X-Ray Generating Machines

In addition to x-ray exposures from ion implanters, the possibility of neutron formation has been postulated if the implanter is operated above 8 MeV or deuterium gas is used as an ion source.psf However, typically implanters are designed to operate at well below 8 MeV and deuterium is not commonly used in the industry. 

Within the industry, cabinet x-ray systems are used to check the thickness ofmetal coatings and to identify defects (e.g., air bubbles in mold compoimd packages). While fypically not a significant source of leakage, these imits need to be checked on a periodic basis with a hand-held survey meter for x-ray leakage and to ensure door interlocks operate properly. The operator manual should be kept adjacent to the unit. 

X-ray dilJiaction units generate an x-ray beam that is used to check the crystalline structure of incoming semiconductor wafers. Under certain circumstances, it may not be practical to fiilly contain the x-ray beam in an interlocked enclosure. In this instance, operators may be required to wear radiation finger badges, and controls similar to those used for a Class 4 lasers are used (e.g., enclosed room with limited access, operator training, enclosing the x-ray beam as much as practical, etc.). 

One advanced technology exposure source used in lithography is x-rays. Emission levels from x-ray lithography sources may result in dose rates approaching 5 rems per year in the center of the equipment. Restricting access to areas inside the shielded wall is recommended to minimize exposure.P7] 

As a minimum, radiation surveys should be performed when x-ray generating equipment is installed, modified, or moved. These surveys are typically performed with a Geiger-Muller (G-M) coimter or other sensitive rate meter with a fast response. The probe of the survey instrument is moved in a zigzag pattern across all surfaces of the tool. Cabinet seams, windows, screw holes, and other penetrations are particularly scmtinized. As part of the survey, any interlocks on the equipment should be checked to ensure they are functioning properly. 

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