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SEMI MF673 Document Information:
Title
TEST METHODS FOR MEASURING RESISTIVITY OF SEMICONDUCTOR WAFERS OR SHEET RESISTANCE OF SEMICONDUCTOR FILMS WITH A NONCONTACT EDDY-CURRENT GAUGE
Semiconductor Equipment and Materials International
Publication Date:
Nov 1, 2005
Scope:
These test methods cover the nondestructive measurement of bulk
resistivity of silicon and certain galliumarsenide wafers and of
the sheet resistance of thin films of silicon or gallium-arsenide
fabricated on a limited range of substrates at the wafer center
point using a noncontact eddy-current gauge.
These test methods are presently limited to single-crystal and
polycrystalline silicon and extrinsically conducting
gallium-arsenide bulk specimens or to thin films of silicon or
gallium-arsenide fabricated on relatively high resistivity
substrates but in principle can be extended to cover other
semiconductor materials.
The bulk silicon or gallium-arsenide specimens may be single
crystal or polycrystalline and of either conductivity type
(p or n) in the form of wafers (round or other
shape) that are free of diffusions or other conducting layers that
are fabricated thereon, that are free of cracks, voids or other
structural discontinuities, and that have (1) an edge-to-edge
dimension, measured through the center point of the wafer, not less
than 25 mm; (2) thickness in the range 0.1 to 1.0 mm, inclusive,
and (3) resistivity in the range 0.001 to 200 O·cm, inclusive. Not
all combinations of thickness and resistivity may be measurable.
The instrument is fundamentally limited to a fixed sheet resistance
range, such as that given in ¶2.2.2.
The thin films of silicon or gallium-arsenide may be fabricated
by diffusion, epitaxial or ion implant processes. The sheet
resistance of the layer shall be in the nominal range from 2 to
3000 O 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 1000 times that of the thin film.
NOTE 1: The effective sheet resistance of a bulk substrate is
its bulk resistivity (in O·cm) divided by its thickness in cm.
These test methods require no specimen preparation. Measurements
are not affected by specimen surface finish.
These test methods require the use of resistivity standards to
calibrate the apparatus (see ¶7.1), and a set of reference
specimens for qualifying the apparatus (see ¶7.1.1).
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 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 temperature coefficient of resistivity.
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 sheet or bulk specimens.
Method I has been evaluated by interlaboratory experiment (see
§12). Until Method II has been evaluated by interlaboratory
comparison, it is not recommended that the test method be used in
connection with decisions between buyers and sellers.
NOTICE: This standard does not purport to
address safety issues, if any, associated with its use. It is the
responsibility of the user of this standard to establish
appropriate safety and health guides and determine the
applicability of regulatory or other limitations prior to use.
Purpose
Resistivity is a primary quantity for characterization and
specification of material used for semiconductor electronic
devices. Sheet resistance is a primary quantity for
characterization, specification, and monitoring of thin film
fabrication processes.
These test methods outline the principles of eddy-current
measurements as they relate to semiconductor substrates and certain
thin films fabricated on such substrates as well as requirements
for setting up and calibrating such instruments for use
particularly at a buyer-seller interface.
An eddy-current instrument directly measures conductance of a
specimen. Values of sheet resistance and resistivity are calculated
from the measured conductance, with the resistivity values also
requiring a measurement of specimen thickness.
Keywords:
- contactless measurements
- eddy current
- nondestructive evaluation
- resistivity
- semiconductor
- sheet resistance
- silicon
- thin films
- wafer
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