CHARGE NEUTRALIZATION APPARATUS FOR ION IMPLANTATION SYSTEM

摘要

Methods and apparatus for neutralization of a workpiece (14) such as a semiconductor wafer in a system wherein a beam of positive ions (12) is applied to the workpiece (14). The apparatus includes an electron source (20) for generating an electron beam (22) and a magnetic assembly (24) for generating a magnetic field for guiding the electron beam (22) to the workpiece (14). The electron beam path (22) preferably includes a first section (34) between the electron source (20) and the ion beam (12) and a second section (36) which is coincident with the ion beam (12). The magnetic assembly (24) generates an axial component of magnetic field along the electron beam path (22). The magnetic assembly (24) also generates a transverse component of the magnetic field in an elbow region (26) between the first (34) and second (36) sections of the electron beam path (22). The electron source (20) preferably includes a large area lanthanum hexaboride cathode (42) and an extraction grid (44) positioned in close proximity to the cathode (42). The apparatus provides a high current, low energy electron beam (22) for neutralizing charge buildup on the workpiece (14).