The Faraday Cup is arranged in the process chamber and beam line, corresponding to an ion beam shooting position. For each positive ion that enters the faraday, an electron is drawn from ground through the current meter to neutralize the positive charge of the ion. The magnetic field stops outside secondary electrons from entering and secondary electrons produced inside from exiting.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The Dose Control Systems
for an ion implantation system of the type
in which the wafers to be implanted are mounted around the periphery of
a disk which rotates and also moves in a radial direction relative to an
ion beam to expose successive sections of each wafer to the radiation.
The control system senses beam current which passes through one or more
apertures in the disk and is collected by a Faraday cup. This current is
integrated to obtain a measure of charge which is compared with a calculated
value based upon the desired ion dosage and other parameters. The resultant
controls the number of incremental steps the rotating disk moves radially
to expose the adjacent sections of each wafer. This process is continued
usually with two or more traverses until the entire surface of each wafer
has been implanted with the proper ion dosage.
United States Patent # 4,517,465
Top of Page
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Top of Page
This page is sponsored by Case Technology Inc. since 5/1/98.
Updated 6/6/99.