Overall equipment efficiency (OEE) calculator
Fab economics and operations. Everything is calculated in your browser; nothing you enter is sent to a server.
KEY POINTS
OEE is the share of operations time spent making good wafers at the theoretical rate: availability efficiency × operational efficiency × rate efficiency × quality efficiency. Front-end fab tools often fall between about 40 and 70%. For bottleneck tools cutting standby pays off most; for cleaning and deposition tools, cutting maintenance and unscheduled downtime does.
Inputs (time categories and output for the period)
The time categories are a simplified version of the SEMI E10 approach. Real fabs classify tool states automatically from the MES or tool logs and may aggregate by chamber for multi-chamber tools.
Breakdown of losses (converted to theoretical processing time)
| Loss | Time | Share of operations time |
|---|---|---|
| Scheduled downtime (PM, maintenance) | 8.0 h | 4.8 % |
| Unscheduled downtime (failures) | 6.0 h | 3.6 % |
| Engineering | 4.0 h | 2.4 % |
| Standby (waiting for WIP or operators) | 20.0 h | 11.9 % |
| Speed loss (gap to theoretical throughput) | 25.8 h | 15.4 % |
| Quality loss (scrap, rework) | 0.8 h | 0.5 % |
Where to start improving tool OEE
OEE is the share of operations time spent making good wafers at the theoretical rate. For front-end fab tools it often falls between about 40 and 70%, and the breakdown of losses varies greatly by tool type. For expensive bottleneck tools such as lithography scanners, eliminating standby comes first; for cleaning and deposition tools, cutting maintenance time and unscheduled downtime pays off.
Standby is a loss set not by the tool itself but by upstream and downstream steps, transport (AMHS) and lot release planning. Treating OEE only as a measure of a single tool's performance leads to the wrong priorities. A typical approach tracks failures separately as MTBF and MTTR and uses predictive maintenance to turn unscheduled downtime into scheduled downtime.
FAQ
What is a good OEE for fab tools?
Front-end tools typically land around 40 to 70%. The right target depends on the tool type and whether it is a bottleneck.
Is standby time the tool's fault?
Usually not. Standby comes from upstream and downstream steps, transport and lot release planning, so it should be improved at the line level.
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Last updated: October 23, 2026