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Hold The Onions

Inside Western Digital: How Tomorrow's Storage Gets Made
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Hold The Onions

The last time I touched an “auger,” it was a drill used for digging post holes in the ground. This tool is an “Auger nanoprobe.” It’s even more surface sensitive than ESCA, but it can’t dig holes, even tiny ones. The device performs Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), giving WD the ability to detect single molecular layers on a surface. In ToF-SIMS, “a beam of primary atomic ions is directed onto a surface, which produces an array of secondary ions characteristic of the surface species.” Essentially, this allows for molecule-specific identification of trace contaminants within the disk drive, especially at the vulnerable head/disk interface. As with ESCA and TEM, materials to be identified must be in an ultra-high vacuum environment.

“The Auger takes a primary ion beam from a gold gun source, shoots it at the sample, and looks at the secondary ions coming off of the sample,” explained WD. “You can get a lot of data fairly quickly from an instrument like this. All analytical instruments have good points and bad points, and you try to play them off of each other to get a complete answer. The good point of this is you have a mass spectrum of your samples, and that can be a very precise way to identify contaminants, even in very small amounts, and what their source is. But because it’s so very sensitive, it can have parts per billion level sensitivity for some elements. You’re looking at such a very fine, fine cut of the surface, so interpretation can be difficult. You have to separate what you’re interested in and what’s extraneous contamination. Interpretation is usually one of the more difficult parts of this technique.”

“If you breathed heavy on a sample,” the Auger’s technician added, “I could probably tell.” Given the sandwich I’d had only minutes before, I suspected atomic analysis wouldn’t be necessary for this. Still, it was the closest thing to a joke I would hear from a technical employee for the entire day.

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