As we move into the research and/or manufacturing aspects of nanotechnology, there is an ever-expanding landscape of facilities in the public and private sector being constructed to support these efforts. Watching and reviewing some of these projects, we have recognized an alarming absence of due diligence concerning the systems and components being installed to support them. Everyone understands the need for some level of controlled environment. This is especially true in the area of contamination control. What seems to be missing is that many of the installations did not take into account the need to review materials of construction for the basic components being used in these facilities.

Introduction
Perhaps, from its title, you already wrote this article off as another attempt to break down the concept of airborne molecular contamination (AMC) into a few simple discussions and clichés, and closing with the tidy “Top 10” lists of the materials to avoid and covet in cleanroom design and construction. This sort of catch-all approach makes us feel more at ease and in control. However, AMC should not be taken this lightly within a short magazine article, at design during the 60% review stage, or in the field when process tools are being installed. The discussion of AMC is not just a discussion of materials selection, but a discussion of ownership, conveyance, and interpretation of materials selection during design and through to construction. Certainly, AMC abatement techniques exist that may be applied to an existing problem in an existing facility or laboratory. However, this article discusses techniques to address AMC at the most opportune time—during the design and construction of these buildings.

Background
Nanotechnology development has arrived at an opportune time with respect to design and construction of manufacturing facilities. Designers, engineers, and constructors of semiconductor facilities have ridden the steep part of the learning curve to a near level plateau over the past 20 years as the industry has developed. Although AMC is a frequent topic of conversation these days due to shrinking chip geometries, it has been on the minds of design professionals and their clients for some time. These professionals honed their abilities in cleanroom design and particle contamination control, learned from their mistakes, and even developed rules of thumb along the way to expedite design. Nanotechnology research labs and eventual manufacturing facilities should be able to benefit from this broad knowledge base, circumvent the mistakes of the past, and hopefully not have to reinvent the wheel.

Accelerated schedules, shrinking budgets, and a short-term perspective on research opportunities (e.g. shrinking chip geometries in the near future) can shift focus away from nebulous problems such as AMC. An argument often made is the lack of concern for high yields in research. Many times, the yield of a single specimen is all that is necessary in studying it. However, when research focus shifts to an order-of-magnitude reduction with processes reaching into <100 nanometer line widths, yields are no longer considered; the lab offers no flexibility for AMC-control retrofit and the only solution is to tear out the lab and start over. Clearly, for small labs, this could be an option to reduce initial cost, but it can also delay generation changes and cost far more than one might anticipate.

In order to avoid poor choices in defining your present and future needs, it is wise to apply historical knowledge, and to make sure everyone involved in a project understands who to ask when questions arise on what you need to consider in your planning. For now, let’s review the tools we have at hand to tackle AMC.

Fundamentals
The fundamentals of AMC have been previously written about in this publication and others, and do not require laborious rehashing here. I assume that you are aware of AMC types, its sources and effects, and control and filtration possibilities. This knowledge is well documented. However, every story needs conflict. Here, the conflict is in the interpretation, distribution, and use of this knowledge.

The AMC cleanliness classification defined by SEMI F21 is deceptively simple and seemingly analogous to the ISO-14644 particle cleanliness classification. (Note: ISO–14644 has replaced FED STD 209E, which has been sunsetted by the IEST.) These similarities and simplifications hide the underlying complexity that is AMC. SEMI presents the various classes in terms of parts per trillion-molar of gas-phase particles in the clean environment. These benchmarks allow a constructed cleanroom at-rest or in-operation to be classified with the measurement of air stream or sample surfaces (e.g. witness wafers).