Electrifying article

Wayne Tan

Senior member of the technical staff

Manufacturing Service Group

Advanced Micro Devices

Sunnyvale, CA

To the Editor:

The article written by Mr. William Larkin, “Particle contamination from air ionizing devices” (CleanRooms, Nov. 1996) clearly revealed that Mr. Larkin may not have evaluated newer generations of non-radioactive ionizers in the last few years.

In Mr. Larkin`s response (See Letters to the Editor, CleanRooms, March 1997, p. 43) to a letter written by Mr. Steinman and Dr. Levit, Mr. Larkin used such sharp phrases that further showed he is less concerned with discussing technical issues than in defending his positions. Has he ever wondered why most fabs are equipped with air ionizers if it is not the accepted method of controlling static in cleanrooms — as he claimed in his response?

Also, I would like to know how he can control charged insulators by making them dissipative or conductive, as he suggested in his response. Even if one can do what he suggested, static dissipative or conductive passivation layers on the wafers would not work well for semiconductor devices. The simple fact is that most products unavoidably contain insulators. I am sure that gold foil alpha and other radioactive ionizers have their uses in static control. However, they are not practical in general room ionization. Even if operators were not concerned about being bombarded with alpha particles all day, most of them feel uneasy working around radioactive sources, no matter how safe they are claimed to be. This is a significant concern to those people who run a cleanroom facility.