Browse Prior Art Database

Mechanically Amplified Piezoresistive SFM Sensor

IP.com Disclosure Number: IPCOM000112081D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+3]

Abstract

Disclosed is a Scanning Force Microscopy (SFM) sensor with an integrated mechanically amplified piezoresistive sensing technique.

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Mechanically Amplified Piezoresistive SFM Sensor

Disclosed is a Scanning Force Microscopy (SFM) sensor with an integrated mechanically amplified piezoresistive sensing technique.

The overall size of this sensor is drastically reduced and allows thus the implementation as "in-situ" sensor within process tools.

With current piezoresistive cantilevers for SFM the sensitivity is not yet sufficient for high resolution measurements and further improvement is necessary in order to replace the conventional optical technique by these piezoresistive sensors.

The proposed piezoresistive sensor with mechanical amplification improves the sensitivity roughly by one order of magnitude. The resulting sensitivity of the SFM sensor is comparable to optical techniques and will exceed those if further miniaturization is applied.

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The sensitivity used in a conductor is defined as the resistance change per unit of initial resistance divided by the applied strain. With semiconductors the sensitivity has values in the range between 100 for single crystal silicon and about 30 for poly-silicon.

The basic design for a piezoresistive sensor is shown in the Figure. The stress in the U-shaped resistor will be enhanced, depending on the actual shape. Assuming a width of the silicon resistor of 0.5 µm, the stiffness will roughly increase by a factor of two compared to the blank cantilever. At the same time the stress induced in the top layer of the U will be almost four times higher. The sensitivity of this sensor therefore will be roughly three times better compared to a simple cantilever sensor with the same stiffness. Bending of the cantilever induces...