Personnel Grounding--A Case History

In many semiconductor manufacturing processes, it is necessary that precautions be taken to prevent dissipation of static electrical charges within the devices being manufactured. Often, one of the major sources of static electrical charges are the people who are performing the manufacture of the semiconductor devices, and, therefore, if static charges are a problem, provision must be made for elimination of the charge on the personnel. In our studies, it has been found that in certain manufacturing areas it is quite easy to obtain a static charge of 1/2 mC, equivalent to 2500 volts, on a person. Several techniques for eliminating static charge build-up on people were investigated, such as the use of radioactive ion generators, humidity control, electrical grounding, and special clothing. Each area was investigated with respect to such parameters as present availability, hazards to personnel, hazards to product, etc. As a result of the studies, it was found that at present, considering all factors, the best method of preventing static electrical charge accumulation on people is the use of an electrical ground through a resistance.