What is it about?
Reticles are uniquely sensitive to electric field and can be damaged in a cumulative way by exposure to them. Since electric field is constantly being generated in a factory environment, and since introducing meters and wires to the environment alters the electric field configuration, the only way to measure the electric field that a reticle will experience during normal use is to make the recording device look like a production reticle. This paper reveals what such a device sees - showing that electric field is everywhere, and also revealing that some of the electrostatic precautions used to counteract static charge in manufacturing can be counterproductive!
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Why is it important?
Reticles are essential for semiconductor production. If they become damaged by electric field, every device printed will exhibit a defect of some kind. Whether this causes the device to fail on final test or merely alters its performance and/or lifetime in use, any kind of reticle damage is undesirable. It can cost hundreds of thousands of dollars in lost production if a reticle is damaged. So finding areas of electrostatic risk in the reticle handling environment and fixing them is essential. This device is the best way to do that.
Perspectives
This device has been a groundbreaking development for aiding the understanding of reticle electrostatic damage. Before it was developed it was only possible to explain the risk to a reticle from electric field to a non-technical person using diagrams and possibly computer simulations. But theories and computer models are only as good as the data that are put into them, so many people disbelieved the warnings that I was giving about the risk from electric field. When this device was developed, which coincidentally was at exactly the same time as I was presenting experimental evidence and explanations about the cumulative damage mechanism in reticles called EFM, it provided for the very first time real measurements of the risks I had been describing for the previous five years. This device has confirmed experimentally the computer simulation work I carried out into electric field interactions with reticles. Now it is possible to measure the electric field interaction with reticles in almost every practical situation where reticles are handled, and it reveals many errors and weaknesses in the electrostatic precautions that are typically being adopted in semiconductor factories.
Dr Gavin C Rider
Read the Original
This page is a summary of: High sensitivity electric field monitoring system for control of field-induced CD degradation in reticles (EFM), April 2009, SPIE,
DOI: 10.1117/12.824302.
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