Semiconductor structure with doped via plug and method for forming the same

A method for forming a semiconductor structure, comprising:

• patterning a substrate to form a fin structure;
• forming a gate structure on the fin structure;
• forming a source/drain structure on the fin structure, wherein the source/drain structure is adjacent to the gate structure;
• forming a contact plug on the source/drain structure;
• forming a dielectric layer on the contact plug;
• forming an opening in the dielectric layer to expose the contact plug;
• filling the opening with a metal material;
• performing an implantation process to induce a compressive stress between the metal material and the dielectric layer caused by an element implanted in the metal material and the dielectric layer, wherein the metal material covers a top surface of the dielectric layer;
• and
• after performing the implantation process, performing a planarization process on the metal material until a top surface of the dielectric layer is exposed.

A method for forming a semiconductor structure, comprising:

• forming a gate structure over a fin structure;
• forming a source/drain structure in the fin structure, wherein the source/drain structure is adjacent to the gate structure;
• forming a contact plug on the source/drain structure;
• forming a dielectric layer on the contact plug;
• forming an opening in the dielectric layer to expose the contact plug;
• depositing a metal material to fill the opening;
• performing an implantation process to implant a first group IV element into the metal material and the dielectric layer, wherein a difference between the mechanical strength of the metal material and the mechanical strength of the dielectric layer is reduced after the implantation process;
• and
• depositing the metal material directly above the dielectric layer,
• wherein the performing the implantation process comprises implanting the first group IV element into the metal material and the dielectric layer that is directly below the metal material.