Power quality management: Engineering boundaries of voltage sags, UPS, and critical process continuity ( part 1)

Introduction: Power issues in advanced manufacturing processes usually don’t begin with a “power outage”.

In mature process fabs, a voltage dip of tens to hundreds of milliseconds often only triggers alarms in a few devices. However, in EUV, High-NA EUV, GAA/Nanosheet, advanced metrology, and high-vacuum deposition/etching environments, short-term disturbances can have more complex consequences: scanner stage repositioning, vacuum pump unit speed reduction, RF generator trip, local flow disturbances in the chiiller/PCW, FFU speed drop, cleanroom differential pressure reversal, chemical/gas valve groups entering protection mode, ultimately manifesting as a batch of wafer hold, tool recovery, recipe re-qualification, and even reticle /FOUP environment reconfirmation.

SEMI F47 has established voltage sag immunity for semiconductor process equipment as a common industry standard. SEMI S2 mandates that equipment must enter a safe state under abnormal power conditions. SEMI E10 standardizes indicators such as availability, MTBF, and MTTR. SEMI S23 reminds us that energy, utility, and material consumption must be included in lifecycle efficiency assessments. Although ISO 14644-1 defines cleanroom particle cleanliness, the FFU, MAU, RAHU, differential pressure control, and automation systems that maintain cleanliness all require power continuity. For top-tier fabs, power quality design is not a localized issue within the electrical room, but rather a shared constraint of process continuity, EHS boundaries, and OEE.

First, the essence of a voltage sag is an energy gap, not a number on a voltmeter.

1. SEMI F47 addresses the minimum consensus of “ensuring equipment does not stop unexpectedly during short-term temporary descent”.

The commonly accepted interpretation of SEMI F47 is that semiconductor process equipment needs to maintain operation under specific voltage sag curves, such as maintaining 50% nominal voltage for 0.2 s, 70% nominal voltage for 0.5 s, and 80% nominal voltage for 1.0 s. Two points should be noted in engineering: First, F47 is not a standard to guarantee product quality; it primarily constrains equipment to avoid immediate shutdown due to short-term sags. Second, F47 generally cannot replace fab-level system verification because the tools contain various dynamic responses, including servo, vacuum, RF, control power, heaters, communication, and safety loops.

For plant managers, passing F47 certification is not the end, but the starting point for the language of procurement and acceptance. True acceptance requires answering: when a disturbance occurs, which loads continue to operate, which loads are allowed controlled shutdown, which loads must remain in a safe state, and which recovery actions cannot be initiated simultaneously.