ESD (Electrostatic Discharge) Overview

Electrostatic discharge is a sudden flow of current between two objects at different electrical potentials, capable of damaging or destroying semiconductor devices in nanoseconds. ESD is the single largest cause of IC damage during handling and manufacturing.

ESD Models

• HBM (Human Body Model): Simulates a person touching a device. 100pF charged to 2-4kV, discharged through 1.5kΩ. Peak current ~1.3A for 2kV. Duration ~150ns.
• CDM (Charged Device Model): Simulates the device itself being charged and then touching ground. Very fast discharge (< 1ns), high peak current. Most relevant for automated handling. Typical spec: 250-500V.
• MM (Machine Model): Simulates tool/machine contact. 200pF, 0Ω. Highest peak current. Less commonly specified today.

Damage Mechanisms

• Gate Oxide Rupture: Voltage exceeds oxide breakdown (~10 MV/cm). Thinner oxides at advanced nodes are more vulnerable.
• Junction Burnout: High current melts silicon at the junction, creating a short circuit.
• Metal Fusing: Narrow interconnect lines melt from ESD current.
• Latent Damage: Partial oxide damage weakens device—passes initial test but fails early in the field.

ESD in Manufacturing

• Controlled humidity (40-60% RH) reduces static charge buildup.
• Ionizers neutralize charge on wafers, FOUPs, and work surfaces.
• ESD flooring, wrist straps, heel straps, smocks—all personnel grounding.
• EPA (ESD Protected Area) designation with regular audits.
• ESD-safe packaging (shielding bags, conductive containers) for transport.

On-Chip ESD Protection

• Clamp diodes, grounded-gate NMOS, SCR (silicon controlled rectifier), and dedicated ESD structures on every I/O pad shunt ESD current safely.