Two implant measurement of pressure compensation factors

The ion beam is neutralized by interactions with the gas molecules present in the process chamber during wafer implant, and thus pressure compensation of this neutralization is necessary to deliver the proper dose. The parameters necessary for pressure compensation have traditionally been determined by implanting a matrix of monitor wafers with various recipe parameters. This paper describes a new method for accurately determining these factors with fewer implants. The new method is faster, much less expensive and is more immune to systematic errors in the implanter and post processing. This procedure has been used to generate tables of pressure compensation factors for several Axcelis high current platforms, and offers improvements to SPC collection at customer sites.