IEC 62047 18 Edition 1 0 2013 07 INTERNATIONAL STANDARD NORME INTERNATIONALE Semiconductor devices – Micro electromechanical devices – Part 18 Bend testing methods of thin film materials Dispositifs à[.]
Design of test piece
The test specimens are designed as cantilever beams, as illustrated in Figure 1, featuring a simple cross-sectional shape to simplify the calculation of the area’s moment of inertia.
The cross-section of the test piece should have a simple shape, such as rectangular or trapezoidal The dimensions must adhere to specific ratios, with the length (L) of the parallel section being greater than five times the width (W) and less than ten times the width, while also being greater than ten times the thickness (S) and less than one hundred times the thickness.
The fixed end of the test piece shall be placed within a substrate as shown in Figure 1
The contact point between the test piece and the substrate is crucial in preventing plastic deformation and fractures at the root of the test piece This is essential to mitigate stress concentration issues.
When utilizing a test piece with a different shape that does not conform to the elastic deformation behavior described by Equation (1), it is essential to document both the new shape of the test piece and the alternative equation that replaces Equation (1).
In order to minimize the influence of size, the size of test piece should have the same order as that of the objective device component.
Preparation of test piece
The test piece must be produced using the same method employed for applying the thin film to actual devices, as the mechanical properties are influenced by the fabrication processes Additionally, the fabrication of the test piece should adhere to the guidelines outlined in IEC 62047-6:2009.
Clause 4.2 emphasizes the importance of selecting an appropriate substrate removal process to avoid damaging both the supporting part of the substrate and the test piece.
The thin film, which has internal stress distribution along the thickness, cannot be tested due to curling after release from the substrate.
Test piece width and thickness
Each test piece's width and thickness must be measured, as film thickness can vary across a wafer The specified accuracy for both dimensions should be within ± 1% for width and ± 5% for thickness Direct measurements of each test piece are essential, as outlined in IEC 62047-6:2009, section 4.3 regarding test piece thickness.
Storage prior to testing
In the case of thin films, storage environment can affect the mechanical properties (see
IEC 62047-6:2009, 4.4 Storage prior to testing)
General
The employed testing machine includes features to facilitate displacement, loading and positioning, and should be equipped with a measurement system of force and displacement
In the cantilever beam test, loading is applied at specific points (A, B, or C) using either a sphere-shaped or knife-edge loading tool, as illustrated in Figures 2a and 2b It is essential to document the relationship between force (P) and displacement (δ) of the beam, as shown in Figure 2c The loading point must be accurately specified within ± 1% of the test piece's length, with the knife-edge tip radius maintained at 5 µm and straightness within ± 1% of the length Additionally, the angle between the knife-edge length direction and the test piece surface, as well as the longitudinal direction of the test piece, should be within 2° and 4°, respectively All measurements and data must be recorded meticulously.
IEC 1713/13 a) Cantilever beam test piece with loading point
IEC 1714/13 b) Cantilever beam test piece with loading tool
IEC 1715/13 c) Relation between force and displacement Key
1 Loading point at A,B or C 3 Test piece
2 Substrate 4 Sphere shaped tip loading tool
Method for mounting of test piece
To ensure accurate testing, the substrate with test pieces must be mounted on the testing equipment with the loading axis perpendicular to the test piece surface It is essential that the test pieces are firmly secured to the substrate and the testing machine to prevent any movement during the testing process.
The substrate must be securely attached to the testing equipment, which should possess greater stiffness than the substrate itself Additionally, during the testing process, the substrate should remain fixed, and the loading axis of the testing machine must be aligned within 5° of perpendicular to the surface of the substrate.
Method for loading
The contacting portion of the tool used for loading test pieces should be shaped like a sphere, as illustrated in Figure 2b), or a knife-edge If the diameter of the spherical shape is significantly smaller than the thickness (S) and width (W) of the test pieces, it is crucial to apply the load carefully to prevent severe local deformation and fracture at the contact point To ensure accurate results, deformation of the test pieces must be limited to a range of pure elastic deformation, and the movement of the loading tool should be straight.
The displacement (δ) of cantilever beam shall be small for minimizing the contact point being off the initial loading point of test piece during bending
A load cell must be selected with a resolution that ensures 5% accuracy for the applied force, and its drift should not exceed 1% of the full-scale force during testing.
