Electrical Test & Measurement · Electrical Test Equipment
Four-point probe testers that read sheet resistance, resistivity and conductivity on wafers, films, coatings and bulk samples, with thickness preset and 3% sheet resistance accuracy.
SJ2663 (4 models) ·
A sheet of conductive film has no length and no width that matter. What it has is a resistance per square, and that is the number a coating line, a wafer fab or a photovoltaic process is actually controlling. Measuring it takes four points on the surface, not two clips on the ends.
These are bench instruments for sheet resistance, resistivity and conductivity, with a plain resistance mode for bulk parts. Each one drives a current through the outer two probes of an in-line four-point head and reads the voltage across the inner two.
Four models cover the range. The compact one reads 100 µΩ to 100 kΩ on a 4.3-inch screen. The three larger ones run from 10 µΩ to 1 MΩ, from 1 µΩ to 20 kΩ, and from 1 µΩ to 100 MΩ, with 7-inch screens and a dual measurement mode that corrects probe drift and edge effects. Sheet resistance accuracy is quoted separately from resistance accuracy, at 3% or 4%, because it depends on geometry as well as on the electronics.
All four take the same probe heads and the same stand, measure temperature alongside the electrical result, and carry HANDLER, RS232, RS485 and USB host as standard.
Four probes are pressed onto the surface in a line, equally spaced. The outer two carry a known current; the inner two measure the voltage that current produces between them. Because the voltage probes draw almost no current, the contact resistance under those two tips does not enter the reading, and the probe resistance does not either.
For a layer thin compared with the probe spacing, the sheet resistance is proportional to the measured voltage divided by the current, with a constant fixed by the geometry. The instrument applies that constant, so the display reads in ohms per square. When the layer is not thin compared with the spacing, or the sample is small, a correction factor applies, and that is where the dual measurement mode and the correct probe spacing earn their place.
Resistivity follows from the sheet resistance multiplied by the thickness. The thickness is entered before the run, which is why the instrument can show resistivity directly instead of asking the operator to multiply afterwards. Conductivity is its reciprocal, displayed in siemens per unit length.
Start with the sheet resistance window. Coated glass and thin metal films sit in the low ohms per square and suit the low-resistance model; semiconductor layers and lightly doped films sit higher and need the wide-range model; a laboratory that sees both needs the wide one and should accept its coarser accuracy at the extremes.
Then the material, because it fixes the probe head. Tungsten carbide at 1 mm for hard wafers, beryllium copper at 2 mm for metals and photovoltaic panels, 4 mm for larger samples, and a conductive rubber tip for films that a needle would pierce. The head, not the instrument, decides whether the sample survives the measurement.
Then the sample size against the probe spacing. A small coupon relative to the spacing needs a correction, and the models with the dual measurement mode handle it better. A 200 mm panel does not.
Then the thickness range. A resistivity reading is only as good as the thickness entered, and a sample whose thickness varies across its area will give a resistivity that varies for a reason the instrument cannot see.
Finally the output. A lab needs the display and the USB record; a coating line needs the handler or the serial link and a comparator with limits per product.
The measurement assumes a homogeneous layer. A coating with a resistive skin over a conductive base, or a wafer with an implant profile, is not a single sheet, and the four-point reading is an average of what the current path samples, weighted towards the surface.
Probe pressure matters. Too little and the contact is unstable; too much and a soft film is pierced or a thin wafer is cracked. The material gives no pressure figure, and the correct pressure depends on the tip and the sample, so it has to be established on the material itself.
The reading is at the surface, under the probes. A sample that has just been handled, cleaned or coated may still be changing; the temperature and humidity readout is there to make that visible, and the temperature compensation only corrects a number, not the drift.
Edge effects are the largest source of error on small samples. Current spreading near an edge lowers the apparent sheet resistance, and the correction depends on the distance from the probe to the edge. A fixture that places the probes at a repeatable distance from the edge is worth more than a better instrument.
