Semi E79

SEMI E79 defines Equipment Productivity, the standard metric set that adds throughput and speed to the state-time accounting SEMI E10 already provides — E10 tells you how much of the time a tool was available to run, while E79 tells you how much actual work it got done during that available time, which are genuinely different questions a fab needs both answers to. A tool can be 95% available by E10's definition and still be a productivity problem if it only processes wafers at half its rated throughput during that available time; E79 is what captures that second failure mode by defining standardized metrics for theoretical throughput, actual throughput, and the ratio between them, so a fab can tell the difference between "this tool isn't running enough" and "this tool is running, but slowly."

Tool is available (good E10 number)
95% availability, by SEMI E10's own accounting
SEMI E79 productivity metricsMeasures what happens during that available time
Theoretical throughput
Rated wafers/hour at this tool's designed process speed
Actual throughput achieved
Wafers/hour actually processed during available time
Productivity ratio reveals a hidden problem
High availability can still mask slow actual processing

E79 and E10 answer genuinely independent questions, which is exactly why a fab needs both rather than treating one as a proxy for the other — a tool can score well on E10 and poorly on E79 (available often, but slow when running), or score poorly on E10 and well on E79 (frequently down, but fast and efficient whenever it's up), and each combination points operations toward a completely different fix. Chasing availability improvements on a tool whose real problem is throughput wastes maintenance effort on the wrong lever, and the reverse is equally true — which is the practical reason E79 exists as its own standard rather than being folded into E10's state-time accounting.

SEMI E79 vs. E10 — Two Independent Axes availability and throughput are different problems with different fixes E79 throughput E10 availability High / High healthy tool Low avail. / High throughput down often, fast when up High avail. / Low throughput up often, slow when running Low / Low needs both fixed a tool can land in any of these four cells — E10 alone cannot tell you which one

SEMI E79 and SEMI E10 are the two building blocks that feed into the fab-wide Overall Factory Efficiency rollup (SEMI E124) — OFE needs both a tool's availability and its productivity to properly weight that tool's real contribution to (or drag on) total factory output, which is why E79 is as foundational to factory-level metrics as E10 is, even though it gets mentioned far less often in day-to-day fab conversation.

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