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Synchronous Current-Induced Thermal Wave Imaging

IP.com Disclosure Number: IPCOM000113354D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Edelstein, DC: AUTHOR

Abstract

Schematic of Synchronous Current-Induced Thermal-Wave Imaging measurement being performed on VLSI electromigration drift velocity sample.

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Synchronous Current-Induced Thermal Wave Imaging

      Schematic of Synchronous Current-Induced Thermal-Wave
Imaging measurement being performed on VLSI electromigration drift
velocity sample.

      A new microcharacterization imaging technique is obtained by
optically detecting the modulated thermoreflectivity induced by and
synchronous with thermal waves from a pulsed electrical current in a
conducting sample.  Subsurface defects (such as voids and
precipitates in VLSI interconnects) are imaged due to local resistive
heating driven by the current pulse.  This imaging contrast is thus
due to local subsurface discontinuities in the electrical properties
of the sample.

      The idea is illustrated in the Figure.  A master oscillator
(OSC) typically at ~1 MHz provides a continuous trigger to three
devices: an electrical current Pulse Generator (PG); a laser
Acousto-Optic Modulator (AOM); and the reference input of a two-phase
Lock-In Amplifier (LIA).  The PG output drives current through the
Device Under Test (DUT).  While the current is being pulsed, the
sample is raster-scanned under a focussed spot of a continuous probe
laser (Pr).  At the same time, a collinear focussed spot from the
AOM-modulated pump laser (Pu) may also impinge on the sample to
generate additional thermal-wave heating.  The reflected probe light
is detected with a photodetector (PD) which provides input to the
lock-in amplifier.  The modulated component of the reflected probe
lase...