Four Point Resistivity Probes

To the  Automatic Resistivity Mapping System page. (ambient or high temperature wafer resistivity mapping).

We manufactures resistivity test equipment including economical four point probe heads, a high temperature four point probe head, a four point probe mounting stand for vertically lowering the probe head into contact with a substrate, and also a completely automated resistivity Wafer Mapping System.

SYS-301 Complete four point probe resistivity probing system consisting of S-301 mounting stand with six inch Teflon disk (for wafers up to six inches in diameter), 2400 Digital Sourcemeter, two (2) SP4-62.5-85-TC four point probe heads, necessary cables with connectors, manuals.

S-301-4 Four point probe mounting stand with microswitch to engage power. Includes four inch diameter Teflon disk for mounting wafers up to four inches in diameter.

S-301-6 Four point probe mounting stand with microswitch to engage power. Includes six inch diameter Teflon disk for mounting wafers up to six inches in diameter.

S-3TD-4 Replacement Teflon disk for S-301-4 four point probe mounting stand

S-3TD-5 Replacement Teflon disk for S-301-5 four point probe mounting stand

S-3TD-6 Replacement Teflon disk for S-301-6 four point probe mounting stand

S-60 Fell Adapter. Allows the mounting of Signatone SP4 four point probe head onto a Fell four point probe stand.

S-70  Adapter. Allows mounting of Signatone SP4 four point probe head onto a Dumas four point probe stand.

Four Point Probe Heads

Four Point Probe Heads model maker part number

There are four parts to the four point probe head model number:

[Head type]

SP4 Disposable plastic four point probe head

HT4 High temperature four point probe head

[Spacing]

[Spacing] is either 40, 50 or 62.5 to specify either 40 mils, 50 mils or 62.5 mils space between each of the four probe tips. [Spring type] is either 45, 85 or 180 to specify 45 grams, 85 grams or 180 grams of spring pressure per tip.

40 mil spacing between the tips

50 mil spacing between the tips

62.5 mil spacing between the tips

[Spring Pressure]

[Spring Pressure] is the pressure that all four probes together exert. The pressure choices are 45, 85 or 180 grams. The 45 gram spring load is used when a lighter pressure is needed to prevent punching through the layer to measured. The 180 gram springs are used when the tips need to dig in harder to make good contact. The 85 gram springs are the most common and are used in most silicon wafer probing applications.

45 grams per tip

85 grams per tip

180 grams per tip

[Tip material]

[Tip material] is either O to specify osmium or TC to specify tungsten carbide. Osmium is a softer metal that is used with gallium arsenide wafers or whenever contact resistance is suspected to be a problem.

Tungsten carbide tips are harder and can have a longer life if care is taken to not break the tips. Tips of either material will break if the wafer is moved while the tips are in contact.

TC Tungsten carbide probe tip material

O Osmium tip material

[Tip radius]

[Tip radius] is an optional specification that can be added to the part number if the standard 1.6 mil diameter probe tips are too sharp and tend to punch through the top layer. The specification "R=.005" or "R=.010" at the end of the part number will specify either 5 mil or 10 mil diameter probe tips.

(blank) Omit the "R=" statement if the standard 1.6 mil radius tips are acceptable

R=.005 Blunt tips with a 5 mil radius

R=.010 Blunt tips with a 10 mil radius

The following is an example of a four point probe head (this is also the most popular model)

The part number shown above defines a plastic four point probe head with 62.5 mil spacing between the tips, 85 gram spring pressure and tungsten carbide tips.

This part number defines a high temperature four point probe head with 50 mil spacing between the tips, 45 gram spring pressure and osmium tips with 5 mil tip diameters.

Information is available regarding Four-Point Probe Theory of Operation from the University of California, Berkeley, EECS web site.