Atomic layer epitaxy of copper
Abstract: The high electric and thermal conductivity of copper has made it to a prime candidate as interconnect material in future integrated circuits. In this thesis, Atomic Layer Epitaxy has been used to deposit thin copper films on a variety of substrates, using both CuCl and Cu(II)2,2,6,6-tetramethyl-3,5-heptanedionate, Cu(thd)2, as precursors and hydrogen as reducing agent. Besides the experimental work, this thesis also comprises a large theoretical investigation where calculations based on Density Functional Theory has been performed in order to elucidate the deposition mechanisms in the CuCl/H2 process.Experiments showed that highly pure copper with low resistivity could be selectively deposited in the Cu(thd)2 process on Pt/Pd seeded substrates at temperatures below 300 °C. At higher temperatures, a selectivity was lost due to a thermal decomposition of the precursor, The selectivity was explained by the high catalytic activity of the seedlayer.Copper deposition by means of the CuCl/H2 process was kinetically controlled with an activation energy of approximately 85 kJmol-1 in the reduction step. Calculations showed that the rate determining step was the surface reaction between hydrogen and CuCl.
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