IEC TS 61994-4-4:2018

IEC TS 61994-4-4 ®
Edition 3.0 2018-11
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Piezoelectric, dielectric and electrostatic devices and associated materials for
frequency control, selection and detection – Glossary –
Part 4-4: Piezoelectric materials – Materials Single crystal wafers for surface
acoustic wave (SAW) devices
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IEC TS 61994-4-4 ®
Edition 3.0 2018-11
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Piezoelectric, dielectric and electrostatic devices and associated materials for

frequency control, selection and detection – Glossary –

Part 4-4: Piezoelectric materials – Materials Single crystal wafers for surface

acoustic wave (SAW) devices
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 01.040.31; 31.140 ISBN 978-2-8322-6283-2

– 2 – IEC TS 61994-4-4:2018 RLV © IEC 2018
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
3.1 Single crystals for SAW wafer . 5
3.2 Terms and definitions related to LN and LT crystals . 6
3.3 Terms and definitions related to all crystals . 7
3.4 Flatness . 7
3.5 Definitions of appearance defects . 11
3.6 Other terms and definitions . 12
Bibliography . 14

Figure 1 – Example of site distribution for LTV measurement All sites have their centres
within the FQA . 8
Figure 2 – LTV is a positive number and is measured at value of each site . 8
Figure 3 – Schematic diagram of Sori . 9
Figure 4 – Wafer indication sketch and measurement points for TV5 determination . 10
Figure 5 – Schematic diagram of TTV . 10
Figure 6 – Schematic diagram of warp . 10

Table 1 – Description of wafer orientations . 12

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PIEZOELECTRIC, DIELECTRIC AND ELECTROSTATIC DEVICES
AND ASSOCIATED MATERIALS FOR FREQUENCY CONTROL, SELECTION
AND DETECTION – GLOSSARY –
Part 4-4: Piezoelectric materials – Materials Single crystal wafers
for surface acoustic wave (SAW) devices

FOREWORD
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– 4 – IEC TS 61994-4-4:2018 RLV © IEC 2018
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when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide whether
they can be transformed into International Standards.
IEC TS 61944-4-4, which is a technical specification, has been prepared by IEC technical
committee 49: Piezoelectric, dielectric and electrostatic devices and associated materials for
frequency control, selection and detection.
This third edition of IEC 61994-4-4 cancels and replaces the second edition published in 2010.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the new terms and definitions given in IEC 62276:2016 have been taken into account;
b) the general title has been changed according to the change in the title of TC 49 in 2009.
c) the part title has been changed according to the title of IEC 62276:2016.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
49/1283/DTS 49/1287/RVC
Full information on the voting for the approval of this technical specification can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61994 series, published under the general title Piezoelectric,
dielectric and electrostatic devices and associated materials for frequency control, selection and
detection – Glossary, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
The committee has decided that the contents of this document will remain unchanged until the
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• reconfirmed,
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• amended.
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PIEZOELECTRIC, DIELECTRIC AND ELECTROSTATIC DEVICES
AND ASSOCIATED MATERIALS FOR FREQUENCY CONTROL, SELECTION
AND DETECTION – GLOSSARY –
Part 4-4: Piezoelectric materials – Materials Single crystal wafers
for surface acoustic wave (SAW) devices

1 Scope
This part of IEC 61994 specifies gives the terms and definition for single crystal wafers applied
for surface acoustic wave (SAW) devices representing the state of the art, which are intended
for use in the standards and documents of IEC technical committee 49.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
ISO 4287, Geometrical Product Specifications (GPS) – Surface texture: Profile method – Terms,
definitions and surface texture parameters
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
acceptable quality level
AQL
AQL is the maximum percent defective (or the maximum number of defects per hundred units)
that, for purposes of sampling inspections, can be considered satisfactory as a process average
[IEC 60410:1973, 4.2]
3.1 Single crystals for SAW wafer
3.1.1
as-grown synthetic quartz crystal
right-handed or left-handed single crystal quartz grown hydrothermally. “As-grown” refers to the
state of processing and indicates a state prior to mechanical fabrication
[SOURCE: IEC 61994-4-1:2007, 3.4 IEC 62276:2016, 3.1.1, modified – Notes 1 and 2 to entry
have been removed.]
– 6 – IEC TS 61994-4-4:2018 RLV © IEC 2018
3.1.2
lanthanum gallium silicate
LGS
single crystals described by the chemical formula to La Ga SiO , grown by Czochralski
3 5 14
(crystal pulling from melt) or other growing methods
[SOURCE: IEC 62276:2005 2016, 3.1.5]
3.1.3
lithium niobate
LN
single crystals approximately described by chemical formula LiNbO , grown by Czochralski
(crystal pulling from melt) or other growing methods
[SOURCE: IEC 62276:2005 2016, 3.1.2]
3.1.4
lithium tantalate
LT
single crystals approximately described by chemical formula LiTaO , grown by Czochralski
(crystal pulling from melt) or other growing methods
[SOURCE: IEC 62276:2005 2016, 3.1.3]
3.1.5
lithium tetraborate
LBO
single crystals described by the chemical formula to Li B O , grown by Czochralski (crystal
2 4 7
pulling from melt), vertical Bridgman, or other growing methods
[SOURCE: IEC 62276:2005 2016, 3.1.4]
3.2 Terms and definitions related to LN and LT crystals
3.2.1
curie temperature
T
c
phase transition temperature between ferroelectric and paraelectric phases measured by
differential thermal analysis (DTA) or dielectric measurement
[SOURCE: IEC 62276:2005 2016, 3.3.1 3.2.1]
3.2.2
polarization (or poling) process
electrical process used to establish a single domain crystal
[SOURCE: IEC 62276:2005 2016, 3.3.3 3.2.3]
3.2.3
reduction process
REDOX reaction to increase conductivity to reduce the harmful effects of pyroelectricity
[SOURCE: IEC 62276:2005 2016, 3.3.4 3.2.4]

