Monolith X-sections

ByGreg Madejski

As the title states, these are images from the monolithically fabricated devices used by Kyle and Vincent in Ottawa. These devices were fractured with tweezers, then tilted and metallized with 5 nm of Pt, mounted on carbon tape.

Patterned Area of Monolithic Device in small strips. The actual active area is much smaller (top center square, ~10 columns).

 

First Montage Crossection. At top left is a flat on image of one repeating unit patterned across the active area. By tilting to 60 degrees, we can see the breadth of the cavity. The next images show the height of the cavity as well as the breadth. It’s interesting to see that only the middle portion of each cavity is porous, and that the underetch goes much much further. There also appears to be debris inside the cavity, but I don’t think my preparation would create debris this size.

 

Another device imaged at 60 degrees, where it’s easier to see the relative thicknesses of each membrane.

 

I tried to FIB a crossection into the strip with Ralph’s help, but ultimately was not successful. The nanofeatures didn’t respond well to constant imaging and FIBing, warping and distorting.

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One Comment

  1. Thanks for getting these Greg. A few comments: The first montage, you point out the large under etch…this was a known condition that was expected. Its due to the XeF2 gas, which is very isotropic. As for the debris, this is also a known condition, also due to the XeF2, I believe this is due to contaminates in the poly-Si as deposited (at RIT) and because the selectivity of XeF2 is absurdly high, it does not etch at all. I do not think these ‘crumbs’ would interfere with pore formation since they are not continuous, and since the pores are actually enlarging, they probably are being dissolved in the KCl solution (and therefore not plugging the pore).

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