Die-scale wafer flatness: 3-dimensional imaging across 20 mm with nanometer-scale resolution

摘要

We present 3-dimensional atomic force profiler (AFP) measurements on die-scale flatness (20 mm x 20 mm) after copper and STI CMP. True metrology is achieved for patterned wafers. Wafers are vacuum-mounted on a flat chuck, as they would be in a stepper, so wafer warpage and strain-related non-planarity are not present. The results of this new technique are compared against current measurement techniques. For logic, memory and System-on-a-chip, we discuss the implications of wafer planarity going into subsequent photolithography steps.