Properties of tantalum oxide thin films grown by atomic layer deposition

Thin tantalum oxide films were deposited using atomic layer deposition from TaCl5 and H2O at temperatures in the range 80–500 °C. The films deposited at temperatures below 300 °C were predominantly amorphous, whereas those grown at higher temperatures were polycrystalline containing the phases TaO2 and Ta2O5. The oxygen to tantalum mass concentration ratio corresponded to that of TaO2 at all growth temperatures. The optical band gap was close to 4.2 eV for amorphous films and ranged from 3.9 to 4.5 eV for polycrystalline films. The refractive index measured at λ = 550 nm increased from 1.97 to 2.20 with an increase in growth temperature from 80 to 300 °C. The films deposited at 80 °C showed low absorption with absorption coefficients of less than 100 cm−1 in the visible region.

[1]  J. Dobrowolski,et al.  Optical coatings deposited by reactive ion plating. , 1993, Applied optics.

[2]  M. Leskelä,et al.  Precursor properties of calcium β-diketonate in vapor phase atomic layer epitaxy , 1994 .

[3]  Katsuhisa Sugimoto,et al.  Ellipsometric Examination of Growth and Dissolution Rates of Ta2 O 5 Films Formed by Metalorganic Chemical Vapor Deposition , 1992 .

[4]  Toyosaka Moriizumi,et al.  The Suitability of Ta2O5 as a Solid State Ion-Sensitive Membrane , 1987 .

[5]  Shigeo Fujita,et al.  Structural and Electrical Properties of Ta2O5 Grown by the Plasma-Enhanced Liquid Source CVD Using Penta Ethoxy Tantalum Source , 1993 .

[6]  H. Kim,et al.  The effect of substrate temperature on the composition and growth of tantalum oxide thin films deposited by plasma-enhanced chemical vapour deposition , 1991 .

[7]  Metallorganic chemical vapor deposition: a new era in optical coating technology , 1992 .

[8]  E. Khawaja,et al.  The optical properties of thin films of tantalum pentoxide and zirconium dioxide , 1975 .

[9]  K. Geib,et al.  Effects of oxygen content on the optical properties of tantalum oxide films deposited by ion-beam sputtering. , 1985, Applied optics.

[10]  H O Sankur,et al.  Deposition of optical thin films by pulsed laser assisted evaporation. , 1989, Applied optics.

[11]  H. Kattelus,et al.  Layered tantalum-aluminum oxide films deposited by atomic layer epitaxy , 1993 .

[12]  A. Watanabe,et al.  Morphology and structure of tantalum oxide deposit prepared by KrF excimer laser CVD , 1993, Journal of Materials Science.

[13]  K. Kuroiwa,et al.  Amorphous Silicon Thin-Film Transistors Employing Photoprocessed Tantalum Oxide Films as Gate Insulators , 1990 .

[14]  Yuliang He,et al.  The structure and properties of nanosize crystalline silicon films , 1994 .

[15]  K. Kukli,et al.  In situ characterization of ALE growth by reagent pulse delay times in a flow-type reactor , 1994 .

[16]  Koichi Kuroiwa,et al.  Investigation on Leakage Current Reduction of Photo‐CVD Tantalum Oxide Films Accomplished by Active Oxygen Annealing , 1992 .

[17]  N. A. Sörensen,et al.  An X-Ray Investigation of the Tantalum-Oxygen System. , 1954 .

[18]  M. Leskelä,et al.  In situ study of a strontium β-diketonate precursor for thin-film growth by atomic layer epitaxy , 1994 .

[19]  M. Pessa,et al.  Characterization of surface exchange reactions used to grow compound films , 1981 .

[20]  Y. Ohji,et al.  Stoichiometry measurement and electric characteristics of thin‐film Ta2O5 insulator for ultra‐large‐scale integration , 1993 .

[21]  Yukio Nishimura,et al.  Deposition of tantalum oxide films by ArF excimer laser chemical vapour deposition , 1993 .

[22]  J. M. Albella,et al.  Sputtered Ta2O5 antireflection coatings for silicon solar cells , 1982 .

[23]  K. Kukli,et al.  Deposition and etching of tantalum oxide films in atomic layer epitaxy process , 1994 .