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 N-2/H-2 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 (alpha) and chemisorbed (beta) water, to low-k dielectric reliability. With the physisorbed water desorbed by an anneal at 190 degrees 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 (E-a) does not change until the chemisorbed water component was desorbed by an anneal at 400 degrees C. The close similarity between E-a and the bond energy associated with the beta water component demonstrates that the beta bond is among the weakest links for the SiOCH low-k dielectric breakdown. (c) 2008 American Institute of Physics.