3.2.4
reduced LN
LN treated with a reduction process, sometimes referred to as “black LN”
[SOURCE: IEC 62276:2005 2016, 3.3.4.1 3.2.5, modified – Note 1 to entry has been removed.]
3.2.5
reduced LT
LT treated with a reduction process, sometimes referred to as “black LT”
[SOURCE: IEC 62276:2005 2016, 3.3.4.2 3.2.6, modified – Note 1 to entry has been removed.]
3.2.6
single domain
ferroelectric crystal with uniform electrical polarization throughout (for LN and LT)
[SOURCE: IEC 62276:2005 2016, 3.3.2 3.2.2]
3.3 Terms and definitions related to all crystals
3.3.1
congruent composition
chemical composition of a single crystal in a thermodynamic equilibrium with a molten solution
of the same composition during the growth process
[SOURCE: IEC 62276:2005 2016, 3.4.2 3.3.2]
3.3.2
lattice constant
length of one unit cell along a major crystallographic axis measured by X-ray using the Bond
method
[SOURCE: IEC 62276:2005 2016, 3.4.1 3.3.1]
3.3.3
twin
crystallographic defect occurring in a single crystal
NOTE The twin is separated from the rest of the material by a boundary, generally aligned along a crystal plane. The
lattices on either side of the boundary are crystallographic mirror images of one another.
two or more same single crystals which are combined together by the law of symmetrical plane
or axis
[SOURCE: IEC 62276:2005 2016, 3.4.3 3.3.3, modified – Notes 1 and 2 to entry have been
removed.]
3.4 Flatness
3.4.1
fixed quality area
FQA
central area of a wafer surface, defined by a nominal edge exclusion, X, over which the
specified values of a parameter apply
[SOURCE: IEC 62276:2005 2016, 3.7.1 3.4.1, modified – Note 1 to entry has been removed.]

– 8 – IEC TS 61994-4-4:2018 RLV © IEC 2018
3.4.2
local thickness variation
LTV
variation determined by a measurement of a matrix of sites with defined edge dimensions (e.g.
5 mm × 5 mm).
Figure 1 – Example of site distribution for LTV measurement
All sites have their centres within the FQA

Figure 2 – LTV is a positive number and is measured at value of each site
Note 1 to entry: All sites have their centres within the FQA.
Note 2 to entry: Measurement is performed on a clamped wafer with the reference plane as defined in 3.30a 3.4.5 a).
A site map example is shown in Figure 1. The value is always a positive number and is defined for each site as the
difference between the highest and lowest points within each site, as shown in Figure 2. For a wafer to meet an LTV
specification, all sites must shall have LTV values less than the specified value.
[SOURCE: IEC 62276:2005 2016, 3.7.8 3.4.8]
3.4.3
focal plane deviation
FPD
deviation measured relative to the 3-point reference plane
Note 1 to entry: The 3-point reference plane is defined in 3.30 b 3.4.5 b).
Note 2 to entry: The value obtained indicates the maximum distance between a point on the wafer surface (within
the FQA) and the focal plane. If that point is above the reference, the FPD is positive. If that point is below the
reference plane, the FPD is negative.
[SOURCE: IEC 62276:2005 2016, 3.7.10 3.4.10]

