An innovative backside focused ion beam application for microelectronic devices failure analysis

• Main Author: Endrinal, Lesly Zaren V.
• Format: text
• Language: English
• Published: Animo Repository 2009
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3790
• Institution: De La Salle University

Electrical and physical failure analysis is a key operation in the expanding and dynamic world of semiconductor product design and manufacturing. It has been known to contribute significantly to the enhancement of performance and reliability of a product, by giving valuable feedback to designers and process stakeholders, thereby further improving the design, fabrication, assembly or testing process. This research investigates a new technique for package failure analysis, using a Dual Beam Scanning Electron Microscope (SEM) Focused Ion Beam (FIB) system. Conventional package failure analysis usually involves mechanical polishing and cross-sectioning. However, these techniques are rather manual, uncontrolled and are prone to human error and damage. Furthermore, with the increasing integration and decreasing sizes of IC components and interconnects, this mechanical polishing technique becomes limited, especially when the defect size or area of concern is within a few microns or in the nanometer range. Additionally, it also poses a challenge to perform a mechanical cross-section at the exact location of the defect, since the package is intact and there is no reference to the top die surface. This often results into a time-consuming process and it is very possible that the location of the failure might be missed during the polishing. Thus, a new technique of Focused Ion Beam micro-machining was developed to analyze the failing device from the backside of the silicon, in order to preserve the top plastic molding compound package and observe its interaction with the die top surface and the succeeding layers of metal and inter-metal dielectric. By utilizing a state-of-the-art tool, the FEI Strata Dual Beam FIB-SEM, a cross-section was made at regular and controlled intervals, thus eliminating the possibility of missing the defect site. With simultaneous slice and view made possible by the combined power of the SEM and the FIB, the Dual Beam can provide snapshots at regular intervals to give a sequential profile of the defect area being analyzed. Since the FIB cross sectioning tool is integrated with an imaging tool, this saves time in performing the cross-section as compared to the conventional technique where you have to polish and then view the sample under the optical microscope or the SEM. The results of the experiments showed the effectiveness of the newly developed technique, which illustrates a filler particle indenting towards the surface of the die, causing both passivation and inter-metal dielectric (IMD) to crack, giving some space for the metal to move in. The newly developed backside dual beam FIB cross-section was compared against the mechanical cross-section and several advantages and disadvantages were pointed out. In the end, the dual beam FIB cross-section is found to be a good alternative to mechanical polishing, especially when dealing with very large scale integration circuits and devices from which we suspect a mechanical damage to have occurred.