Spectral reflectometry for process monitoring in high aspect ratio TSV fabrication to improve uniformity

Three-dimensional chip stacking enables by through silicon via (TSV) has become a critical focus in semiconductor manufacturing. However, as high-volume 3-D integration process demand faster etching rates, maintaining uniform etch quality across the wafer becomes crucial. We have designed an in-house spectroscopic reflectometry module to offer a non-destructive, and rapid metrology solution for in-line wafer etch uniformity monitoring. This module is capable of measuring via depth and optimize etching parameters in real-time. Several experimental trials utilizing reflectometer feedback data in a deep reactive ion etch (DRIE) process have demonstrated substantial improvements in etch depth uniformity. For TSV with a nominal 5 μm CD and aspect ratio of 10, uniformity improved from 5.18% to 2.47% by adjusting the parameter of outer/inner current ratio.