Anne E. Miller

An overview of corrosion - wear interaction for planarizing metallic thin films

Corrosion-wear interactions play a very crucial role in developing many technological processes. One of them is chemical-mechanical planarization (CMP) of metallic thin films for manufacturing semiconductor devices such as computer chips. In this paper, we present research approaches undertaken in developing CMP for different metallic thin films, such as tungsten and copper in aqueous media. Mechanisms of material removal during CMP are presented. The role of corrosion, wear, and their synergistic effect are explained. The importance of constructing corrosion-wear maps for these complicated tribo-corrosion-metallic thin film systems is addressed. The application of corrosion-wear maps in developing reliable CMP slurries and processes is discussed.

Chemically induced defects during copper polish

A high yielding copper damascene process requires defect-free copper surfaces after Cu polish. Critical defects derive from corrosion processes such as pitting corrosion, galvanic corrosion and excess etching. Changes in process conditions for Cu polish as well as the interaction with Ta polish step in a two-step (Cu/Ta) Ta polish can assist in defect reduction. Since these corrosion defects derive from the slurry chemistry itself, their quantities can be significantly reduced but not eliminated with process module changes.

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 300 μm range while electropolishing thin Cu films is addressed by optimizing applied current. For a typical electropolish solution of 6.4 M H 3 PO 4 , 5.4 M glycerin and 17.5 M H 2 O, an rms value of 38 A, comparable to the incoming post-CMP wafers, is demonstrated for 2500 A Cu removal.