(See IEC 62047-6:2009, 5.4 Method of loading.)
Speed of testing
The displacement speed or loading speed should be constant, and it shall be within the measurement equipment ability.
Displacement measurement
The displacement sensor must have a resolution greater than 0.5% of the maximum measurement range It is advisable to directly measure the bending displacement (δ) of the test piece, as low-force load cells exhibit low stiffness.
Test environment
Testing temperature and humidity shall be controlled to avoid fluctuations during testing, and a particular attention is required for testing temperature.
Data analysis
The relation between force (P) and displacement (δ) of cantilever beam can be expressed as
In the elastic region defined by Equation (1), precise measurements of the test piece's shape are essential Additionally, data on force (P) and displacement (δ) must be accurately recorded for effective analysis.
The relationship between force (P) and displacement (δ) in a cantilever beam is influenced by the cross-sectional shape of the test piece, specifically the moment of inertia of the area (I_z), as well as the distance from the loading point to the root of the test piece It is essential to document the shape of the test piece, the measurement method used, and the accuracy of the measurements.
Regarding the force and displacement relationship obtained as schematically shown in
The initiation of the increasing force, as shown in Figure 2c), is often non-linear due to factors such as the twisted or curved shape of the test piece, partial delamination from the substrate, or micro-fractures at the contact point with the loading tool Therefore, only data from the linear region should be considered Once plastic deformation, substrate fracture, or slip of the loading tool occurs, the relationship between force and displacement becomes non-linear (refer to Annex B).
Material for test pieces
When selecting cantilever beam test pieces, it is essential to choose types that allow for the simultaneous production of over five pieces on the same substrate under identical conditions The elastic modulus of the materials must be known for accurate data analysis, and it should be equal to or less than that of the substrate materials to prevent stress concentration at the fixed portion, specifically at the root of the cantilever beam test piece.
Furthermore, higher yield stress is desirable for avoiding plastic deformation at the contact point of the root of the test piece with the substrate
Test reports shall include at least the following information a) Mandatory
1) reference to this international standard
2) test piece material and elastic modulus for test pieces and substrate in the case of a single crystal: crystallographic orientation
3) method and details of test piece fabrication
– method of thin film deposition
4) shape and dimensions of test pieces; especially
– the moment of inertia of area (I z)
– type of testing machines with resolution and capacity of force sensor and displacement sensor
– testing environment (temperature and relative humidity)
– displacement rate or loading rate
– comments in particular (defects, delamination or twist in test piece) b) Optional
3) Surface roughness of test piece
Precautions for the test piece/substrate interface
The contact point between the test piece and the substrate is crucial for preventing stress concentration, which can lead to plastic deformation or fracture in both the test piece and the substrate To mitigate this issue, the contact angle between the substrate and the test piece should be maintained between 45° and 90°, as indicated by arrow 3.
Figure A.1, and attention shall be paid to ensure that there is no critical etching damage at the corner
Figure A.1 – Finishing angle of substrate contact area with test piece
Precautions necessary for the force displacement relationship
Figure B.1 illustrates a cantilever bend test specimen made of metallic glass (Pd78Cu6Si16, atomic percentage), which was produced and evaluated following the specified standard The dimensions of this test specimen are 500 µm in length and 50 µm in width.
Figure B.1 – Cantilever type bend test piece of metallic glass in accordance with IEC 62047-18
The test piece behaviour during the test following this standard is shown in Figure B.2
The displacement relationship is represented as a straight line during the elastic deformation of the test piece, as indicated by arrow 1 in Figure B.2a When the tip of the test piece makes contact with the substrate during loading (arrow 2 in Figure B.2a and arrow 10 in Figure B.2b), the force and displacement relationship alters, as shown by arrow 3 in Figure B.2a If the test piece undergoes plastic deformation or if the contact point or tip of the loading tool fractures, the unloading curve diverges from the loading curve, as illustrated by arrows 3, 4, and 5 in Figure B.2a.
