Capturing Defects in Flip-Chip CMOS Devices Using Backside EBAC Technique and SEM Microscopy

This paper presents backside physical failure analysis methods for capturing anomalies and defects in advanced flip-chip packaged, bulk silicon CMOS devices. Sample preparation involves chemically removing all the silicon, including the diffusions, to expose the source/drain contact silicide and the gate of the transistors from the backside. Scanning Electron Microscopy (SEM) is used to form high resolution secondary and/or backscattered electron images of the transistor structures on and beneath the exposed surface. If no visual defects/anomalies are found at the transistor level, the Electron Beam Absorbed Current (EBAC) technique is used to isolate short/open defects in the interconnect metallization layers by landing nano-probe(s) on a transistor's source/drain silicide or on the gate. Using the combination of secondary and backscattered electron imaging and backside EBAC thus allows defects residing in either the transistors or the metal nets to be found. Case studies from 20 urn technology node graphics processing units (GPU) are presented to demonstrate the effectiveness of this approach.