Impact of oxide liner properties on TSV Cu pumping and TSV stress

We investigated the impact of oxide liner elastic modulus and thickness on through-silicon via (TSV) Cu pumping and stress. A low-k dielectric liner showed a decrease in residual Cu pumping and TSV stress compared to O₃-TEOS SiO₂ and ALD SiO₂ liners. For TSVs with a post-plating anneal, residual Cu pumping decreases from (102 ± 7) nm to (11 ± 1) nm (99.9th percentile) when the O₃-TEOS SiO₂ liner thickness increases from 50 to 630 nm, while the TSV stress increases from 220 to 610 MPa. The latter is attributed to permanent liner densification under compressive thermal stress at high temperature. This liner densification generates a significant part of the room temperature TSV stress. For our O₃-TEOS SiO₂ liner system, this was estimated to be 50 % of the total stress for a liner of 100 nm, and 90 % for a liner of 200 nm.