Developments in the abatement of ion implant process effluents

Abstract

The toxic and reactive nature of the materials utilized during ion implantation generates safety and environmental challenges. Recent introduction of reduced-pressure gas sources alleviated many concerns associated with delivering dopant species into the tool. However, materials not implanted onto wafers are instantly exhausted from the tool through roughing pumps or accumulated and later discharged using cryo pumps. Both pumps contribute ballast or carrier gas flows (typically nitrogen) resulting in tool effluent streams containing low concentrations of hydride and/or acid species. Due to their toxicity, point-of-use abatement methods are recommended in order to minimize the risk of human exposure or release into the environment. Chemisorption-based technologies are the method of choice for the removal of highly toxic materials to levels below threshold values. This paper describes recent developments related to the performance of an integrated zero footprint dry scrubber. Individual scrubber canisters were installed at the exhaust of roughing and cryo-pumps of an Axcelis GSD-VHE tool at Axcelis Technologies Inc. (Beverly, MA, USA). The abatement efficiencies and pressure drops of the abatement tools were characterized during implantation of common dopant species and cryo-regeneration. Highly sensitive hydride and acid sensors were used to monitor the exhausts of the abatement devices while scrubber inlet concentrations were analyzed using FT-IR techniques. Comparison of inlet and outlet concentrations provided information about the effectiveness of the scrubber. Pressure drop information was collected during chamber pumpdown, implantation, and cryo-regeneration. Pressure-drop and scrubbing efficiency will be periodically examined to validate long term operation of the abatement device.