Defect detection method using heat

A method for detecting a defect in a substrate, the method comprising:

• loading the substrate on a wafer holder of a chamber, the substrate comprising an interface layer, first contacts and second contacts, the first contacts aligned to physically contact the second contacts at the interface layer;
• heating a portion of the substrate;
• cooling the substrate after the heating for a cooling period;
• during the cooling period, imaging the substrate to obtain a heat map of the substrate;
• and
• determining the defect between the first and the second contacts in the interface layer of the substrate based on comparing the heat map with a design map of the substrate.

A system for detecting a defect in a bonded wafer, the system comprising:

• a wafer holder disposed in a chamber;
• a light source and a light detector;
• and
• a controller coupled to the wafer holder, the chamber, the light source, the light detector, and a memory storing instructions to be executed in the controller, the instructions when executed cause the controller to:
• receive the bonded wafer on the wafer holder, the bonded wafer comprising a first structure bonded to a second structure, the first structure comprising first contacts, the second structure comprising second contacts, and the first structure bonded to the second structure forming a bonding layer comprising metal contacts between the first contacts and the second contacts;
• illuminate, using the light source, a portion of the first structure for a first time duration to heat the portion of the first structure to a starting temperature;
• detect, using the light detector, a temperature map of the bonded wafer, the temperature map being detected after a second time duration;
• and
• determine, based on the temperature map, the defect in the bonding layer of the bonded wafer.