Presentation given to the NMI about the future of DFT Includes current and future problems for consumer and automotive test solutions The new MSA standard Analogue Defect Coverage 1687 extention

1. Confidential © ams AG 2015
Looking to the Future
for DFT and Analogue Test
National Microelectronic Institute
Peter Sarson CEng MIET CMgr MCMI
Full Service Foundry
16th April 2015

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Automotive Test
Existing Challenges
Historically Low Volume, High Reliability
More extensive and exhaustive testing
• Very long test times
• Limited resources needed extensively around the device
 Potentially compromising loadboard design
• Long time to market
Expensive RMA process – 2 man years at ams AG
• Extensive failures analysis
• 8D reports

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Consumer Test
Existing Challenges
High Volume
Bare bones testing, system tests
• Short test times
• Complicated multi-site boards, high parallelism
 Long down times due to setup issues during production
• Fast time to market
Non-existent RMA flow
• Generally only receive RMA during cost negotiations

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Automotive test
Future Challenges
A move to higher supply voltages, more complex test boards
• Fewer resources available, and lower accuracy
• Requires more resource sharing
Higher volume
An even greater focus on product quality and reliability
• As devices get larger and more complex, more defects missed by test

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Consumer
Future Challenges
Our current high-volume consumer customers requesting more
automotive-style product qualifications
More precision
• Less chance for parallelism, which increases cost
More RMA received – More than 2 man years?
Even higher volume
• Need more parallelism

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Automotive and Consumer
Future Challenges
• Automotive and consumer requirements will merge
and a single standard will be adopted for all semiconductor segments
• Larger ASICS, smaller geometries, more defects per sq. mm
 More focus on defect-based testing,
since spec testing simply doesn’t find all defects.
• We will need more design tools to calculate analogue test coverage
to show where test coverage is missing

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Automotive and Consumer
Future Challenges
• We need to focus more on automated analogue DFT to allow muxing
signals on-chip, to single points on loadboards
 To aid test board reliability, device debug, automated test generation
 Access to nodes we simple don’t have access to today

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Measurement System Analysis V4 spec change
• Automotive industry has seen a requirement to change the MSA spec
due to very tight requirements becoming unrealistic
 Means? No need for such accuracies and test repeatability to pass
requirements  use Cp(observed) rather than Cp
 Possibly built-in test measurement accuracy can be relaxed
• Applicable to Consumer parts for high volumes, not just Automotive!

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New Release Criteria

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IEEE 1687 Standard
• A new approach to scan access based on IEEE 1149.1 and 1500
 Allows faster, simpler access to IP blocks (“instruments”) via scan
• Intended to also allow test access to the IP blocks in the field
• Tools currently available from some EDA vendors

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Analogue Defect Simulation
• No commercially available tools
• Published papers proposed many different techniques over last 30
years, with no really usable result
• With larger ASICS and more defects in the analogue circuitry,
it becomes much more critical to finding reliability-related defects
• Analogue Defect Simulation shows where coverage is lacking
and hence where more test access is needed
• “An analysis of random sampling for analog fault simulation,”
Stephen Sunter, Mentor Graphics, ETS 2014 STEM Workshop

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Ad hoc working group
• A group of motivated people from industry working together to find
common ground in mixed-signal DFT and test generation
• Work on-going to develop standard way to describe Analogue Test Bus
and ADC/DAC serial access using 1687 syntax, to allow automation
• Focused on Defect-Oriented Test (DOT), rather than spec testing
 This simplifies the problem for an Analogue BIST approach
• “A Mixed-Signal Test Bus and Analog BIST with 'Unlimited' Time and
Voltage Resolution,” Stephen Sunter, Mentor Graphics, ETS 2011

13. Confidential © ams AG 2015
Thank you
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