Browse Prior Art Database

Contactless Microwave Measurement of Wafer Sheet Resistance with Improved Spatial Resolution

IP.com Disclosure Number: IPCOM000119673D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Braslau, N: AUTHOR

Abstract

Disclosed is a method for determining the sheet resistance of thin films or epitaxial layers on semi-insulating substrate materials without requiring electrical contact and with a spatial resolution of about 2 mm2, as compared with areas of 2 cm2 for other microwave contactless measurements 1, or approximately 4 cm2 for contactless eddy current measurements at lower frequencies 2. The complex reflection coefficient of a coaxial line terminated by suitable means by the sheet to be measured, is measured at microwave frequencies (1-12 Ghz) conventionally, either with a Network Analyzer or with a slotted line, together with directional couplers oriented to sample forward and reflected power.

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Contactless Microwave Measurement of Wafer Sheet Resistance with
Improved Spatial Resolution

      Disclosed is a method for determining the sheet
resistance of thin films or epitaxial layers on semi-insulating
substrate materials without requiring electrical contact and with a
spatial resolution of about 2 mm2, as compared with areas of 2 cm2
for other microwave contactless measurements 1, or approximately 4
cm2 for contactless eddy current measurements at lower frequencies 2.
The complex reflection coefficient of a coaxial line terminated by
suitable means by the sheet to be measured, is measured at microwave
frequencies (1-12 Ghz) conventionally, either with a Network Analyzer
or with a slotted line, together with directional couplers oriented
to sample forward and reflected power.

      It is important that no gap exist between the center conductor
of the coaxial line and the surface of the sample to be measured.
This is done by means of a coaxial line carefully terminated in a
conducting plane 3 with the sample placed face down on the plane, or
by providing a spring-loaded center conductor at the termination of
the coaxial line which is lowered to contact the sample placed
face-up on a non-conducting plane.  Such a termination is
conveniently provided by modifying a commercially available connector
(Part number KMC-SL 9325002, Kelvin Microwave Corp., Woburn, MA).

      Sheet resistances between approximately 1 and 2500 ohm/square
can be measured by this technique.  Because th...