Bath and method for high rate copper deposition

Abstract

A plating bath for electroplating copper on a microelectronic workpiece in a through-mask plating application at a rate of at least 2 μm / min where the bath includes: (a) 50-85 g / L of Cu2+; (b) 50-100 g / L of H2SO4; (c) 30-150 ppm of Cl—; (d) a brightener; (e) a wetting agent; (f) optionally a leveler; and (g) water. A process for electroplating copper on a microelectronic workpiece in a through-mask plating application at a rate of at least 2 μm / min where the process includes the steps of: (a) providing the plating bath described above; (b) providing a workpiece which has one or more through-mask openings having a conductive layer at the bottom of the openings; (c) contacting the conductive layer with the plating bath; and (d) providing electroplating power between the conductive layer and an anode disposed in electrical contact with the bath, whereby copper is deposited onto the conductive layer at a rate of at least 2 μm / min.

Description

FIELD OF THE INVENTION [0001] The invention is in the field of electroplating copper on a microelectronic workpiece using a plating bath. More particularly, the invention relates to electroplating copper on a microelectronic workpiece in a plating bath wherein the copper is deposited at a high rate in a through-mask plating application. BACKGROUND OF THE INVENTION [0002] Copper electroplating uses the process of electrolysis to deposit copper atoms on an object acting as the cathode, or negative electrode. Applications of electroplating of copper on microelectronic substrates in a plating bath can be divided into several categories, such as interconnect plating applications, micro-electro-mechanical systems (MEMS) plating applications, and bump plating applications. These pattern plating applications can be mainly divided into through-mask plating applications (photoresist pattern plating applications such as bump applications, MEMS applications, and redistribution applications) and...

AI Technical Summary

Benefits of technology

[0006] Baths of the present invention are useful for the high rate electroplating of copper in a through-mask plating application and can achieve (a) a copper deposition rate of at least 2 μm / min, e.g., 4 μm / min or faster; (b) a smooth surface morphology (Ra<30 nm) for the deposited feature; (c) a flat surface (good conformality with photoresist or other dielectric); (d) no dewetting, doming or skewing of the deposited feature; (e) no visible delamination of the deposited feature from the substrate and an adequate adhesion; (f) low dependency of morphology and flatness on feature shape, size, and open area; and (g) a thickness variation of less than 10% (3-sigma).

[0008] The baths of the present invention are formulated to fully wet all the features on a workpiece, particularly the surface to be electroplated without having a substantial adverse effect on the ability of the brightener to reduce the size of the metal grains and make the surface of the deposit brighter. The bath wets all features on the workpiece so that bubble trapping, pore formation, and / or dendritic growth is minimized. The baths have a low surface tension such that doming and skewing of the deposited copper is minimized. The baths are formulated so that the wetting agent does not have a substantial suppressing effect on the deposition of copper from the bath and does not react and absorb unevenly so as to result in crater-type defect formation within the deposited feature.

Problems solved by technology

One of the shortcomings of this commercial technology is that a copper deposition rate of 0.4-1.0 μm per minute is undesirably slow, not only for bumping applications, but for other through-mask plating applications requiring relatively thick deposits, e.g., microns thick.

These slow deposition rates increase the process time required to deposit thick features in through-mask applications.

Accordingly, microelectronic device manufacturers must bear the added cost and reduced productivity resulting from such long process times.

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