Bonded assembly containing oxidation barriers and/or adhesion enhancers and methods of forming the same

A method of forming a bonded assembly, comprising:

• providing a first semiconductor die comprising a first substrate, first semiconductor devices, and first bonding pads that are electrically connected to a respective node of the first semiconductor devices, located in a first bonding dielectric layer, and comprise physically exposed surfaces located above a horizontal plane including a bottom surface of the first bonding dielectric layer;
• forming a first carbon-based oxidation barrier layer on the physically exposed surfaces of the first bonding pads by performing a selective deposition process that selectively deposits a first carbon-based oxidation barrier material that includes carbon at a weight percentage greater than 50% without forming the first carbon-based oxidation barrier layer on physically exposed surfaces of the first bonding dielectric layer;
• providing a second semiconductor die comprising a second substrate, second semiconductor devices, and second bonding pads that are electrically connected to a respective node of the second semiconductor devices;
• and
• bonding the second bonding pads to the first bonding pads with at least the first carbon-based oxidation barrier layer located between the respective first and second bonding pads, wherein metal-to-metal bonding occurs between the second bonding pads and the first bonding pads while the first carbon-based oxidation barrier material, or individual atoms or groups of atoms of the carbon-containing material formed by breakage of the first carbon-based oxidation barrier material, diffuse into the first bonding pads and into the second bonding pads during a bonding process and carbon atoms from the first carbon-based oxidation barrier material are distributed in surface regions of the second bonding pads and the first bonding pads.