sheet resistance mapping

**Sheet Resistance Mapping** is a **metrology technique that measures the spatial distribution of sheet resistance ($R_s$) across an entire wafer** — revealing uniformity of doping, film thickness, or annealing conditions through contour maps of $R_s$ variation. **How Does It Work?** - **Four-Point Probe**: Move a four-point probe head across the wafer on a grid (e.g., 49 or 121 sites). - **Eddy Current**: Non-contact measurement using eddy current interaction for metal films. - **Map**: Generate a contour map of $R_s$ across the wafer surface. - **Statistics**: Report mean, standard deviation, and uniformity (% variation). **Why It Matters** - **Implant Monitoring**: $R_s$ directly reflects ion implant dose and activation uniformity. - **Film Uniformity**: For metal and polysilicon films, $R_s$ maps reveal deposition thickness uniformity. - **Process Control**: $R_s$ uniformity specifications (typically < 2% 1σ) are critical SPC parameters. **Sheet Resistance Mapping** is **the uniformity report card** — visualizing how consistently a process step has been performed across the entire wafer.