Improved pumping strategy for ion implanter end stations

The variety and complexity of ion implants required in modern semiconductor fabrication has placed increasing burdens on high vacuum pumps on the end stations of implanters. More high energy and high current implants, combined with increasingly stringent process requirements for greater uniformity of implant and higher product throughput, mean a requirement for a pumping scheme that yields high speed (and, more importantly, constancy of speed), while maintaining high tool availability. In this paper, we trace the logic that leads to these requirements and describe the resultant pumping scheme that uses high hydrogen speed cryopumps, a regeneration scheduling strategy that minimizes tool downtime, and improved regeneration methodologies that restore full pump capacity and speed in minimum time. When applied to operating fab tools, these techniques have resulted in significantly increased implanter availability, as well as improved process results.