Article Abstract

Second Place Award: Radiation versus Voltage: Ion Implantation Exposures and Controls
Kaprice J. Knaup; University of Wisconsin - Stout

Semiconductor device fabrication involves a process known as ion implantation. This process is used to alter silicons ability to conduct electricity by introducing impurities into a selected region of the wafer (Slattery, 2000). A typical ion implanter consists of an ion source, accelerator, and a target chamber. The ion source houses a feed gas of the desired implanted species: boron trifluoride, arsine, or phosphine, (BF3, AsH3, or PH3 respectively), while the accelerator is used to electrostatically accelerate the dopant ion to a higher energy towards the silicon wafer at the end of the implanter in the target chamber (Slattery, 2000). Currently, high-energy implanters are more desirable then high-current or mediumcurrent implanters because of their ability to produce a higher potential beam current energy of up to 4 MeV; whereas medium-current and high-current implanters are capable of producing potential energies in the range of 10 keV to 500 keV. In a highenergy ion implanter, the ion beam accelerates as it passes through a radio frequency (RF) linear accelerator. This higher potential energy allows for a greater depth of penetration of ions into the silicon wafer. Although the use of these three types of implanters in industry results in process simplification and higher doping concentrations deeper in the well than at the surface, it also generates hazards (Rubin & Morris, 1997). Such hazards include radiation exposure and high voltage exposure.

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