Why not?

They stopped and stared as he meandered through the aisles of CleanRooms West 2003, clutching a space shuttle-like model, and stopping to explain what it was to anyone who would listen.

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Some were genuinely intrigued, while others winced with skepticism, perhaps writing him off as some eccentric cosmonaut-wannabe.

But George Meyers is anything but that. In fact, the founder of Space Island Group Inc. says his West Covina, Calif.-based company is a commercial real estate developer for a very unique place: The infinite frontier.

Is it all that far-fetched—to reuse spent space shuttle fuel tanks and renovate them into not only orbiting cleanroom manufacturing facilities of tomorrow, but also the tourist resorts like those depicted in Stanley Kubrick's 2001: A Space Odyssey?

From a commercial perspective, it is rather lucrative, but in terms of science and technology, the advancements will be as illimitable as space.

And for cleanroom end users, as one contributor to the effort says:

It is a chance to perceive the unpredicted, unexpected behaviors of materials and processes; to be in a position to be inspired; to make the discoveries; to gain insight through observation; and to experience the insight that only comes with complete immersion in a new environment.

If that isn't enough inspiration, lest we forget the words of George Bernard Shaw:

“You see things; and you say, 'Why?' But I dream things that never were; and I say, 'Why not?'”

Mark A. DeSorbo
Associate Editor

Those pesky water spots

Addressed to Robert Donovan:

Thank you for the efforts you put into your recent presentation at CleanRooms West in Anaheim (Ultrapure Water Systems: Components, Monitoring and Conservation).

You mentioned that an excess of dissolved oxygen in UPW could cause a water-spotting problem. We have been experiencing some water spotting, so we decided to run an analysis and found that the level of dissolved oxygen is 8.5 mg/L.

I looked through the notes from your lecture and found nothing regarding a spec for dissolved oxygen or a level at which it might create problems.

Can you tell me at what level you would expect to see water spotting?

We make focal planes for IR detectors, and water spotting can be a problem. We have been able to avoid spotting by having the lab tech blow the parts dry with N2 after the final rinse; but as you can imagine, this is very time consuming.

Any information you could provide would be appreciated.

Bill Cooper
Facilities Lead, IDO, Indigo Systems Corp.
[email protected]

The water spotting I referred to occurs when dissolved oxygen in the UPW is in excess of say 10 ppb, and this UPW is used to rinse HF-etched silicon surfaces. The oxygen dissolved in the UPW chemically reacts with the silicon surface to form trace quantities of silica that is non-volatile and remains as “water spots” after the water evaporates or is otherwise removed. This interaction occurs only with silicon surfaces, or possibly other surfaces that chemically react with oxygen. The dissolved oxygen in your water is well above the concentrations at which this silica formation typically occurs; but I'm not sure what your surface composition is.

Blowing the water off or spin-drying the surface helps remove some of the silica that may have been formed, but is generally not completely satisfactory. A technique sometimes used by the semiconductor folks is to displace the rinse water with isopropyl alcohol (IPA), so that the last liquid evaporated from the silicon surface is not water but IPA—which doesn't attack a silicon surface. This displacement action thwarts both the formation of silica and the deposition of any silica that does form.

The formation of silica on silicon by dissolved oxygen in UPW was mentioned in my column of August 2002 (see www.cleanrooms.com). Reference 1 discuses the water-spotting problem in more detail.

Bob Donovan
[email protected]


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