Test measurements of the prototype Aerogel Threshold Detector
Leveraging Test Data for Quality · 2019. 10. 11. · Fab Process 28% Test Program 10% Test...
Transcript of Leveraging Test Data for Quality · 2019. 10. 11. · Fab Process 28% Test Program 10% Test...
Michael Schuldenfrei, CTO
Leveraging Test Data for Quality
GSA Quality Team Meeting December, 2014
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The Need
Shifting from “Defects per Million” to “Defects per Billion”
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The Problem
No Problem Found 32%
Fab Process 28%
Test Program 10%
Test Operation 4%
Test Equipment 26%
RMA Source
No Problem Found Fab Process Test Program Test Operation Test Equipment
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The Challenge
BIG DATA
EXPERTISE
COST
TIME
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Big Data – Device DNA
ECID
ECID ECID
ECID
ECID
WAT WS1 WS2
WAT WS1 WS2
WAT WS1 WS2
WAT WS1 WS2 WS3
WAT WS1 WS2 WS3
FT1 Burn in
FT2
Example: One package contains: 5 dice x ~2 WS operations per die x ~1.2 iterations per operation x 3000 parametric measurements + 1000 per-site WAT measurements + 3000 FT measurements A DNA consisting ~35K measurements!
An SLT lot with 5000 parts could have 150M historical measurements from hundreds of wafers & FT lots
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Back to Basics
THE QUALITY QUESTION;
IS “GOOD” REALLY GOOD?
Outlier Detection Geographic Parametric
Escape Prevention Test program issues ATE issues
Data Feed Forward (More intelligent decision making)
Drift Smart Pairing
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Quality Solutions
Outlier Detection
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Outlier Detection – Algorithms
D-PAT: Dynamic Part Average Testing
NNR: Nearest Neighbor Residual
Z-PAT: Z-Axis Part Average Testing
GDBN: Good Die in Bad Neighborhood
Zonal: Low yield zone-based detection
Final Test
Post Final-Test operation and Based on Die-ID (ECID etc.)
In real-time at Final-Test operation without Die-ID
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Cross-Operation Outlier Detection
Cross-operational quality based on Die ID
Contributing operations ETEST/PCM/WAT Wafer Sort Final-Test Burn-In System Level Test
Example: E-Test based bin-switching performed post-Wafer Sort
The ability to identify potential bad devices based on E-test data geographical analysis Bin switching occurs post-wafer sort Requires data-feed-forward within the supply chain
Escape Prevention
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Escape Prevention – ATE Freeze A freeze occurs when a tester instrument becomes “stuck” and repeatedly returns the same or similar result for a sequence of parts
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Escape Prevention – ATE / TP
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The STDF “PRR.NUM_TESTS” field tells us the number of tests executed on the part. It should be relatively stable throughout the lot
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Escape Prevention – Test Ops
Excessive probing – when operation ignores probe mark spec for a device and keeps on probing to get the yield
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Escape Prevention – Test Program Human error is one of the main contributors for test escapes and RMA. Here the PE commented a few blocks in the TP for debug and forgot to uncomment before production release:
Traditional SBL is design to detect yield issues in which a specific bin count spikes. However human error can result in a drop to 0 which is missed.
SBL SBL drop of soft bin 11
from ~3% to 0 following new TP revision
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Escape Prevention – Test Program
Extremely loose test limits may mask real test performance problems
~95 Sigmas
~95 Sigmas
Advanced Quality Solutions
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Implementations: Within the same test area (e.g. WS, FT, etc.) Between test areas (e.g. from WAT to WS to FT) Within a single subcon Between multiple subcons (hub and spoke) Real-time (test program integration) Offline bin-switching
Example scenarios: Outlier Detection – drift analysis Pairing – cherry-picking for power & speed combinations Test program tuning SLT / Burn-in reduction
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Data Feed Forward
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Data Feed Forward – Drift
Database at subcon Tester
1. ECID Data
2. FT1 Measurements
Test Program running FT2 operation
Real-time data! No test time impact!
One or more numeric values representing the perceived quality of a part based on:
Wafer geography (e.g. edge vs. center)
Outlier detection rule inputs (e.g. GDBN, Z-PAT, D-PAT, etc.)
Number of iterations to PASS Overall lot/wafer yield Equipment health during test Parametric test results from multiple operations Etc…
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Quality Index
Quality Index
Lot/Wafer Yield etc.
Quality Rule
Inputs
Wafer Geography
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“No Problem Found” Combinations of chips causing issues:
IC3
IC2
PCB
IC1
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Smart Pairing
• New methodology to pair IC’s for optimal compatibility
• Customer and suppliers agree on recipe for “Best Match” between IC’s (e.g. based on power consumption and speed)
• “Quality Index” created based on manufacturing and test data to categorize chips
• Data fed-forward to assembly to ensure IC’s pre-sorted into “buckets” based on Quality Index
• MCPs and boards are assembled with well-matched components
Grade A
Grade B
Grade C
Grade A
Grade B
Grade C
Supreme Quality requires a comprehensive end-to-end approach which takes into account problems arising from: • Equipment • Test Process • Human Error • Material …and much more
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Conclusions
Q&A
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