Measurement of Aluminium Remnant Thickness on Copper Wire Bonding using 3D Laser Scanning Microscope

The integrity of bond pad Aluminum(Al) thickness is essential in silicon wafer processing. The extensive usage of electronic devices in automotive applications suggests that high reliability and long life are required. Therefore, the reliability of copper ball onto aluminum bond pad depends on the aluminum remnant and Cu-Al intermetallic formation. An assessment will be done between (3D) Laser Scanning Microscope versus conventional cross-sectioning used to measure the Aluminum remnant thickness on base bond pad. These two measurements will be compared with PFIB-Plasma Focused Ion Beam in terms of measurement accuracy and total turn-around time (TAT) taken to perform sample preparation and measurement. For 3D Laser Scanning Microscope, a comparison was done between centralized and average measurement method to derive the imprint base bond pad thickness. The centralized method measurement with fitted imprint ball bond automatically detects the center homogenous surface whereas for average method, the measurement automatically detects at edge non-homogenous surface of imprint bond pad which results in higher thickness measurement. Centralized method using fitted ball imprint area measured with 3D Laser Scanning Microscope showed comparable measurement results or near perfect measurement with reference to cross section & PFIB measurement for Aluminium remnant thickness. 3D Laser Scanning Microscope has a better edge than conventional cross-sectioning for measurement of base bond pad aluminum remnant thickness. In the future, a 3D Laser Scanning Microscope will be used as a standard tool/technique for aluminum remnant thickness measurement as it significantly improves TAT> 90%-time reduction compared to the conventional method using cross-sectioning.