Iridium precursor pyrolysis and oxidation reactions and direct liquid injection chemical vapor deposition of iridium films

Abstract

Pyrolysis and oxidation reactions of the iridium precursor, (methylcyclopentadienyl)(1,5-cyclooctadiene)iridium (I), were studied to identify the role of O 2 in chemical vapor deposition film growth. A toluene solution of (methylcyclopentadienyl)(1,5-cyclooctadiene)iridium (I) was used in a direct liquid injection chemical vapor deposition process with O 2 to deposit iridium films on SiO 2 and TiN(111) substrates. The precursor decomposition studies revealed O 2 decreases the reaction temperature of (methylcyclopentadienyl)(1,5-cyclooctadiene)iridium (I) from near 760 K to temperatures below 465 K. Oxidation of the precursor ligands acts to prevent greater than 99% of the carbon from incorporating into the deposited film, making the growth surface more reactive. The precursor and oxygen react to form CO, CO 2 and H 2O. Pure iridium films were deposited on SiO 2 and TiN(111) substrates at temperatures between 550 and 625 K. Under identical conditions, the film nucleation and coalescence rates are nearly 2 times higher on the TiN(111) substrate with 0.22 torr O 2. The ratio of (111) to (200) X-ray diffraction intensities resembled Ir powder for films deposited on SiO 2, the same ratio was more than 9 times larger than that of Ir powder for Ir films produced on TiN(111). Decreasing the oxygen partial pressure from 0.66 to 0.22 torr resulted in a 75% reduction in the film growth rate and a 40% reduction in film roughness. Conformal (step coverage approaching unity) iridium films were produced at 550 K in aspect ratio 1–0.25 μm vias in SiO 2 and in aspect ratio 2.5–0.35 μm vias in TiN(111).