Patent ID: 7427787
Filing Date: 2008-09-23
Classification: H01L

Abstract:
1. An ESD protection cell comprising: an SCR circuit having first and second terminals for coupling in an electrical path of an associated circuit to provide ESD protection for the associated circuit, wherein the SCR circuit includes a lightly doped region of a first conductivity type; a first highly doped region of a second conductivity type opposite the first conductivity type, wherein the first highly doped region is disposed within the lightly doped region at a surface of the lightly doped region, and at least a portion of the boundary between the first highly doped region and the lightly doped region forms a forward-biased SCR junction; a second highly doped region of the first conductivity type forming a guardring disposed within the lightly doped region at the surface, wherein the guardring surrounds the first highly doped region in a plane coplanar to the surface; and a pair of resistors dividing the guardring into first and second regions, wherein the resistors are disposed at the surface and the resistors are used to trigger the SCR circuit at the onset of an ESD event, wherein the first region of the guardring is electrically connected to the first terminal; and the second region of the guardring is electrically connected to the first terminal through the resistors.