Jandel Universal Probe
Bridge Technology since 1995
Four-Point-Probes

Universal Probe

    APPLICATION
  • 4-Point measurement of wafer resistivity
  • 4-Point measurement of epitaxial and diffused layer resistivity (where the layer is of the opposite conductivity type to the substrate, or the substrate is an insulator)
  • 3-Point Spreading resistance measurements
Download the one page product brochure (39K PDF file) for the Universal Probe
Download the instruction manual (736K PDF file) for the Universal Probe

    PRINCIPAL FEATURES
  • Highly repeatable needle contact conditions owing to controlled velocity of descent
  • Individually adjustable needle loadings with direct indication of set load
  • Kinematic needle guidance system employing precision ruby ball guides and polished tungsten carbide rods
  • Solid tungsten carbide needles with precision radiused tips
  • Accuracy of needle spacing +/- 0.01mm, no side play
  • Needles may be readily replaced without fear of derangement or loss of accuracy
  • Fully visible contact area
  • Micrometer controlled slice displacement for determination of resistivity gradient or junctions on a beveled slice.
  • Hinged steel cover to eliminate effects of light and electrical interference during measurement

GENERAL CONSTRUCTION
The probe guidance system is kinematic and thus free of all lateral play. The needles are positioned by upper and lower jeweled guides, each needle being constrained by a spring-loaded ruby ball at each guide. The needles slide through their guides with minimum friction, and exchanging new needles for old or broken ones is a simple, quick operation. Changing needles does not affect the characteristics of the unit - provided that replacement needles are the same diameter - spacing and co-linearity will be retained. Variation in needle diameter do not introduce play.

VELOCITY CONTROL
This device controls the velocity of the needle descent and the rate of applying load and thus offers uniform contact conditions from one measurement to the next. An air dashpot has been employed, since it's mechanism is vibration free and has a continuous motion. A spring is applied to the raising and lowering lever, tending to lower the needles. The dashpot is attached to the lever so that the lever is retarded by the piston.

METHOD OF OPERATION
A cam shaft operated by a small lever projecting through the perspex cover sets the machine for either four probe operation (lever up) or three probe operation (lever down).
i) During four probe operation all four needles rise and fall normally. The velocity control should be set as desired.
ii) During three probe operation for spreading resistance measurements, the tension on the first probe should be reduced to zero and the lever pulled down. This lifts the first probe tension gauge finger so that it is inoperative. the central probe finger is raised slightly so that this probe contacts the specimen last. The velocity control knob should be set to give a probe descent rate of approximately 1mm per second.

A complete four point probing system consists of the Universal Probe shown above, combined with the RM3 Test Unit


SPECIFICATION - PROBE NEEDLES
Material 0.5mm diameter tungsten carbide, 26mm long, 45 degree included angle, 25 micron tip radius (or larger up to 100 microns)
Spacings 1.00mm, 1.27mm, 1.59mm - tolerance +/- 0.01mm
Travel 4mm
Insulation resistance 2 x 105 megOhms at 500 volts
Load 0-100 grams applied by adjustable individual tension gauges
Specimen Slice only, 76mm diameter is normal maximum
Mounting table Ball bearing co-ordinate table with 0-25mm x 0.01mm micrometer screws (others available to order) carries a rotary table with 76mm diameter vacuum slice adaptor 14mm high
Packed for shipment 480mm x 320mm x 320mm high
Net weight 7 Kg
Gross weight 9 Kg


SPECIAL VERSION
Due to requests, the Universal Probe is available in a version which has a conductive brass chuck. When making regular four point probe measurements on materials that can make electrical contact through the backside, a non-conductive chuck is used so that the material is isolated from other conductors which wouod affect the measurement. When ordering this special version, one will also receive, if desired, the standard non-conducting chuck so that regular four point probe measurements can be made on homogeneous materials that would otherwise be affected by placement upon a conductive chuck. This special version uses five BNC connectors for connection to the two voltage reading probes, the current forcing probes, and for the backside connection. When ordered, the customer supplies the BNC connectors and Jandel mounts them using the special mounting brackets as shown in the image links below.

Our understanding is that this special version of the Universal Probe has been used in an application "Pseudo-MOS Transistor in SOI Wafers: Operation, Parameter Extraction, and Applications"

Click on any photo to see a larger image.


Four-Point-Probes is a division of Bridge Technology. To request further information please call Bridge Technology at (480) 988-2256 or send e-mail to Larry Bridge at: sales@bridgetec.com
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