RELIABILITY &
FAILURE ANALYSIS
SEM 2 2020/2021
DIE EXPOSURE
• Electronic package cases may or may not have a cavity.
• Cavity-type cases have a recessed area for housing the active
and passive elements, interconnects and substrates. The
cavity-type case is typically sealed with a lid.
• The lid could also be made from ceramic, plastic, quartz or
glass.
INTRODUCTION
Pre-molded cavity package
(Reproduced from Amkor Technology, “ Packaging the Micro-machine”)
• In non-cavity packages, the active and passive elements and
interconnects are usually assembled on a leadframe, which
is then encapsulated.
• Non-cavity packages are generally plastic encapsulated. The
circuitry and part of the leadframe (excluding the lead) are
completely encased in the molding compound.
• Plastic packages are non-hermetic.
INTRODUCTION
Dual In-line Package (DIP)
• If the physical cause of failure is on the die or elsewhere
inside the package, the first destructive failure analysis
process is exposing the die and bonding.
• Decapsulation can refer to a procedure performed on either
hermetic devices or polymer encapsulated devices.
Decapsulation is the removal of a cap, lid, or encapsulating
material from a packaged integrated circuit by mechanical,
thermal, or chemical techniques.
INTRODUCTION
• Chemical techniques generally apply to plastic or epoxy
encapsulated devices.
CHEMICAL
TECHNIQUES
• The chemicals used for decapsulation are usually strong
acids, bases or solvents (substances especially liquids that
can dissolve other substances) to attack and remove
portions of packages.
• Several methods of chemical decapsulation are available. Such
methods include:
(i) manual chemical etching → manual cavity etching and
total package removal
(ii) jet etching (automated)
CHEMICAL • Fuming nitric acid (HNO3), sulfuric acid (H2SO4) or a mixture of
TECHNIQUES – the two acids are commonly used
Decapsulation of
• Nitric acid (HNO3) is a strong acid that attacks most metals
plastic packages including silver, copper, mercury, lead, and iron. There are two
kinds of concentrated nitric acid. White fuming nitric acid
consists of almost pure HNO3 whereas red fuming nitric acid
contains a considerable amount of dissolved nitrogen oxides.
(i) Manual Chemical Etching (type: Cavity Etching)
• In this technique, a cavity was formed in the top of the
package by milling
CHEMICAL
TECHNIQUES –
Decapsulation of (Reproduced from
plastic packages http://images.pennet.com/articles/ap/
thm/th_137718.jpg)
• The device was placed on a heater block and a
decapsulating acid (predominantly fuming nitric acid or
fuming sulfuric acid) was dropped into the cavity.
• The acid was dumped and replenished until the die was
exposed.
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages
(Reproduced from
http://www.semitracks.com/reference/FA/pack_analysis/
delid_decap/delid_decap.htm)
(ii) Manual Chemical Etching (type: Total package removal )
• Total package removal is performed by dissolving the entire
package in a beaker of sulfuric acid\leaving only the silicon
die and some amount of undissolved metal.
• This technique is primarily used to inspect for cracks on the
CHEMICAL back of the die
TECHNIQUES –
Decapsulation of
plastic packages
(Reproduced from
http://www.semitracks.com/reference/FA/pack_analysis/
delid_decap/delid_decap.htm)
(iii) Jet etching
• Jet etching is an automated version of decapsulation and
was developed largely to provide a more efficient method
of decapsulation
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages
• A low-level vacuum is used to create a jet of hot
decapsulating acid and to hold the device in place.
• This equipment pumps a small jet of the etchant (fuming
nitric or sulfuric acid) against the surface of the package in
the area of interest.
CHEMICAL
TECHNIQUES – • The unit is self-contained, which minimizes the exposure of
Decapsulation of these chemicals to the operator.
plastic packages
• The jet etch provides several advantages
(a) The acid can be heated to a high temperature without
excessively heating the device.
CHEMICAL
TECHNIQUES – (b) The time to decapsulate can be controlled by the
temperature. (If decapsulation time is too short, it is
Decapsulation of difficult to control the extent of etching. If the time is too
plastic packages long, acid tends to be adsorbed into the mold compound
causing swelling and ultimately damage to the bonding)
(Reproduced from
https://www.nisene.com/jetetch-pro)
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages
(Reproduced from
https://www.nisene.com/jetetch-pro)
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages
(Reproduced from
http://www.semitracks.com/reference/FA/pack_analysis/
delid_decap/delid_decap.htm
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages IC Package after chemical decapsulation. Note the missing wire
contacts on the bond pads
CHEMICAL
TECHNIQUES –
Decapsulation of
plastic packages Metallographic microscope Metallographic microscope
image of image of
good transistor after failed transistor after
decapsulation decapsulation
CHEMICAL
TECHNIQUES –
Decapsulation of Close-up metallographic
microscope image of die 1 from
SEM image of die 1 at 450X
plastic packages the failed transistor after
decapsulation
• As seen previously, chemical decapsulation produces fast
and effective results on standard plastic packaged parts.
Several factors, however, make acids incapable of
processing all packaged styles.
• For instance, when package contains materials that are slow
or impossible to remove with acids, or when the total
packaging cross-sectional thickness is large –thus
exacerbating the non-directionality of acid attack and
MECHANICAL potentially leading to harmful corrosion of bond pads and
TECHNIQUES wires.
