Safety and Health Considerations of an X-Ray Lithography Source.
Hazard Assessment and Control Technology in Semiconductor Manufacturing, Lewis Publishers, Inc., Chelsea, Michigan 1989:265-270
The use of x-rays as a lithography source to develop circuit patterns on resist/coated silicon wafers was discussed, in relation to health and safety. Hazards associated with the production of x- rays through an electron storage ring was exposure to cryogenics. Liquid nitrogen and helium have been used to cool the bending magnets. Another potential hazard was exposure to nonionizing radiation. Magnetic fields of 0.01 to 5 Tesla (T) were also a concern. However, the greatest safety and health concern were exposure to ionizing radiation. Sources of ionizing radiation included the synchrotron x-rays, Bremsstrahlung x-rays, and neutrons. The greatest potential exposure existed at the end of a beamline. Bremsstrahlung radiation was a hard x-ray produced when the electron collides with gas molecules or other obstructions in its path. Lead was the preferred shield material for x-rays and should be placed in locations likely to be in the path of high energy x-rays. These areas included the injector beam dump, the magnets, and line of sight locations around the ring structure and beam lines. Lead bricks were recommended rather than large lead plates as bricks can be configured to maximize shield effectiveness. Distance also contributed to the effectiveness of the shield. One disadvantage to the use of lead as a shield was that it acts as a source of photoneutrons. Materials likely to be in the neutron paths must be carefully chosen so that they will not activate easily or will decay quickly once activated. The authors recommend the use of area monitoring.
Ionizing-radiation; Semiconductors; Electronics-industry; Control-technology; X-ray-equipment; Nonionizing-radiation;
Control Technology and Personal Protective Equipment; Research Tools and Approaches; Control-technology;
Hazard Assessment and Control Technology in Semiconductor Manufacturing, Lewis Publishers, Inc., Chelsea, Michigan