Method of detecting neutral particles in the ion beam in an ion implantation system and apparatus

摘要

An improved neutral particle detector (52) for an ion implantation system (10) is provided for detecting the neutral particle content of an ion beam (28) which is comprised primarily of neutral particles and positively charged ions. The neutral particle detector (52) comprises (i) a deflector plate (78) residing at a negative electrical potential; (ii) a first collecting electrode (82) residing at a positive electrical potential with respect to said deflector plate (78) for collecting secondary electrons emitted by the deflector plate (78) as a result of neutral particles in the ion beam impacting the deflector plate (78); and (iii) a second collecting electrode (84) residing at a positive electrical potential with respect to said deflector plate (78) for collecting secondary electrons emitted by the deflector plate (78) as a result of positively charged ions in the ion beam impacting the deflector plate (78). The deflector plate (78) and the collecting electrodes (82, 84) are separated by a distance through which the ion beam passes. The neutral particle detector (52) determines the neutral particle fraction of the ion beam independent of the composition or pressure of the residual background gas through which the ion beam propagates.