SEMI PV28 - Test Method for Measuring Resistivity or Sheet Resistance with a Single-Sided Noncontact Eddy-Current Gauge
This Standard was technically approved by the Photovoltaic - Materials Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on December 4, 2015. Available at www.semiviews.org and www.semi.org in March 2016; originally published February 2012.
Resistivity is a primary quantity for characterization and specification of material used for photovoltaic (PV) devices. Sheet resistance is a primary quantity for characterization, specification, and monitoring of thin films. An eddy-current gauge directly measures conductance of a specimen. Values of resistivity or sheet resistance are calculated from the measured conductance, with the resistivity values also requiring a measurement of specimen thickness.
These test methods outline the principles of eddy-current measurements as they relate to silicon bricks and ingots or silicon films on nonconductive substrates that are used in photovoltaic sensors. These test methods are very similar to those in SEMI MF673, which covers the principles of eddy-current measurements as they relate to silicon wafers and certain thin films fabricated on such substrates, but the nature of the apparatus is significantly different to accommodate the bricks and ingots. Such an instrument can also be used for measurements on thin silicon or other thin conducting films on nonconductive substrates. SEMI MF673 should be referred to for measurements on silicon wafers and certain thin films fabricated on such substrates.
In addition to providing the procedures for eddy-current measurements on both single crystalline and multicrystalline silicon bricks and ingots as well as silicon or other thin conducting films on nonconductive substrates, these test methods cover the requirements for setting up and calibrating such instruments for use, particularly at a buyer-seller interface.
For measurements on thin conducting films, the sheet resistance of the film shall be in the nominal range from 0.04 to 3,000 Ω per square. The substrate on which the thin film is fabricated shall have a minimum edge to edge dimension of 25 mm, measured through the center point and an effective sheet resistance at least 1,000 times that of the thin film.
These test methods require no specimen preparation. Measurements are not affected by specimen surface finish or crystallinity of the test specimen.
For measurements on silicon specimens, these test methods require the use of single crystal silicon resistivity standards to calibrate the apparatus (see ¶ 7.1), and a set of similar reference specimens for qualifying the apparatus (see ¶ 7.1.1). For measurements on transparent conducting oxide (TCO) films, it is possible to use TCO film standards, calibrated by four-point probe sheet resistance measurements.
Two test methods are covered by this Standard.
Method I ascertains the conformance of the apparatus to linearity and slope limits (±1 digit) over a broad range (2 decades) of calibration standard values. It qualifies apparatus for use over a wide range of sample values.
Method II, for use on silicon specimens only, assumes instrument linearity between calibration standards whose values are narrowly separated (typically ±25% of the anticipated sample range median point). Method II is particularly well suited to computer-based systems where all measurements can be quickly and automatically corrected for value offset and for the temperature coefficient of the resistivity of silicon.
These methods differ in calibration technique, sample measurement value range, data correction techniques, and suitability of instrumentation as indicated in Table 1. Either method may be applied to brick or ingot specimens with resistivity in the range from 0.1 to 10,000 Ω·cm or to silicon or other thin films of sheet resistance 2 to 3,000 Ω/square provided that suitable calibration standards can be obtained.
Referenced SEMI Standards
SEMI M59 — Terminology for Silicon Technology
SEMI MF43 — Test Methods for Resistivity of Semiconductor Materials
SEMI MF84 — Test Method for Measuring Resistivity of Silicon Wafers with an In-Line Four-Point Probe
SEMI MF374 — Test Method for Sheet Resistance of Silicon Epitaxial, Diffused, Polysilicon, and Ion-Implanted Layers Using an In-Line Four-Point Probe with the Single-Configuration Procedure
SEMI MF533 — Test Method for Thickness and Thickness Variation of Silicon Wafers
SEMI MF673 — Test Method for Measuring Resistivity of Semiconductor Wafers or Sheet Resistance of Semiconductor Films with a Noncontact Eddy-Current Gauge
SEMI MF1527 — Guide for Application of Certified Reference Materials and Reference Wafers for Calibration and Control of Instruments for Measuring Resistivity of Silicon