Wafer processing method

Abstract

A wafer processing method including the step of removing a ringlike reinforcing portion formed along the outer circumference of a wafer on the back side thereof. The ringlike reinforcing portion is ground by a grinding stone in such a manner that the locus of the grinding stone rotating intersects the ringlike reinforcing portion as viewed in plan. The grinding of the ringlike reinforcing portion is ended when the ground surface of the ringlike reinforcing portion becomes higher by 20 to 1 μm than the upper surface of a metal film deposited on the back side of a device area of the wafer. It is unnecessary to accurately align the grinding stone to the ringlike reinforcing portion on the upper side thereof, so that the position control can be easily performed. Further, the grinding of the ringlike reinforcing portion is ended when the difference in height between the ground surface of the ringlike reinforcing portion and the upper surface of the metal film becomes 20 to 1 μm, so that there is no possibility that the metal film may be damaged.

1 . A wafer processing method comprising:
 a ringlike reinforcing portion forming step for holding a wafer on a chuck table of a first grinding unit in the condition where the front side of said wafer is placed on said chuck table, the front side of said wafer being composed of a device area where a plurality of devices are formed so as to be partitioned by a plurality of streets and an outer circumferential marginal area surrounding said device area, and for grinding the back side of said device area of said wafer to form a recess and a ringlike reinforcing portion around said recess;   a metal film deposition step for depositing a metal film on the back side of said wafer after performing said ringlike reinforcing portion forming step; and   a ringlike reinforcing portion removing step for removing said ringlike reinforcing portion after performing said metal film deposition step;   said ringlike reinforcing portion removing step using a second grinding unit having a rotatable chuck table having a holding surface for holding said wafer, grinding means having a rotatable grinding wheel and a ringlike grinding stone fixed to said grinding wheel for grinding said wafer held on said chuck table, and feeding means for feeding said grinding means in a direction perpendicular to said holding surface of said chuck table;   said ringlike reinforcing portion being ground by said grinding stone in such a manner that the locus of said grinding stone rotating intersects said ringlike reinforcing portion as viewed in plan as rotating said chuck table on which the front side of said wafer is held and feeding said grinding stone by operating said feeding means during rotation of said grinding wheel;   the grinding of said ringlike reinforcing portion being ended when the ground surface of said ringlike reinforcing portion becomes higher by 20 to 1 μm than the upper surface of said metal film deposited on the back side of said device area.   
   
   
       2 . The wafer processing method according to  claim 1 , further comprising a separating step for separating said wafer into said individual devices along said streets in the condition where a dicing tape is attached to the back side of said wafer and said wafer is supported through said dicing tape to a dicing frame, after performing said ringlike reinforcing portion removing step. 
   
   
       3 . The wafer processing method according to claim  2 , wherein said dicing tape has a thickness of 80 to 100 μm.