Wafer processing method including uniting a wafer, a ring frame and a polyester sheet without using an adhesive layer

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 accomodating the wafer;
• a polyester sheet providing step of positioning the wafer in the inside opening of the ring frame and providing a polyester sheet in the wafer and on a back side of the ring frame;
• a uniting step of heating the polyester sheet as applying a pressure to the polyester sheet after performing the polyester sheet providing step, thereby uniting the wafer and the ring frame through the polyester sheet by thermocompression bonding to form a frame unit;
• a dividing step of positioning a focal point of a laser beam inside the wafer, the laser beam having a transmission wavelength to the wafer, and applying the laser beam to the wafer along each division line, thereby sequentially forming a plurality of shield tunnels in the wafer along each division line to divide the wafer into the individual device chips, after performing the uniting step;
• and
• a pickup step of cooling the polyester sheet in each region of the polyester sheet corresponding to each device chip, pushing up each device chip through the polyester sheet and picking up each device chip from the polyester sheet after performing the dividing step,
• wherein the polyester sheet is larger in size than the ring frame, and the uniting step includes an additional step of cutting the polyester sheet after the heating of the polyester sheet, thereby removing a part of the polyester sheet outside an outer circumference of the ring frame.