Tantalum oxide thin films for dielectric applications by low-pressure chemical vapor deposition

Journal Article · Wed Sep 01 04:00:00 EDT 1993 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2220872· OSTI ID:5627485

Hitchens, W R; Krusell, W C; Dobkin, D M ^[1]

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1. Watkins-Johnson Co., Scott's Valley, CA (United States)

High quality Ta[sub 2]O[sub 5] films have been deposited by low-pressure chemical vapor deposition (LPCVD) from Ta (OC[sub 2]H[sub 5])[sub 5] (tantalum pentaethoxide) and oxygen. The films have been deposited on silicon, polysilicon, and SiO[sub 2]. Thickness reproducibility, across-the-wafer uniformity, and conformality and step-coverage all are excellent. As-deposited films are amorphous with smooth surfaces. Annealed films are polycrystalline, and their surfaces are characterized by 2 nm high, 1[mu]m diam nucleation centers surrounded by circular crystallization fronts. The films must be annealed to get acceptable leakage currents. Leakage currents for annealed 10 to 40 nm Ta[sub 2]O[sub 5] films are independent of film thickness and are [<=][sup [minus]9] A/cm[sup 2] at a gate voltage of 1.5 V. Effective dielectric constants decrease with Ta[sub 2]O[sub 5] film thickness. The smallest observed equivalent SiO[sub 2] thickness, t[sub ox,eff,] is 3.5 nm for 7.5 nm Ta[sub 2]O[sub 5]/Si. The minimum practical t[sub ox,eff] for the Ta[sub 2]O[sub 5]/Si system is approximately 3 nm. These electrical results are explained by the presence of a thin SiO[sub 2] layer at the Ta[sub 2]O[sub 5]/Si interface. The SiO[sub 2] layer dominates the electrical behavior of thin annealed Ta[sub 2]O[sub 5] films on Si. Effects of the surface structure and minimum t[sub ox,eff] on device integration are discussed.

• OSTI ID: 5627485
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 140:9; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360601* -- Other Materials-- Preparation &amp; Manufacture
360606 -- Other Materials-- Physical Properties-- (1992-)
CHALCOGENIDES
CHEMICAL COATING
CHEMICAL VAPOR DEPOSITION
CRYSTALS
CURRENTS
DATA
DEPOSITION
DIELECTRIC PROPERTIES
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
ELEMENTS
EXPERIMENTAL DATA
INFORMATION
LEAKAGE CURRENT
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLYCRYSTALS
REFRACTORY METAL COMPOUNDS
SEMIMETALS
SILICON
SILICON COMPOUNDS
SILICON OXIDES
SUBSTRATES
SURFACE COATING
TANTALUM COMPOUNDS
TANTALUM OXIDES
TRANSITION ELEMENT COMPOUNDS