IEC 1718/13 a) Force displacement relationship of the test piece shown in Figure B.1 tested following this standard
IEC 1719/13 b) Schematic behavior of test piece during test Key
2 turning point at which the tip of the test piece touches the substrate thereby constraining the bending of the test piece, as shown by arrow 10 in Figure B.2.b)
7 substrate for supporting the test piece
10 touch to substrate during loading
Figure B.2 – Typical example of relationship between force and displacement
4.3 Largeur et épaisseur des éprouvettes d’essai 19
5.2 Méthode de montage de l’éprouvette d’essai 21
5.8 Matériau pour les éprouvettes d’essai 22
Annexe A (informative) Précautions pour l'interface entre éprouvette d’essai et substrat 24
Annexe B (informative) Précautions nécessaires pour la relation entre la force et le déplacement 25
Figure 1 – Représentation schématique de l’éprouvette d’essai avec substrat 18
Figure A.1 – Angle de finition de la zone de contact entre le substrat et l’éprouvette d’essai 24
Figure B.1 – Éprouvette d’essai de flexion de type en porte-à-faux faite de verre métallique, conformément à la CEI 62047-18 25
Figure B.2 – Exemple typique de relation entre force et déplacement 26
Tableau 1 – Symboles et désignation d’éprouvette d’essai 18
DISPOSITIFS À SEMICONDUCTEURS – DISPOSITIFS MICROÉLECTROMÉCANIQUES – Partie 18: Méthodes d’essai de flexion des matériaux en couche mince
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La Norme internationale CEI 62047-18 a été établie par le sous-comité 47F: Systèmes microélectromécaniques, du comité d’études 47 de la CEI: Dispositifs à semiconducteurs
Le texte de cette norme est issu des documents suivants:
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Cette publication a été rédigée selon les Directives ISO/CEI, Partie 2
Une liste de toutes les parties de la série CEI 62047, publiées sous le titre général Dispositifs à semiconducteurs – Dispositifs microélectromécaniques, peut être consultée sur le site web de la CEI
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DISPOSITIFS À SEMICONDUCTEURS – DISPOSITIFS MICROÉLECTROMÉCANIQUES – Partie 18: Méthodes d’essai de flexion des matériaux en couche mince
This section of IEC 62047 outlines the testing method for bending thin films with a length and width of less than 1 mm and a thickness ranging from 0.1 µm to 10 µm Thin films are the primary structures utilized in materials for microelectromechanical systems (MEMS).
MEMS, Micro-Electromechanical Systems) et des micromachines
The main material structures for microelectromechanical systems and micromachines exhibit unique characteristics, such as dimensions in the micrometer range and fabrication techniques including deposition and photolithography, as well as non-mechanical machining for test specimens This International Standard specifies the bending tests and the design of smooth cantilever-type test specimens that ensure precision aligned with these special characteristics.
Conception de l’éprouvette d’essai
Test specimens are designed in the shape of a cantilever beam, as illustrated in Figure 1, with a simple cross-sectional shape to facilitate the calculation of the area’s moment of inertia The cross-section of the test specimen should ideally be straightforward, such as rectangular or trapezoidal Additionally, the relationship between the length (L) of the parallel section of the test specimen, the width (W), and the thickness (S) should adhere to the constraints of \(10 > \frac{L}{W} > 5\) and \(100 > \frac{L}{S} > 10\).
The fixed end of the test specimen must be positioned in a substrate, as shown in Figure 1 The contact point between the test specimen and the substrate is crucial to prevent plastic deformation and/or failure at the root contact point due to stress concentration (refer to Appendix A) If a different shape of the test specimen is used, which does not conform to the elastic deformation behavior described by Equation (1), the new shape and its corresponding equation must be documented.
Afin de minimiser l’influence de la taille, il convient que la taille des éprouvettes d’essai soit du même ordre que celle du composant objectif du dispositif.
Préparation des éprouvettes d’essai
It is essential to produce test specimens using a process identical to that of applying the thin film for actual devices, as the mechanical properties are influenced by the manufacturing processes Additionally, the test specimens must be fabricated in accordance with the procedures outlined in IEC 62047-6:2009.
Article 4.2 Préparation de l’éprouvette d’essai Il convient de choisir avec soin le processus de retrait du substrat pour prévenir l'endommagement de la partie de support du substrat (voir
Annexe A) et de la partie de support des éprouvettes d’essai
La couche mince, qui comporte une distribution de contrainte interne le long de son épaisseur, ne peut pas être manipulée en raison d’ondulations après libération du substrat.
