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High Resolution Stress Measurements with a Kelvin Probe Force Microscope

IP.com Disclosure Number: IPCOM000110680D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Nonnenmacher, M: AUTHOR [+3]

Abstract

A method to measure stress or strain of a sample surface with high lateral resolution (< 50 nm) is disclosed. The method is based on the measurement of changes in the work function of a stressed sample using an AC force microscope. The technique can be applied to metals and semiconductors and is nondestructive.

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High Resolution Stress Measurements with a Kelvin Probe Force Microscope

       A method to measure stress or strain of a sample surface
with high lateral resolution (< 50 nm) is disclosed.  The method is
based on the measurement of changes in the work function of a
stressed sample using an AC force microscope. The technique can be
applied to metals and semiconductors and is nondestructive.

      Techniques exist which allow local stress measurements in a
silicon substrate and the most frequently used is micro-raman
spectroscopy.

      In this technique, a laser impinges upon the substrate and some
small fraction of the photons undergo interactions with the lattice
generating phonons.  The energy of the phonon, and hence the energy
lost by the photon, can be related to the stress in the silicon
crystal.  In this way, stress fields can be mapped.  Unfortunately,
this technique utilizes visible light as a probe and hence the
lateral resolution is limited to the minimum probe size as dictated
by the wavelength, which is around N0.5 mm.  Since current
semiconductor technologies utilize features of N0.5 mm, micro-raman
spectroscopy is of very limited use for stress field determination in
present technologies.

      It is rather well known that the band structure, and hence work
function, of a material changes if a stress is applied [1].  In a
simple model the contact potential between two materials is VCPD =
1/e (D2 - D1), where D1 and D2 are the work functions of the
conductors (including changes due to adsorption layers on the
surface) and e is the charge of an electron.  The measurement of the
contact potential difference (CPD) therefore can be used to to
measure the stress.

      High lateral resolution potentiometry measurements can be
achieved by...