Logic Built in Self Test

1. 19 Jan 2004 BIST/ESG Seminar 1 Logic Built in Self Test Neeraj Goel 2002vls017

2. 19 Jan 2004 BIST/ESG Seminar 2 Plan Introduction to Testing Various testing techniques BIST BIST and synthesis Various approaches and algorithm suggested Conclusion

3. 19 Jan 2004 BIST/ESG Seminar 3 Verification Vs Testing Verification Design errors Testing Manufacturing defects Aging defects In-field regular testing is required

4. 19 Jan 2004 BIST/ESG Seminar 4 Fault models and Detection Gate level Stuck-at Fault model Transistor level Stuck-at Fault model Bridging Fault Model Delay faults

5. 19 Jan 2004 BIST/ESG Seminar 5 Stuck at Fault model

6. 19 Jan 2004 BIST/ESG Seminar 6 Bridging Fault Models

7. 19 Jan 2004 BIST/ESG Seminar 7 Fault models and Detection Gate level Stuck-at Fault model Transistor level Stuck-at Fault model Bridging Fault Model Delay faults

8. 19 Jan 2004 BIST/ESG Seminar 8 Testing Problem at Deep Sub-Micron Decreasing feature size Low power supply Increasing Number of pins Test equipment cost More test vectors Increasing gate count Memories, RF, MEMS on the chip Different test methodologies

9. 19 Jan 2004 BIST/ESG Seminar 9 Various DFT methods Full scan Boundary scan Logic BIST Quiescent current (IDDq test)

10. 19 Jan 2004 BIST/ESG Seminar 10 Scanning

11. 19 Jan 2004 BIST/ESG Seminar 11 Scanning

12. 19 Jan 2004 BIST/ESG Seminar 12 Scan Design Techniques Flip-flop of design? Scan registers Use of Multiplexer Increased controllability and observability Two step synthesis approach: scan mode and scan chain connection are done at second step Special scan registers

13. 19 Jan 2004 BIST/ESG Seminar 13 Full scan Additional wiring and mux : area and performance effect Long test time Less effort in ATPG Cost increases with number of pins.

14. 19 Jan 2004 BIST/ESG Seminar 14 Full Scan (cont.) To prevent the problem other alternatives Multiple scan chains Partial scan design

15. 19 Jan 2004 BIST/ESG Seminar 15 Boundary Scan Use reduced number of pins Less cost of tester Need scannble latches at non-test I/O Additional cost of Mux (Performance) Large handling capabilities of ATPG system required

16. 19 Jan 2004 BIST/ESG Seminar 16 IDDQ test Relatively cheap Time require for each pattern is long Very convenient for bridge faults

17. 19 Jan 2004 BIST/ESG Seminar 17 Basic BIST Architecture

18. 19 Jan 2004 BIST/ESG Seminar 18 Advantages of BIST Can be used at all level of testing System level testing in field At speed testing No need for external test machines Less I/O pins needed for testing Burn-in Test made easy No need for test vector development

19. 19 Jan 2004 BIST/ESG Seminar 19 Disadvantages of BIST Area overhead -more susceptibility to manufacturing defects Performance penalties Designing and verifying proper operation of BIST at design level. Additional risk in project

20. 19 Jan 2004 BIST/ESG Seminar 20 Traditional LBIST architecture- STUMPS Self-testing using MISR and parallel shift (Stumps) PRPG generate input for internal scan chains Compress the response in MISR Linear Feedback Shift Register (LFSR) generate pseudo random pattern.

21. 19 Jan 2004 BIST/ESG Seminar 21 Traditional LBIST architecture- STUMPS

22. 19 Jan 2004 BIST/ESG Seminar 22 Built-in Logic Block Observer

23. 19 Jan 2004 BIST/ESG Seminar 23 Concurrent BILBO

24. 19 Jan 2004 BIST/ESG Seminar 24

25. 19 Jan 2004 BIST/ESG Seminar 25 BIST and Synthesis Circuit optimization for test Incomplete information available => use estimation Goal: Test concurrency Minimum area overhead

26. 19 Jan 2004 BIST/ESG Seminar 26 High level synthesis approach GOAL: test concurrency Issues involved: Hardware conflicts Probable Solution: Choose the data path such that less conflicts

27. 19 Jan 2004 BIST/ESG Seminar 27 Synthesis stages Data-flow Scheduling for Testability Binding for Testability Test concurrency matrix Test Register Selection Incremental approach Test Path Definition Test point insertion Test Scheduling

28. 19 Jan 2004 BIST/ESG Seminar 28 SyncBIST Test Synthesis Overview

29. 19 Jan 2004 BIST/ESG Seminar 29 Some Experimental Results

30. 19 Jan 2004 BIST/ESG Seminar 30 Another approach-by Gonzalez et al Minimizing testability cost and time by - multiple concurrent test sessions - register sharing

31. 19 Jan 2004 BIST/ESG Seminar 31 Algorithm[1] Preprocessing Built compatibility graphs of the FUs Built test status Matrix and call the cost function Apply minimal register allocation procedure

32. 19 Jan 2004 BIST/ESG Seminar 32 Yang and Muzio’s Approach[3] Module allocation and register allocation are performed incrementally -Module allocation is guided by testability balance technique -Register allocation aims at increasing the sharing degree

33. 19 Jan 2004 BIST/ESG Seminar 33 Algorithm Perform default allocation For all normal registers do Do life time analysis of variables end for For all register do Change to register according to functionality end for Repeat Perform module allocation Perform test register allocation for all normal register do Estimate the incremental hardware cost end for Select pair with smallest cost Merge the select pair and change the data path and registers accordingly. until no merger exist

34. 19 Jan 2004 BIST/ESG Seminar 34 Experimantal Results

35. 19 Jan 2004 BIST/ESG Seminar 35

36. 19 Jan 2004 BIST/ESG Seminar 36 Conclusion At deep submicron test cost and test time are major issues to be considers BIST can be a good option in this scenario To ensure good test performance, it is necessary to estimate the quality of test behavior during synthesis.

37. 19 Jan 2004 BIST/ESG Seminar 37 Reference J A Q Gonzalez, J R Amazonas, M Strum, W J Chau, “Self Test Built-in plan for Data-Path Functional Units” IEEE Latin American Test Workshop, 2000. A Orailoglu, G Harris, “Microacritectural Synthesis for Rapid BIST Testing”, IEEE trans. On CAD of ICS, June 1997 L T Yang, J Muzio, “Built in Self Testable Data Path Synthesis” , In proc. Of IEEE Int. conf. On VLSI, April 2001. C Feige, M j Geuzebroek, “Logic BIST technology evalution: an industrial case study”, European test workshop 2001. Charles E. Strode, “A Designers guide to Built-in Self-test”, Kluwer Academic Publisher,2002.