Process and reliability of SF6/O2 plasma etched copper TSVs

The formation of a TSV for three-dimensional interconnects using SF
₆
/O
₂
plasma is explored. Adjusting the O
₂
gas concentration to 45 sccm, while the SF
₆
concentration is set to 35 sccm, produced the best combination of chemical and physical etching to provide sidewall angles of 88°. Three TSV aspect ratios are etched (5/58, 10/100, and 20/100 μm) and subsequently analyzed using the finite element method. The TSVs' series resistance, current density, thermo-mechanical stress, and electromigration induced stress after 300 hours of operation at a 2MA/cm
²
current density are analyzed. An additional comparison to ideal TSVs with sidewall angles at 90° is performed.