Distributions of via Depth and bottom CD for TSV wafer have been studied by scanning interference microscopy
(Unifire 7900, Nanometrics Inc.). We plotted whole wafer maps for each via depth and bottom CD and found useful
relationship between them (i.e. via depth is in inverse proportion to bottom CD in general). Average values of via depth
and bottom CD are ~60um and ~4um and their standard deviation values are 1.28% and 5.14% respectively. We also
demonstrated kinds of defects at via top (or bottom) which can cause disturbance of total via count during 3D inspection.
Our results can be a good introduction to scanning interference tool as a monitoring tool for TSV high volume