Machine and metrology issues for dose accuracy, repeatability, and uniformity of ion implanters

This paper reviews those vacuum-, beam-, and scan-related problem areas which mean that small dose variations and micro-uniformity must be accounted for during implant processing. A major focus of this paper is the relatively new topic of synchronous noise. Systematic dose fluctuations due to certain resonance combinations of wafer rotation speeds and beam scanning frequencies for electrostatic- and hybrid-scan implanters are reviewed and synchronous noise to disk/wheel spin frequency, scan speed, and voltage frequency in high-current implanters is explored. Finally, both electrical and optical metrology techniques are reviewed for their sensitivity to dose and their ability to resolve small feature scan variations caused by various contributors to small dose fluctuations and micro-uniformity.