint failure Poor solder joints are the most common issue related to board fabrication Commonly responsible for latent failures due to joint fatigue driven by thermal
cycling
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Top Reasons for Component Failures (2 of 3)
3) Contamination Leads to failures stemming from corrosion or electrical leakage paths Can rapidly destroy wire bond interconnects and metallization. Sources of contamination
Human by-products (Spittle) Chemicals used in the assembly process.
4) Cracked Ceramic Packages Ceramics are used for the majority of high reliability military and space
applications Packages are very brittle and are susceptible to cracking
Stress risers from surface anomalies General mounting stresses (exacerbated by thermal cycling
Root causes can be traced to either design implementation or process controls 5) Timing Issues
Intermittent failures often due to Inadequate timing margins Through timing analysis should be part of any design when asynchronous signals
are present
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Top Reasons for Component Failures (3 of 3)
6) Power Sequencing Issues Many IC technologies susceptible to damage if core bias voltages are not
applied prior to control or data input voltages
7) Poor Design Habits Lack of adequate derating (voltage, power, thermal)
Most common of these is due to not managing component temperature
Running parts outside their rated power dissipation specification Leaving CMOS inputs floating Not properly controlling resets Low bias voltage / Step Load “Droop”
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Recommended Trouble ShootingPrior to Part Failure Analysis (1 of 3)
Isolate and confirm part failure while still on the board to the extent possible Review initial failure data Exonerate Test Equipment and if necessary:
Use a known good reference unit to check test set-up Confirm failure on different test set and assembly levels
Confirm the following are within spec: Input conditions (bias, addressing, strobe, logic) Output parameters Take DC probe measurements on part (Use micro-clip probes if necessary) Look at all signals with an Oscilloscope to assure no AC oscillations Check Line-to-line & line-to-ground isolation
Lift solder joints as required to isolate part from circuit For RF circuits, consider soldering a coax onto part before removing and confirm
input/output is out-of-spec Use connectorized measurements as much as possible.
Probe based RF measurements are typically not consistent and unreliable
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Recommended Trouble ShootingPrior to Part Failure Analysis (2 of 3)
Inspect / Photograph / X-ray part on board Perform general examination under magnification Focus on the following:
Solder joints Connectors Component (cracks, exterior finish) Foreign Object Debris (FOD) Suspect component
Photograph guidelines Minimum of four angles Solder interfaces to board Photograph each side of part
X-ray on board prior to removal as required
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Recommended Trouble ShootingPrior to Part Failure Analysis (3 of 3)
Part Removal Guidelines Review removal process if new steps are required Cut leaded wire connections when possible to remove part Witness removal as necessary If heat is required to remove part
Take as much data as available, excessive solder heat may corrupt evidence
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Basic Failure Analysis Techniques
Electrical Testing / Characterization Non-Invasive Tests Invasive (Destructive) Tests
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Basic Failure Analysis Process FlowElectrical Testing / Characterization
Test / Characterize over temperatureCurve Tracer I-V check of Inputs
Non-Invasive TestsExternal Microscopic Exam / Photo
Fine & Gross LeakVacuum Bake (Non-Hermetic Parts)
X-rayPINDXRF
SAM / C-SAM
Invasive TestsLid Removal / Decapsulate
Die ExaminationDie Probing
IR Microscopic ExamLiquid Crystal
Cross-SectioningSEM
EDS/EDXFIB
AugerSIMSFTIR
TEM/STEM
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Electrical Testing / Characterization
First FA Step - Fully Characterize Failure Mode
Test / Characterize / Look for Sensitivities Over temperature Voltage range Clock speed
Perform Curve tracer assessments on all Inputs / Outputs Compare to known good devices Can help isolate which pin may be damaged
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Non-Invasive Tests
Second FA Step - Perform Non-Invasive Tests External Microscopic Exam / Photo X-ray (Film, Realtime, 3D) Fine & Gross seal tests for hermetic devices Vacuum Bake & Retest PIND Test XRF X-ray Fluorescence Acoustic tests (SAM / C-SAM)
