Liquid Particle Counter

Liquid and process-gas particle counters extend airborne particle monitoring into the two other media a wafer actually contacts in the fab — the ultrapure water and chemicals it's wet-processed in, and the process gases that flow through every deposition, etch, and implant chamber — because a particle hiding in either of those media reaches the wafer just as surely as one floating in cleanroom air.

Particle source anywhere in the fab's fluid or gas supply
Not just airborne — liquids and gases carry particles too
Particle monitoring medium
Liquid particle counter
Monitors UPW and process chemical lines for particle counts in-line
Process-gas particle counter
Monitors gas delivery lines feeding deposition/etch/implant chambers
Particle excursion caught at the supply source
Before it reaches a wafer and shows up as an unexplained defect

A particle excursion in a shared chemical or gas line is a much bigger problem than one airborne particle, because every wafer processed through that line until the excursion is caught inherits the contamination. Airborne particle contamination tends to be probabilistic and localized — a given particle lands on one wafer or it doesn't; a contaminated UPW supply line or a contaminated process gas feed, by contrast, delivers particles to every single wafer that passes through that line until someone identifies and fixes the source. In-line liquid and gas particle counters exist to catch that kind of systemic contamination quickly, since the alternative is discovering it only after a run of wafers has already failed inspection downstream.

Liquid and Process-Gas Particle Counters a shared supply line's contamination reaches every wafer that passes through it UPW/chemical supply line in-line counter every wafer wet-processed downstream inherits any excursion Process gas supply line in-line counter feeds deposition, etch, implant chambers catching the excursion at the supply line is far cheaper than discovering it wafer by wafer downstream

Process-gas particle counting has to operate under far more demanding conditions than liquid monitoring, since the gas itself is often corrosive, pressurized, or flammable. A liquid particle counter can often use relatively standard optical scattering methods adapted for flow-through sensing; monitoring particle counts in a process gas line feeding a deposition or etch chamber means doing that same kind of detection inside a line carrying gases that may be toxic, pyrophoric, or under significant pressure, which demands specialized, chemically compatible sensor hardware rather than a simple adaptation of liquid-counting technology.

Liquid and process-gas particle counters close the same monitoring gap for wet chemistry and process gas that airborne counters close for cleanroom air, recognizing that a wafer picks up contamination from whatever medium touches it, not only from the air it sits in between process steps.

Take liquid particle counter further

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