Guard rings are structures fabricated along the perimeter of an integrated circuit chip to prevent delamination of the various layers of the integrated circuit chip and other edge damage during “dicing” of individual integrated circuit chips from a wafer on which multiple integrated circuit chips have been fabricated. Wafers are flat, thin (typically less than one millimeter (0.04 inch) thick), large in diameter (typically being up to 300 mm (about 12 inches)), and relatively brittle.
At a final stage of fabrication, the wafer is cut or diced into individual integrated circuit chips, either by sawing or by scribing and breaking. During the cutting or dicing process, the wafer is subjected to high shear stresses which can cause cracks to form that extend inwardly from the edges of each chip. Due to the stresses encountered when dicing the chip, or even later during use, cracks can propagate inward from the edges of the chip and eventually reach the active portion of the chip, damaging semiconductor devices disposed in the active portion.
Guard rings are typically in the form of a metallic ring-like structure positioned between the active region of the chip and the edge of the chip so as to encompass the active region of the chip. Generally, the active region of the chip is an internal circuit region containing semiconductor devices. Cracks that extend inwardly from the edges of a chip are halted by the guard ring. The guard ring typically extends vertically upward from a semiconductor device layer of the chip through all of the back-end-of-line (“BEOL”) metallization layers (also referred to herein as wiring levels) of the chip.