Victor Maurice Benveniste

Ion beam Profile and Emittance Measurements

In an ion implanter, the beam is extracted from an ion source, propagates through a sequence of optical elements that typically include a mass resolving system and drift spaces, and terminates at the target. The optics are designed to transport the beam with minimum losses and appropriate size and shape to the wafer. Because of the process implications of beam shape at the target, and the many variables and uncertainties that may affect the actual beam envelope, it is highly desirable to verify the beam shape and emittance at various places along the beam line. For efficient beam transport and other packaging considerations, the beamline length is kept to a minimum. This precludes the use of conventional beam profile monitors such as those used in the large particle accelerators. We review here the various techniques available to acquire a beam profile and emittance diagram, and describe a compact instrument that we have developed for use in our implanter beam lines.