Notebook: Wet Process · Bench 3 · Bath #7 (SC-1 sibling chemistry, anonymized)
Rule of this book: ink only; no “we’ll update MES later”
2026-07-12 — Install / fill
New bath mixed to target. TOC and particles baseline recorded. Operator: J.K.
Note: heater PID tuned; recirculation filter DP = 0.4 bar.
2026-07-18 — “Still fine”
Visual OK. No titration. Production asked to defer changeout “until weekend.”
Margin note (supervisor): weekend is not a chemical property.
2026-07-21 — First whisper
Metrology: slight particle uptick on wafers exiting this bench only. Split lot confirms bench-correlated.
Action taken: none. Action discussed: “monitor.”
2026-07-23 — Titration (finally)
Active species low vs target. Stabilizer odd. Filter DP 1.1 bar.
Bath age: 11 days against a soft SOP max of 7 “or by titration.”
If titration is optional, lifetime is folklore.
2026-07-23 — Changeout
Drain / rinse / refill. Filter replaced. Baseline restored within two lots.
Scrap already booked to “unknown fab particles” for three days.
2026-07-25 — Rule rewrite in this book (not in a slide)
Changeout triggers (any one fires):
- Calendar max hours (hard)
- Titration outside window (hard)
- Filter DP limit (hard)
- Bench-correlated particle signature (hard)
- Production preference (never)
Cross-checks pasted from adjacent pages
| Signal | Bath #7 | Bath #6 (control) | | --- | --- | --- | | Particle delta | + | flat | | Titration | late | on schedule | | Filter DP | high | nominal | | Ownership | shared shrug | named wet owner |
Adjacent fences
UPW owns facility water purity. CDA owns dry air. Photoresist track owns coat/develop. AMC hunts own airborne organics. None of them own bath titration cadence on Bench 3. Do not blame UPW for a bath you refused to titrate.
The notebook is the control system until MES enforces the same gates.
Last line (2026-07-28)
Bath #7 is a reminder: wet lifetime is measured, not negotiated. If it is not in the book with a time, it did not happen.