Patent ID: 6137112
Filing Date: 2000-10-24
Classification: H01J

Abstract:
An ion beam implanter for directing an ion beam against a workpiece, the implanter comprising:a) an implantation station defining an implantation chamber, the workpiece supported within the implantation chamber;b) an ion source and ion acceleration assembly generating the ion beam, the ion beam comprising a series of ion pulses, the pulses spaced apart by a predetermined period, T, and traversing an interior region of the ion implanter extending from an ion source to the implantation chamber; andc) a time of flight energy measurement apparatus for measuring an average kinetic energy of an ion included in a selected ion pulse of the ion beam, the energy measurement apparatus including:1) a first sensor and a second sensor disposed adjacent the ion beam and spaced a predetermined distance apart, the second sensor being downstream of the first sensor, the first sensor generating a signal when an ion pulse of the ion beam passes the first sensor and the second sensor generating a signal when an ion pulse of the ion beam passes the second sensor;2) timing circuitry electrically coupled to the first and second sensors and;a) calculating an average number of ion pulses, N, in the ion beam between the first and second sensors based on the approximation of the ion beam energy;b) calculating an offset time, t(offset), for the selected ion pulse using the formula, t(offset)=N.times.T; andc) determining an elapsed time, t, for the selected ion pulse to traverse the predetermined distance between the first and second sensors utilizing the signals generated by the first and second sensors and the calculated offset time t(offset); and3) conversion circuitry for converting the elapsed time, t, for the selected ion pulse into a measure of the energy of the ion beam.