Under-Bump Metallization Contact Resistance ( $R_{c}$ ) Characterization at 10- $\mu \text{m}$ Polymer Passivation Opening

Under-bump metallization R
_c
is a critical metric for high-density interconnect in electronic devices. We developed a test vehicle to characterize the impact of unit processes on R
_c
for 10-
$\mu \text{m}$
polymer passivation opening. We demonstrate that advanced preclean is necessary to achieve low (R
_c
< 20
$\text{m}\Omega$
) for future node extendibility, owing to reduction of both Al oxide and organometallic formation. This is achievable through a combination of low-temperature (<100 °C) preclean and fast residual gas purging from the chamber. A mechanism is proposed to explain the role of preclean in R
_c
performance. Influence of SiN etch on R
_c
is also investigated, and it was found that Cl-chemistry is better than F-chemistry to achieve low R
_c
.