Study on CMP of Carbon Films Using Zirconia Particles

Abstract

Carbon films, which are applied as hard masks to the manufacture of high-performance semiconductor devices such as 3D NAND flash memory, are difficult to process with simple CMP slurries including silica or ceria particles, so oxidizing agents and metal complexing agents have been used in combination. However, the use of these additives is undesirable in terms of slurry stability, handling, and cleanability. We focused on zirconia as a new abrasive material and investigated the mechanochemical reaction between zirconia particles and carbon films to clarify the correlation between the reaction efficiency, particle properties that promote it, and the polishing rate. In the experiment, three different types of zirconia particles were investigated by evaluating the amount of oxygen vacancy, modulus, and chemical reactivity with carbon films. XPS and nanoindentation methods were used for these evaluations. While the amount of oxygen vacancies of the particle was not a parameter that affected the covalent bond formation, it was found that zirconia particles with high hardness efficiently formed covalent bonds with carbon materials, which may be expected to result in a high polishing rate. The actual polishing rate is up to about 15 times higher than silica slurry used at the same particle concentration, which may make it possible to reduce slurry consumption without the use of oxidizers or metal complexing agents.