ASTM E2245-05

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E2245 – 05
Standard Test Method for
Residual Strain Measurements of Thin, Reflecting Films
1
Using an Optical Interferometer
This standard is issued under the fixed designation E2245; 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 3.1.4 anchor lip, n—in a surface-micromachining process,
the freestanding extension of the structural layer of interest
1.1 This test method covers a procedure for measuring the
around the edges of the anchor to its underlying layer.
compressive residual strain in thin films. It applies only to
3.1.4.1 Discussion—In some processes, the width of the
films, such as found in microelectromechanical systems
anchor lip may be zero.
(MEMS) materials, which can be imaged using an optical
3.1.5 bulk micromachining, adj—a MEMS fabrication pro-
interferometer. Measurements from fixed-fixed beams that are
cess where the substrate is removed at specified locations.
touching the underlying layer are not accepted.
3.1.6 cantilever, n—a test structure that consists of a free-
1.2 This test method uses a non-contact optical interferom-
standing beam that is fixed at one end.
eter with the capability of obtaining topographical 3-D data
3.1.7 fixed-fixed beam, n—a test structure that consists of a
sets. It is performed in the laboratory.
freestanding beam that is fixed at both ends.
1.3 This standard does not purport to address all of the
3.1.8 in-plane length (or deflection) measurement, n—the
safety concerns, if any, associated with its use. It is the
experimental determination of the straight-line distance be-
responsibility of the user of this standard to establish appro-
tween two transitional edges in a MEMS device.
priate safety and health practices and determine the applica-
3.1.8.1 Discussion—This length (or deflection) measure-
bility of regulatory limitations prior to use.
ment is made parallel to the underlying layer (or the xy-plane
2. Referenced Documents
of the interferometer).
2
3.1.9 interferometer, n—a non-contact optical instrument
2.1 ASTM Standards:
used to obtain topographical 3-D data sets.
E2244 Test Method for In-Plane Length Measurements of
3.1.9.1 Discussion—The height of the sample is measured
Thin, Reflecting Films Using an Optical Interferometer
along the z-axis of the interferometer. The interferometer’s
E2246 Test Method for Strain Gradient Measurements of
x-axis is typically aligned parallel or perpendicular to the
Thin, Reflecting Films Using an Optical Interferometer
transitional edges to be measured.
3. Terminology
3.1.10 MEMS, adj—microelectromechanical system.
3.1.11 microelectromechanical systems, adj—in general,
3.1 Definitions:
this term is used to describe micron-scale structures, sensors,
3.1.1 2-D data trace, n—a two-dimensional group of points
actuators or the technologies used for their manufacture (such
that is extracted from a topographical 3-D data set and that is
as, silicon process technologies), or combinations thereof.
parallel to the xz-or yz-plane of the interferometer.
3.1.12 out-of-plane measurements, n—experimental data
3.1.2 3-D data set, n—a three-dimensional group of points
taken on structures that are curved in the interferometer’s
with a topographical z-value for each (x, y) pixel location
z-direction (that is, perpendicular to the underlying layer).
within the interferometer’s field of view.
3.1.13 residual strain, n—in a MEMS process, the amount
3.1.3 anchor, n—in a surface-micromachining process, the
of deformation (or displacement) per unit length constrained
portion of the test structure where a structural layer is inten-
within the structural layer of interest after fabrication yet
tionally attached to its underlying layer.
before the constraint of the sacrificial layer (or substrate) is
removed (in whole or in part).
1
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue
3.1.14 sacrificial layer, n—a single thickness of material
and Fracture and is the direct responsibility of Subcommittee E08.05 on Cyclic
that is intentionally deposited (or added) then removed (in
Deformation and Fatigue Crack Formation.
Current edition approved Nov. 1, 2005. Published December 2005. Originally
whole or in part) during the micromachining process, to allow
approved in 2002. Last previous edition approved in 2002 as E2245–02. DOI:
freestanding microstructures.
10.1520/E2245-05.
2 3.1.15 stiction, n—adhesion between the portion of a struc-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
turallayerthatisintendedtobefreestandinganditsunderlying
contact ASTM Customer Service at service@astm.org.
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