Method for cutting object to be processed

An object cutting method comprising the steps of:

• preparing a first sheet-like object to be processed comprising a silicon substrate having a main face in a (100) plane and a second sheet-like object to be processed the size of the silicon substrate being larger than the size of the second object when seen in the thickness direction of the first object;
• bonding a first-side end face of the first object and a second-side end face of the second object such that the second-side end of the second object face opposes the main face and an outer edge of the silicon substrate is located on the outer side of an outer edge of the second object when seen in the thickness direction of the first object;
• irradiating the first object with laser light so as to form a molten processed region within the silicon substrate along each of lines set like a grid for cutting the second object and cause a fracture generated from the molten processed region acting as a start point to reach a second-side end face of the first object along the line, the molten processed region being formed a part located on the outer side of the second object as well as a part opposing the second object in the silicon substrate when seen in the thickness direction of the first object;
• and
• generating a stress in the first object so as to cause the fracture to reach a first-side end face of the second object along each of the lines and cut the second object along each of the lines.