Control of wafer charging on the Varian EXTRION 1000 ion implanter

Abstract

Wafer charging during high current implantation has been one of the major concerns to implanter users not only because of ever-shrinking device structures, but especially because of two to three-fold increases of beam currents available on next-generation high current implanters. In this paper, wafer charging on the Varian EXTRION 1000 was studied under various beam, electron flood gun and vacuum conditions and it was found that it can provide a much better environment in terms of wafer charging control than the previous generation machines. A relatively new technique, J- t test, has been used to measure the charge to breakdown as well as the traditional breakdown voltage measurement. The device yields from the tests were close to 100% for all the tested device wafers. The Q bd results from J- t tests showed good correlation with flood/vacuum conditions and pinpointed the best operating condition. However some results posed difficulty in interpretation, which suggests wafer charging is a very complex phenomenon.