Beam scanning method and apparatus for ion implantation

摘要

Method of and apparatus for scanning a charged particle beam over a semiconductor wafer in a prescribed pattern. A triangular waveform, including alternating positive and negative ramp portions of constant slope and controllable time durations, is applied to a horizontal deflection system and produces horizontal scanning of the beam. The time durations of the ramp portions determine the length of the horizontal scan lines and are controlled according to a predetermined sequence so as to provide the prescribed pattern. The triangular waveform is provided by an integrator which receives a square wave from a frequency source of controllable frequency. The predetermined sequence is stored in a read only memory which controls the frequency of the frequency source. At the completion of each ramp portion, a voltage applied to a vertical deflection system is incremented so as to step the beam vertically up or down.