Method for bonding substrates together, and substrate bonding device

A substrate bonding apparatus comprising:

• a first substrate holder that holds a first substrate;
• a second substrate holder that holds a second substrate with a bonding surface of the second substrate facing a bonding surface of the first substrate, the first substrate holder being located below the second substrate holder;
• hydrophilization treatment means that causes water or an OH containing substance to adhere to the respective bonding surfaces of the first substrate and the second substrate;
• a first protruding mechanism that bows the first substrate in such a way that a central portion of the bonding surface protrudes toward the second substrate side relative to an outer circumferential portion of the bonding surface;
• a second protruding mechanism that bows the second substrate in such a way that a central portion of the bonding surface protrudes toward the first substrate side relative to an outer circumferential portion of the bonding surface;
• and
• a controller, wherein
• the controller causes the bonding surface of the bowed first substrate and the bonding surface of the bowed second substrate to abut each other with (i) the first substrate being bowed by the first protruding mechanism in such a way that the central portion protrudes toward the second substrate side relative to the outer circumferential portion of the bonding surface and (ii) the second substrate being bowed by the second protruding mechanism in such a way that the central portion protrudes toward the first substrate side relative to the outer circumferential portion of the bonding surface, and causes the bonding surface of the first substrate and the bonding surface of the second substrate to abut each other across the entirety of the bonding surfaces, decreasing a distance between an outer circumferential portion of the first substrate and an outer circumferential portion of the second substrate with (i) distances from bottoms of the first substrate and the second substrate to the respective central portions being maintained and (ii) the respective central portions abutting each other at a pressure that maintains a non-bonded condition.