Method of monitoring high tilt angle of medium current implant

A method of monitoring and adjusting the position of a wafer with respect to an ion beam comprising:

• placing a first test wafer in a wafer holder positioned at a 45 degree tilt angle and a twist angle of 45 degrees with the anticipated path of an ion beam from an ion implanter;
• implanting ions in a region of the first test wafer at a first energy and a first dose level, and measuring the sheet resistivity of the implanted region of the first test wafer;
• implanting a plurality of production wafers with ions;
• implanting ions in a region of a second test wafer at the first energy level and the first dose level, and measuring the sheet resistivity thereof and readjusting the position of the wafer holder so that the wafer has a 45 degree tilt angle if the sheet resistivity of the second wafer is greater than 30 ohms/square with respect to the sheet resistivity measured for the first test wafer.

A method of adjusting the wafer tilt angle to arrive at a tilt angle that is substantially at a true 45 degree angle comprising:

• (A) holding a semiconductor wafer in a wafer holder in a first implant position believed to be approximating 45 degrees with respect to anticipated path of an ion beam from an ion implanter, implanting ions into the wafer at a first energy and a first dose level, and measuring the sheet resistivity of the wafer implanted in the first position;
• (B) holding the wafer in the wafer holder and tilting the wafer in a first direction to a second implant position, and implanting ions into the wafer at the first energy and first dose level, and measuring the sheet resistivity of the wafer implanted in the second implant position and comparing to the sheet resistivity measured in the immediately prior implant position of the wafer, and if the sheet resistivity of the wafer implanted in the second implant position is less than the sheet resistivity of the wafer implanted in the first immediately prior implant position of the wafer and if the difference between the measured sheet resistivity of the wafer in the second implant position and the measured sheet resistivity of the wafer in the immediately prior position is greater than a target range then repeating (B), and if the difference in the measured sheet resistivity is within the target range then stopping the monitoring and adjusting of the wafer tilt angle, an if the sheet resistivity of the wafer implanted in the second implant position is greater than the sheet resistivity of the wafer implanted in the immediately prior implant position, and the difference between the sheet resistivity of the wafer implanted in the second implant position in the wafer implanted in the first position is greater than a target range then
• (C) holding the wafer in the wafer holder and tilting the wafer, in the direction opposite to the direction that the wafer was tilted to arrive at the immediately prior implant position of the wafer in the holder, to a third implant position, implanting ions into the wafer at the first energy and first dose level and measuring the sheet resistivity of the wafer implanted in the third implant position and comparing to the sheet resistivity measured in the third implant position to the resistivity measured for the wafer implanted in the immediately prior implant position, and if the sheet resistivity of the wafer implanted in the third implant position is greater than the sheet resistivity of the wafer implanted in the immediately prior implant position, and if the difference between the sheet resistivity of the wafer implanted in the third implant position in the wafer and the sheet resistivity of the wafer in the implanted in the immediately prior implant position is greater than a target range, then repeating (C), and if the difference in the measured sheet resistivity of the wafer implanted in the third implant position and implanted in the immediately prior implant position is within the target range then stopping the adjusting of the wafer tilt angle.