Electroplating method

Abstract

The surface of a metal base is electroplated by utilizing an induction codeposition phenomenon using at least one of carbon dioxide and inert gas, an electroplating liquid containing a metal powder dispersed therein, and a surfactant in a supercritical state or a subcritical state. The concentration of the metal in the electroplating liquid is in a saturated or supersaturated state. Accordingly, the dissolution speed of the metal base can be suppressed, and, at the same time, a plating layer having a smooth surface can be formed in a short time by utilizing an induction codeposition phenomenon. The electroplating method can be applied even when the metal base is formed of a metallic thin film provided on a surface of an insulating film provided on the substrate, or even when the metal is copper, zinc, iron, nickel, or cobalt. The above constitution can provide an electroplating method which, in electroplating on the surface of a metal base, can prevent the dissolution of the metal base to realize normal electroplating even in the case of a very thin metal base.

Description

TECHNICAL FIELD[0001]The present invention relates to an electroplating method for electroplating the surface of a metal base, and particularly relates to an electroplating method in which the dissolution of the metal base that has not yet been electroplated can be prevented, and a uniform film can be obtained by electroplating in a short time using an induction codeposition phenomenon even on a very thin metal base.BACKGROUND ART[0002]In conventional methods for forming a fine metal wiring within a semiconductor element, a thin aluminum film is first formed, for example, on a substrate by sputtering; a photoresist is then applied; a pattern is formed by exposure and development; and a designated wiring is formed by etching. However, such wiring methods have come to be difficult to use with the progress in the increased integration and miniaturization of semiconductor circuit elements, prompting wider use of so-called Damascene methods, in which a wiring groove or hole is formed in ...

AI Technical Summary

Benefits of technology

[0022]By adopting a method such as the one described above, the present invention provides excellent effects as described hereinafter. In other words, when the surface of a metal base is electroplated according to the electroplating method of the present invention, the electroplating solution and the metal base are in contact with each other in an emulsion state because an arrangement is adopted in which electroplating is performed by utilizing the induction codeposition phenomenon using at least one of a carbon dioxide and an inert gas, as well as an electroplating solution containing a metal powder dispersed therein, and a surfactant in a supercritical or a subcritical state. For this reason, the electroplating solution rapidly penetrates into fine holes and grooves, and even a metal base having a complex shape can therefore be effectively electroplated in applications in which fine metal wiring is formed in highly integrated, miniaturized semiconductor circuit elements.

[0023]According to the electroplating method of the present invention, electroplating is performed in a state in which the metal powder is dispersed in the electroplating solution, and the concentration of the metal in the electroplating solution therefore corresponds to a saturated or supersaturated state. Therefore, the dissolution rate of the metal base can be reduced when the metal base is immersed into the electroplating solution, and a uniform film can be obtained by electroplating in a short time by using the induction codeposition phenomenon.

[0024]According to the electroplating method of the present invention, the dissolution rate of the metal base can be reduced when the metal base is immersed into the electroplating solution, for which reason electroplating can be performed in the regular manner even if the metal base is a thin metal film formed on the surface of an insulating film provided on a substrate. In particular, effective use can be made of the method in a Damascene method, dual Damascene method, or other application in which fine wiring is formed in miniaturized semiconductor circuit elements.

[0025]According to the electroplating method of the present invention, because the average particle diameter of the metal powder is set within a range of from 1 μm or greater to 100 μm or less and the solubility of metal powder in the electrolytic solution is high, metal ions can be efficiently fed to the electrolytic solution. In this case, the substrate microstructure to be deposited must be precise to 1 μm or more. An average particle diameter of the metal powder exceeding 100 μm is not preferred because the dissolution rate of the metal powder will be low.

[0026]According to the electroplating method of the present invention, the average particle diameter of the metal powder is set within a range of from 1 nm or greater to less than 1 μm. Therefore, the metal powder can be easily dispersed into the electrolytic solution, not only making aggregation more difficult, but also facilitating electroplating in microstructures having a precision of less than 1 μm.

[0027]The present invention is particularly suited for applications involving formation of fine wiring. The reason is that because a voltage at which the metal base will not dissolve is applied before the metal base is immersed into the electroplating solution, the metal base will not dissolve even if the metal base is immersed into the electroplating solution, and the voltage required for electroplating can be applied once a sufficiently stable state is established after the metal base has been immersed into the electroplating solution.

Problems solved by technology

Our experiments showed, however, that when this metal base was immersed into an electroplating solution to electroplate a similar metal, the metal base was often dissolved even if the metal base was a thick plate, and the plating failed without producing a smooth, normal surface.

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