Method for fabricating nmos high-k metal gate and pmos high-k metal gate

A method for fabricating an NMOS high-k metal gate and a PMOS high-k metal gate, comprising the following steps:

• S1:
• providing a substrate, wherein a gate stack region is formed on the substrate;
• the gate stack region comprises a high-k layer formed on the substrate, and a dummy polysilicon layer formed on the high-k layer;
• S2:
• forming a first bottom anti-reflective coating over a wafer;
• S3:
• coating a first photoresist layer over the bottom anti-reflective coating, and performing a lithography process to expose the first bottom anti-reflective coating on an NMOS gate region of the gate stack region, while retaining the first photoresist layer on a PMOS gate region of the gate stack region;
• S4:
• performing etching to remove the first bottom anti-reflective coating on the NMOS gate region of the gate stack region, stopping on the dummy polysilicon layer of the NMOS gate region of the gate stack region;
• S5:
• performing boron ion implantation to dope the dummy polysilicon layer of the NMOS gate region of the gate stack region with boron ions;
• S6:
• removing the first photoresist layer and the first bottom anti-reflective coating from the wafer;
• S7:
• performing wet etching sequentially using diluted hydrofluoric acid and ammonia to remove the dummy polysilicon layer of the PMOS gate region of the gate stack region, stopping on the high-k layer;
• S8:
• forming a PMOS metal gate structure on the high-k layer within the PMOS gate region of the gate stack region;
• S9:
• forming a barrier layer over the wafer;
• S10:
• coating a second photoresist layer over the barrier layer, performing a lithography process to expose the barrier layer on the NMOS gate region of the gate stack region, while retaining the second photoresist layer on the PMOS gate region of the gate stack region;
• S11:
• performing etching to remove the barrier layer on the NMOS gate region of the gate stack region, stopping on the dummy polysilicon layer of the NMOS gate region of the gate stack region;
• S12:
• performing dry etching to remove the dummy polysilicon layer of the NMOS gate region of the gate stack region, stopping on the high-k layer;
• S13:
• removing the second photoresist layer and the barrier layer from the wafer;
• and
• S14:
• forming an NMOS metal gate structure on the high-k layer of the NMOS gate region of the gate stack region.