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ELF18 test status and current results

Detailed overview of test status & current results for ELF18, including stuck-at & transition tests, defect analysis, and future work presented at the RATS seminar in Fall 2005.

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ELF18 test status and current results

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  1. ELF18 test status and current results By Intaik Park RATS (Reliability and Testability Seminar) Intaik Park, RATS, Fall 2005

  2. Outline • Introduction • Stuck-at tests • Transition tests • Sequence-dependent defects • Future work Intaik Park, RATS, Fall 2005

  3. ELF18 Test Chips • Test chips • Fabricated by Philips • 0.18µ process • 6 DSP cores (core freq. 20Mhz) • Test environment • Agilent 93k tester • Single device cycle (5Mhz) • Advantek Handler Intaik Park, RATS, Fall 2005

  4. Current Test Status • 2nd round of LOT test finished (10/11/05) • Total: 2,842 chips tested • 2,041 good chips • 489 Control Fails • 271 Logic Failures (435 cores) scan chain test fails: 276 cores valid logic fails: 159 cores • 40 Contact Fails Intaik Park, RATS, Fall 2005

  5. Tests Applied • Stuck-at Tests • Single Stuck-at test (new conversion flow) • Gate Exhaustive test • Transition Tests • Transition tests (tool A, tool B) • Transition test for Fanout-Free Region (hazard-free and robust transition tests) • Gate super-exhaustive test Intaik Park, RATS, Fall 2005

  6. Outline • Introduction • Stuck-at tests • Transition tests • Sequence-dependent defects • Future work Intaik Park, RATS, Fall 2005

  7. Stuck-at tests • Stuck-at test (converted using new flow) • 430 vectors • 98.53% coverage • Gate Exhaustive Test • 1,527 vectors • 98.54% coverage Intaik Park, RATS, Fall 2005

  8. New Conversion Flow • Old conversion flow • .vhdl  .wgl • Using LTran • New conversion flow • .vhdl  .pat • conversion script Philips ATPG .PAT New Flow Old Flow .WGL .SWAV .HP .BINL Tester Intaik Park, RATS, Fall 2005

  9. Conversion flow comparison • In .WGL file Idle cycles Capture Cycle New flow Old flow Intaik Park, RATS, Fall 2005

  10. Stuck-at test escapes • Test Escapes • 2 cores detected only by Stuck-at test (new flow) (no other test detected) SSF GE 3 11 6 Escapes Intaik Park, RATS, Fall 2005

  11. Outline • Introduction • Stuck-at tests • Transition tests • Sequence-dependent defects • Future work Intaik Park, RATS, Fall 2005

  12. Transition tests Intaik Park, RATS, Fall 2005

  13. Transition test for FFR • Restrict transition test to propagate transitions on output of gates • Targets only inputs of Fanout-free Region • Top-off with normal transition test Intaik Park, RATS, Fall 2005

  14. A A A A A A Z Z Z Z Z Z B B B B B B Normal Tr Hazard-free Tr Robust Tr Transition test for FFR (cont.) Str A Stf A 10 01 X0 01 X1 X1 May have no transition or have hazard 10 01 01 10 11 X1 10 01 10 01 11 11 Intaik Park, RATS, Fall 2005

  15. Transition test for FFR (cont.) • If output transition is guaranteed, dominance can be used for fanout-free region (same as SSF) • Tests for inputs of FFR  tests all the faults inside the FFR Intaik Park, RATS, Fall 2005

  16. Transition test for FFR escapes Intaik Park, RATS, Fall 2005

  17. Gate Super-Exhaustive Test • Gate Super-Exhaustive • Extension of gate exhaustive test for transition test • Apply all possible input transition combinations • GSE transition • Subset of GSE patterns producing transitions on output of gates Intaik Park, RATS, Fall 2005

  18. GSE test escapes GSE GSE tr 6 1 5 Intaik Park, RATS, Fall 2005

  19. GSE tr and HF & RB tr FFR • GSE tr and Robust and hazard-free tr have similar concepts • Restrict on test to produce transition on output • Differences • GSE tr == union of hazard-free tr & robust tr • XOR and MUX • GSE: xor, mux tested exhaustively • HF, RB tr: xor, mux tested non-exhaustively Intaik Park, RATS, Fall 2005

