Precursor compositions for the deposition of electrically conductive features

Abstract

A precursor composition for the deposition and formation of an electrical feature such as a conductive feature. The precursor composition advantageously has a viscosity of at least about 1000 centipoise and can be deposited by screen printing. The precursor composition also has a low conversion temperature, enabling the deposition and conversion to an electrical feature on low temperature substrates. A particularly preferred precursor composition includes silver and / or copper metal for the formation of highly conductive features.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 327,621 filed Oct. 5, 2001 and U.S. Provisional Patent Application No. 60 / 338,797 filed Nov. 22, 2001. The disclosure of each of these applications is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to precursor compositions that are useful for the deposition of conductive electronic features. The precursor compositions can advantageously have a low conversion temperature to enable low-temperature treatment of the precursors to form conductive features on a variety of substrates. The precursor compositions have a relatively high viscosity and can be deposited onto a substrate using methods such as thick-film deposition or syringe dispensing. [0004] 2. Description of Related Art [0005] The electronics, display and energy industries rely on the formation of coatings a...

AI Technical Summary

Benefits of technology

[0111] The precursor compositions of the present invention can in addition include rheology modifiers such as additives that have a thickening effect on the liquid vehicle. The advantageous effects of these additives include improved particle dispersion, reduced settling of particles, and reduction or elimination of filter pressing during syringe dispensing or screen-printing. Rheology modifiers can include SOLTHIX 250 (Avecia Limited), styrene allyl alcohol, ethyl cellulose, carboxy methylcellulose, nitrocellulose, polyalkylene carbonates, ethyl nitrocellulose, and the like.

[0112] One difficulty that can arise with respect to the precursor compositions of the present invention is that during drying, molecular metal precursors present in the liquid can crystallize and form large crystallites, which can be detrimental to conductivity upon conversion to the conductor. This problem can be reduced or eliminated by adding small amounts of a crystallization-inhibiting agent to the precursor composition. It has been found, for example, that in some silver precursor compositions small additions of lactic acid completely prevent crystallization. In other cases, such as aqueous Cu-formate compositions, small amounts of glycerol can inhibit crystallization. Other compounds useful for inhibiting crystallization are other polyalcohols such as malto dextrin, sodium carboxymethylcellulose and polyoxyethylenephenylether such as TRITON (Mallinckadt Baker, Phillipsburg, N.J.) or IGEPAL (Rhone-Poulenc, Cranbury, N.J.). In general, solvents with a higher melting point and lower vapor pressure inhibit crystallization of a compound more than a lower melting point solvent with a higher vapor pressure. Preferably, not greater than about 10 wt. % crystallization inhibitor (as a percentage of the total solution) is added to a precursor formulation, more preferably not greater than 5 wt. % and even more preferably not greater than 2 wt. %.

[0113] For example, preferred silver precursor formulations / solvent systems include Ag-nitrate and DMAc; Ag-nitrate, Ag-acetate, lactic acid and H2O; Ag-acetate and ethanolamine; Ag-trifluoroacetate and DMAc; Ag-trifluoroacetate, polyamic acid and DMAc; Ag-acetate, lactic acid and H2O; Ag-pentafluoropropionate, DMAc and polyamic acid prepolymer; Ag-trifluoroacetate and NMP; Ag powder, trifluoroacetic acid and DMAc; Ag-neodecanoate and DMAc; Ag-neodecanoate, DMAc and diethyleneglycol butylether (DEGBE).

[0114] The precursor compositions above can also include other components such as humectants and surface tension modifiers.

[0115] According to certain embodiments of the present invention, the precursor composition can be carefully selected to reduce the conversion temperature required to convert the molecular metal precursor compound to the conductive metal. The molecular metal precursor converts at a low temperature by itself or in combination with other molecular metal precursors and provides for a high metal yield. As used herein, the conversion temperature is the temperature at which the metal species contained in the molecular metal precursor compound, is at least 95 percent converted to the pure metal. As used herein, the conversion temperature is measured using a thermogravimetric analysis (TGA) technique wherein a 50-milligram sample of the precursor composition is heated at a rate of 10° C. / minute in air and the weight loss is measured.

[0116] A preferred approach for reducing the conversion temperature according to the present invention is to bring the molecular metal precursor compound into contact with a conversion reaction inducing agent As used herein, a conversion reaction inducing agent is a chemical compound that effectively reduces the temperature at which the molecular metal precursor compound decomposes to the metal. The conversion reaction inducing agent can either be added into the original precursor composition or added in a separate step during conversion on the substrate. The former method is preferred. Preferably, the conversion temperature of the metal precursors can be preferably lowered by at least about 25° C., more preferably by at least about 50° C. even more preferably by at least about 100° C., as compared to the dry metal precursor compound.

Problems solved by technology

Existing thick film conductor compositions cannot provide this combination of features.

These pastes provide processing temperatures close to 100° C., but offer poor reliability and performance.

Thin film techniques offer high reliability and high performance, but have a high cost and provide limited materials and geometries.

Paste compositions including conductor particles that must be sintered require firing temperatures of 600° C. or higher, limiting their application to glass or ceramic substrates.