This document provides an overview of VLSI design and testing processes. It discusses various stages in the design flow from behavioral to physical design. It describes the importance of verification, validation, and testing at each stage to detect errors and ensure quality. These include simulation, emulation, formal methods, probe testing, and burn-in testing. Factors like process variations that affect speed are addressed through speed binning. The document emphasizes that testing is crucial throughout the design and manufacturing cycles to find faults and prevent defective chips from reaching customers.
2. Acknowledgement…..
This presentation has been summarized from
various books, papers, websites and
presentations on VLSI Design and its various
topics all over the world. I couldn’t item-wise
mention from where these large pull of hints and
work come. However, I’d like to thank all
professors and scientists who created such a
good work on this emerging field. Without those
efforts in this very emerging technology, these
notes and slides can’t be finished.
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Dr
Usha
Mehta
25-01-2022
6. • Design Errors
• Misinterpretation of specification
• Fabrication Errors
• Wrong component
• Incorrect Wiring
• Fabrication Defects
• Imperfect Process Variations
• Physical Failure
• During life time of a system 25-
01-
202
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Dr
Usha
Mehta
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9. Role of Testing in General
• Verification
• will any fault occur?
• Validation
• will fault occur during mass production?
• Detection
• Is there any fault? Yes or no?
• Diagnosis
• Where is the fault?
• Device Characterization
• Why the fault occurred? (Is design wrong or test process wrong?)
• Failure Mode Analysis (FMA)
• How that fault can be prevented? (Is manufacturing process wrong?)
• Burn-In
• Will it work for longer life?
• Speed Binning
• What is the speed of device?
• Acceptance Testing/Incoming Inspection
• Should I use it in my system?
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Dr
Usha
Mehta
25-01-2022
10. Verification
• Verifies the correctness of Design
• Performed once prior to manufacturing
process
• Performed by simulation, hardware
emulation or formal methods
• Responsible for quality of design
• Like sonography used for unborn baby
during pregnancy
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Dr
Usha
Mehta
25-01-2022
11. Validation
Verification Testing/Characterization / Design Debug
• After the first lot of prototypes are
manufactured, IC goes through, design
validation/pilot-run stage.
• It checks that either the fabrication process
was correct and fabricated IC is correct. ( Here
it is assumed that design was error free)
• Also verifies the correctness of test procedure.
• AC, DC, Functional Test
• Probing internal chip nodes also
• Special tools like scanning electron
Microscope, electron beam scanner, artificial
intelligent technique etc, are used
• Like Newborn sreening tests for baby
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Dr
Usha
Mehta
25-01-2022
12. Diagnosis
• Identify the fault that exists in system.
• Which fault is there (type of fault)?
• Where is that fault (fault location)?
• Like after a set of pathological test, the
doctor diagnosis your disease.
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Dr
Usha
Mehta
25-01-2022
13. Device Characterization
• Determination and correction of errors
in device and/or test procedure
• So that the next lot of IC will be error
free.
• Like doctor writes a prescription of
medicine to cure your disease.
• Here there is a difference between man
and IC!!!!!!!!!
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Dr
Usha
Mehta
25-01-2022
14. Failure Mode Analysis
• Why/How/when the fault had occurred?
• Determine the manufacturing process
errors that may have caused the fault.
• Like determining why that disease
occurred and find the preventive actions
(bad health /food habits) which created
disease
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Dr
Usha
Mehta
25-01-2022
15. Detection (testing in general…)
• Does any of the fault exists?
• Which, why, how, where, when is out of scope here.
• Only YES/NO. Go/No Go test for IC to be shipped to market
or not.
• At fabrication unit
• For all fabricated IC
• Less comprehensive than characterization
• Test should have high fault coverage, low cost and minimum
test time
• Are you completely fit? Does any of the disease
there?
• Like medical test for army ( if fit then go, otherwise
no go)
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Dr
Usha
Mehta
25-01-2022
16. Burn-In/Stress Test
• To stress the chip to accelerate the
failure mechanism
• Some chip passes the production test
but will fail very quickly thereafter
• To increase temp and/or voltage while
applying test patterns
• Infant Mortality Failures: 10-30 Hrs
• Freak Failure: 100-1000Hrs
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Dr
Usha
Mehta
25-01-2022
17. Acceptance Testing/
Incoming Inspection
• Customer performs this test
• Like universal tester to test the IC at our
Digital Electronics Labs
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Dr
Usha
Mehta
25-01-2022
18. Place of Verification in Design Flow
• Specification
• Finalization of
specification
• Behavioural
Description/RTL code
• Functional Verification
• Gate level netlist
• Static timing analysis
• Circuit level
• Propagation delay
• Physical Domain
• Layout vs Schematic
(LVS)
• During Fabrication
• Wafer testing
• Pilot lot production
• Validation
• Mass production
• Testing
• Burn-In
• Speed Binning
• Yield loss
• Diagnosis
• Failure Mode
Analysis
• Before use
• Acceptance/Incomin
g Testing
• In-System
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Dr
Usha
Mehta
25-01-2022
19. Speed Binning
• CMOS is made of pMOS and nMOS.
• Generally, the design is such a way that
both of them have same speed
• But the performance can vary because
of PVT
• Process variations (P), Supply Voltage (V),
Temperature (T)
• But during fabrication process, due to
process variations speed may be
degraded
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Dr
Usha
Mehta
25-01-2022
20. Speed Binning……
Process Variations
• Variations in the process parameters
can be impurity concentration densities,
oxide thicknesses and diffusion depths.
• This introduces variations in the sheet
resistance and transistor parameters
such as threshold voltage.
• Dimension variations of the devices, are
mainly resulted from the limited
resolution of the photolithographic
process.
• This causes (W/L) variations in MOS
transistors
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Dr
Usha
Mehta
25-01-2022
21. Speed Binning…..
Process Corners
• There are five possible corners of an n vs. p
mobility graph:
• typical-typical (TT) (not really a corner !), fast-
fast (FF), slow-slow (SS), fast-slow (FS), and
slow-fast (SF).
• TT, FF and SS (even corners)
• Both types of devices are affected evenly, and generally
do not adversely affect the logical correctness of the
circuit.
• FS, SF ("skewed" corners)
• one type of FET will switch much faster than the
other, and this form of imbalanced switching can
cause one edge of the output to have much less
slew than the other edge.
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Dr
Usha
Mehta
25-01-2022
22. Verification
• On Design
(functionality,
estimated speed)
• Pre-silicon
• One time
• Methods:
• Simulation
• Emulation
• formal methods
• A Design Bug
• Makes all Fabricated
IC useless
Detection/Testing
• On Device
(manufactured
hardware)
• Post-Silicon
• On each and every IC
being fabricated
• Methods:
• Test Generation
• Test Application
• A fabrication defect
• May cause all ICs or
Some of the ICs
useless. 22
Dr
Usha
Mehta
25-01-2022