• Mechanical decapsulation is also being used if the package
contains two or more stacked dice
• Mechanical techniques usually apply to metal, glass and
ceramic packages. Special tools and equipments for
mechanical decapsulation include round style can openers,
low-speed diamond saws, grinding wheels etc.
• If the package being opened is of cavity packages, exposure
of the die typically consists in mechanically removing the
lid, commonly called delidding or decapping.
MECHANICAL
TECHNIQUES
TO-39 hermetically sealed metal can
(Reproduced from http://www.semitracks.com/reference/FA/
pack_analysis/delid_decap/delid_decap.html)
• In cavity packages, the die and wires are not connected to
the lid and thus mechanical removal of the lid will expose
the die.
• Removal of the lid can be done by grinding away the lid or
prying off the combo lid, or by the application of opposite
torques to the top and bottom parts of the ceramic DIP to
MECHANICAL break the seal glass in order to remove the lid.
TECHNIQUES
Ceramic
DIP, glass
seal
• However, in many ceramic lid packages, the lead seal also
contains the pins. Cracking this seal can result in damage to
the pins and loss in electrical connections.
• In these cases (ceramic packages with ceramic lids),
grinding provides a more reliable method of maintaining
MECHANICAL connectivity i.e without loss of electrical connections.
TECHNIQUES
Package after 120 seconds Mechanical Decap on
ASAP- decap. 1 step diamond tool process. Process
Endpoint is approx. 15 microns above front-side
circuitry
MECHANICAL-
CHEMICAL Packaged part after an additional 8 second chemical
decapsulation process. Using nitric acid @ 130C
DECAPSULATION
• Both chemical and mechanical decapsulation allow for
internal examination of the die and interconnects by
optical, electron, magnetic or emission microscopy.
• Additional destructive evaluation can also be performed
MECHANICAL & using either focused ion beam (FIB) imaging or transmission
electron microscopy
CHEMICAL
TECHNIQUES • These techniques permit detection of bond pad corrosion,
passivation cracking, ball bond lifting and other failure at
die level
Backside • Access to the die is a fundamental requirement for physical
Preparation for failure site isolation techniques.
Characterization
• Several developments have created interest in accessing the
Analysis device from the backside through the substrate (instead of
from the front-side) such as:
(a) Growing application of flip-chip technology
In the wire bond method
(top), the die faces up
and is attached to the
package via wires.
Backside The flip chip (bottom)
Preparation for faces down and is
typically attached via
Characterization solder bumps similar to
the larger ones that
Analysis attach BGA packages to
the printed circuit board
(also shown here)
(b) Rapid increase in the number of layers of metallizationon
a device. (This blocks access to many areas of the device
for conventional failure site isolation. In many cases, it
easier to isolate failures from the back of the die rather
than the front)
Backside
Preparation for
Characterization
Analysis
Backside
Preparation for
Characterization
Analysis Pictures of an advanced IBM chip with 7 metallization layers, completely
done in W and Cu.
(c) Introduction of new dielectric materials that can be
Backside etched by the same acids used to etch the plastic
package
Preparation for
Characterization
Analysis
Backside imaging
• It is possible to detect failures from backside of the devices
because of the transparency of the silicon in the near IR
(electromagnetic radiation with a wavelength between 0.7-
Backside 1.4m). Dopants added to the silicon substrate reduce this
transparency.
Preparation for
Characterization • This means that to image a modern die effectively with a
backside microscope, generally requires the planar
Analysis thinning, and subsequent polishing, of the substrate to
make imaging and thus backside analysis possible.
Accessing the backside consist of 3 processes:
(1) Removal of any heat sink or package material below
Backside the die:
The most common procedure to remove the heat sinks and
Preparation for other materials from the back is by using a milling machine
Characterization with carbon steel bits to grind the material away. In the
case of ceramics, diamond encrusted bits are used
Analysis
(2) Thinning and polishing the silicon
• Device is thinned to 100 microns or less with a highly
polished surface.
• Techniques, which require greater thinning, are expected to
be performed locally using techniques such as focused ion
Backside beam (FIB) milling, chemically enhanced laser etching or
mechanical methods.
Preparation for
Characterization • Thinning and polishing of the die allows Near Infra Red
Analysis (NIR) light to penetrate the backside so that imaging of the
circuitry can be done. It also allows the transmission of
emission sites to be seen when viewed under an emission
microscope (PEM), thermal emission microscopy or IR
microscopy.
(3) Anti-reflective coating
• The coating minimizes beam reflection and refraction from
Backside the backside surface at the point of entry, and in some
cases, also aid with image resolution
Preparation for
Characterization • Backside preparations are typically more complex than
topside
Analysis
Backside
Preparation for
Characterization
Analysis Anti-reflective coating
(Reproduced from
http://www.ultratecusa.com/PDFlibrary/UT_Cat_H.pdf)
Backside
Preparation for
Characterization
Analysis IR microscope image of backside of polished device. Note the bottom of
the device circuitry is visible through the GaAs substrate
(Reproduced from GaAs MANTECH, Inc.,”Biased, Backside Failure Analysis
Techniques for Small Plastic Packages”, 2001)
