A new fast QC method for testing contact hole roughness by defect review SEM image analysis

We propose a new and fast method for testing contact-hole-roughness (CHR), which is a major yield-loss factor for advanced SRAMs. This proposed method is using defect-review SEM image processing. The method can monitor CHR 100 times faster than the conventional method by CD-SEM. The speed can facilitate faster identification of process countermeasures by, for example, making detailed monitoring of CHR variation within a wafer practicable. Obtained results of CHR using new and traditional methods show similar trends on process condition dependencies. Through evaluation by the new method, we demonstrate that the standby electric current of advanced SRAM depends not only on overlay error but also on CHR.