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External Microscopic Exam / Photo
Thorough external visual examination of the suspect part using a stereo microscope should be performed early in the failure analysis process
Typical inspection scopes range from 10X to 30X magnification Magnification levels up to 100X can be employed to further examine any
anomalies identified. The following conditions should be specifically looked for:
External contamination and/or solder balls Possibly shorting out pins on the device
Damaged leads or package seals Seal integrity Lead integrity
Gross cracks in the package Corrosion Thermal or electrical damage
Representative Photos should be taken of the part and any anomalies
Crack
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X-Ray - Film / Realtime / 3D X-Ray (Radiograph) is a very powerful tool for non-invasive failure analysis X-Ray examinations can detect actual or potential defects within enclosed packages There are multiple types of X-Ray equipment available
Basic film X-Rays Real time X-Ray 3-D X-Ray
While film X-Rays can be useful, modern Real Time X-Ray provide extensive capabilities Resolution for film X-Ray = 1 mil particle size, or bond wires down to 1 mil diameter Limitation of film X-Ray - only one exposure level can be taken at a time
Not all characteristics can be observed at a single exposure level Real time X-Rays typically have a resolution range from 1um to 0.4 um Real time allows for a continuous adjustment of exposure levels and conditions, as
well as real time part rotation to obtain the most revealing X-Ray view Special digital filtering / image processing can also be used to detect possible
delinations in the image not otherwise observable on the image screen Refer to Mil-Std-883 Method 2012
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X-Ray Examinations X-Rays allow internal part examination looking for:
Internal particles Internal wire bond dress
Make sure the wire bonds are not touching each other or package lids Die attach quality (voiding, die attach perimeter) Solder joint quality for connectors
Insufficient or excessive solder Substrate or printed wiring board trace integrity Obvious voids in the lid seal Foreign metallic particles within the package Internal part orientation, etc.
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Real-Time X-ray of Coaxial Connector
Normal X-ray View X-ray with Image Filtering
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Acoustic tests (SAM / C-SAM)
Acoustic testing is popular for finding voids / delaminations / cracks Plastic Encapsulated Microcircuits (PEMS) Ceramic capacitors.
Acoustic tests rely on acoustic energy transfer through the part If there is a void, the acoustic energy is blocked, and therefore voids can be
detected The acoustic tests can also be tuned to attempt to determine the depth of any
void Acoustic tests involve either reflected acoustic energy, or transmitted energy
through the part The energy transmission medium is typically DI water
Parts to be examined need to be able to withstand exposure to water
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Acoustic Scan of a Discoidal Ceramic Capacitor
CSAM identified significant void Confirmed to exist via cross-sectioning
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Invasive (Destructive) Tests - Last but Not Least
Internal Package Exam / DIE Exam Cross Sectioning Die Probing IR Microscopic Liquid Crystal die thermal mapping SEM Auger EDS/EDX FIB FTIR SIMS (TOF SIMS / D-SIMS) TEM (transmission electron microscopy STEM (scanning transmission electron microscopy) ESD Testing
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Microscopic Internal / Die Exam Look for:
Damaged metal traces Die cracks Broken or damaged wirebonds
Typically performed using a microscope at magnifications of 100X up to 1000X Deep UV optical microscopes can reach 16,000 X magnification and are capable of resolving 10
microns Microscopes equipped with both dark and light field illumination are helpful, as changing the
lighting conditions can help reveal issues. Photographs should be taken to document the condition of the die and to record any
anomalies
Open Wire Bond Disturbed Bonds
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Cross Sectioning Cross-Sectioning is a very important means of failure analysis Often used for:
Connectors Printed wiring board Substrates Solder joints capacitors, resistors, transformer Semiconductors
Prior to cross-sectioning, samples are potted in a hard setting acrylic or polyester rosin Failed item is literary cut in a cross-sectioned fashion then highly polished for detailed
microscopic examination The potted sample can be cut in half initially to find target the failure site, or the cross-
