Applications of C-AFM analysis techniques at advanced IC on SRAM soft failure

Abstract

The application of the Conductive Atomic Force Microscope (C-AFM) has been widely used in the semiconductor industry for failure analysis on nanometer scale technology. Its main application in SRAM analysis for high/low resistance and junction leakages differentiation had proven to be very useful in determining the failure mechanism. We had successfully utilized a methodology using C-AFM to help us detect soft defect failure such as LDD missing/shallowing without using nanoprobing. This paper will demonstrate a new approach of the C-AFM to identify the electric characteristic of ATPG/Scan failure in CMOS process. Current FA methodology for ATPG/Scan failure utilizes layout and top view SEM image comparison to determine any abnormality between the physical chip and the intended masking. The beam tracer module, which is an added function from nanoprobe system, had demonstrated its feasibility in helping to improve the success rate of ATPG/Scan failure analysis (Figure 1). However the cost of setting up the nanoprobe system and purchasing the beam tracer module can be substantially high. Other methodologies include utilizing TIVA/OBRICH/EMMI techniques to deduce fault localization within the tracing path, but the success rate is layout design and failure mechanism dependant.