SEMI F70.1 is a standardized semiconductor industry method for quantifying the number of particles a gas delivery system component sheds into the process gas stream. In contrast to steady-state methods such as SEMI F70, SEMI F70.1 deals with transient, pulse-induced particle generation. This makes the results more representative of real-life conditions, as mass flow controllers (MFCs) and valves are known to shed significantly more particles during actuation than during steady flow.
This article summarizes the SEMI F70.1 test method, covering suitable samples and sample preparation, the experimental setup, and the presentation of the results. Further advantages of the pulsed test regime are also discussed toward the end.
Sample selection and test preparation
Gas delivery components that can be tested using the SEMI F70.1 method include:
Mass flow controllers and mass flow meters
Diaphragm valves and air-operated shut-off valves
Pressure regulators
In-line filters and purifiers
Fittings and short subassemblies of gas panels and gas boxes
The component under inspection is plumbed into a low-background gas delivery test stand using electropolished, high-purity stainless steel tubing and fittings, so that the fixture itself does not contribute significantly to the measured particle count. The system is baked out and purged with UHP nitrogen or argon until the downstream background particle count stabilizes at or near zero. This establishes a clean baseline and leaves the component as the only variable in the measurement.
Experimental setup
In the SEMI F70.1 test, a condensation nucleus counter (CNC) or a laser particle counter (LPC) is connected downstream of the gas delivery component to continuously sample the outlet gas stream and count particles. The minimum detectable particle size depends on the instrument and is typically ≥0.1 µm. However, counters capable of resolving particles down to the low nanometer range (~4.5 nm) are also available.
The gas delivery component is driven through repeated pulsed cycles or step-change actuations (e.g., rapid open/close, 0 to full scale and back to 0) at a defined frequency and duty cycle. This cyclic approach simulates the repeated recipe-to-recipe or step-and-repeat flow transitions that an MFC experiences in an actual process tool.
Particle counts are logged pulse-by-pulse over a statistically significant number of cycles, so that transient spikes coinciding with actuation events can be distinguished from the steady-state background.
Presentation of the results
The results of the SEMI F70.1 test are presented as a particle count histogram or a time-series trace synchronized to the actuation events. The trace shows sharp count spikes coinciding with each actuation, superimposed on a low steady-state baseline. Numerical metrics are also reported, and these can include:
Particles added per liter of gas passed
Particles per actuation cycle
Counts resolved into specified particle size bins
Advantages of pulsed testing
SEMI F70.1 catches failure modes that steady-state SEMI standards can miss because it isolates particle generation tied specifically to mechanical actuation, such as valve seating, diaphragm flexing, and orifice transients. This matters because modern lithography and etch processes cycle gas delivery components on and off more often than they hold a steady flow.
The results give equipment makers and fabs a common, repeatable basis to compare MFC and valve designs for particle robustness under realistic dynamic duty cycles, which is critical as node sizes shrink and even nanometer-scale particle contamination on a wafer becomes yield-limiting.
Ordering the test
Measurlabs offers pulsed particle testing in accordance with SEMI F70.1 and other semiconductor industry standards. The test setup can be customized to match your specific requirements, including minimum detectable particle sizes down to 4.5 nm.
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