Patent ID: 6924215

Claim:
A method of monitoring and adjusting the position of a wafer with respect to an ion beam comprising: (A) setting the position of a wafer holder so that a wafer to be held therein is positioned at a tilt angle of 45 degrees and a twist angle of 45 degrees with respect to the path of an ion beam; (B) positioning a n-type wafer without screen oxide in the wafer holder; (C) implanting boron species into a region of the wafer at 160 KeV and a dose level of 5.0×10 13 atoms/cm 2 , (D) repeating (B)-(C); (E) periodically measuring the sheet resistivity of an implanted wafer and readjusting the wafer holder when the difference in sheet resistivity measured is greater than 30 ohms/square.