ASTM E1217-11(2019)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1217 − 11 (Reapproved 2019)
Standard Practice for
Determination of the Specimen Area Contributing to the
Detected Signal in Auger Electron Spectrometers and Some
X-Ray Photoelectron Spectrometers
This standard is issued under the fixed designation E1217; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This practice describes methods for determining the
mendations issued by the World Trade Organization Technical
specimen area contributing to the detected signal in Auger
Barriers to Trade (TBT) Committee.
electron spectrometers and some types of X-ray photoelectron
spectrometers (spectrometer analysis area) when this area is
2. Referenced Documents
defined by the electron collection lens and aperture system of
2.1 ASTM Standards:
the electron energy analyzer. The practice is applicable only to
E673 Terminology Relating to SurfaceAnalysis (Withdrawn
those X-ray photoelectron spectrometers in which the speci-
2012)
men area excited by the incident X-ray beam is larger than the
E1016 Guide for Literature Describing Properties of Elec-
specimen area viewed by the analyzer, in which the photoelec-
trostatic Electron Spectrometers
trons travel in a field-free region from the specimen to the
2.2 ISO Standards:
analyzer entrance. Some of the methods described here require
ISO 18115:2001 Surface Chemical Analysis—Vocabulary
an auxiliary electron gun mounted to produce an electron beam
ISO 18516:2006 Surface Chemical Analysis – Auger Elec-
of variable energy on the specimen (“electron-gun method”).
tron Spectroscopy and X-ray Photoelectron Spectroscopy
Other experiments require a sample with a sharp edge, such as
– Determination of Lateral Resolution
a wafer covered with a uniform clean layer (for example, gold
(Au) or silver (Ag)) and cleaved to obtain a long side
3. Terminology
(“sharp-edge method”).
3.1 Definitions—See Terminology E673 and
1.2 This practice is recommended as a useful means for
ISO 18115:2001 for terms used inAuger electron spectroscopy
determining the specimen area viewed by the analyzer for
and X-ray photoelectron spectroscopy.
different conditions of spectrometer operation, for verifying
adequate specimen and beam alignment, and for characterizing
4. Summary of Practice
the imaging properties of the electron energy analyzer.
4.1 Electron-Gun Method—An electron beam with a se-
1.3 The values stated in SI units are to be regarded as
lected energy is scanned across the surface of a test specimen.
standard. No other units of measurement are included in this
The beam may be scanned once, that is, a line scan, or in a
standard.
pattern, that is, rastered. As the electron beam is deflected
1.4 This standard does not purport to address all of the
across the specimen surface, measurements are made of the
safety concerns, if any, associated with its use. It is the
intensities detected by the electron energy analyzer as a
responsibility of the user of this standard to establish appro-
function of the beam position for selected conditions of
priate safety, health, and environmental practices and deter-
analyzer operation. The measured intensities may be due to
mine the applicability of regulatory limitations prior to use.
electrons elastically scattered by the specimen surface, to
1.5 This international standard was developed in accor-
electrons inelastically scattered by the specimen, or to Auger
dance with internationally recognized principles on standard-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This practice is under the jurisdiction of ASTM Committee E42 on Surface Standards volume information, refer to the standard’s Document Summary page on
Analysis and is the direct responsibility of Subcommittee E42.03 on Auger Electron the ASTM website.
Spectroscopy and X-Ray Photoelectron Spectroscopy. The last approved version of this historical standard is referenced on
Current edition approved Nov. 1, 2019. Published November 2019. Originally www.astm.org.
approved in 1987. Last previous edition approved in 2011 as E1217 – 11. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/E1217-11R19. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1217 − 11 (2019)
electrons emitted by the specimen. The intensity distributions 5.5 Information about the shape and size of the area viewed
for particular detected electron energy can be plotted as a by the analyzer can also be employed to predict the signal
function of beam position in several ways and can be utilized intensityinXPSexperimentswhenthesampleisrotatedandto
to obtain information on the specimen area contributing to the assess the axis of rotation of the sample manipulator.
detected signal and on analyzer performance for the particular
5.6 Examples of the application of the methods described in
conditions of operation. This information can be used to
this practice have been published (1-7).
determine the analysis area (see Terminology E673 or
5.7 There are different ways to define the spectrometer
ISO 18115:2001).
