End point detection in grinding

A method comprising:

• predetermining a target wheel current, wherein the predetermining comprises:
• grinding a sample wafer;
• during the grinding the sample wafer, monitoring wheel currents for grinding the sample wafer;
• inspecting the sample wafer to determine an optimal end point of the grinding;
• and
• recording one of the wheel currents corresponding to the optimal end point as the target wheel current;
• pre-selecting an extended grinding process;
• performing a grinding on a wafer, wherein the wafer has a same structure as the sample wafer;
• during the grinding, monitoring a wheel current of a grinding wheel used for grinding the wafer;
• starting the pre-selected extended grinding process once the wheel current reaches the target wheel current;
• and
• stopping the grinding once the pre-selected extended grinding process is finished.