Patent ID: 9099546
Filing Date: 2015-08-04
Classification: H01L

Abstract:
1. A workpiece dividing method for dividing a workpiece along a plurality of crossing streets into each device, said workpiece having a substrate and a metal film formed on the front side of said substrate, said streets being formed on the front side of said metal film to partition said substrate into a plurality of regions where a plurality of devices are respectively formed, said workpiece dividing method comprising: a metal film cutting step of applying a first laser beam having an absorption wavelength to said metal film from the front side of said workpiece along said streets to form a plurality of laser processed grooves along said streets, thereby completely cutting through said metal film along said streets to expose said substrate, wherein during said metal film cutting step, the focal point of the first laser beam is set at a position slightly above the metal film, and said substrate is at most only minimally ablated by said first laser beam; a tape mounting step of attaching the front side of said workpiece to an adhesive tape supported by an annular frame after performing said metal film cutting step; a modified layer forming step of applying a second laser beam having a transmission wavelength to said substrate from the back side of said workpiece along said streets in the condition where the focal point of said second laser beam is set inside said substrate after performing said tape mounting step, thereby forming a plurality of modified layers inside said substrate along said streets; a dividing step of expanding said adhesive tape to apply an external force to said substrate after performing said modified layer forming step, thereby dividing said substrate along said streets; and a back grinding step of grinding the back side of said substrate to remove said modified layers after performing said dividing step, wherein during said back grinding step, said modified layers are removed by reducing the thickness of the substrate to a predetermined thickness by using a rotatable grinding wheel, without reducing the length or width of individual devices of the divided substrate.