- SEMI MF84 - Test Method for Measuring Resistivity of Silicon Wafers With an In-Line Four-Point Probe
This Standard was technically approved by the Silicon Wafer Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on February 1, 2018. Available at www.semiviews.org and www.semi.org in July 2018; originally published by ASTM International as ASTM F84-67T; previously published March 2012.
The resistivity of a silicon wafer is an important materials acceptance requirement.
Resistivity values measured by this Test Method are a primary quantity for characterization and specification of silicon wafers used for fabrication of semiconductor ICs and other electron devices.
This Test Method covers the measurement of the resistivity of silicon wafers with an in-line four-point probe. This Test Method describes a procedure that enables inter-laboratory comparisons of the room temperature resistivity of silicon wafers. The precision that can be expected depends on both the resistivity of the wafer and on the homogeneity of the wafer. Round-robin tests have been conducted to establish the expected precision for measurements on p-type wafers with room temperature (23°C) resistivity between 0.0008 and 2000 Ω·cm and on n-type wafers with room-temperature (23°C) resistivity between 0.0008 and 6000 Ω·cm.
This Test Method is intended for use on single crystals of silicon in the form of circular wafers with a diameter greater than 16 mm (0.625 in.) and a thickness less than 1.6 mm (0.0625 in.). Geometrical correction factors required for these measurements are available in tabulated form.
Procedures for preparing the specimen, for measuring its size, and for determining the temperature of the specimen during the measurements are also given.
This Test Method includes procedures for checking both the probe head and the electrical measuring apparatus.
The spacing between the four-probe tips is determined from measurements of indentations made by the probe tips in a polished silicon surface. This test also is used to determine the condition of the probe tips.
The accuracy of the electrical measuring equipment is tested by means of an analog circuit containing a known standard resistor together with other resistors that simulate the resistance at the contacts between the probe tips and the semiconductor surface.
The current level, probe force, and specimen surface preparation specified in this Test Method are to be preferred for all referee measurements on bulk silicon wafers. However, many changes in these conditions may be made for non-referee applications without severe changes in measurement results.
A table of temperature coefficient as a function of resistivity and abbreviated tables of correction factors appropriate to circular wafer geometry are included with the test method so that appropriate calculations can be made conveniently.
This Test Method is to be used as a referee method for determining the resistivity of single crystal silicon wafers in preference to SEMI MF43.
The values stated in SI units are to be regarded as the standard. Any values given in parentheses are for information only.
Referenced SEMI Standards
SEMI C19 — Specification for Acetone
SEMI C28 — Specification and Guide for Hydrofluoric Acid
SEMI C31 — Specification for Methanol
SEMI C35 — Specification and Guide for Nitric Acid
SEMI M59 — Terminology for Silicon Technology
SEMI MF42 — Test Method for Conductivity Type of Extrinsic Semiconducting Materials
SEMI MF43 — Test Method for Resistivity of Semiconductor Materials
SEMI MF1527 — Guide for Application of Certified Reference Materials and Reference Wafers for Calibration and Control of Instruments for Measuring Resistivity of Silicon
SEMI MF2074 — Guide for Measuring Diameter of Silicon and Other Semiconductor Wafers