Wafer processing method

A wafer processing method for dividing a wafer along a plurality of division lines to obtain a plurality of individual device chips, the division lines being formed on a front side of the wafer to thereby define a plurality of separate regions where a plurality of devices are individually formed, the wafer processing method comprising:

• a ring frame preparing step of preparing a ring frame having an inside opening for accommodating the wafer;
• a thermocompression bonding sheet providing step of positioning the wafer in the inside opening of the ring frame and providing a thermocompression bonding sheet on a back side of the wafer and on a back side of the ring frame, the thermocompression bonding sheet having a first surface and a second surface opposite to the first surface, the first surface of the thermocompression bonding sheet coming into contact with the back side of the wafer and the back side of the ring frame;
• a uniting step of heating the thermocompression bonding sheet as applying a pressure to the thermocompression bonding sheet after performing the thermocompression bonding sheet providing step, thereby uniting the wafer and the ring frame through the thermocompression bonding sheet by thermocompression bonding to form a frame unit in the condition where the front side of the wafer and the front side of the ring frame are exposed;
• a dividing step of cutting the wafer along each division line by using a cutting apparatus including a rotatable cutting blade after performing the uniting step, thereby forming a dividing groove along each division line to divide the wafer into the individual device chips;
• a flattening step of flattening the second surface of the thermocompression bonding sheet in its central area where the first surface of the thermocompression bonding sheet has been bonded to the wafer, before or after performing the dividing step;
• and
• a back side observing step of observing a back side of each device chip through the thermocompression bonding sheet from the second surface thereof after performing the flattening step, thereby checking a condition of the dividing groove formed in the dividing step.