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Stylus for an Atomic Force Microscope Disclosure Number: IPCOM000036455D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 46K

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Hodgson, RT: AUTHOR [+2]


Disclosed is a low mass tip for an atomic force microscope (AFM).

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Stylus for an Atomic Force Microscope

Disclosed is a low mass tip for an atomic force microscope (AFM).

The invention of the AFM teaches that the feedback and vibration isolation methods invented for the scanning tunnelling microscope (STM) can be used to make an improved profilometer. The sensitivity of the device depends on using a point suspended from a soft spring. The point and spring must have low mass so that the resonant frequency of the point is higher than the few hundred hertz vibrational frequencies found in normal vibration isolation systems.

The methods outlined in the figures teach how to make such a point with tip radius of a hundred angstroms and mass of 1E-12 grams.

(Image Omitted)

Fig. 1 shows a wafer 1 of <100> silicon which has a layer 2 of silicon nitride of 100 - 1000 Ao thickness grown on the polished surface. By techniques well known in the art, a hole 3 of micron dimensions is opened in the silicon nitride.

When the backside of the wafer is protected by a suitable coating, immersion of the wafer in pyrocatecal or KOH will etch the silicon through the hole in the nitride film until only four <111> surfaces remain; then the etching stops. The result is a pyramidal hole in the wafer with corners and a point of atomic dimension. If the wafer is then cleaned, re-introduced into the nitriding furnace to grow a few hundred angstroms of silicon nitride 4, and covered with a layer of metal or silicide conductor 5, it can be planarized by sputtering or by laser melting to give the structure of Fig. 2.

Finally, silicon is etched away from the backside using the anisotropic etch solution to give a thin film 6, supported around the edges by relatively massive silicon 7, with a micron high, sharp point of very hard silicon nitride, as in Fig....