Via chains for defect localization

A method comprising:

• simultaneously manufacturing integrated circuit chips on a wafer and forming via chain test structures in kerf areas of said wafer, said kerf areas of said wafer being located between said integrated circuit chips;
• testing said via chain test structures;
• and
• after testing said via chain test structures, dividing said wafer to separate said integrated circuit chips from each other in a process that destroys said kerf areas;
• said forming of said via chain test structures comprising forming a first via chain and a second via chain in a first kerf area such that geometrically shaped portions of said first via chain and geometrically shaped portions of said second via chain alternate along a length of said first kerf area,
• said testing comprising performing first magnification testing to identify a defective geometrically shaped portion, said defective geometrically shaped portion containing a defective via structure,
• said testing further comprising performing second magnification testing only within said defective geometrically shaped portion,
• said first magnification testing being performed at a lower magnification relative to said second magnification testing, and
• said second magnification testing being slower and more destructive to said kerf areas than said first magnification testing.

A wafer structure comprising:

• integrated circuit chips;
• kerf areas located between said integrated circuit chips;
• and
• via chain test structures in said kerf areas,
• said via chain test structures comprising a first via chain and a second via chain located in a first kerf area,
• geometrically shaped portions of said first via chain and geometrically shaped portions of said second via chain alternating along a length of said first kerf area,
• said first via chain comprising a first electrical circuit beginning and ending at a first location within said first kerf area, and
• said second via chain comprising a second electrical circuit beginning and ending at said first location within said first kerf area.