Workpiece processing method

A processing method for processing a plate-shaped workpiece having a division line on a front side and a multilayer member containing metal formed on a back side, wherein the front side includes a plurality of devices thereon, said processing method comprising:

• a holding step of holding the front side of said plate-shaped workpiece on a holding table in a condition where said multilayer member formed on the back side of said plate-shaped workpiece is exposed;
• a cutting step of cutting said plate-shaped workpiece along said division line by using a cutting blade after performing said holding step, thereby forming a cut groove dividing said multilayer member, with a remainder portion of said plate-shaped workpiece remaining below a base of the cut groove;
• and
• a laser processing step of applying a laser beam to said plate-shaped workpiece along said cut groove after performing said cutting step, wherein the laser beam passes through said cut groove before passing into said plate-shaped workpiece, wherein said laser beam is applied to the back side of said plate-shaped workpiece in said laser processing step;
• said cutting step including supplying a cutting fluid containing an organic acid and an oxidizing agent to said plate-shaped workpiece, and
• wherein the base of said cut groove formed during said cutting step is slightly lower in level than a lower surface of the multilayer member, such that a depth of said cut groove is less than a thickness of the remainder portion of said plate-shaped workpiece remaining below the base of the cut groove, and
• wherein said laser processing step includes applying a laser beam having a wavelength capable of being transmitted through said plate-shaped workpiece along said cut groove to thereby form a modified layer inside said plate-shaped workpiece along said cut groove;
• said processing method further comprising a dividing step of dividing said plate-shaped workpiece along said modified layer after performing said laser processing step.