Methods for bonding semiconductor structures involving annealing processes, and bonded semiconductor structures formed using such methods

A method of directly bonding a first semiconductor structure to a second semiconductor structure, comprising:

• depositing metal over a first semiconductor structure;
• subjecting the metal deposited over the first semiconductor structure to a first thermal budget and annealing the metal deposited over the first semiconductor structure in a first annealing process by subjecting the metal deposited over the first semiconductor structure to a first average annealing temperature over a first annealing time period;
• removing a portion of the metal deposited over the first semiconductor structure after subjecting the metal to the first thermal budget;
• subjecting a remaining portion of the metal deposited over the first semiconductor structure to a second thermal budget by subjecting the remaining portion of the metal to a second average annealing temperature over a second annealing time period and annealing the remaining portion of the metal deposited over the first semiconductor structure in a second annealing process;
• directly bonding at least one metal feature of the first semiconductor structure comprising the remaining portion of the metal deposited over the first semiconductor structure to at least one metal feature of a second semiconductor structure to form a bonded metal structure comprising the at least one metal feature of the first semiconductor structure and the at least one metal feature of the second semiconductor structure;
• and
• subjecting the bonded metal structure to a third thermal budget by subjecting the bonded metal structure to a third average annealing temperature over a third annealing time period and annealing the bonded metal structure in a third annealing process, the third thermal budget being less than the second thermal budget.