Chemical-mechanical polishing (CMP) process for shallow trench isolation

摘要

A method of forming shallow trench isolation using CMP is described. A pad oxide layer is grown overlying a silicon semiconductor substrate. A polysilicon layer and a nitride layer are deposited. Trenches are etched through the nitride layer, polysilicon layer, and pad oxide layer into the silicon semiconductor substrate and filled with an oxide layer. A silicon oxynitride layer is deposited overlying the oxide layer. A first polishing is performed to polish away the silicon oxynitride layer and oxide layer using a first slurry having high selectivity of oxide to nitride. A second polishing is performed to polish away the oxide layer using a second slurry having a low selectivity of oxide to nitride. The nitride layer is removed and a third polishing is performed to planarize the oxide layer using a third slurry having high selectivity of oxide to polysilicon.