关键词: 化学机械抛光, 电化腐蚀, 球面平整度

Abstract: Chemical_mechanical polishing (CMP) is a process whereby mechanical and chemical forces are combined to remove material from a wafer and polish it to a flat surface. Tungsten CMP is an important process to gain the global planarity of silicon wafers with tungsten (W) plugs. Tungsten is actually deposited on a thin adhesive layer of titanium nitride (TiN) on silicon. When close to the final stage of polishing, TiN and W will be simultaneously exposed to the polishing chemistry, forming a galvanic couple. The corrosion of TiN and W couple will result in different polish rate. This work studied the potential difference and galvanic currents on particulate contamination of the abrasive on the patterned surface and on corrosion behaviors of TiN and W. The polarization curves of TiN and W were, respectively, obtained in 0.01 mol/L KNO 3 solutions in the absence and presence of three typical oxidants (H 2O 2, KIO 3, Fe(NO 3) 3) by DC polarization technique. The corrosion potentials and galvanic currents were measured when TiN and W were placed in a specially designed electrochemical cell to form electro_couple. The preliminary results revealed that the corrosion rate of TiN_W electro_couple significantly increased in the presence of 4.5% H 2O 2 at pH 4.0, while reduced to the minimal in the presence of Fe(NO 3) 3 at pH 1.5. Agitation significantly enhanced the corrosion rate of TiN_W couple.

Key words: Chemical mechanical polishing, Galvanic corrosion, Global planarity