Semi E78

SEMI E78 defines Equipment Electrostatic Discharge and Attraction, the standard that specifies acceptance-test limits for how much static charge a piece of equipment itself is allowed to generate on wafers and surfaces during normal operation, and how strongly a charged surface is allowed to attract particles — turning SEMI E43's measurement method into a pass/fail qualification standard a tool must meet before acceptance. E43 defines how to measure voltage, polarity, and decay rate on a surface; E78 is the standard that sets the actual numeric limits equipment must stay within, the same relationship SEMI E14's particle-contribution test method has to whatever acceptance threshold a fab applies against its results — one standard defines the measurement, the other defines what counts as passing.

SEMI E43 measures voltage, polarity, decay rate
The test method — how to quantify static charge
SEMI E78 acceptance limitsPass/fail thresholds applied to E43's measured values
Maximum allowed charge generation
Equipment must stay below this during normal operation
Maximum allowed particle attraction
Charged-surface particle pull-in rate, limited separately
Tool passes or fails ESD/attraction acceptance
Quantified qualification, not a subjective judgment call

E78's particle-attraction limit is the piece that connects static-charge control directly to contamination control: a charged wafer or carrier surface doesn't just risk electrostatic discharge damage to sensitive device structures, it also actively pulls airborne particles toward itself through simple electrostatic attraction, meaning a tool that generates excessive static charge can become a contamination source even if its minienvironment otherwise passes SEMI E44's airflow and particle-count acceptance testing cleanly. This is why E78 treats charge generation and particle attraction as two separate limits rather than one combined metric — a tool could conceivably generate modest static charge but still exhibit excessive particle attraction depending on surface material and geometry, so both numbers need independent acceptance thresholds for the standard to catch every real failure mode rather than just the more obvious one.

SEMI E78 — Two Independent Acceptance Limits charge generation and particle attraction, tested separately Charge generation limit Voltage/decay rate (SEMI E43 measurement) stays below threshold Pass/fail against E43's measured data Particle attraction limit How strongly a charged surface pulls particles toward it Independent threshold — not inferred from charge alone Both limits must pass for acceptance a tool can fail attraction without failing charge, or vice versa

E78's two limits sit at the intersection of static-charge control and contamination control, directly connecting SEMI E43's measurement method to the acceptance side of the same contamination picture SEMI E14's particle-contribution testing and SEMI E44's minienvironment qualification already cover.

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