  20. A A Z Z B B GSE tr = Union of HF, RB tr • GSE tr: method1 AND method2 • HF tr: method1 OR method2 • RB tr: method2 only A str test 01 01 01 01 01 11 method1 method2 Intaik Park, RATS, Fall 2005

  21. XOR and MUX • GSE tr: method1 AND method2 • HF tr: method1 OR method2 • RB tr: method1 OR method2 A str test A A 01 XOR 01 XOR 01 10 Z Z B B 00 11 method2 method1 Intaik Park, RATS, Fall 2005

  22. GSE tr, HF, RB tr escapes GSE tr 1 10 3 RB Tr HF tr Escapes Intaik Park, RATS, Fall 2005

  23. Test escape summary Intaik Park, RATS, Fall 2005

  24. Outline • Introduction • Stuck-at tests • Transition tests • Sequence-dependent defects • Future work Intaik Park, RATS, Fall 2005

  25. Sequence-dependent defects • 3 different tests • Test1 (LOC), Test2 (Stuck-at), Reference test • if Test1 fail, Test2 pass (or vise versa), seq. dep. defect • if ref test fails, invalidate • check all individual vectors Intaik Park, RATS, Fall 2005

  26. Test 1 (LOC transition test) Previous state Shift-in Activation vector System clock capture Propagation vector System clock capture Output response Shift-out Intaik Park, RATS, Fall 2005

  27. Test 2 (stuck-at test) Previous state 1 bit shifted prop. vector Shift-in Propagation vector System clock capture Output response Shift-out Intaik Park, RATS, Fall 2005

  28. Reference test (stuck-at test) Shift-in Activation vector System clock capture Propagation vector Shift-out (Output response) Intaik Park, RATS, Fall 2005

  29. Tester cycle logs • Tester limits 1,024 failing cycle logs / chip • 6 cores/chip, 184 scan cells, 819 vectors • To log all possible fails, need 904k cycle logs (882 test rounds) • Assigned 65 cycles for test1 and test2 40 cycles for ref. test Intaik Park, RATS, Fall 2005

  30. Tester cycle logs (cont.) • Different failing cycles • Some fail > 65 cycles for one vector • Some fail < 65 cycles for 819 vectors • Iterative method • Apply tests starting from 0, 100, 200 … 700 • If found seq. dep. defect  seq. dep. • If finished logging w/o seq. dep.  possible seq. indep. Intaik Park, RATS, Fall 2005

  31. Sequence-dependent cores • 37 seq. dep. cores • 3 test1 (loc) fail only • 2 test2 (stuck-at) fail only • 32 fail mixed • 23 finished logging without seq. dep. • possible seq. indep. cores • 99 need more failing cycle logs Intaik Park, RATS, Fall 2005

  32. Outline • Introduction • Stuck-at tests • Transition tests • Sequence-dependent defects • Future work Intaik Park, RATS, Fall 2005

  33. Future work • Apply stuck-at test (using old flow) • New HF & RB tr test (XOR, MUX tested exhaustively) • At-speed transition tests Intaik Park, RATS, Fall 2005

  34. Backup slides Intaik Park, RATS, Fall 2005

  35. Gate exhaustive test • All the possible input combinations • To each gate • Gate response • To primary output (or scan F/F) From 2004 Fall RATS by Kyoung Youn Cho Intaik Park, RATS, Fall 2005

  36. Gate super-exhaustive test • Apply all possible two input combinations • To each gate • Sensitize the effect of the second input • To some observation points From 2005 Summer RATS by Kyoung Youn Cho Intaik Park, RATS, Fall 2005

  37. Sequence dependent defect • Defect that makes the output of a combinational circuit depend on the sequence of the input patterns applied • Examples: • Stuck-open fault • Feedback bridging fault From 2005 summer RATS by Intaik Park Intaik Park, RATS, Fall 2005

  38. Hazard-free transition test • Transition delay test in which all sensitizing inputs do not change in one of the transitions such that a transition is produced on the output of the gate • AND gate: restrict stf at input • OR gate: restrict str at input Intaik Park, RATS, Fall 2005

  39. Robust transition test • Transition delay test in which all sensitizing inputs do not change Intaik Park, RATS, Fall 2005

  40. ELF18 primitives • Total 52,282 primitives • XOR : 637 • XNOR: 479 • MUX: 3,324 Intaik Park, RATS, Fall 2005

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