analysis area. An ISO Technical Report provides guidance on
4.2 Sharp-Edge Method—A sample with a sharp edge is
determinations of lateral resolution, analysis area, and sample
scanned through the focal area of the analyzer with its sharp
area viewed by the analyzer in AES and XPS(8), and
edge perpendicular to the scanning direction (knife edge
ISO 18516:2006 describes three methods for determination of
experiments). As the sample is moved to different positions,
lateral resolution in AES and XPS. Baer and Engelhard have
measurements are made of the intensity of a characteristic
used well-defined ‘dots’ of a material on a substrate to
photoelectron peak of the sample surface (for example, Au 4f determine the area of a specimen contributing to the measured
peak if the sample was covered with gold) for selected
signal of a ‘small-area’XPS measurement (9). This area could
conditions of the analyzer operation. The measured intensity is be as much as ten times the area estimated simply from the
maximum when the sampled area is completely contained by
lateral resolution of the instrument. The amount of intensity in
the sample surface, and minimum when there is no overlap ‘fringe’or ‘tail’regions could also be highly dependent on lens
between the analysis volume of the analyzer and the sample operation and the adequacy of specimen alignment. Sche-
surface. The length of the intermediate region will depend on ithauerdescribedanalternativetechniqueinwhichPtapertures
thesizeoftheanalysisarea.Theareaofthephotoelectronpeak of varying diameters were utilized to determine the fraction of
can be plotted as a function of sample position. The behavior ‘long-tail’ X-ray contributions outside each aperture on the
ofthiscurvecanbeusedtoassessthewidthoftheanalysisarea measured Pt photoelectron signal compared to that on a Pt foil
(10). In test measurements on a commercial XPS instrument
in the scanning direction.
with a focused X-ray beam and a nominal lateral resolution of
10 µm (as determined from the distance between the positions
5. Significance and Use
for 20 % and 80 % of maximum signal when scans were made
5.1 Auger electron spectroscopy and X-ray photoelectron
across an edge), it was found that aperture diameters of about
spectroscopy are used extensively for the surface analysis of
100 µm and 450 µm were required to reduce the photoelectron
materials. This practice summarizes methods for determining
signals to 10 % and 1 %, respectively, of the maximum value
the specimen area contributing to the detected signal (a) for
(10). Knowledge of the effective analysis area is important
instruments in which a focused electron beam can be scanned
when making tradeoffs between lateral resolution and detect-
over a region with dimensions greater than the dimensions of
ability. In scanning Auger microscopy, the area of analysis is
the specimen area viewed by the analyzer, and (b) by employ-
determinedmorebytheradialextentofbackscatteredelectrons
ing a sample with a sharp edge.
than by the radius of the primary beam (11, 12, 13).
5.2 This practice is intended as a means for determining the
6. Apparatus for the Electron-Gun Method
observed specimen area for selected conditions of operation of
6.1 Test Specimen, preferably a conductor, is required and is
the electron energy analyzer. The observed specimen area
mounted in the Auger electron or X-ray photoelectron spec-
depends on whether or not the electrons are retarded before
trometer in the usual position for surface analysis. It is
energy analysis, the analyzer pass energy or retarding ratio if
recommended that the test specimen be a metallic foil with
the electrons are retarded before energy analysis, the size of
lateral dimensions larger than the dimensions of the field of
selected slits or apertures, and the value of the electron energy
view of the electron energy analyzer. The test specimen should
to be measured. The observed specimen area depends on these
be polycrystalline and have grain dimensions much less than
selected conditions of operation and also can depend on the
the expected spatial resolution of the analyzer or the width of
adequacy of alignment of the specimen with respect to the
the incident beam on the specimen in order to avoid artifacts
electron energy analyzer.
due to channeling or diffraction effects. The specimen surface
5.3 Any changes in the observed specimen area as a
should be smooth and be free of scratches and similar defects
function of measurement conditions, for example, electron
that are observable with the unaided eye (see 8.6). It is
energy or analyzer pass energy, may need to be known if the
desirablethatthesurfaceofthetestspecimenbecleanedbyion
specimen materials in regular use have lateral inhomogeneities
sputtering or other means to remove surface impurities such as
withdimensionscomparabletothedimensionsofthespecimen
oxides and adsorbed hydrocarbons; the degree of surface
area viewed by the analyzer.
cleanliness can be checked with AES or XPS measurements.
