3D ESD Verification: Tackling New Challenges in Advanced IC Design

 

3D ESD Verification: Tackling New Challenges in Advanced IC Design

Categories: 3D IC, EDA, Siemens EDA

Introduction

As semiconductor designs evolve toward heterogeneous 2.5D and 3D integration, long-established verification methodologies are being pushed beyond their limits. One area where this shift is especially evident is electrostatic discharge (ESD) verification. While ESD protection has been well understood in traditional 2D ICs, stacked-die architectures introduce new connectivity, new failure modes, and new verification complexity. Addressing these challenges requires a fundamentally different approach.

This blog explores why ESD verification is critical for 3D ICs, what makes it more complex than conventional designs, and how modern automation tools enable reliable and cost-effective verification.

Why ESD Verification Is Critical for 3D IC Designs

Electrostatic discharge remains one of the most common causes of IC damage throughout the product lifecycle—from wafer fabrication and packaging to board assembly and end use. An ESD event can introduce a sudden surge of current capable of melting interconnects, degrading oxides, or permanently damaging junctions.

For advanced ICs, ESD robustness is not optional. It directly impacts product reliability, field failure rates, and long-term operational stability. As integration density increases in 3D designs, the consequences of inadequate ESD protection become even more severe.

How ESD Protection Circuits Prevent Damage

Effective ESD protection depends on two key elements:

  • Robust circuit architectures capable of safely discharging ESD currents

  • Accurate physical implementation that preserves the original design intent

Designers introduce ESD protection structures at the schematic and layout levels, followed by rule-based verification to ensure topology correctness and current-handling capability. This pre-manufacturing verification step is essential to confirm that the design can survive real-world ESD events.

What’s Different About ESD Protection in 3D ICs

3D IC integration fundamentally changes how dies are connected and how signals propagate:

  • 2.5D designs place multiple dies side-by-side on a silicon interposer, using micro-bumps or hybrid bonds.

  • 3D designs stack dies vertically and connect them through through-silicon vias (TSVs).

These architectures often mix different process nodes, foundries, and packaging technologies within a single product. While this heterogeneity enables performance and power benefits, it also introduces new ESD exposure paths and verification challenges that do not exist in 2D designs.

Why 3D ESD Verification Is More Complex Than 2D

In traditional 2D verification, all pads are assumed to interface with the external environment and therefore require full ESD protection. In 3D ICs, this assumption no longer holds true.

External vs. Internal IOs

A critical distinction must be made between IO types:

  • External IOs connect to package pins and are exposed to both Human Body Model (HBM) and Charged Device Model (CDM) events.

  • Internal IOs are die-to-die connections and face significantly fewer ESD threats.

This differentiation enables internal IOs to use smaller, area-efficient ESD devices, reducing silicon cost while maintaining system-level robustness. However, it also increases verification complexity.


System-Level ESD Challenges in 3D ICs

Unlike 2D designs, ESD protection in 3D ICs must be evaluated at the assembly level, not just per die. Key challenges include:

  • Differentiating ESD requirements for external versus internal IOs

  • Handling HBM and CDM constraints across die-to-die connections

  • Determining the minimum ESD protection required for the final assembled product

  • Managing multiple technology nodes and foundries

  • Sharing ESD components such as clamps and resistors across dies

  • Supporting different ESD design methodologies from multiple vendors

These factors demand an architecture-driven verification approach rather than a purely foundry-specific one.

Automating ESD Verification for 3D IC Designs

Manual verification is not scalable for modern 3D architectures. Advanced automation tools are essential.

A proven methodology combines die-level and assembly-level verification:

  1. Die-level verification ensures each die and interposer meets ESD robustness requirements.

  2. System-level verification analyzes the complete 3D stack, checking point-to-point connectivity, topology rules, and geometrical constraints across dies.

Tools such as Calibre 3DPERC enable this holistic approach by performing cross-die ESD checks and identifying violations that would otherwise be missed using traditional 2D flows.



The Bottom Line

ESD protection remains a cornerstone of reliable IC design, but 3D integration requires a new verification mindset. Internal and external IOs have fundamentally different ESD requirements. ESD devices may span multiple dies and technology nodes. Vendor diversity and shared protection structures further complicate verification.

To meet these challenges, designers must adopt automated, system-level ESD verification methodologies tailored for 3D ICs. Doing so ensures consistent ESD robustness, improves product reliability, and extends the operational lifetime of advanced semiconductor products—ultimately delivering greater value to the market.

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