Method of direct plating of copper on a substrate structure

Abstract

The present invention teaches a method for depositing a copper seed layer onto a substrate surface, generally onto a barrier layer. The barrier layer may include a refractory metal and / or a group 8, 9 or 10 metal. The method includes cathodically pre-treating the substrate in an acid-containing solution. The substrate is then placed into a copper solution (pH≧7.0) that includes complexed copper ions and a current or bias is applied across the substrate surface. The complexed copper ions are reduced to deposit a copper seed layer onto the barrier layer. In one aspect, a complex alkaline bath is then used to electrochemically plate a gapfill layer on the substrate surface, followed by overfill in the same bath. In another aspect, an acidic bath ECP gapfill process and overfill process follow the alkaline seed layer process.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims benefit of U.S. provisional patent application Ser. No. 60 / 621,173 [APPM 9762L], filed Oct. 21, 2004, which is herein incorporated by reference. [0002] This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11 / 007,857 [APPM 9200], filed Dec. 9, 2004, which claims benefit of U.S. Provisional Patent Application Ser. No. 60 / 579,129, filed Jun. 10, 2004. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 11 / 012,965 [APPM 9201], filed Dec. 15, 2004, which claims benefit of U.S. Provisional Patent Application Ser. No. 60 / 579,129, filed Jun. 10, 2004, and U.S. Provisional Patent Application Ser. No. 60 / 621,215, filed Oct. 21, 2004. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 10 / 616,097 [APPM 8241], filed Jul. 8, 2003. Each of the aforementioned related patent applications is herein incorporat...

AI Technical Summary

Benefits of technology

[0012] The present invention teaches a method for depositing a copper seed layer onto a substrate surface, generally onto a barrier layer or an adhesion layer. The barrier or adhesion layer may include a refractory metal and/or a group VIII metal. The method includes cathodically pre-treating the substrate surface in an acid-containing solution that is free of copper ions. The substrate is then placed into a neutral or alkaline (pH≧7.0) copper solution that includes complexed copper ions and a current or bias is applied across the substrate surface. The complexed copper ions include a carboxylate ligand, such as oxalate or tartrate, or ethylenediamine (ED), EDTA and/or acetate. The complexed...

Problems solved by technology

However, as interconnect sizes decrease and aspect ratios of device features increase, void-free filling of interconnect features via conventional metallization techniques becomes increasingly difficult.

As a result thereof, conventional plating processes will likely be inadequate to support the demands of future interconnect technologies.

However, it is extremely difficult to have adequate seed step coverage with PVD techniques, as discontinuous islands of copper agglomerates are often obtained close to the feature bottom in high aspect ratio features with PVD techniques.

For PVD techniques, a thick copper layer (e.g., >200 Å) over the field is generally needed to have continuous sidewall coverage throughout the depth of the features, which often causes the throat of the feature to close before the feature sidewalls are covered.

For CVD processes, copper purity is generally questionable due to difficult complete precursor-ligand removal.

ALD techniques, though capable of giving generally conformal deposition with good adhesion to the barrier layer, suffer from very low deposition rates for depositing a continuous copper film on the sidewalls of adequate thickness to serve as a seed layer

Direct electroplating on barrier materials, such as tantalum or tantalum nitride, is difficult, since these traditional barrier materials generally have insulating native oxides across the surface.

Therefore, the integrity of the barrier layer may be compromised during the electroplating of a copper layer.

However, these techniques have suffered from several problems, such as adhesion failure between the copper seed layer and the barrier layer, as well as the added complexity of a complete electroless deposition system and the associated difficulties of process control.

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