5.4 Thispracticecangiveusefulinformationontheimaging
6.2 Electron Gun—Anelectrongunmustbeavailableonthe
properties of the electron energy analyzer for particular con-
spectrometertoprovideabeamofelectronsincidentonthetest
ditions of operation. This information can be helpful in
comparing analyzer performance with manufacturer’s specifi-
The boldface numbers in parentheses refer to the list of references at the end of
cations. this practice.
E1217 − 11 (2019)
specimen surface with energy typically between 100 eV and 7.2.2.1 Use of Waveform Generators—In this approach, use
2000 eV (the normal range of detected energies in AES and two waveform generators to generate triangular waveforms at
XPS). The gun must be equipped with a deflection system so frequencies typically in the range of 0.5 kHz to 1 kHz. The
that the electron beam can be deflected to different regions of waveforms are amplified and coupled through a transformer to
thespecimensurface.Thewidthoftheelectronbeam(FWHM) the deflection plates of the electron gun, one output being
at the test specimen should be less than the spatial resolution designated for horizontal deflection and the other for vertical
desired in the following measurements. deflection. A resistive center-tap is connected across each
transformer output with the midpoints grounded. The wave-
6.3 Electronic Equipment, is required to scan the electron
formsarealsoconnectedtothehorizontalandverticalinputsof
beam on the surface of the test specimen and to record and
anoscilloscope.Adjustthefrequenciesoftheoscillatorssothat
display the selected signals.
there is a uniform intensity distribution on the oscilloscope,
6.3.1 Equipped Spectrometer—Some commercial
thatis,absenceofanyLissajou’sfigures.Selectthegainsofthe
spectrometers, particularly those designed for scanning Auger
amplifiers to deflect the electron beam across the test specimen
microscopy, have electronic instrumentation, which can be
by amounts corresponding at least to the anticipated analyzer
used to scan the electron beam across the test specimen
field of view; for a desired deflection on the test specimen, the
surface, either on a selected line or on a raster pattern with
maximum deflection-plate voltage will scale with the selected
selected dimensions. The selected analyzer signals may be
electron energy. Make a line scan with a single waveform
recorded in a computer system or be displayed directly on an
generator and with the scan voltage applied to either the
oscilloscope or X-Y recorder.
horizontal or the vertical deflection plates. Apply a dc voltage
6.3.2 Unequipped Spectrometer—If the spectrometer is not
totheotherdeflectionplatestoselectthepositionofthelineon
equipped with instrumentation for scanning the electron beam,
the specimen.
this instrumentation will have to be provided. A line scan can
7.2.2.2 Use of Programmable Power Supplies—Program a
be accomplished with a suitable wave-form generator (either
computer to control the output voltages of two programmable
triangular or sawtooth) or a programmable power supply.
power supplies. Connect the outputs of the power supplies to
Anotherdcsupplymayberequiredtodefinethepositionofthe
the deflection plates of the electron gun. Make these connec-
line on the specimen, that is, in the direction orthogonal to the
tions as in 7.2.2.1; connect center taps across each power
scan. Raster scans can be made with two waveform generators
supply, also as in 7.2.2.1.At a given vertical position, step the
or two programmable power supplies.
electron beam horizontally across the test specimen surface.
The beam then can be stepped vertically prior to the next
7. Procedure for the Electron-Gun Method
horizontal sweep, and so on. Make measurements for each
horizontalsweepandforequallyspacedhorizontallineswithin
7.1 Choose the energy of the electron beam incident on the
the vertical sweep range. The interval between the positions of
surface of the test specimen. This choice should be made
the electron beam on the specimen surface together with the
depending on the nature of the tests to be made. For example,
width of the beam at the surface will determine the spatial
electron energies between 100 eV and 2000 eV may be chosen
resolution in the measurement of the specimen area contribut-
forAuger electron experiments with specific choices related to
ing to each detected signal.
the energies of Auger electron peaks of particular interest. In
7.2.3 The maximum amount of deflection of the electron
X-ray photoelectron spectroscopy experiments with magne-
beam on the test specimen should be less than that which
sium characteristic X-rays, electron energies between approxi-
would cause significant (>5 %) reduction of incident electron-
mately 254 eV and 1254 eV might be chosen to determine the
beam current, for example, reduction due to interception of the
analyzer performance for the binding-energy range between 0
beam by electrodes of the electron gun.
eV and 1000 eV.
