How thinner the epitaxial on heavily doped substrate the better fro latch-up?

[sathi.ec]

Can someone explain me
Thinner the epitaxial on heavily doped substrate is better for LATCH-UP? HOW?

 

[electronrancher]

Thin Epitaxial Layer

Latchup is often triggered by current injected accidentally from a well. If the current is high enough to give a 0.5-0.6v drop between the source and the closest pickup, it can begin turning on parasitic bjt.

Thinner epi will have a lower resistance path to substrate and therefore can tolerate more current before the resistive drop reaches 0.6v turn-on of the "base" of the parasitic bjt.