section can commence at one end of the sample and then progressively cross-section up to and through the failure site. This progressive cross-sectioning can provide a “3D” view of the failure site. Photograph at all steps
Solder Joint
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Cross-Sectioning of PWB
Blister area above electrically stressed signal traces caused un-
expected resistance <10ohms
Deformation/ Delamination due to excessive heating
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Damage located above the trace
Distorted signal trace,Evidence of high current
thru trace
+28V Trace maintains shape,No evidence of over-current
Signs of Overheating of Center Trace
Material appears carbonized
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Scanning Electron Microscope (SEM) SEM is an important tool for semiconductor die failure analysis, as well as
metallurgical failure analysis SEM can provide detailed images of up to 120,000X magnification
Typical magnifications of 50,000X to 100,000X Resolve features down to 25 Angstroms NANO SEMs can resolve features down to 10 Angstroms
With a SEM image, the depth of field is fairly large, providing a better overall three-dimensional view of the sample
SEM examinations are often used to verify semiconductor die metallization integrity and quality Refer to Mil-Std-883 Method 2018
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Auger Electron Spectroscopy (AES) Sample surfaces are exposed to an electron beam designed to dislodge secondary
electrons (Auger electrons)
Materials identified by energy level spectra unique to each material’s valence bands
Auger useful for detecting organic materials on surfaces
Depth profiling can occur, useful to 2000 Angstroms deep
Auger profile of contamination on the surface of a wire bond pad
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Energy Dispersive X-ray analysis (EDS, EDAX or EDX)
EDX is a technique used along with an SEM to identify the elemental composition of a sample
During EDX, a sample is exposed to an electron beam inside the SEM
SEM electrons collide with the electrons within the sample, causing some of them to be knocked out of their orbits
The vacated positions are filled by higher energy electrons which emit X-rays in the process
By a spectrographic analysis of the emitted X-rays, the elemental composition of the sample can be determined
EDS is a powerful tool for microanalysis of elemental constituents
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Energy Dispersive X-ray (EDX, EDAX, EDS)
EDS maps of a Cadmium particle
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Secondary Ion Mass Spectrometry (SIMS)
SIMS is a technique which can detect very low concentrations of dopants and impurities in semiconductors
By ion milling deeper into the sample, SIMS provides elemental depth profiles from a few angstroms to tens of microns
SIMS works by sputtering the sample surface with a beam of primary ions Secondary ions formed during the sputtering are analyzed using a mass
spectrometer These secondary ions can range down to sub-parts-per-million trace
levels Advanced SIMS analyses such as Time-of-Flight SIMS (TOF-SIMS) and
Dynamic SIMS (D-SIMS) provide additional means of elemental detection and resolution
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Focused Ion Beam FIB FIB uses an ion beam to microscopically mil / ablate material away to allow for
cross-sectioning of semiconductor die (ion milling) Gallium or Tungsten ion sources are used
FIB cross-sections are examined by SEM to see features such as Die metallization construction Pinhole in dielectrics (oxides/nitrides) EOS or ESD damage sites
FIB cross sections are very “polished” revealing features down to 200 to 250 Angstroms
FIB can also be used to cut semiconductor metallization lines to isolate circuitry on the die, and if necessary, a Platinum ion beam can be used to actually deposit metallization creating new circuit traces
In this case, die level design changes (known as “Device Editing”) can be implemented to allow for a design “try-out”
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Focused Ion Beam (FIB)
FIB cross-sectionof a Schottky diode
FIB cross-sectionof a MOSFET GATE
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Transmission Electron Microscopy (TEM/STEM)TEM (Transmission Electron MicroscopySTEM (Scanning Transmission Electron Microscopy)
TEM and STEM use a high energy electron beam to image through an ultra-thin sample allowing for image resolutions on the order of 1 - 2 Angstroms
S/TEM has better spatial resolution then a standard SEM and is capable of additional analytical measurements
