BMD impact on silicon fin defect at TSV bottom

Abstract

A new type of through‐silicon via (TSV) defect, silicon fin defect, which was found after the TSV deep‐reactive‐ion‐etching process at the TSV bottom is reported. These defects are considered killer TSV defects that may cause process or mechanical failures and have to be eliminated. A scanning electron microscope automatic process inspection approach, which is non‐destructive and proven to be effective, has been established to image the fin defects at the bottom of the trench. A possible root cause of this defect is also explored. Both simulation and benchmarking test results indicate that bulk micro defects (BMDs) in the silicon substrate could serve as a micro‐mask during etching and result in silicon fin defects.

Optimization of TSV Leakage in Via-Middle TSV Process for Wafer-Level Packaging

“…As shown in Figure 8, hot spots were found at the TSV bottom (Figure 8a), and Cu diffusion was also found at the hot spot from the FIB cross-section, which is shown in Figure 8b. It is known that the BMD layer serves as an intrinsic gathering layer to improve device layer impurity and device performance [18], which makes it indispensable in Sibased processes. However, the correlation between the BMD density and Si striation in a silicon substrate clearly suggests that BMD is a critical factor that should be addressed and optimized in TSV wafer-level packaging.…”