Why is esd damage always on edge of a line?

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Why is esd defect always on edge of a line on die surface? And why is it always just a small dot? Is esd damage always like this? What are other kinds of esd damage?

New FA Eng

Joined: 20 Jun 2026 Posts: 76

The ESD 'spot' that you're seeing at the edge of a metal line (usually at an intersection of two metal lines) is called a 'dielectric rupture' or 'dielectric punchthrough.' This just means that the dielectric isolating the metal line from another line or the substrate broke down as a result of the high ESD voltage and got 'punched through'. This will lead to loss of isolation at that point (current can now flow through that spot). It is always at the edge of a line because dielectric coverage is thinnest at the vertical 'step' of the line.

No, not all ESD damage looks like a small spot. Some look like a 'bubble', or a 'hairline crack', or even mechanical/EOS damage (the worst ones). You'll soon encounter these other ESD attributes as you build experience.

FARel Engr