Selective Chemical Mechanical Polishing of Silicon Dioxide over Silicon Nitride for Shallow Trench Isolation Using Ceria Slurries

For the shallow trench isolation process, in which a thin silicon nitride film acts as a polish stop layer, a polishing slurry with a high oxide to nitride removal rate selectivity is required to remove the overburden oxide.In this work, we show that using ceria-based slurries and only 0.05% of any one of three different cyclic amine additives, namely, pyridine HCl, piperazine, and imidazole, very low nitride 2 to 3 nm/min and high oxide 350 nm/min removal rates can be obtained for blanket films.The role of these additives in the slurry toward achieving the desired removal rate selectivities of silicon dioxide over silicon nitride is discussed considering pyridine HCl as an example, using zeta potential, contact angle, adsorption isotherm, and thermogravimetric analysis data.