Long Wavelength Roughness Optimization during Thin Cu Film Electropolish

Recent studies of Cu electropolish indicate planarization is not possible due to a large diffusion layer thickness relative to a small post-electroplate step height and small Cu overburden available for electropolish. Assuming an integration scheme that includes a CMP step followed by electropolish, the subsequent challenge of maintaining surface roughness over range while electropolishing thin Cu films is addressed by optimizing applied current. For a typical electropolish solution of , glycerin and , an rms value of , comparable to the incoming post-CMP wafers, is demonstrated for Cu removal.