SELF-ALIGNED CONTACTS FOR SEMICONDUCTOR DEVICE

摘要

A method for etching, in a plasma processing chamber, through a selected portion of an oxide layer of a wafer's layer stack to create a self-aligned contact opening is described. The wafer stack includes a substrate, a polysilicon layer disposed above the substrate, a nitride layer disposed above the polysilicon layer, the oxide layer being disposed above the nitride layer. The first method includes etching through the oxide layer of the layer stack with a chemistry and a set of process parameters, the chemistry includes C4F8 and CH2F2. The second method includes a first etching step for etching partially through the oxide layer of the layer stack with a first chemistry including C2F6 and C2HF5 and a first set of process parameters for etching through the oxide layer without creating a spiked etch. The second etching step for etching the oxide layer through to the substrate with a second chemistry includes C4F8 and CH2F2 and a second set of process parameters different from the first set of process parameters without substantially damaging the nitride layer.