Carbon-based liner to reduce contact resistance

A method of forming a semiconductor structure, comprising:

• forming a first metal structure in a first oxide layer, wherein the first metal structure is a gate interconnect in contact with a gate contact and the gate contact is in contact with a gate that is associated with a source or drain,
• wherein the gate contact fully covers a top surface of the gate in a first dimension, and
• wherein the gate contact and the gate have substantially a same length in the first dimension;
• forming a first dummy metal structure in the first oxide layer, wherein a bottom surface of the first dummy metal structure is in contact with only a second oxide layer below the first oxide layer;
• forming a first carbon-based layer directly on a top surface of the first metal structure;
• forming a second carbon-based layer directly on a top surface of the first dummy metal structure,
• wherein a thickness of the second carbon-based layer is greater than a thickness of the first carbon-based layer;
• forming a third oxide layer above the first oxide layer, the first metal structure, the first dummy metal structure, the first carbon-based layer, and the second carbon-based layer;
• forming a second metal structure above the first metal structure and in the third oxide layer, wherein the second metal structure has a first barrier layer on sidewalls of the second metal structure and the first barrier layer is absent from a bottom surface of the second metal structure;
• and
• forming a second dummy metal structure in the third oxide layer,
• wherein the second carbon-based layer is separated from the second dummy metal structure by the third oxide layer, and
• wherein, in a side view of the semiconductor structure, the second dummy metal structure is aligned with and resides directly above the second carbon-based layer.

A method of forming a semiconductor structure, comprising:

• forming a first metal structure and a first dummy metal structure in a first oxide layer,
• wherein the first metal structure is a gate interconnect in contact with a gate contact and the gate contact is in contact with a gate that is associated with a source or drain,
• wherein a bottom surface of the first dummy metal structure is in contact with only a second oxide layer below the first oxide layer,
• wherein the gate contact fully covers a top surface of the gate in a first dimension, and
• wherein the gate contact and the gate have substantially a same length in the first dimension;
• forming a first carbon-based layer above a top surface of the first metal structure;
• forming a second carbon-based layer above the first dummy metal structure,
• wherein a thickness of the second carbon-based layer is greater than a thickness of the first carbon-based layer;
• forming a third oxide layer over the first oxide layer, the first metal structure, the first dummy metal structure, the first carbon-based layer, and the second carbon-based layer;
• forming a first barrier layer on sidewalls of a recess above the first carbon-based layer using precursor materials that selectively react with dielectrics and avoid reacting with organic materials that include the first carbon-based layer;
• forming a second metal structure in the third oxide layer above the first oxide layer,
• wherein the second metal structure has the first barrier layer on sidewalls of the second metal structure and the first barrier layer is absent from a bottom surface of the second metal structure;
• and
• forming a second dummy metal structure in the third oxide layer,
• wherein, in a side view of the semiconductor structure, the second dummy metal structure is aligned with, and resides directly above, the second carbon-based layer.