A small step towards solving the global chip shortage problem – physical failure analysis

• Main Author: Tan, Yi Kai
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Materials::Microelectronics and semiconductor materials::Nanoelectronics and interconnects; Engineering::Electrical and electronic engineering::Microelectronics
• Online Access: https://hdl.handle.net/10356/161581
• Institution: Nanyang Technological University

Driven by an insatiable demand for Integrated Circuits (ICs) from massive industries and supply chain disruptions due to the Covid-19 pandemic, a global chip shortage has emerged in recent years. In response, the Physical Failure Analysis (PFA) of defective ICs has been explored to improve production yields and circuit design. However, due to a transition of interconnect material from Aluminium (Al) to Copper (Cu), this PFA process has been inhibited by the poor milling finish of these interconnects. Hence, this study was performed to provide solutions for the uniform deprocessing of copper interconnects using Xe+ Plasma Focused Ion Beams (Xe+ PFIBs), through the improvement of existing Gas-Assisted Milling (GAM) techniques and the pioneering of surface disruption strategies to counter channelling effects in aligned grains. This was achieved by first identifying and studying sources of the poor mill uniformity such as channelling effects, followed by a detailed study into beneficial phenomenon such as the dependence of sputtering yield on angle incidence, which could be exploited to improve the mill quality. Then, GAM and surface disruption techniques were performed and characterised using Secondary Electron Images (SEIs), Secondary Ion Images (SIIs) or Backscattered Electron Images (BEIs). Upon analysis of these images, each technique was evaluated, with surface disruption techniques being found to provide the greatest success only when complemented with a weak I2 background. Ion implantation of I2 could thus be further explored to introduce crystal structure disruptions within the interconnect without the risk of sample contamination.