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Vacuum chuck

More fun in the clean room.

Today we are spinning glass. In order to get some boron ions into our wafers, we have to put some onto the wafers first, in the form of a liquid boron-silicon mixture. The coated wafers will then be baked and the ions will worm their way into the silicon. In order to get a nice, even coating, the wafer is spun at a very high rate (2000 rpm) after the liquid is put onto its surface.

Using special wafer tweezers, I place the wafer on the chuck (the spinning thing that the wafer sits on) and try to center it. If the wafer is off center, it will fly off the spinner and break. I press the vacuum button so that the wafer is sucked onto the chuck and give it a little spin. It looks sort of centered, it's difficult to tell because the wafer is not circular (it has a couple flats ground into the edges). Also, I can hardly see because of my old glasses prescription (no contact lenses in the clean room), the safety glasses I have to wear over them, and the fact that we're in the exposure area which is lit with yellow light.

I turn off the vacuum and nudge the wafer with the tweezers, turn the vacuum back on again and evaluate its centeredness. "Is this okay?" I ask one of the others. "I'm a real perfectionist—I could be here all day."

"That's fine."

"Okay." I squeeze the liquid glass from an eyedropper onto the wafer, put the cover over the spinner, and let it spin.

The wafer does not fly off and shatter. The honor of the Tuesday lab group remains unstained by wafer breakage.

290 words | March 1, 2005 09:51 PM | Ivory tower