Patent ID: 11538923

Abstract:
A method for etching back a hard mask layer on top of dummy polysilicon gates in a gate last process comprises: step 1: forming a plurality of dummy gate structures; step 2: depositing a spin-on carbon (SOC) layer to fill the space regions between the sidewalls of the dummy gate structures to a level above the top surface of each of the plurality of dummy gate structures; step 3: performing a first etching-back to the spin-on carbon layer to remove the SOC layer outside the space regions and keep the SOC layer in the space regions below the top surfaces of each of dummy polysilicon gate; step 4: performing a second etching-back by using the remaining spin-on carbon layer as a mask to remove the hard mask layer and the sidewalls of the dummy polysilicon gates on both sides of the hard mask layer at the same time; step 5: removing the SOC layer. This technique saves one photomask and improves the process window.