The correct answer is: A. Remove silicon oxide.
Chemical mechanical polishing (CMP) is a process used to planarize wafer surfaces. It is a combination of chemical and mechanical actions that remove material from the wafer surface. The chemical action is typically a strong acid or base, while the mechanical action is typically a rotating abrasive pad.
CMP is used in a variety of semiconductor manufacturing processes, including the fabrication of integrated circuits (ICs). It is used to remove the silicon oxide layer that is used to protect the IC’s active devices. CMP is also used to remove the silicon nitride and pad oxide layers that are used to protect the IC’s metal interconnects.
CMP is a very precise process that can be used to remove very thin layers of material. It is also a very versatile process that can be used to remove a variety of materials, including silicon oxide, silicon nitride, and polysilicon.
Here is a brief explanation of each option:
- Option A: Remove silicon oxide. This is the correct answer. CMP is used to remove the silicon oxide layer that is used to protect the IC’s active devices.
- Option B: Remove silicon nitride and pad oxide. This is not the correct answer. CMP is used to remove the silicon nitride and pad oxide layers that are used to protect the IC’s metal interconnects.
- Option C: Remove polysilicon gate layer. This is not the correct answer. CMP is not typically used to remove the polysilicon gate layer.
- Option D: Reduce the size of the layout. This is not the correct answer. CMP is not used to reduce the size of the layout.