Step-by-step analysis walkthrough

Use when you own Scenario: Coverage Storm in a DFT closure review.

1. Open release criteria and failing metric dashboard.

2. Partition failures by pattern family and operating context.

3. Inspect constraints, clocks, masks, and unknown handling.

4. Check architecture assumptions against implementation reality.

5. Review diagnosis evidence for repeatability.

6. Assign owner and propose smallest high-confidence change.

7. Run timing, power, and quality regressions.

8. Capture final signoff or waiver decision.

Artifacts to collect

• coverage gap snapshot, fault bucket analysis, closure plan

• pattern tag manifest

• tester program revision

• signoff checklist

• owner tracker

Decision memo template

DFT DECISION MEMO - Scenario: Coverage Storm
scenario:
metric:
hypothesis:
fix:
regression:
owners: ATPG owner, DFT lead, product quality owner

Reference visuals

Coverage crisis triage

coverage gap
  -> untestable? constraint? model?
  -> targeted fixes
  -> pattern budget check

DFT deep dive

Senior DFT interviews test tradeoff judgment under imperfect data.

Concept diagram

INTERVIEW ANSWER LOOP

state metric -> explain mechanism -> request evidence -> propose fix -> list regression

Metric graph

ANSWER QUALITY

mechanism clarity + ownership clarity + regression discipline

Reports and artifacts

• whiteboard rubric

• scenario scorecard

• trap checklist

• follow-up depth index

Mini case study

Candidate improved from tool-only answers to mechanism-first narratives by using metric->artifact->decision template.

Debug branches

• Always state assumptions

• Name cross-team owners

• Discuss risk and fallback plan

Senior review question

Ask: what evidence proves this DFT decision is safe for production?

Key takeaways

• State metric, lot/corner context, and pattern tag with every claim.

• Treat timing, power, and quality as one signoff problem.

Common pitfalls

• Chasing coverage without legality checks.

• Ignoring test-power side effects of pattern changes.

• Debugging silicon without reproducible tags.

Principal DFT review addendum

Coverage crises require separating true untestable faults from constraint/model issues and choosing the smallest high-impact closure plan.

Metric: coverage shortfall under schedule pressure, pattern growth slope