Ion beam and dual ion beam sputter deposition of tantalum oxide films

Mirza Cevro; George Carter

doi:10.1117/12.192101

4 November 1994 Ion beam and dual ion beam sputter deposition of tantalum oxide films

Mirza Cevro, George Carter

Proceedings Volume 2253, Optical Interference Coatings; (1994) https://doi.org/10.1117/12.192101
Event: 1994 International Symposium on Optical Interference Coatings, 1994, Grenoble, France

Abstract

Ion beam sputter deposition (IBS) and dual ion beam sputter deposition (DIBS) of tantalum oxide films was investigated at room temperature and compared with similar films prepared by e-gun deposition. Optical properties ie refractive index and extinction coefficient of IBS films were determined in the 250 - 1100 nm range by transmission spectrophotometry and at (lambda) equals 632.8 nm by ellipsometry. They were found to be mainly sensitive to the partial pressure of oxygen used as a reactive gas in the deposition process. The maximum value of the refractive index of IBS deposited tantalum oxide films was n equals 2.15 at (lambda) equals 550 nm and the extinction coefficient of order k equals 2 X 10^-4. Films deposited by e-gun deposition had refractive index n equals 2.06 at (lambda) equals 550 nm. Films deposited using DIBS ie deposition assisted by low energy Ar and O₂ ions (E_a equals 0 - 300 eV) and low current density (J_i equals 0 - 40 (mu) A/cm²) showed no improvement in the optical properties of the films. Preferential sputtering occurred at E_a(Ar) equals 300 eV and J_i equals 20 (mu) A/cm² and slightly oxygen deficient films were formed. Different bonding states in the tantalum-oxide films were determined by x-ray spectroscopy while composition of the film and contaminants were determined by Rutherford scattering spectroscopy. Tantalum oxide films formed by IBS contained relatively high Ar content (approximately equals 2.5%) originating from the reflected argon neutrals from the sputtering target while assisted deposition slightly increased the Ar content. Stress in the IBS deposited films was measured by the bending technique. IBS deposited films showed compressive stress with a typical value of s equals 3.2 X 10⁹ dyn/cm². Films deposited by concurrent ion bombardment showed an increase in the stress as a function of applied current density. The maximum was s approximately equals 5.6 X 10⁹ dyn/cm² for Ea equals 300 eV and Ji equals 35 (mu) A/cm². All deposited films were amorphous as measured by the x-ray diffraction method.

Citation Download Citation

Mirza Cevro and George Carter "Ion beam and dual ion beam sputter deposition of tantalum oxide films", Proc. SPIE 2253, Optical Interference Coatings, (4 November 1994); https://doi.org/10.1117/12.192101

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