Large logic device manufacturer reports reduction of defects related to the CMP de-chuck rinse cycle though the use of TENSOR D-Rinse, a CMP pad rinse additive from Intersurface Dynamics.
Shrinking transistors force the use of CMP planarization in building advanced semiconductors. The use of low resistive Cu as an inter-connect metal increases circuit speed but complicates the CMP process.
Relatively soft Cu metal scratches easily compared to W and Al. Cu can interact with barrier metals, corrode more easily and be an impetus to galvanic reactions. The use specialized abrasive and non-abrasive CMP slurries help to reduce these associated defects. However, these slurries (particularly those containing BTA) can form a semi-soluble reaction by-product with Cu and other chemistry forming a glaze on the polishing pad. This particle-containing glaze must be cleaned off prior to the next cycle for low defectivity and better uniformity. TENSOR D-Rinse efficiently removes Cu complexes from the pad yielding a clean uniform pad surface.
Water and water/BTA mixtures are used during the de-chucking of the wafer and during the high pressure spray rinsing of the pad. However, neither solution is effective at protecting the wafer while cleaning the glaze and particles from the pad surface. Specular surfaces produced during the polishing cycle may be damaged during de-chuck water rinse, through pad/particle/wafer/water contact. These defects can be classified as micro-scratching, staining and corrosion. TENSOR D-Rinse provides surface protection to the wafer during de-chuck eliminating the associated defects.
Water and water/BTA mixtures used during the de-chuck cycle are also ineffective at removing slurry particles (especially BTA based slurries) from the wafer surface prior to the next step. Ineffective removal of these slurry particles can contribute defectivity as they are transported to the next step. Residual slurry particles on the wafer surface after the final step, contribute greatly to inefficient post-CMP cleans. TENSOR D-Rinse greatly enhances post-CMP cleans by effective removal of slurry and pad residue from the wafer prior to entering the CMP cleaning steps.
Water/BTA mixtures can form a molecular layer on Cu surfaces that create downstream problems during additional processing. TENSOR D-Rinse removes BTA films and provides a proprietary molecular film that does not require removal prior to additional processing steps.