ASTM International - ASTM F81-00
Standard Test Method for Measuring Radial Resistivity Variation on Silicon Wafers
|Publication Date:||10 June 2001|
|ICS Code (Semiconducting materials):||29.045|
1.1 This test method provides procedures for the determination of relative radial variation of resistivity of semiconductor wafers cut from silicon single crystals grown either by the Czochralski or floating-zone technique.
1.2 This test method provides procedures for using Test Method F84 for the four-point probe measurement of radial resistivity variation.
1.3 This test method yields a measure of the variation in resistivity between the center and selected outer regions of the specimen. The amount of information obtained regarding the magnitude and form of the variation in the intervening regions when using the four-point probe array depends on the sampling plan chosen (see 7.2). The interpretation of the variations measured as radial variations may be in error if azimuthal variations on the wafer or axial variations along the crystal length are not negligible.
1.4 This test method can be applied to single crystals of silicon in circular wafer form, the thickness of which is less than one-half of the average probe spacing, and the diameter of which is at least 15 mm (0.6 in.). Measurements can be made on any specimen for which reliable resistivity measurements can be obtained. The resistivity measurement procedure of Test Method F84 has been tested on specimens having resistivities between 0.0008 and 2000 cm for p-type silicon and between 0.0008 and 6000 cm for n-type silicon. Geometrical correction factors required for these measurements are included for the case of standard wafer diameters, and are available in tabulated form for other cases.
Note 1--In the case of wafers whose thickness is greater than the average spacing of the measurement probes, no geometrical correction factor is available except for measurement at the center of the wafer face.
1.5 Several sampling plans are given which specify sets of measurement sites on the wafers being tested. The sampling plans allow differing levels of detail of resistivity variation to be obtained. One of these sampling plans shall be selected and agreed upon by the parties to the measurement. The basic resistivity measurements of Test Method F 84 are then applied at each site specified in the chosen sampling plan.
1.6 Results are expressed as relative changes in resistivity between the several measurement sites. To obtain absolute values of resistivity it is necessary to measure and correct for specimen temperature (see 11.1.4).
1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.