Chemical Mechanical Planarization (CMP) Metrology for 45/32 nm Technology Generations

In-plane geometrical defects on wafer surfaces following Chemical Mechanical Planarization (CMP) processing in the lateral millimeter range and in vertical dimensions in the nanometer range are of increasing importance. They will become a severe yield limiting factor in the 32 nm generations and below. At the wafer edge these defects are known as edge roll off (ERO). The feasibility of measuring flatness and geometry of bare silicon wafers and patterned wafers from different process steps as e.g. shallow trench isolation (STI) and interconnect metallization was successfully demonstrated using wave front sensing. The used wave front sensing methods were according to Makyoh and Shack Hartmann. The specifications achieved were for the Makyoh method a lateral resolution of 2.4 mm and for Shack Hartmann method 1.1 mm. The vertical resolution was 100 nm for the Makyoh method and 50 nm for the Shack Hartmann method