SIDEWALL MICROSTRUCTURE ANALYSIS OF LASER DICED ULTRATHIN SILICON WAFER USING FOCUSED ION BEAM AND TRANSMISSION ELECTRON MICROSCOPY
Michael RM*, Foo KY, Zainuriah H and Kuan YC
Abstract
Sidewall Microstructure Analysis of Laser Diced Ultrathin Silicon Wafer using Focused Ion Beam and Transmission Electron Microscopy
Michael RM1,2[*], Foo KY1, Zainuriah H2 and Kuan YC3
1Infineon Technologies (Kulim) Sdn. Bhd., Kulim Hi-Tech Park, 09000 Kulim, Kedah, Malaysia
2School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia
3School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
Transmission electron microscopy (TEM) analysis is crucial for the understanding of the effect of laser dicing on the sidewall defects of ultrathin Si dies. A focused ion beam (FIB) lamella preparation technique for the full height of the sidewall of 20 µm Si dies singulated by laser was shown to be feasible. Energy dispersive spectroscopy (EDS) in scanning transmission electron microscopy (STEM) mode was done to determine the elemental composition of defects and phases in the die sidewall. Diffraction analysis in nanobeam diffraction (NBD) mode was done to determine the crystal structure of the defects and phases. Among the sidewall defects found were amorphous Si, polycrystalline Si, epitaxial Si, microcracks, pores and metal silicide phases. A marginally higher defect density and heat affected zone (HAZ) were found in the sidewall region near the die frontside compared to the backside. The TEM findings agree well with three-point bend (3PB) measurements where the die frontside characteristic fracture load was marginally lower than the backside characteristic fracture load.
Keywords: ultrathin silicon, laser dicing, sidewall defects, die mechanical strength
[*] Corresponding author: Tel: +6 04 427 8619
E-mail: MichaelRaj.Marks@infineon.com
