Influence of absorbed water components on SiOCH low-$k$ reliability

We investigated plasma treatment induced water absorption in a SiOCH low-$k$ dielectric and the influence of the absorbed water components on the low-$k$ dielectric reliability. By using thermal desorption spectroscopy (TDS), water absorption in SiOCH was evidenced for $N2/H2$ plasma treatments. Based on these TDS results, two anneal temperatures were selected to separate and quantify the respective contributions of two absorbed water components, physisorbed $(α)$ and chemisorbed $(β)$ water, to low-$k$ dielectric reliability. With the physisorbed water desorbed by an anneal at $190°C$⁠, the low-$k$ dielectric shows reduced leakage currents and slightly improved time-dependent dielectric breakdown (TDDB) lifetimes. However, the observed failure mechanism represented by the TDDB thermal activation energy $(Ea)$ does not change until the chemisorbed water component was desorbed by an anneal at $400°C$⁠. The close similarity between $Ea$ and the bond energy associated with the $β$ water component demonstrates that the $β$ bond is among the weakest links for the SiOCH low-$k$ dielectric breakdown.