Finally, this is not a mapping instrument. It measures where the probes are placed; a wafer or a panel has a distribution, and characterising that distribution needs a stage that moves the sample between readings.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| Measurement parameter | Resistance, sheet resistance, resistivity and conductivityStandard |
|---|---|
| Measurement principle | Four in-line probes; outer pair drives current, inner pair senses voltageStandard |
| Resistance range by model | 100 µΩ to 100 kΩ; 10 µΩ to 1 MΩ; 1 µΩ to 20 kΩ; 1 µΩ to 100 MΩStandard |
| Resistance range, one model on its card | 1 µΩ to 500 MΩ, against 1 µΩ to 100 MΩ in the parameter tableInformation required |
| Test current | ≤10 mA; ≤100 mA; ≤500 mA; ≤500 mAStandard |
| Resistance accuracy | 0.05% in the middle of the range; 0.2% at or below 20 mΩ; 0.2% or 0.5% at the top, depending on modelStandard |
| Sheet resistance accuracy | 3% on three models; 4% on the low-resistance model; 5% above 2 MΩ on the wide modelStandard |
| Measurement mode | Single or dual electrical measurement, the dual mode correcting probe drift and edge effectsOptional |
| Displayed quantities | Resistance, sheet resistance, resistivity, conductivity, sorting result and temperature togetherStandard |
| Thickness input | Sample thickness preset before the run, so resistivity needs no separate lookupStandard |
|---|---|
| Probe stand | SJ26301 four-probe stand, 200 × 200 mm table, aluminium body, for the fixed probe headsOptional |
| Probe head, 1 mm tungsten carbide | SJ26500, for semiconductor and silicon wafers and other hard materialsOptional |
| Probe head, 2 mm beryllium copper | SJ26501, for metals, films, photovoltaic panels and graphiteOptional |
| Probe head, 1 mm beryllium copper | SJ26501-1, for smaller metal, film, photovoltaic and graphite samplesOptional |
| Probe head, 2 mm conductive rubber | SJ26501S, for fragile films, with a flexible rubber tipOptional |
| Probe head, 4 mm beryllium copper | SJ26505, for larger metal, film, photovoltaic and graphite samplesOptional |
| Temperature measurement | −10 to 99.9 °C, 0.1 °C, on all four modelsStandard |
|---|---|
| Humidity measurement | 0 to 100% RH, ±1.5%, on three models; not fitted on the compact modelOptional |
| Temperature compensation | Fitted, for temperature-sensitive materialsStandard |
| Comparator | Three levels with absolute limits; percentage limits against a nominal value on three modelsStandard |
| Beeper | Pass, fail or off; pass lamp green, fail lamp redStandard |
| Stored setups | None on the compact model; 5 groups on one; 10 groups on twoStandard |
| Interfaces | HANDLER, RS232, RS485, USB host and USB device on all four modelsStandard |
|---|---|
| USB host | Memory stick for results and for firmware updateStandard |
| Reference standards | GB/T 1551-2009 and GB/T 1552-1995Standard |
| Mains | 198 to 242 V AC, 47 to 63 HzStandard |
| Body, compact model | 264 × 107 × 361 mm, about 4 kg, 4.3-inch displayStandard |
| Body, other models | 350 × 130 × 400 mm, about 8 kg, 7-inch displayStandard |
| Operating environment | Not stated in the materialInformation required |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| SJ2663 | Compact four-probe meter, 4.3-inch display, single measurement mode | 100 µΩ to 100 kΩ; test current ≤10 mA; sheet resistance 3% | No humidity measurement and no stored setups; absolute limits only |
| SJ2665 | Bench meter, 7-inch display, single or dual measurement mode | 10 µΩ to 1 MΩ; test current ≤100 mA; sheet resistance 3% | 5 stored setups; humidity measurement fitted |
| SJ2667 | Low-resistance four-probe meter, dual measurement mode | 1 µΩ to 20 kΩ; test current ≤500 mA; sheet resistance 4% | For low sheet resistance films and conductors |
| SJ2668 | Wide-range four-probe meter, dual measurement mode | 1 µΩ to 100 MΩ; test current ≤500 mA; sheet resistance 3% to 2 MΩ and 5% above | The model card states 1 µΩ to 500 MΩ; the parameter table states 100 MΩ |
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
Sheet resistance is a property of a layer and has units of ohms per square; it does not depend on how wide the square is, only on the material and its thickness. Resistivity is a property of the material and has units of ohm-metres. The instrument measures sheet resistance directly and computes resistivity by multiplying by the thickness entered for the sample, which is why the thickness has to be set before a resistivity reading means anything.
Spacing sets the volume of material sampled and the correction factor, and the tip sets what the probe will survive. Tungsten carbide at 1 mm is for hard wafers; beryllium copper at 2 mm or 4 mm is for metals, films and photovoltaic panels; the conductive rubber tip is for layers thin enough that a metal needle would pierce them. Choosing the wrong tip damages the sample before the reading matters.
When the sample is small relative to the probe spacing, or when the probes have drifted between measurements. The dual mode measures with the current path reversed and combines the two results, which cancels a good part of the offset from probe contact and from the sample edge. On a large, uniform panel the single mode is adequate; on a small coupon it is not.
The material and its thickness range, since those fix the probe head and whether resistivity can be computed; the sheet resistance window, which selects between the low-resistance and the wide-range model; the sample size, which decides whether a stand is needed and how much edge correction applies; and the output the line expects, handler, serial or USB.
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