scribe line

The scribe line (also called kerf or street) is the region between die on a wafer that contains alignment marks, process control monitors (PCMs), test structures, and is ultimately where the wafer is cut during dicing. Scribe line width: typically 50-100 μm (80 μm common at advanced nodes)—represents lost silicon area between die. Contents: (1) Alignment marks—registration targets for lithography overlay between layers; (2) Process control monitors (PCMs)—transistors, resistors, capacitors measured at wafer sort for process monitoring; (3) Test structures—reliability structures (EM, TDDB), sheet resistance, contact resistance, linewidth measurements; (4) Overlay marks—targets for measuring layer-to-layer alignment accuracy; (5) CD targets—features for critical dimension measurement; (6) E-test pads—probe pad arrays for electrical measurement. PCM measurement: automated e-test probes scribe line structures after specific process steps and at wafer completion—provides SPC data for process monitoring. Scribe line design: must be carefully designed to not interfere with die—guard rings, seal rings at die edge protect active circuitry from dicing damage. Die seal ring: continuous metal structure around die perimeter preventing crack propagation from dicing into active area. Dicing: diamond blade saw (30-50 μm kerf) or laser dicing cuts through scribe line to separate die. Scribe line optimization: (1) Minimize width to maximize die count; (2) Pack sufficient test structures for process monitoring; (3) Balance between monitoring needs and area efficiency. Advanced: stealth dicing (laser-induced internal stress) enables narrower kerf and less chipping than mechanical dicing. The scribe line is valuable real estate that serves multiple critical functions for process control and manufacturing despite being discarded after dicing.