Understanding Electrostatic Discharge (ESD) Damage in Integrated Circuits: A Comprehensive Analysis

Electrostatic discharge (ESD) damage is a critical concern in the manufacturing and reliability of integrated circuits (ICs). This phenomenon occurs when a sudden flow of electricity between two electrically charged objects causes component failure. Proper identification and analysis of ESD-induced damage are vital to improving IC design and implementing effective ESD-safe handling procedures.

The failure of integrated circuits due to ESD events can significantly impact both manufacturers and end-users. Identifying these failures helps manufacturers refine their IC designs, particularly in enhancing input protection circuits, and also validates the need for stringent ESD-safe handling protocols. However, distinguishing ESD damage from other forms of electrical overstress (EOS) failures can be challenging. Incorrect diagnosis can lead to ineffective countermeasures and increased production costs.

The study by Taylor, Woodhouse, and Feasey outlines a systematic approach to ESD failure analysis. This approach involves several steps to ensure accurate identification of failure sites:

1. Initial Examination

Components suspected of ESD damage are first examined visually and electrically tested. Automatic test equipment is used to perform full parametric measurements and functional checks to determine any deviations from expected performance.

2. Curve Tracing

A curve tracer helps predict the location of potential ESD failure sites by examining the voltage-current (Z/V) characteristics of the IC pins. This technique can identify areas where the ESD transient may have caused damage.

3. Decapsulation and Microscopy

To expose the IC die, decapsulation procedures are used. The exposed die is then examined using optical and scanning electron microscopy (SEM) to locate physical damage. However, damage sites often hidden beneath metal or polysilicon layers may require further analysis.

4. Controlled ESD Stress Testing

Identical, undamaged components are subjected to controlled human-body-model (HBM) ESD testing to replicate damage conditions. This helps correlate field failures with laboratory-induced failures, providing insights into the damage mechanisms.

5. Chemical Etching

When visual evidence is insufficient, chemical etching techniques can reveal the extent of ESD-induced damage at the silicon level. This step is crucial for understanding the mechanisms behind junction shorts and other forms of ESD damage.

6. Thermal Imaging and EBIC

Techniques like liquid crystal thermal imaging and electron beam-induced current (EBIC) imaging help detect ‘hot spots’ and leakage currents, respectively, which indicate areas of ESD damage.

The study found that ESD-induced junction shorts result from a combination of localized heating at the breakdown site and the heat generated by the discharge current. The damage is often more severe when the ESD transient is of higher magnitude or opposite polarity. Moreover, the sensitivity of an IC to ESD damage is closely related to the physical spacing between input contact windows and nearby metallization.