H. S. Lin, T. H. Chen, W. C. Shu, UMC, Hsin-Chu City, Taiwan

Summary: It has been long recognized that SRAM memory is an ideal vehicle for defect monitoring and yield improvement during process development because of its highly structured architecture and simplified approach by memory bitmapping. However, the success rate of defect detection, especially for soft single column failure which is one of the most complex failure modes of an SRAM failure, is decreasing by traditional standard PFA with only the bit map available for guidance due to a variety of invisible or undetectable defects causing leakage behavior in the device. In order to understand the leakage behavior in advanced high voltage (HV) process, Conductive Atomic Force Microscope (C-AFM) [1-3] is introduced to perform junction level fault isolation prior to attempting physical failure analysis (PFA). According to J. P. Morniroli, crystalline defects affect convergent-beam electron diffraction (CBED) and large angle convergent-beam electron diffraction (LACBED) patterns, so CBED and LACBED techniques were also applied to the specimens containing dislocations for further characterization of these defects [4]. In this study, the quantified data extracted by C-AFM can also be used to build up a connection between a failure mechanism discovered and the soft single column failure mode.