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.