Substrate transfer device and bonding system

A bonding system comprising:

• a substrate transfer device configured to transfer a first substrate and a second substrate in a normal pressure atmosphere:
• a surface modifying apparatus configured to modify surfaces of the first substrate and the second substrate to be bonded with each other in a depressurized atmosphere:
• a load lock chamber in which the first substrate and the second substrate are delivered between the substrate transfer device and the surface modifying apparatus and in which an internal atmosphere of the load lock chamber is switchable between an atmospheric pressure atmosphere and the depressurized atmosphere;
• a surface hydrophilizing apparatus configured to hydrophilize the modified surfaces of the first substrate and the second substrate;
• and
• a bonding apparatus configured to bond the hydrophilized surfaces of the first substrate and the second substrate by an intermolecular force,
• wherein the substrate transfer device includes:
• a first holding part configured to hold the first substrate from an upper surface side, a lower surface of the first substrate serving as a bonding surface;
• and
• a second holding part provided below the first holding part and configured to hold the second substrate from a lower surface side so that the second substrate faces the first substrate, a upper surface of the second substrate serving as a bonding surface to be bonded to the lower surface of the first substrate.