Within the context of
indicates that the results of a measurement -- or a series of measurements
-- are in a known, valid, and authenticated relationship to internationally
recognized standards and, that a thoroughly documented, unbroken
chain of reference is established to a specific measurement authority.
methods relate to PSI Traceability -- Mainly to the United States National
Standardization Authority -- The NATIONAL INSTITUTE OF STANDARDS
AND TECHNOLOGY (NIST).
1. Calibration of metrology tools and measurement
instruments, using NIST Standard Reference Material (SRM).
2. Measurements and certification using NIST methods
and same apparatus.
3. Measurement and analysis using well-established,
scientific FIRST PRINCIPLES, and CONSTANTS OF NATURE.
4. Artifacts submitted to NIST for calibration and
certification by their laboratories.
5. Calibration in accordance with INDUSTRY STANDARDS,
implying a rigorous adherence to industry standard methods, practices,
procedures and definitions, such as ASTM or ANSI/NCSL Z540.1
This method provides what is defined as a “consensus
traceability” through the rigorous application of test and measurement
methods. These protocols and methodology have been developed by
expert groups, and subjected to inter-laboratory comparisons and
Most often, new SRM are developed in this way, such
as ultra thin film thickness standards and nitride standards.
By far, the most
understood method is Method 1, in which a laboratory
acquires SRM from NIST or another internationally recognized authority,
and uses these as primary standards for the calibration of instruments.
PSI Film thickness standards are most frequently
rendered traceable via a combination of at least 4 of the above
methods. PSI uses NIST SRM material to calibrate and monitor
internal metrology equipment, which in turn is used in measuring and establishing
“secondary standards”. In addition PSI Standards is
ISO/IEC 17025 Accredited by NVLAP/NIST, and is a nationally recognized
calibration laboratory. Lab code: 200669-0.
is by far the most reliable and accurate
measurement technique for producing secondary standards for various
1. It is the technique used by NIST to create and
develop a film thickness SRM. A research grade ellipsometer can
be easily configured to reproduce the exact measurement conditions
of NIST (AOI -- or Angle of Incidence -- and wavelength), with comparable
accuracy and precision.
2. The measurement of the changes in polarization
state-of-light (Delta and Psi) are straight forward, and directly
comparable to those of NIST.
3. The calibration of the instrument and measurements
are based on Scientific First Principle – the fundamental properties
4. The calculations of the derived values are based
upon the same mathematical model that is used by NIST.
5. The nominal values of the standards manufactured
by PSI are selected to ensure that the Delta and Psi values are
as close to identical as those of the SRMs manufactured by NIST.
This ensures that the nominal thickness and index values are the
same as –or multiples of – the primary standards issued by NIST.
6. The conceptual and mathematical models used to
convert the measured values to useful, physical data are the same
as the ones mandated by NIST.
The physical standards made by PSI Standards are
manufactured from identical or superior materials, in identical
or superior conditions, as are the ones produced by NIST - thermally
grown Silicon Dioxide or LPCVD Silicon Nitride on Prime grade P type <100>
Silicon wafers, in a sub “Class 10” Semiconductor Fab.
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