Modifications to improve lifetime of the ELS ion source

The Extended Life Source, ELS, generally provides improved source life compared to the more commonly used Bernas source. The ELS source uses an indirectly heated cathode to keep the filament out of the arc chamber. Typical lifetime for NV-GSD sources running a mix of species in production has been about 100 to 300 hrs. Failure has often been associated with the cathode insulation, filament failures, or filament shorts. A new cathode assembly is discussed, which has allowed the source life to exceed 1300 hrs in production use on a NV-GSD/HE. Multiple-charged species are more challenging to produce and require high arc power to achieve useable currents. Requirements for 100 μA of He⁺⁺ with a source life of at Least 100 hrs on the Axcelis 8250 implanter necessitated a factor of two increase in source life. A special ELS source was developed which uses a thicker cathode, tungsten repeller, and other modifications to tolerate high arc power to enhance He⁺⁺ current. These modifications and their effect on performance is described