Sacrificial alignment ring and self-soldering vias for wafer bonding

A method of bonding a first substrate to a second substrate, wherein the first substrate includes first electrical contacts on a top surface of the first substrate, and wherein the second substrate includes second electrical contacts on a bottom surface of the second substrate, the method comprising:

• forming a first material over the top surface of the first substrate and over the first electrical contacts;
• forming vias extending through the first material to expose the first electrical contacts;
• forming Sn—Cu material in the vias;
• forming a layer of polyimide over the top surface of the first substrate;
• selectively removing one or more portions of the layer of polyimide, leaving a block of the polyimide over the top surface of the first substrate, wherein the block of polyimide has a rounded upper corner;
• and
• vertically moving the top surface of the first substrate and the bottom surface of the second substrate toward each other until the Sn—Cu material abuts the second electrical contacts, wherein during the vertical moving, the second substrate makes contact with the rounded upper corner of the polyimide causing the first and second substrates to move laterally relative to each other.