Semi E91

SEMI E91 defines the Prober Specific Equipment Model (PSEM) — the GEM-based state/event model for wafer probers, the test tools that step a probe card across a wafer's die to perform electrical test before dicing, covering the prober-specific states and events (site positioning, contact/overdrive, die-level pass/fail reporting) that a generic GEM model doesn't address. GEM's base specific-equipment-model concept already standardizes communication for broad equipment categories, but a prober's operational behavior is distinct enough — moving to a die site, making electrical contact, recording a per-die test result, stepping to the next site — that it needs its own SEM, the same way E30.1/E30.5 gave inspection/review and metrology tools their own specific models rather than forcing every tool type into one generic template.

The reason probers needed a dedicated SEM rather than relying on GEM's generic equipment model is that die-level test data has a structure no other tool type produces — a result tied to a specific (x,y) die coordinate on a specific wafer, generated one site at a time across potentially thousands of sites per wafer — and a host system needs that structure standardized to build wafer maps, bin die for packaging decisions, or correlate test failures back to process excursions. Without E91, each prober vendor would report per-die results in its own format, forcing a host to write custom parsing logic per vendor before it could even build a reliable wafer map, which defeats the entire purpose of GEM-standard communication for the one tool type whose output data is most directly tied to yield and binning decisions.

E91 is the equipment model that makes a prober's output usable directly by downstream yield-mapping and binning systems without vendor-specific translation — the standard exists precisely because die-level pass/fail data is too consequential to leave unstandardized across vendors.