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21 November 2009

Answer to Question #6258 Submitted to "Ask the Experts"

Category: Industrial Radiation — Industrial Exposures

The following question was answered by an expert in the appropriate field:

I work on ion implantation machines in the semiconductor industry. Although these are mostly enclosed in lead shielding, there are areas where tools go through the shielding to where the ion implantation occurs. We accelerate arsenic, boron, and phosphorous to final energies from 10 keV to 1 MeV. What is the radiation risk of being in close proximity to these machines for extended periods of time? Typical machine manufacturers are Varian, Axcelis, and AMAT.

X rays produced in a 10 keV to 1 MeV device would be a result of free electrons accelerated to the metal parts that are charged to a voltage of 10 keV to 1 MeV, thus it is possible to generate some x rays inside an ion implantation device. The resulting x-ray intensity would be weak, but it would have energies up to 1 MeV. These x rays could penetrate the walls of the vacuum vessel, if poorly shielded. Check with a local radiation safety expert who can measure x rays—such as those at a hospital that does diagnostic x rays, or a state or federal inspector—to take measurements to see if your ion implantation devices are producing unsafe levels of x-ray radiation.

John P. Hageman, MS, CHP

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