Laser processing method for plate-shaped workpiece

A laser processing method for forming a laser processed groove on a plate-shaped workpiece by using a laser processing apparatus including a chuck table for holding said plate-shaped workpiece, laser beam applying means for applying a laser beam to said plate-shaped workpiece held on said chuck table, and feeding means for relatively feeding said chuck table and said laser beam applying means, said laser processing method comprising:

• a supporting step of attaching an adhesive tape to an annular frame having an opening for accommodating said plate-shaped workpiece and attaching said plate-shaped workpiece to said adhesive tape in a condition where said plate-shaped workpiece is positioned in said opening of said annular frame, thereby supporting said plate-shaped workpiece through said adhesive tape to said annular frame, said adhesive tape being composed of a base film, an adhesive layer formed on one side of said base film, and a functional layer formed on the other side of said base film, said functional layer including fine particles of metal oxide, emulsion particles of thermoplastic resin as a binder, and a dispersing medium;
• a holding step of holding said plate-shaped workpiece on said chuck table in a condition where said functional layer of said adhesive tape attached to said plate-shaped workpiece is in contact with said chuck table, after performing said supporting step, wherein the surface roughness of a surface of said functional layer that is in contact with said chuck table during said holding step is greater than or equal to 0.2 μm and less than or equal to 1.5 μm;
• and
• a laser processed groove forming step of applying said laser beam from said laser beam applying means to said plate-shaped workpiece held on said chuck table and relatively feeding said chuck table and said laser beam applying means by operating said feeding means, after performing said holding step, thereby forming said laser processed groove on said plate-shaped workpiece,
• wherein said functional layer prevents adhering of the base film to the chuck table during said laser processed groove forming step.