S/TEM and requires significantly more sample preparation as very thin samples need to be prepared, often using FIB techniques
S/TEM provides outstanding image resolution and it is possible to characterize crystallographic phase and orientation as well as produce elemental maps
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TEM of a gold ball bond on an Aluminum pad confirmed Good Bond Intermetallics
TEM analysis of a gold/aluminum interface of a wire bondData from the TEM provided assurance that the gold/aluminum
stoichiometry was correct even after extensive life aging
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Suggestions for Your Own Failure Analysis Capabilities
Suggestions are provided for Failure Analysis capabilities for a typical electronics firm Three levels of Failure Analysis capabilities are suggested
Basic Moderate Advanced
Beyond these three levels, one might consider using commercial failure analysis laboratories for the more esoteric capabilities such as TEM / STEM SIMS
Usually its more cost effective to subcontract out those types of analyses vs. establishing them in-house
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Basic Failure Analysis Lab
Basic Meters (DVMMs) Stereo Microscope (10X to 30X) (Preferably with digital camera) Cross Sectioning Equipment Power Supplies / Signal generator Curve Tracer
Cross-Section Equipment
Curve Tracer showingI/V Curve
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Moderately Equipped Failure Analysis lab
Metallurgical Microscope (1000X) (Preferably with digital camera) Film X-Ray SEM Chemical Hood with De-capsulating chemicals Die Probe Station Liquid Crystal Acoustic Scan
Metallurgical Microscope withDigital Camera
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SEM and Acoustic Testing (CSAM)
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Scanning Electron Microscope
Acoustic Testing (CSAM)
2010 RAMS –Tutorial 11B – Cassady
Advanced Failure Analysis lab
Real-time X-ray SEM/EDS Auger Analysis System FIB IR Thermal Imaging RF Test Equipment (If necessary)
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Real-time X-ray
Comparison Between Film & Real-time X-ray
Film X-ray Real Time X-ray
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Scanning Electron Microscope with EDS
EDX used for Spectral
Element Analysis
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Focused Ion Beam (FIB) Cross-Sectioning
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FIB Cross-Section – Contact Windows
FIB Cross-Section – MOSFET Gates
2010 RAMS –Tutorial 11B – Cassady
Thermal Imaging
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A hotspot in a CMOS gate is indicated by the liquid crystal technique at 1000X
IR Thermal Imaging System
2010 RAMS –Tutorial 11B – Cassady
Understanding Electronic Part Failure MechanismsExcerpts from the 1997 Alan O. Plait Award for Tutorial Excellence
Five subjects covered: Interconnects Semiconductor elements Passive elements Substrates Packages.
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Purpose of Failure Mechanisms Section
Understanding common part failure mechanisms for various technologies necessary to provide effective corrective action to avoid failures
Typical Hybrid, Transistor, and IC
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Wire Bonds
ISSUES: Bond placement Wire dress Bonding energy Bonding temperature Bondability Dissimilar metals Corrosion Contamination Electrical overstress
Mis-Placed bonds caused shorts
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Wire Bonds
ISSUES: Bond placement Wire dress Bonding energy Bonding temperature Bondability Dissimilar metals Corrosion Contamination Electrical overstress
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Poor Stress Relief
2010 RAMS –Tutorial 11B – Cassady
Wire Bonds
ISSUES: Bond placement Wire dress Bonding energy Bonding temperature Bondability Dissimilar metals Corrosion Contamination Electrical overstress
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Wire Bonds
ISSUES: Bond placement Wire dress Bonding energy Bonding temperature Bondability Dissimilar metals Corrosion Contamination Electrical overstress
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Wire Bonds
Gold / Aluminum Intermatallic“Purple Plague”
ISSUES: Bond placement Wire dress Bonding energy Bonding temperature Bondability Dissimilar metals Corrosion Contamination Electrical overstress
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Wire Bonds
ISSUES: Bond placement Wire dress Bonding energy Bonding temperature Bondability Dissimilar metals Corrosion Contamination Electrical overstress
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Solders
ISSUES Die and substrate attach
voiding
Corrosion
Intermetallic formation
Reflow
