nx_litho_stepper.nx

nx_litho_stepper.nx -- Arc D1: MASKLESS-STEPPER CONTROL (the chip-fab exposure step; the assignment generator queued this). A maskless stepper is an XY motion stage + a UV source that EXPOSES the mask pattern (nx_mask_geom) onto photoresist, field by field. The control loop is EXPOSURE DOSE -- the direct analog of the jam-physics gate: dose (mJ/cm^2) = intensity (mW/cm^2) * time (s). The resist clears only inside a DOSE WINDOW: UNDER-dose -> resist never clears -> MISSING features (the litho "too cold") OVER-dose -> features BLOOM, the critical dimension blows out, neighbors SHORT (litho "too hot") Over/under exposure also BIASES the critical dimension (CD): actual_CD = drawn_CD + dose-bias; a layout that passed DRC can still fail in resist if the dose is wrong. FOCUS: the stage Z must hold the pattern within the depth of focus or features blur. The S-class RECIPE GATE names the failing cause (UNDER_DOSE / OVER_DOSE / OUT_OF_FOCUS / CD_OUT) -- the same "tell me WHERE the hardware is failing" discipline as nx_jam_check, now for lithography. Composes nx_mask_geom (pattern + CD) + nx_motion_plan (field stepping) + nx_metrology. Units: dose mJ/cm^2, intensity mW/cm^2, time ms, lengths nm. LAWS: struct-free, integer-only. license_tier: ORIGINAL