Optical technologies for TSV inspection

In this paper, Frontier Semiconductor will introduce a new technology that is referred to as Virtual Interface Technology (VIT™). VIT™ is a Fourier domain technique that utilizes temporal phase shear of the measurement beam. The unique configuration of the sensor enables measurement of wafer and bonded stack thicknesses ranging from a few microns to millimeters with measurement repeatability ~ nm. We will present data on high aspect ratio via measurements (depth, top critical dimension, bottom critical dimension, via bottom profile and side wall angle), bonded wafer stack thickness, and Cu bump measurements. Another tool developed at FSM is a high resolution μRaman spectrometer useful in measuring stress-change in Si lattice induced by Through Silicon Via (TSV) processes. These measurements are important to determine Keep-Out-Zone in the areas where devices are built so that the engineered gate strain is not altered by TSV processing induced strain. Its stress resolution ~ 20 MPa. Applications include via post-etch; via post fill, and bottom Cu nail stress measurements. The capabilities of and measurement results from both tools are discussed below.