Semiconductor OCAP (Out-of-Control Action Plan) Template
An out-of-control action plan tells operators and engineers exactly what to do when an SPC chart shows a violation. This template captures the trigger, containment, checks, disposition and sign-off in one document.
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Semiconductor OCAP Out-of-Control Action Plan Template
OCAP Record
Site: Fab 2, Bay 4 Process area: Etch Tool: ETCH-07 PM2 Parameter: Oxide etch rate (nm/min) Date: 2026-10-20 Owner: Process engineer on shift
Trigger
SPC rule violated: Two of three beyond 2 sigma
Lots processed since the last good check: L2610-0412, L2610-0413, L2610-0415
Containment
Decision: Tool restricted, monitor lots only
Identify all lots processed since the last in-control point and place them on hold in the MES until disposition is approved.
Suspected Cause
Mean rate trending down over three runs after chamber clean. Possible incomplete seasoning or gas flow drift.
Check Steps
| Step | Check | Result | Initials |
|---|---|---|---|
| 1 | Confirm data entry and metrology tool status | ||
| 2 | Review recent maintenance and recipe changes on ETCH-07 PM2 | ||
| 3 | Check gas flows, pressure, power and temperature logs | ||
| 4 | Run monitor wafer and compare to control limits | ||
| 5 | Compare to sister chambers for matching |
Lot Disposition
| Lot ID | Impact assessment | Disposition | Approver |
|---|---|---|---|
Corrective and Preventive Action
Root cause confirmed: Corrective action: Preventive action: Chart or limit change required:
Approvals
This is a starting point for your own OCAP procedure. Follow your fab's SPC rules, control limits and customer notification requirements. Rule names are generic Western Electric / Nelson style rules.
Link excursions to lots and customers
Optional: ask how to connect OCAP events to lot genealogy and customer records, privately.
Optional. The tool and every export work without this. No spam.
How to use the template
Fill in the site, area, tool, parameter and the SPC rule that fired. List the lots processed since the last in-control check, then choose the containment decision. Complete the check steps in order and record results. Use the lot disposition table for each lot on hold and the CAPA section for root cause and prevention. Export to PDF or Word for the lot history, or to Excel if you want to track multiple events together.
- Fill in the header at the time of the alarm, not after.
- List every lot since the last good point, not only the flagged one.
- Get the disposition approved before releasing any held lot.
What an OCAP should contain
A good OCAP is a decision flow, not a narrative. It states the trigger, the immediate containment, the checks that separate a measurement problem from a process problem, and the disposition rules for affected lots. Checking the metrology tool and data entry first avoids unnecessary tool downtime. Comparing against sister chambers helps separate a tool shift from a material or recipe change.
Reading the example
The sample entry shows two of three points beyond 2 sigma on etch rate after a chamber clean. The decision is to restrict the tool to monitor lots only while seasoning is checked. All product lots since the last good point are held until the monitor wafer confirms the rate is back inside control limits. If the monitor wafer fails, the tool goes down and engineering reviews maintenance records and gas flow logs before any release.
Common mistakes
Treating each alarm as a one-off leads to repeated excursions. Record the root cause and look for patterns by chamber and by maintenance event. Another mistake is releasing the tool on a single in-control point. Many procedures require more than one good monitor point, or a defined recovery run. Lastly, check whether customer or quality agreements require notification of an excursion.
Frequently Asked Questions
What is an OCAP?
An OCAP, or out-of-control action plan, is a documented set of steps that operators and engineers follow when an SPC chart signals an out-of-control condition. It defines containment, checks, disposition and ownership.
Which SPC rules should trigger an OCAP?
That is set by your SPC procedure. Commonly used rules include a point beyond 3 sigma, two of three beyond 2 sigma, runs on one side of the center line and trends. Use the rule set your fab has validated.
How is an OCAP different from an 8D?
An OCAP is a fast, in-line response to a control chart signal. An 8D is a formal problem-solving report for a larger issue. A serious or repeating OCAP event can lead to an 8D or CAPA.
Do I need approvals to release held lots?
Usually yes. Most fabs require engineering and quality sign-off based on the lot impact assessment. Follow your own disposition procedure, and record who approved and when for traceability.
If your OCAP records and lot holds are spread across forms, MES and ERP, Netray can help build a private view that links excursions to affected lots and customers.
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