7.3 The amount of deflection of the electron beam on the
7.2 Choosethetypeofscanfortheelectronbeamonthetest
test specimen can be determined from electron intensity
surface, either line scan or raster scan (6.3). If a line scan is
measurements with test objects, for example, grids or holes, of
selected, choose the position of the line on the specimen.
known dimensions (1). The test object is mounted on the test
7.2.1 Aline scan is a relatively simple procedure and can be
specimen and features of known shape and size are located in
made for two orthogonal directions.This method for determin-
the recorded data (see 7.7). Alternatively, a feature can be
ing the active area of the analyzer may suffice for many
located in plots of absorbed current (see 7.4) due to, for
applications but has the disadvantage that the active area may
example, specimen roughness or a specimen mounting clip (3).
not be symmetrical about the two scan lines (1, 2). The raster
The specimen can then be moved a known amount using a
scan method allows convenient observation of any instrumen-
manipulator and a new plot made of absorbed current. The
tal asymmetries.
difference in the positions of the selected feature on the two
7.2.2 The following suggestions are made if the instrument
plots corresponds to the displacement of the specimen.
is not already equipped with instrumentation to scan the
electron beam. The specific suggestions are made to generate a 7.4 It is recommended that measurements be made of the
raster scan for an electron gun equipped with deflection plates. current to the specimen (the absorbed current) as the electron
Line scans can be made in a similar way. An analogous beam is scanned across the specimen surface. These measure-
procedure would be used for an electron gun operated with an ments can give information about the topography of the
electromagnetic deflection system. specimen surface and are useful for ensuring that any structure
E1217 − 11 (2019)
in the other intensity measurements (see 7.5) is not associated ment conditions for practical measurements for which charac-
with specimen topography. terization of the instrument is desired.
7.5 Select the electron signals to be measured from the
7.7 The selected electron signals (see 7.4 and 7.5) can be
analyzer.
displayed by several different methods. On scanning Auger
7.5.1 Elastic Peak—The electron energy analyzer can be
electron microscopes, software often will be available for the
adjusted to detect electrons elastically scattered by the speci-
manipulation and display of the acquired data. On other
men surface, that is, at the energy of the incident electron
instruments, the user may be able to export data from the
beam. This choice is recommended for initial survey measure-
instrumental computer for subsequent analysis and display
mentssincethissignalisthestrongest.Apossibledisadvantage
using software on another computer. If these options are not
of this choice is that incorrect intensity measurements may be
available, the following suggestions may be useful for data
made if, for energy analyzers with sufficiently high energy
display. Examples of different types of data displays are given
resolution, the instrument does not remain aligned on the
in Figs. 1-3.
elastic peak as the electron beam is deflected on the specimen
7.7.1 Display of Line Scan—A voltage proportional to the
(4); see also Guide E1016.
detected electron intensity can be applied either to an X-Y
7.5.2 Inelastically Scattered Electrons—Theelectronenergy
recorder or to an oscilloscope as the electron beam is scanned
analyzer can be adjusted to detect electrons inelastically
across the test specimen, that is, y modulation (see Fig. 1(b)).
scattered by the specimen surface. The electron energy being
7.7.2 Display of Raster Scan—A choice can be made of
detected may be between zero and the energy of the incident
several methods for displaying measured intensities.
beam.
7.7.2.1 z-Modulation of Oscilloscope—A voltage propor-
7.5.2.1 This choice is recommended for avoiding the pos-
tionaltothedetectedelectronintensitycanbeusedtomodulate
sible artifact described in 7.5.1. It is suggested that the region
the intensity of an oscilloscope, that is, z-modulation. The
of the scattered-electron energy distribution about 100 eV
pulse signal from the electron detector can be used in the same
below the elastic peak be utilized because the intensity is
way.The oscilloscope beam is deflected in the same way as the
relatively high. The actual electron energy should be chosen to
electron beam is rastered on the specimen so that the oscillo-
avoid any structure that may be present in this region due to
scope display
...