ASTM E2244-05
(Test Method)Standard Test Method for In-Plane Length Measurements of Thin, Reflecting Films Using an Optical Interferometer
Standard Test Method for In-Plane Length Measurements of Thin, Reflecting Films Using an Optical Interferometer
SIGNIFICANCE AND USE
In-plane length measurements are used in calculations of parameters, such as residual strain and Young’modulus.
In-plane deflection measurements are required for specific test structures. Parameters, including residual strain, are calculated given these in-plane deflection measurements.
SCOPE
1.1 This test method covers a procedure for measuring in-plane lengths (including deflections) of patterned thin films. It applies only to films, such as found in microelectromechanical systems (MEMS) materials, which can be imaged using an optical interferometer.
1.2 There are other ways to determine in-plane lengths. Using the design dimensions typically provides more precise in-plane length values than using measurements taken with an optical interferometer. (Interferometric measurements are typically more precise than measurements taken with an optical microscope.) This test method is intended for use when interferometric measurements are preferred over using the design dimensions (for example, when measuring in-plane deflections and when measuring lengths in an unproven fabrication process).
1.3 This test method uses a non-contact optical interferometer with the capability of obtaining topographical 3-D data sets. It is performed in the laboratory.
1.4 The maximum in-plane length measured is determined by the maximum field of view of the interferometer at the lowest magnification. The minimum deflection measured is determined by the interferometers pixel-to-pixel spacing at the highest magnification.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E2244 – 05
Standard Test Method for
In-Plane Length Measurements of Thin, Reflecting Films
1
Using an Optical Interferometer
This standard is issued under the fixed designation E2244; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E2245 Test Method for Residual Strain Measurements of
Thin, Reflecting Films Using an Optical Interferometer
1.1 This test method covers a procedure for measuring
E2246 Test Method for Strain Gradient Measurements of
in-plane lengths (including deflections) of patterned thin films.
Thin, Reflecting Films Using an Optical Interferometer
It applies only to films, such as found in microelectromechani-
cal systems (MEMS) materials, which can be imaged using an
3. Terminology
optical interferometer.
3.1 Definitions:
1.2 There are other ways to determine in-plane lengths.
3.1.1 2-D data trace, n—atwo-dimensionalgroupofpoints
Using the design dimensions typically provides more precise
that is extracted from a topographical 3-D data set and that is
in-plane length values than using measurements taken with an
parallel to the xz-or yz-plane of the interferometer.
optical interferometer. (Interferometric measurements are typi-
3.1.2 3-D data set, n—a three-dimensional group of points
cally more precise than measurements taken with an optical
with a topographical z-value for each (x, y) pixel location
microscope.) This test method is intended for use when
within the interferometer’s field of view.
interferometric measurements are preferred over using the
3.1.3 anchor, n—in a surface-micromachining process, the
design dimensions (for example, when measuring in-plane
portion of the test structure where a structural layer is inten-
deflections and when measuring lengths in an unproven fabri-
tionally attached to its underlying layer.
cation process).
3.1.4 anchor lip, n—in a surface-micromachining process,
1.3 This test method uses a non-contact optical interferom-
the freestanding extension of the structural layer of interest
eter with the capability of obtaining topographical 3-D data
around the edges of the anchor to its underlying layer.
sets. It is performed in the laboratory.
3.1.4.1 Discussion—In some processes, the width of the
1.4 The maximum in-plane length measured is determined
anchor lip may be zero.
by the maximum field of view of the interferometer at the
3.1.5 bulk micromachining, adj—a MEMS fabrication pro-
lowest magnification. The minimum deflection measured is
cess where the substrate is removed at specified locations.
determinedbytheinterferometer’spixel-to-pixelspacingatthe
3.1.6 cantilever, n—a test structure that consists of a free-
highest magnification.
standing beam that is fixed at one end.
1.5 This standard does not purport to address all of the
3.1.7 fixed-fixed beam, n—a test structure that consists of a
safety concerns, if any, associated with its use. It is the
freestanding beam that is fixed at both ends.
responsibility of the user of this standard to establish appro-
3.1.8 in-plane length (or deflection) measurement, n—the
priate safety and health practices and determine the applica-
experimental determination of the straight-line distance be-
bility of regulatory limitations prior to use.
tween two transitional edges in a MEMS device.
2. Referenced Documents 3.1.8.1 Discussion—This length (or deflection) measure-
2
ment is made parallel to the underlying layer (or the xy-plane
2.1 ASTM Standards:
of the interferometer).
3.1.9 interferometer, n—a non-contact optical instrument
1
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue
used to obtain topographical 3-D data sets.
and Fracture and is the direct responsibility of Subcommittee E08.05 on Cyclic
3.1.9.1 Discussion—The height of the sample is measured
Deformation and Fatigue Crack Formation.
along the z-axis of the interferometer. The interferometer’s
Current edition approved Nov. 1, 2005. Published December 2005. Originally
approved in 2002. Last previous edition approved in 2002 as E2244–02. DOI:
x-axis is typically aligned parallel or perpendicular to the
10.1520/E2244-05.
transitional edges to be measured.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.1.10 MEMS, adj—microelectromechanical system.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
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