Automatic determination of pressure compensation factors without requiring wafer implants

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 a matrix of implants with various parameters. This paper describes a new method for accurately determining these factors without any wafer implants. The method involves measuring the beam neutralization that results from an intentionally created pressure ramp in the process chamber. Results will be shown for pressure compensation of shower gas mixtures. The method can be extended to photoresist outgassing using special mixtures of gases chosen to simulate the outgassing from photoresist. The new method is faster, much less expensive and is immune to nonimplant processing effects.