3.4.4
percent local thickness variation
PLTV
percentage of sites that fall within the specified values for LTV
Note 1 to entry: As with the LTV measurement, this is a clamped measurement.
[SOURCE: IEC 62276:2005 2016, 3.7.9 3.4.9]
3.4.5
reference plane
depends plane depending on the flatness measurement and needs to be specified. It which can
be any of the following:
a) for clamped measurements, the flat chuck surface that contacts the back surface of the
wafer;
b) for without clamped measurements, three points at specified locations on the front surface
within the FQA;
c) for without clamped measurements, the least-squares fit to the front surface using all
measured points within the FQA
d) the least squares fit to the front surface using all measured points within one site
[SOURCE: IEC 62276:2005 2016, 3.7.2 3.4.2]
3.4.6
site
square area on the front surface of the wafer with one side parallel to the OF
Note 1 to entry: Flatness parameters are assessed either globally for the FQA, or for each site individually.
[SOURCE: IEC 62276:2005 2016, 3.7.3 3.4.3]
3.4.7
Sori
sori describes the deformation of an unclamped wafer and is defined as the maximum difference
between a point on the front surface and a reference plane

Figure 3 – Schematic diagram of Sori
Note 1 to entry: Sori describes the deformation of an unclamped wafer, as shown in Figure 3.
Note 2 to entry: In contrast to warp, in this case the reference plane is defined by a least-squares fit to the front
surface (3.4.5 c)).
[SOURCE: IEC 62276:2005 2016, 3.7.7 3.4.7]
3.4.8
thickness variation for five points
TV5
measure of wafer thickness variation defined as the maximum difference between five
thickness measurements
– 10 – IEC TS 61994-4-4:2018 RLV © IEC 2018

Figure 4 – Wafer indication sketch and measurement points for TV5 determination
Note 1 to entry: Thickness is measured at the centre of the wafer and at four peripheral points shown in Figure 4.
[SOURCE: IEC 62276:2005 2016, 3.7.4 3.4.4]
3.4.9
total thickness variation
TTV
difference between the maximum thickness (A) and the minimum thickness (B) as shown in
Figure 4.
Figure 5 – Schematic diagram of TTV
Note 1 to entry: The maximum thickness is represented by the letter A and the minimum thickness is represented by
the letter B in Figure 5.
Note 2 to entry: Measurement of TTV is performed under clamped conditions with the reference plane as defined in
3.30a) 3.4.5 a).
[SOURCE: IEC 62276:2005 2016, 3.7.5 3.4.5]
3.4.10
warp
warp describes the deformation of an unclamped wafer and is defined as the maximum
difference between a point on the front surface and a reference plane

Figure 6 – Schematic diagram of warp
Note 1 to entry: Warp (shown in Figure 6) describes the deformation of an unclamped wafer.

Note 2 to entry: The reference plane is defined by 3-points as described in 3.30b 3.4.5 b). Warp is a bulk property of
a wafer and not of the exposed surface alone.
[SOURCE: IEC 62276:2005 2016, 3.7.6 3.4.6]
3.5 Definitions of appearance defects
3.5.1
chip
region where material has been removed from the surface or edge of the wafer
Note 1 to entry: The size can be expressed by its maximum radial depth and peripheral chord length.
[SOURCE: IEC 62276:2005 2016, 3.16.4 3.5.4]
3.5.2
contamination
the first is defined as area and the second as particulate. The first is caused by surface
contaminants that cannot be removed by cleaning or are stained after cleaning. Those may be
foreign matter on the surface of, for example a localized area that is smudged, stained,
discoloured, mottled, etc., or large areas exhibiting a hazy or cloudy appearance resulting from
a film of foreign materials
foreign matter on a surface of wafer which cannot be removed after cleaning
[SOURCE: IEC 62276:2005 2016, 3.16.1 3.5.1]
3.5.3
crack
fracture that extends to the surface and may or may not penetrate the entire thickness of the
wafer
[SOURCE: IEC 62276:2005 2016, 3.16.2 3.5.2]
3.5.4
dimple
smooth surface depression larger than 3 mm in diameter
[SOURCE: IEC 62276:2005 2016, 3.16.5 3.5.5]
3.5.5
orange peel
large featured, roughened surface visible to the unaided eye under diffuse illumination
Note 1 to entry: This is also called pear skin.
[SOURCE: IEC 62276:2005 2016, 3.16.7 3.5.7]
3.5.6
pit
non-removable surface anomaly such as a hollow, typically resulting from a bulk defect or faulty
manufacturing process
[SOURCE: IEC 62276:2005 2016, 3.16.6 3.5.6, modified – The example has been included into
the definition.]
– 12 – IEC TS 61994-4-4:2018 RLV © IEC 2018
3.5.7
scratch
shallow groove or cut below the established plane of the surface, with a length to width ratio
greater than 5:1
[SOURCE: IEC 62276:2005 2016, 3.16.3 3.5.3]
3.6 Other terms and definitions
3.6.1
back surface roughness
definitions of R are given in ISO 4287
a
roughness which scatters and suppresses bulk wave spurious at back surface
[SOURCE: IEC 62276:2005 2016, 3.8 3.6.4]
3.6.2
bevel
slope or rounding of the wafer
...