Good and Poor Solder Coverage
10X
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Solders
Poor Die Attachment
ISSUES Die and substrate attach
voiding
Corrosion
Intermetallic formation
Reflow
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Corrosion of Indium Solder
25X
Solders
ISSUES Die and substrate attach
voiding
Corrosion
Intermetallic formation
Reflow
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Solders
ISSUES Die and substrate attach
voiding
Corrosion
Intermetallic formation
Reflow
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Solders
ISSUES Die and substrate attach
voiding
Corrosion
Intermetallic formation
Reflow
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Epoxies
ISSUES: Outgassing
Poor adhesion
Electrical resistance
Electrolyic corrosion
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Epoxies
ISSUES: Outgassing
Poor adhesion
Electrical resistance
Electrolyic corrosion
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Detached Diode Mounted With Conductive Epoxy
Epoxies
ISSUES: Outgassing
Poor adhesion
Electrical resistance
Electrolyic corrosion
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Electrotyic Corrision Between Conductive Epoxy and Gold Track
Epoxies
ISSUES: Outgassing
Poor adhesion
Electrical resistance
Electrolyic corrosion
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Semiconductor Elements ISSUES:
Metallization Overstress
Electrical overstress (EOS)
Electrostatic discharge (ESD)
Oxide
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Open in Metallization Stripe Due to Poor Step Coverage
Metallization
ISSUES: Step coverage
Misalignment
Mechanical damage
Corrosion
Electromigration
Stress voiding
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Metallization
ISSUES: Step coverage
Misalignment
Mechanical damage
Corrosion
Electromigration
Stress voiding
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Damaged Metallization
200X
Metallization
ISSUES: Step coverage
Misalignment
Mechanical damage
Corrosion
Electromigration
Stress voiding
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Metallization
ISSUES: Step coverage
Misalignment
Mechanical damage
Corrosion
Electromigration
Stress voiding
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Metallization
ISSUES: Step coverage
Misalignment
Mechanical damage
Corrosion
Electromigration
Stress voiding
Aluminum Metal - Electromigration
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Semiconductor Elements ISSUES:
Metallization Overstress
Electrical overstress (EOS)
Electrostatic discharge (ESD)
Oxide
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Electrical Overstress
Overstress
Electrical overstress (EOS)
Electrostatic discharge (ESD)
Over Voltage electrical overstress resulted in G-S-D Short in FET
Not visible at 100XDamage only visible with SEM
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Overstress
Electrical overstress (EOS)
Electrostatic discharge (ESD)
Electrical Overstress due to Voltage Transient Spike on input to RF Schottky Diode
FIB Through The Short Site Pin Pointed with
Liquid Crystal Analysis
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Overstress
Electrical overstress (EOS)
Electrostatic discharge
(ESD)
Electrical Overstress due to Intentional ESD Exposure on input to RF Schottky Diode
Not as much damage as a high voltage transient
~500V Human Body Model Exposure
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Oxide
ISSUES: Ionic impurities
Oxide defects
Hot carrier effects
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Oxide
ISSUES: Ionic impurities
Oxide defects
Hot carrier effects
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Ceramic Capacitors
ISSUES: Cracking Barrier metals Base Metal Electrodes
• Cracking
50X
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Film Resistors
ISSUES: Overstress Corrosion (Nichrome) Cracks ESD Physical Damage
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Overstressed Thick Film Resistor
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Substrates
ISSUES: Cracking
Metallization failures
Multilayer failures
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Substrates
ISSUES: Cracking
Metallization failures
Multilayer failures
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Incomplete Via Fill
2010 RAMS –Tutorial 11B – Cassady
Packages
ISSUES: Hermeticity
Insulation resistance
Loose particles
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Packages
ISSUES: Hermeticity
Insulation resistance
Loose particles
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Packages
ISSUES: Hermeticity
Insulation resistance
Loose particles
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Questions?
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