Existing States of Co-Deposited Hydrogen in Electrolessly Deposited Copper Films from EDTA Complex Bath

Abstract

The existing states of co-deposited hydrogen in copper films electrolessly deposited from an ethylenediaminetetraacetatic acid complex bath were investigated using thermal desorption spectroscopy. Small desorption peaks at 500–700 K and large desorption peaks at 900–1300 K were observed in the as-deposited copper film, and these were attributed to the break-up of vacancy-hydrogen clusters and the desorption of molecular hydrogen from nanovoids, respectively. Moreover, an unknown desorption peak appeared at around 390 K. The total amount of desorbed hydrogen from the copper film in atomic ratio was 1.2 × 10−2, most of which was non-diffusible hydrogen desorbed above 800 K. A large number of nanovoids distributed in the grains were observed in the copper film. After 7 days, no significant change in hydrogen desorption above 500 K was observed, while the unknown desorption peak around 390 K disappeared. The as-deposited copper film showed lattice expansion and compressive residual stress, which were reduced after 7 days. Therefore, we attributed the unknown desorption peak appearing at around 390 K to the desorption of hydrogen atoms trapped by regular interstitial sites in the copper lattice.