Contents:
Properties
Physical Data
Applications
Handling and Cleaning
Safety
Forms and Sizes Available
Other Precursors & Custom Preparations

Tantalum Ethoxide and
Niobium Ethoxide

Introduction
Tantalum and niobium ethoxides are available as convenient precursors in the production of their respective oxides in various applications. Chemical formulas are Ta(OC₂H₅)₅ and Nb(OC₂H₅)₅, sometimes referred to as metal pentaethoxides or metal salts of ethanol. These materials are liquid products which can be handled easily in vapor deposition systems and are readily hydrolyzed or pyrolyzed to form the desired oxide films. Both of these materials are available from from CERAC and can be shipped from stock in research quantities and production amounts.

Properties
Tantalum ethoxide is a clear, colorless, slightly viscous liquid at room temperature. It is soluble in most organic solvents, very moisture sensitive, and yields Ta₂O₅ upon reaction with water.

Niobium ethoxide is a yellow-to-orange liquid with similar chemical properties to tantalum ethoxide, yielding Nb₂O₅ upon hydrolysis.

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Physical Data

	Ta(OC2H5)5	Nb(OC2H5)5
CAS#	6074-84-6	3236-82-6
mp(°C)	21	6
bp(°C)/pressure	145/0.1mm	142/0.1mm
density (g/cc)	1.566	1.268
nD20	1.488	1.516
Trace impurities	Nb<100 ppm	Ta<50 ppm

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Applications
The main use of these metal ethoxides is the production of oxide films. The oxides of tantalum and niobium are used in thin film optical and semiconductor applications. The optical properties of Ta(OC₂H₅)₅ films have been extensively characterized - see our product data sheet on this material for more information. These coatings are transparent in the visible and near-IR and reflect in the IR region.

Ta(OC₂H₅)₅ and Nb(OC₂H₅)₅ have also been used in low-pressure chemical vapor deposition (LPCVD) systems to produce films over fairly large areas. This process is being developed for the production of advanced metal-oxide semiconductor (MOS) memory devices and dynamic random-access memory (DRAM).¹ The advantage of the deposited Ta₂O₅ film is a dielectric constant higher than that obtained by many commonly used dielectric materials. This property permits smaller capacitor dielectrics and subsequently smaller features on semiconductor devices. The deposited films often need to be annealed in oxygen to produce the desired properties.

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Handling and Cleaning
Tantalum and Niobium ethoxides are soluble in, and can be removed by most organic solvents. Hydrolyzed material (containing oxides) can be removed by mild scrubbing or abrasion, especially if the reaction with water is recent. Long-standing or dried coatings need more vigorous scrubbing or, possibly, washing with fluoride containing liquids such as hydrofluoric acid or ammonium bifluoride solution. These liquids can etch or otherwise damage glassware, so use with caution.

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Safety
These materials are considered flammable liquids due to evolution of ethanol upon hydrolysis. The hydrolysis products (metal oxides) are stable and require no special handling. Both Niobium and Tantalum ethoxide are listed on the EPA's Toxic Substances Control Act (TSCA) inventory.

Tantalum and niobium oxide are quite stable to most environmental conditions. The precursor ethoxides can thus be used where coatings of certain chemical or optical properties are desired.

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Forms and Sizes Available

Ta(OC₂H₅)₅

Item No.	Purity	Description
T-1100	99.999% (excl. Nb)	Liquid
T-2037	99.9% (excl. Nb)	Liquid

Nb(OC₂H₅)₅

Item No.	Purity	Description
N-1055	99.999% (excl. Ta)	Liquid

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Other Precursors & Custom Preparations
For over 30 years, CERAC has been known for its interest in and ability to prepare R&D quantities of less-common specialty inorganics. Although the ethoxides of tantalum and niobium are currently used in commercial applications, other organometallic compositions may have specific areas of interest. In general, ethoxides are a convenient starting point for preparing oxides, and titanium, zirconium, germanium and the rare earth oxides all have been synthesized. Please contact the CERAC sales department via e-mail or by phone at 414-289-9800 for technical assistance and discussions regarding ethoxides not mentioned here.

Reference

"MOCVD of Tantalum Pentoxide for Large-Area ULSI Circuit Wafers," Journal de Physique IV, Colloque C2, Suppl. au Journal de Physique II, Vol. 1, p. C2-311 ff. (Sept. 1991).

NOTE: Facts pertaining to properties and processing parameters of these materials were derived from published literature and testing sources. Although this information is believed to be correct, CERAC does not guarantee its accuracy.

Phone:  414-289-9800 /  FAX: 414-289-9805  /   ceracinfo@beminc.com