Largeur et épaisseur des éprouvettes d’essai
The width and thickness of each test specimen must be measured, as the thickness of the layer on a wafer is typically not uniform The width and thickness in the parallel section of the test specimen should be specified within a precision range of ± 1% and ± 5% Each test specimen should be measured directly.
(voir CEI 62047-6:2009, 4.3 Épaisseur de l’éprouvette d’essai).
Stockage avant essais
Dans le cas de couches minces, l’environnement de stockage peut affecter les propriétés mécaniques (voir CEI 62047-6:2009, 4.4 Stockage avant essais)
Généralités
The testing machine is equipped with features that facilitate movement, loading, and positioning, and it is essential that it includes a system for measuring force and displacement.
In the case of a measurement, the load is applied at a point on the cantilever beam test specimen using a spherical or tapered loading tool, as illustrated in Figures 2a) and 2b) It is essential to record the positions of the load points (A, B, or C) on the test specimens, as shown in Figure 2a), along with the relationship between the force (P) and the displacement (δ) of the cantilever beam depicted in Figure 2c) The location of the load point on the parallel section of the test specimen must be specified within a precision range of ± 1% of the specimen's length The radius of the tapered end is 5 mm, and the straightness tolerance should also be ± 1% of the specimen's length The angles between the direction of the tapered end and the test specimen surface, as well as the longitudinal direction of the specimen, are 2° and 4°, respectively These measurements must be accurately recorded.
IEC 1713/13 a) Éprouvette d’essai de poutre en porte-à-faux avec point de charge
IEC 1714/13 b) Éprouvette d’essai de poutre en porte-à-faux avec outil d'application de charge
IEC 1715/13 c) Relation entre force et déplacement Légende
1 Point de charge en A, B ou C
4 Outil d'application de charge à extrémité sphérique
Méthode de montage de l’éprouvette d’essai
A test specimen substrate must be mounted on the testing equipment so that the load axis and the test specimen surface are perpendicular to each other The attachment of test specimens to the substrates and testing machines must meet specific requirements: a) Test specimens should be securely fastened to the substrate to prevent any movement during testing, and the substrate must be firmly attached to the testing equipment, which should have a higher rigidity than the substrate b) During testing, the substrate of the test specimen must be secured, ensuring that the load axis of the testing machine does not deviate more than 5° from the perpendicular to the substrate surface.
Méthode de charge
The contact region of the spherical part of the loading tool should ideally be spherical, as shown in Figure 2b), or feature a tapered end If the diameter of the sphere is significantly smaller than the thickness (S) and width (W) of the test specimens, care must be taken when applying the load to prevent severe local deformations and fractures at the contact point between the test specimen and the sphere It is essential to minimize deformations in the test specimens to ensure they remain within a range of pure elastic deformations Additionally, the movement of the load application tool should be direct.
The deflection (\( \delta \)) of the cantilever beam must be minimal to ensure that the contact point does not deviate significantly from the initial load point of the test specimen during bending.
A load cell with an appropriate resolution is essential to ensure an accuracy of 5% of the applied force Additionally, the drift of the load cell should be less than 1% of the full-scale force during testing, as outlined in IEC 62047-6:2009, section 5.4.
Vitesse des essais
Il convient que la vitesse de déplacement ou la vitesse de charge soient constantes et elles doivent pouvoir être mesurées par l'équipement de mesure.
Mesure de déplacement
The displacement sensor's resolution must exceed 0.5% of the maximum measurement range It is advisable to directly measure the bending displacement of the test specimen (δ), as low-range force load cells exhibit low stiffness.
Environnement d'essai
L'humidité et la température d'essai doivent être contrôlées pour éviter les fluctuations pendant les essais; la température d'essai devant faire l'objet d'une attention particulière.
Analyse des données
The relationship between force (P) and displacement (δ) in a cantilever beam can be described by Equation (1) within the elastic region When using a test specimen of a different shape, it is essential to measure the shape accurately with a disc Data on force (P) and displacement (δ) must be recorded and readily available for analysis.
The relationship between force (P) and displacement (δ) in a cantilever beam is influenced by the shape of the cross-section of the test specimen, specifically the moment of inertia of the area.
