Particulate Silver Powder and Method of Manufacturing Same

Abstract

A particulate silver powder has an average particle diameter measured by TEM observation (DTEM) of 200 nm or less, an aspect ratio of less than 2.50, and a {(DTEM) / (Dx)} of 5.0 or less (where (Dx) denotes X-ray crystallite size). The particulate silver powder has a content of each of I−, Cl−, SO42−, NO3− and CN− of 100 ppm or less. The particulate silver powder is obtained by subjecting a silver compound other than silver nitrate to reduction in an organic solvent having a boiling point of 85° C. or greater at a temperature of 85° C. or greater and in the presence of an organic protective agent.

Description

TECHNICAL FIELD[0001]The present invention relates to a spherical, fine, particulate powder of silver (especially one of a particle diameter on the nanometer order) and a liquid dispersion thereof, particularly to a particulate silver powder low in corrosive components that is a suitable interconnect forming material for fabricating fine circuit patterns, especially for forming interconnects by the ink-jet method, and a method of manufacturing the powder. The particulate silver powder of the present invention is also a suitable material for forming interconnects on LSI substrates, and electrodes and interconnects of flat panel displays (FPDs), and for filling in fine trenches, via holes and contact holes. It is also suitable for use as a coloring material for automobile paints and the like. Moreover, its low impurity content and toxicity level make it useful as a carrier for adsorbing biochemical substances and the like in the fields of medical treatment, diagnostics and biotechnolo...

AI Technical Summary

Benefits of technology

[0012]Therefore, an object of the present invention is to overcome such problems by providing a nanoparticle powder of silver low in corrosive components that is suitable for fine interconnect formation applications, and a liquid dispersion thereof, at low cost and in large quantities. Moreover, since monodispersion of spherical silver nanoparticles of uniform diameter is preferable, another object is to provide a liquid dispersion of such silver particles.Means for Solving the Problems

Problems solved by technology

This makes it difficult to synthesize large quantities of silver nanoparticles for industrial use.

In contrast, the liquid phase method is basically suitable for large-volume synthesis but has a problem in that the metal nanoparticles in the liquid have a strong tendency to agglomerate, making it difficult to obtain a monodispersed nanoparticle powder.

This is a barrier to its industrial application.

The use of a dispersant of high molecular weight is not a problem when the silver nanoparticles are to be used as a coloring material, but when the particles are to be used in circuit fabrication applications, a firing temperature that is equal to or higher than the polymer boiling point is required and, in addition, pores readily form in the interconnects after the firing, so that problems of high resistance and breakage arise, making the particles not altogether suitable for fine interconnect applications.

However, the thiol type surfactant contains sulfur (S), and sulfur causes corrosion of interconnects and other electronic components, making it an unsuitable element for interconnect formation applications.

The method is therefore not suitable for interconnect formation applications.

Moreover, the liquid phase method uses silver nitrate, silver halide or the like as the silver source material (Patent Documents 2 and 3), so that the reaction solution unavoidably contains many ions originating from the silver source material, such as I−, Cl−, SO42−, NO3− and CN−.

In the case of nanoparticles, specific surface area is extraordinarily large, solid-liquid separation and washing are difficult, and the reactivity of the ions with silver is high since most of the ions originating from the starting material originally formed compounds with silver.

On the other hand, the increasingly sophisticated performance capabilities of electronic equipment in recent years has placed severe demands on the components of such equipment, and the content of constituents and elements that degrade reliability is required to be managed on the ppm order.

Under such circumstances, it is undesirable for corrosive components like I−, Cl−, SO42−, NO3− and CN− to be entrained in the liquid dispersion of the particulate silver powder.

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