electrical test structures
**Electrical test structures** are **on-wafer structures for measuring electrical parameters** — specialized patterns that enable precise measurement of resistance, capacitance, transistor characteristics, and other electrical properties critical for semiconductor process control and device performance.
**What Are Electrical Test Structures?**
- **Definition**: Dedicated patterns for electrical parameter measurement.
- **Purpose**: Characterize materials, interfaces, and device properties.
- **Types**: Resistors, capacitors, diodes, transistors, interconnects.
**Key Test Structures**
**Van der Pauw**: Four-point probe for sheet resistance.
**Greek Cross**: Sheet resistance with better accuracy.
**CBKR (Cross-Bridge Kelvin Resistor)**: Contact resistance measurement.
**MOS Capacitor**: Oxide quality, interface states, doping.
**Gated Diode**: Junction characterization.
**Contact Chains**: Via and contact resistance.
**Comb Structures**: Shorts and opens detection.
**Measured Parameters**
**Resistance**: Sheet resistance, contact resistance, line resistance.
**Capacitance**: Oxide capacitance, junction capacitance.
**Voltage**: Threshold voltage, breakdown voltage, flat-band voltage.
**Current**: Leakage current, drive current, saturation current.
**Mobility**: Carrier mobility from transistor characteristics.
**Measurement Techniques**
**DC**: I-V curves, resistance, leakage.
**AC**: C-V curves, capacitance vs. frequency.
**Pulsed**: Fast measurements to avoid heating.
**Four-Point Probe**: Eliminate contact resistance in measurements.
**Applications**: Process monitoring, yield analysis, device modeling, failure analysis, process development.
**Tools**: Semiconductor parameter analyzers, probe stations, C-V meters, automated test systems.
Electrical test structures are **fundamental to semiconductor manufacturing** — providing quantitative electrical characterization essential for process control, yield improvement, and device performance optimization.