BURN-IN, RELIABILITY TESTING, AND MANUFACTURING OF.ppt

8/14/2019 BURN-IN, RELIABILITY TESTING, AND MANUFACTURING OF.ppt

1/19

C.Bozturk,School of Technology,KSU

BURN-IN, RELIABILITY TESTING, AND

MANUFACTURING OFSEMICONDUCTORS

Prepared By Cagatay Bozturk


2/19


Index

What is BURN-IN?

Reliability of Semiconductors

What is Reliability&Life Testing

Semiconductor Manufacturing


3/19


What is BURN-IN?

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 resultingfrom manufacturing aberrations which cause

time and stress dependant failures.


4/19


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 valuesgenerally change overtime as shown below


5/19


Early Failure Stage

During this stage, failures occur at a high ratefollowing the initial operation of semiconductordevices. They occur very soon and thus the failurerate declines rapidly over time. This Is because thepotential' failures that could not be removed through

a selective process are included and surface in ashort time if a stress such as temperature or voltageis applied after use of the device is started. In thecase of semiconductors, these failures are usuallydue to defects that could not be removed duringproduction, such an micro dust collecting on the

wafer, or to material defects.


6/19


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 accidentallyoccurring after a long time. Consequently

the failure rate never decreases to zero. It

is almost constant because failures occur

sporadically


7/19


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.


8/19


What is Reliability & Life Testing?

The reliability of a semiconductor device is

determined by its ability to perform its

required functions under the stipulated

conditions for a finite period of time.Quantifiable yardsticks such as the

reliability rate, failure rate, and mean time

to failure (MTTF) are used to measure

reliability.


9/19


Objective of Reliability Testing

The objective of reliability testing is to

confirm a semiconductor device's fault-free

operation and estimated useful life by

exposing the device to accelerated ormarginal stress, based on the amount of

stress (thermal stress, mechanical stress,

electrical stress etc) that the device is

estimated to undergo during manufacture,

shipping and normal use.


10/19


Semiconductor Manufacturing

Semiconductor manufacturingconsists of

the following steps:

1) production of silicon wafers from verypure silicon ingots

2) fabrication of integrated circuits ontothese wafers

3) assembly of every integrated circuit onthe wafer into a finished product

4) testing and back-end processing of thefinished products.


11/19


Wafer Fabrication

Wafer fabrication generally refers to the process of

building integrated circuits on silicon wafers. Priorto wafer fabrication, the raw silicon wafers to beused for this purpose are first produced from verypure silicon ingots, through either the Czochralski(CZ) or the Float Zone (FZ) method. The ingots areshaped then sliced into thin wafers through aprocess called wafering.

Wafer fab processes, allowing the device designerto optimize his design by selecting the best fab

process for his device.
http://www.semiconfareast.com/crystal.htmhttp://www.semiconfareast.com/crystal.htm


12/19


Assembly

The process of putting the integratedcircuit inside a package to make itreliable and convenient to use is knownas semiconductor package assembly, or

simply 'assembly'.In general, an assembly process wouldconsist of the following steps:

1. die preparation

2. die attach3. bonding

4. encapsulation
http://www.semiconfareast.com/dieprep.htmhttp://www.semiconfareast.com/dieattach.htmhttp://www.semiconfareast.com/wirebond.htmhttp://www.semiconfareast.com/molding.htmhttp://www.semiconfareast.com/molding.htmhttp://www.semiconfareast.com/wirebond.htmhttp://www.semiconfareast.com/dieattach.htmhttp://www.semiconfareast.com/dieprep.htm


13/19


Steps of Assembly

die preparation, which cuts the wafer intoindividual integrated circuits or dice;

die attach, which attaches the die to thesupport structure (e.g., the leadframe) ofthe package;

bonding,which connects the circuit to theelectrical extremities of the package,thereby allowing the circuit to beconnected to the outside world; and

encapsulation(usually by plastic molding),which provides 'body' to the package ofthe circuit for physical and chemicalprotection.
http://www.semiconfareast.com/dieprep.htmhttp://www.semiconfareast.com/dieattach.htmhttp://www.semiconfareast.com/wirebond.htmhttp://www.semiconfareast.com/molding.htmhttp://www.semiconfareast.com/molding.htmhttp://www.semiconfareast.com/wirebond.htmhttp://www.semiconfareast.com/dieattach.htmhttp://www.semiconfareast.com/dieprep.htm


14/19


Test

Once assembled, the integrated circuit is

ready to use. However, owing to the

imperfection of this world, assembled

devices don't always work. Many things

can go wrong to make a device fail, e.g.,

the die has wafer fab-related defects, or

the die cracked during assembly, or the

bonds were poorly connected or not

connected at all. Thus, prior to shipment tothe customer, assembled devices must first

be electrically tested.


15/19


Electrical Testing

Electrical testingof devices in big volumesmust be done fast and inexpensively.

Mass-production electrical testing thereforerequires an automated system for doing

the test. Equipment used to test devicesare called, well, testers, and equipmentused to handle the devices whileundergoing testing are called, well,handlers. Tester/handler systems are alsoknown as automatic test equipment (ATE).
http://www.semiconfareast.com/etest.htmhttp://www.semiconfareast.com/etest.htm


16/19


BURN-IN

Burn-inis an electrical stress test thatemploys voltage and temperature toaccelerate the electrical failure of adevice. Burn-in essentially simulates the

operating life of the device, since theelectrical excitation applied during burn-inmay mirror the worst-case bias that thedevice will be subjected to in the course ofits useable life. Depending on the burn-in

duration used, the reliability informationobtained may pertain to the device's earlylife or its wear-out.


17/19


BURN-IN

Burn-in is usually done at 125deg C, with electricalexcitation applied to thesamples. The burn-in processis facilitated by using burn-inboards (see Fig. 1) where the

samples are loaded. Theseburn-in boards are theninserted into the burn-in oven(see Fig. 2), which suppliesthe necessary voltages to thesamples while maintaining theoven temperature at 125 degC. The electrical bias appliedmay either be static ordynamic, depending on thefailure mechanism beingaccelerated.

Figure 1

Photo of Bare and Socket-populated Burn-in Boards

Figure 2

Two examples of burn-in

ovens


18/19


Conclusion

Burn-in helps us to detect problem trends /determine critical components in a systemfailure (s), and, analyze the system forEffective reliability. Thanks to burn-in, we

can predict reliability performance and Life-cycle of the products. Itprovides valid fieldfailure data and timely corrected actions.


19/19


References

http://www.semiconfareast.com

http://www.reltech.co.uk

Date post:	04-Jun-2018
Category:	Documents
Upload:	abhinav-srivastav
View:	220 times
Download:	0 times

BURN-IN, RELIABILITY TESTING, AND MANUFACTURING OF.ppt

Documents