Adaptive Testing Techniques at Qualcomm, a Fabless Experience

1. Adaptive Testing Techniques at Qualcomm, a Fabless Experience Glenn Plowman Qualcomm Inc. glennp@qualcomm.com Michael Schuldenfrei OptimalTest Michael.Schuldenfrei@optimaltest.com

2. Abstract Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • Adaptive testing techniques are becoming more and more popular as a means to reduce cost of test.  • This paper explores adaptive testing challenges and benefits at Qualcomm.

3. Executive Summary • Traditional methods of test time reduction are both volume and man power intensive. • OptimalTest Adaptive TTR (ATTR) can help achieve TTR savings while reducing manpower for TTR in high volume manufacturing. • Test programming and use of concurrency features must be reviewed to avoid interference with ATTR. • Data collection, simulation and review processes must be put in place to define ATTR rules. • Infrastructure is required to deliver, execute and monitor ATTR rules in production.

4. Overview • What is OT ATTR? • Benefits • Challenges • ATTR Rule Logistics: simulation, definition, deployment and execution. • Tester Integration

5. What is Adaptive Test? Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • “Adaptive Test is a broad term used to describe methods that change test conditions, test flow, test content and test limits (potentially at the die/unit or sub-die level) based on manufacturing test data and statistical data analysis.” (ITRS Definition) • Feed-forward data from in-line test • Feed-back data from post-test statistical analysis • Real-time & near real-time data analysis • Statistical Process Control (SPC) • Adjust test limits and content on-the-fly.

6. OptimalTest Adaptive TTR Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • OptimalTest has 2 Advanced Adaptive TTR (ATTR) methodologies • Parametric Method – performed on parametric tests while analyzing & evaluating, in real-time, the process stability and making test time reduction decisions • P/F Method – performed on low fallout tests • Leverage information from actual & historic device test results • Applicable at WS and FT • Selection is based on device & test characteristics and needs • Can be applied simultaneously or individually • No modifications required to existing test programs • Patents pending & issued

7. linked reports OptimalTest Database

8. Overview • What is OT ATTR? • Benefits • Challenges • ATTR Rule Logistics: simulation, definition, deployment and execution. • Tester Integration

9. Benefits of Advanced Adaptive Test Lower test costs – Reduce TTR manpower Better Quality - Test sampling not test removal Achieved without changing test programs

10. Qualcomm TTR Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • OT TTR Simulation reports help guide engineering to optimal and automated TTR faster than engineers using manual techniques and the results have a higher degree of statistical rigor. • Example: Half of the manual TTR savings obtained on a product was attributed to information found in the simulation reports. • OT is used to produce rules (recipes) for ATTR on testers with much lower PTE time commitment. • Impact: EVEN AFTER  manual TTR additional saving can be obtained using ATTR rules with no loss to product quality.

11. Overview • What is OT ATTR? • Benefits • Challenges • ATTR Rule Logistics: simulation, definition, deployment and execution. • Tester Integration

12. Challenges for ATTR – Deferred Calculation Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • Tests like DSP are farmed out to special processors that calculate results in the background. • When test results are available the test record is generated with the correct instance and test. • Test instance integrity is preserved but test order is not. • Deferred tests with low failure rates and high test times can be TTRed. • The current TTR Simulator will be overly pessimistic (see COF).

13. Challenges for ATTR – Concurrent Test Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • Concurrent test is coming in IGXL 8.0. • Concurrent execution of instances will require novel solutions. • As of Jan 2011 Teradyne and OptimalTest are actively discussing the topic of concurrent test.

14. Challenges for ATTR – Instance/Variable Dependencies Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde • Setup Instances cannot be removed. • Instances that output information cannot be removed. • Instances that create any dependencies for following Instances must not be removed (e.g. global variables). • TE must decide whether to support ATTR by minimizing inter-instance dependencies during programming. • TE must identify instances which are not ATTR candidates due to inter-instance dependencies during simulation. • Instances coded in VBT must also be included in the flow sheet.

15. Challenges – Continue on Fail • Tests 6 & 7 each have an additional failure if COF is used. • Fails for tests 6 & 7 are over-reported. • TTR opportunity for Instance D is missed. Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde

16. Overview • What is OT ATTR? • Benefits • Challenges • ATTR Rule Logistics: simulation, definition, deployment and execution • Tester Integration

17. Process Flow for Test Time Reduction AnalysisHistorical Data Test Candidates TTR Recipe Adaptive TTR Rule TTR Rule in Real Time TTR Results OTPortal

18. ATTR Simulation at Qualcomm Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde

19. ATTR Rule Checkout at Qualcomm Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde

20. ATTR Rule Deployment The same rule may be deployed more quickly at additional subcons (e.g. Subcon 2)

21. Overview • What is OT ATTR? • Benefits • Challenges • ATTR Rule Logistics: simulation, definition, deployment and execution. • Tester Integration

22. ATTR Rule Example

23. OptimalTest – Teradyne Interface for TTR Before injection of Enable Words After injection of Enable Words

24. Executive Summary • Traditional methods of test time reduction are both volume and man power intensive. • OptimalTest Adaptive TTR (ATTR) can help achieve TTR savings while reducing manpower for TTR in high volume manufacturing. • Test programming and use of concurrency features must be reviewed to avoid interference with ATTR. • Data collection, simulation and review processes must be put in place to define ATTR rules. • Infrastructure is required to deliver, execute and monitor ATTR rules in production.