BS EN-62276-2016 pdf free download.Single crystal wafers for surface acoustic wave (SAW) device applications — Specifications and measuring methods
6.2 Thickness
Thickness at the centre of the wafer as measured by a sufficiently accurate (typically 1 µm) thickness meter, in accordance with ASTM test method F533.
6.3 Dimension of OF
Measurement of the OF length as a straight cut line of the intersection with the circle using callipers of sufficient accuracy.
6.4 Orientation of OF
Deviation of the geometrical orientation flat from the reference orientation of the lattice plane as measured with an X-ray diffractometer. The method is explained in detail in 1 0.4 and Figure 1 0.
6.5 TV5
TV5 is measured at the centre and at the four points located 6 mm from the edge of the wafer using callipers of sufficient accuracy (typically 1 µm) in accordance with ASTM test method F533.
6.6 Warp
Warp and other flatness parameters are measured using optical flatness equipment.
6.7 TTV
TTV is measured on clamped wafers using optical flatness equipment.
6.8 Front surface defects
Surface defects on the wafer shall be inspected using the method explained in Clause 1 1 .
6.9 Inclusions
Inspection for inclusions shall be performed using light reflected from the polished wafer surface. Inspection should be carried out in a clean environment using a high intensity optically condensed light against a dark background to prevent interference from diffuse light reflections.
6.1 0 Back surface roughness
Surface roughness may be measured by either the contact or optical method. The average roughness (R a ) values listed in Table 2 were determined by contact profilometry. Measured values for a given wafer generally depend on the method (stylus radius, sampling interval,optical parameters).
6.1 1 Orientation
Crystallographic orientation is determined by X-ray diffraction (see 1 0.1 and Figure 1 0).
6.1 2 Curie temperature
The Curie temperature of a ferroelectric material may be determined by either calorimetric or dielectric measurement methods (see 8.1 ).
6.1 3 Lattice constant
The crystal lattice constant may be determined by XRD (see Clause 9).
6.1 4 Bulk resistivity
The bulk resistivity is determined by applying a voltage of 500 V across the wafer at room temperature and measuring the current one minute after the voltage has been applied. The inner-electrode shall have a diameter between 30 mm and 70 mm (see Clause 1 1 ).
7 Identification, labelling, packaging, delivery condition
7.1 Packaging
Wafers shall be packaged so as to avoid contamination or damage during shipping or storage.
Special packaging requirements shall be subject to agreement between the user and the supplier.
7.2 Labelling and identification
All wafer containers shall include labels with the following information:
a) supplier’s name or trade mark;
b) material type;
c) wafer orientation;
d) manufacturing lot number;
e) quantity.
7.3 Delivery condition
Additional documentation or shipping requirements are to be negotiated between each user and supplier.
8 Measurement of Curie temperature
8.1 General
Curie temperature (T c ) determinations are performed on single crystal lithium tantalate (LT) and lithium niobate (LN). Both the DTA (differential thermal analysis) and dielectric constant methods used to determine T c
are destructive tests. Which measuring method should be used
depens on the agreement between a user and a supplier.
8.2 DTA method
The DTA (differential thermal analysis) method is based on the endothermic or exothermic reaction observed when a single crystal transitions from the ferroelectric to paraelectric states.Typically, the sample and a reference material are symmetrically positioned in an oven (see Figure 7) and heated at a constant rate, while recording the temperature difference between the materials. Alumina (α-Al 2 O 3 ) is often used as the reference when running DTA experiments on LN or LT. Heat is released at the LN or LT sample passes upward through the phase transition temperature, and the temperature profile relative to the alumina reference is recorded. The Curie temperature T c is defined as the temperature at which the temperature difference arises.BS EN-62276 pdf download