Sucharita Madhukar

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 2 O. 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).

Pt Film Growth with Tetra-Kis(Triflurophosphine)Platinum

Platinum film growth using Pt(PF 3 ) 4 precursors was investigated. The study focused on three aspects of film growth: conformality, adhesion and selective growth. Pt(PF 3 ) 4 deposited pure Pt films over a wide range of temperatures (∼200 to 400 °C). At 200 °C, the step coverage for a via with an aspect ratio of three was poor. Lower growth temperatures showed a significant decrease in the growth rate. In addition, these films had poor adhesion to the substrate as indicated by separation between the Pt and the substrate in cross sectional scanning electron microscopy images. Oxygen addition during Pt film growth from Pt(PF 3 ) 4 improved both film conformality and adhesion. With oxygen, the step coverage on the side wall was greater than 90 % The dependence of the film growth rate on oxygen varied with the growth temperature: the growth rate decreased at 200 °C, while it changed slightly at 260 °C when oxygen was added. The substrate effect on the initial growth rate was studied on various substrates. The initial growth rate on metals is much faster than that on other substrates. The growth rate decreased on various substrates in the order of iridium > titanium nitride > barium strontium titanate > silicon nitride > silicon oxide.