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The Toyota Production System Sanity Check

Many semiconductor companies have instituted “lean” manufacturing. Perhaps you are already following the Toyota Production System without knowing it. Try taking the TPS test. Be sure to ask a few different fab people these questions. You may get some very different answers.

Questions

1. Do you know the theoretical minimum time to process a wafer?

2. Do you know exactly how many process steps are required to complete a wafer?

3. Is your actual manufacturing process time less than twice your theoretical minimum process time?

a. Do you know the critical process step that constrains the throughput capacity of your fab?

b. Is the uptime of the process equipment in that step predictable?

c. Is there a fundamental reason that the manufacturing process time cannot approach the theoretical minimum process time in your fab?

4. Do you know the cost per wafer of each process step?

a. Is your scrap rate less than 2 percent?

b. Is your rework rate less than 2 percent?

5. Do you know exactly how many wafers are in your fab?

a. How many are product wafers?

b. How many are test wafers or process-monitor wafers?

c. How many are engineering wafers?

d. What is the ratio of product-wafer processing to non-product-wafer processing?

6. Were you able to rapidly identify and trace the latest drop in yield in your fab?

a. Did you have enough data to empirically correlate the yield drop to a piece of equipment or specific process step?

b. How do you know that the process equipment is operating within specifications?

7. Did everyone give you the same answers?

Were they all in the fab today?