Chemical and mechanical properties of a surface reaction layer are essential to improve planarization in Cu-CMP. We compared the reaction layers on Cu surfaces formed by dipping in APS and H2O2 slurries and show that a thinner, mechanically stronger, and corrosion-resistant layer is preferable. It enables preferential polishing of the convex surfaces and consequently relaxes dishing after Cu-CMP. Controlling Cu oxidation reaction to form Cu2O in the slurry is essential for achieving further improvements of the planarization.

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In order to achieve high throughput Cu-CMP compatible with low step heights in 32nm Node copper interconnect technologies and beyond, we believe it is crucial a passivation layer on the Cu surface in the slurry during the CMP process. We show that the formation of a passivation layer which achieves good planarization with high Cu removal rate can be controlled by selecting the rest potential of the Cu ions in the slurry.

In this paper, we describe technologies to produce fine-pitch Cu wiring that provides high reliability and connects between chips for 2.1D/2.5D packaging. We have developed a semi-additive process to fabricate L/S = 1/1 μm wiring on an organic dielectric layer. The wiring uses Metal Cap barrier applied to LSI technology in order to suppress Cu diffusion and corrosion. This cap barrier oxidizes to form a passivation layer which prevents corrosion of the Cu wiring. The reliability of this wiring has been verified under HAST (Highly Accelerated temperature and humidity Stress Test) conditions, with a CoWP barrier in particular realizing higher reliability.

In the chemical mechanical polishing (CMP) process, we have discovered that the Cu etching rate can be enhanced without affecting the Cu slurry's pH by adding a small amount of the sulfur compounds MPS and Na 2 S 2 O 3 . Adding the sulfur compounds to the H 2 O 2 slurry results in an increment in the oxidation reduction potential (ORP). The electrochemical model (mixed potential) showed that the ORP increment leads to enhancement of the Cu oxidizing reaction. Because XPS and Raman analysis of the Cu surface revealed that the Cu etching rate in CMP is limited by the Cu oxidizing reaction, we concluded that the Cu etching rate is enhanced by the addition of sulfur compounds to the Cu oxidizing reaction to increase the ORP increment.