It is essential to document the shape of the test specimen, the measurement method, and the measurement accuracy, as well as the distance between the charge point and the root of the test specimen The relationship between force and displacement, as illustrated in Figure 2c), shows that the initial increase in force is not always linear This non-linearity is attributed to the twisted and/or curved shape of the test specimen, which can lead to partial detachment between the support part of the specimen and the substrate, or micro-fractures at the contact point between the specimen and the load application tool Therefore, it is advisable to use the data results only within the linear region In cases of plastic deformation, rupture of the substrate support, or slippage of the load application tool on the test specimen, the force-displacement relationship becomes non-linear (see Appendix B).
Matériau pour les éprouvettes d’essai
When selecting cantilever beam test specimens, it is essential to choose types that allow for the production of more than five cantilever beams on the same substrate simultaneously and under identical conditions The elastic modulus of the materials should be the reference known for data analysis, and these elastic moduli must be less than or equal to those of the substrate materials to prevent stress concentration at the fixed part (i.e., the root of the cantilever beam test specimen) Additionally, a higher yield strength is desirable to avoid plastic deformation at the contact point between the root of the test specimen and the substrate.
Les rapports d'essai doivent au moins comporter les éléments suivants a) Obligatoire
1) la référence à la présente Norme internationale
2) les matériaux de l’éprouvette d’essai et le module élastique pour les éprouvettes d’essai et le substrat dans le cas d'un monocristal: orientation cristallographique
3) méthode et détails de fabrication d’éprouvette d’essais
– méthode de dépôt de couches minces
– conditions de traitement thermique (recuit)
4) forme et dimensions des éprouvettes d’essai; en particulier
– le moment d'inertie de la zone (I z)
5) les conditions d’essai de flexion
– type des machines d'essai avec la résolution et la capacité du capteur de force et du capteur de déplacement utilisés
– environnement d’essai (température et humidité relative)
– taux de déplacement ou taux de charge
6) les résultats d’essai de flexion
– numéro de l’éprouvette d’essai testé
– commentaires, en particulier (défauts, décollement interlaminaire, ou torsion dans une éprouvette d’essai) b) En option
3) rugosité de surface de l’éprouvette d’essai
Précautions pour l'interface entre éprouvette d’essai et substrat
The contact point between the test specimen and the substrate is crucial to prevent stress concentration, which can lead to plastic deformation or failure in both the test specimen and the supporting part of the substrate To mitigate this issue, the contact angle between the substrate and the test specimen should be maintained between 45° and 90°, as indicated by arrow 3 in Figure A.1 Additionally, it is essential to ensure that there is no critical engraving damage.
3 Région de concentration de contrainte
Figure A.1 – Angle de finition de la zone de contact entre le substrat et l’éprouvette d’essai
Précautions nécessaires pour la relation entre la force et le déplacement
Figure B.1 illustrates a cantilever bending test specimen made of metallic glass (Pd78Cu6Si16 in atomic percentage), produced and tested in accordance with the current standard This test specimen measures 500 µm in length and 50 µm in width.
Figure B.1 – Éprouvette d’essai de flexion de type en porte-à-faux faite de verre métallique, conformément à la CEI 62047-18
The schematic behavior of the test specimen during the testing process, as outlined in the standard, is illustrated in Figure B.2 The displacement relationship is linear, indicated by arrow 1 in Figure B.2.a), when the test specimen is elastically deformed Once the end of the test specimen contacts the substrate under load, as shown by arrow 2 in Figure B.2.a) and arrow 10 in Figure B.2.b), the force-displacement relationship follows a different curve, represented by arrow 3 in the figure.
When the specimen experiences plastic deformation or when the contact point of the specimen or the ends of the loading tool fractures, the discharge curve does not align with the loading curve, as indicated by arrows 3, 4, and 5.
IEC 1718/13 a) Relation entre force et déplacement de l’éprouvette d’essai représentée sur la Figure B.1, soumise à un essai conforme à la présente norme
IEC 1719/13 b) Comportement schématique de l’éprouvette d’essai pendant l'essai
1 partie linéaire de la charge
The two points of curvature where the tip of the test specimen contacts the substrate hinder the bending of the test specimen, as indicated by arrow 10 in Figure B.2.b).
3 partie non linéaire de la charge
4 partie non linéaire de la décharge
5 partie linéaire de la décharge
7 substrat pour soutenir l’éprouvette d’essai
10 contact avec le substrat pendant la charge
Figure B.2 – Exemple typique de relation entre force et déplacement