Single-Strip Decohesion Test to Characterize Nano-Scale Thin Film Delamination

2005 ◽  
Author(s):  
Jiantao Zheng ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Interfacial Fracture ◽  
Critical Energy ◽  
Test Method ◽  
Interfacial Fracture Toughness ◽  
Critical Energy Release Rate ◽  
Nano Scale ◽  
Thin Film Adhesion ◽  
Single Strip

A new test method, Single-Strip Decohesion Test (SSDT), has been developed and used to measure the interfacial fracture toughness of nano-scale thin film on substrate. This fixtureless test employs a stress-engineered superlayer deposited on patterned titanium (Ti) film strips to supply the energy for the delamination from a thick silicon (Si) substrate. The amount of energy available for delamination propagation is varied by fabricating an etchable thin release layer of varying width between the film strips and the substrate. By designing a decreasing area of the release layer, it is possible to arrest the delamination at a given location, and the interfacial fracture toughness or critical energy release rate can be found at the location where the delamination ceases to propagate. Common IC fabrication techniques are used to prepare the sample and execute the test, thereby making the test compatible with current microelectronic or MEMS facilities and suitable for in process measurement of thin film adhesion strength. The methodology presented in this paper is generic in nature, and can be used to measure the process-dependent interfacial fracture toughness of various micro-scale and nano-scale thin film interfaces. Ti thin film with thickness ranging from 5nm to 100nm can be studied using this method.

Superlayer Test for Interfacial Fracture Toughness Measurements

2004 ◽  
Author(s):  
Jiantao Zheng ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Interfacial Fracture ◽  
Critical Energy ◽  
Interfacial Fracture Toughness ◽  
Mode Mixity ◽  
Critical Energy Release Rate ◽  
Component Reliability ◽  
Interfacial Delamination ◽  
Interface Delamination

Knowledge of the mode-mixity (?) dependent interfacial fracture toughness (Γ) is needed to predict the interface delamination and the component reliability of thin-film structures. Mode-mixity, ?, is a measure of the relative shearing to tensile opening of the interface crack near the tip. Typically, Γ increases as ? increases, such that the delamination is less likely when the loading on the interface is shear-dominated. The measurement of mode-mixity dependent Γ has been a challenge for thin film interfaces. The single-strip superlayer test, developed by the authors, eliminates the shortcomings of current testing methods. This test employs a stress-engineered superlayer to drive the interfacial delamination between the thin-film and the substrate. An innovative aspect of the proposed test is to introduce a release layer of varying width between the interested interfaces to control the amount of energy available for delamination propagation. By designing a decreasing area of the release layer, it is possible to arrest the interfacial delamination at a given location, and the interfacial fracture toughness or critical energy release rate can be found at the location where the delamination ceases to propagate. Design, preparation, and execution of the test are presented. Results are shown for Ti/Si interfaces of different mode mixities.

Modified Decohesion Test (MDT) for Interfacial Fracture Toughness Measurement in Microelectronic/MEMS Applications

2002 ◽  
Author(s):  
Mitul B. Modi ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Fracture Toughness ◽  
Energy Release ◽  
Physical Vapor Deposition ◽  
Interfacial Fracture ◽  
Interfacial Fracture Toughness ◽  
Testing Methods ◽  
Structural Variations ◽  
Metal Thin Film

Delamination of intrinsically or residually stressed thin films is commonly encountered in microelectronics and MEMS systems. Thin films typically accrue stresses through micro structural variations caused by physical vapor deposition, thermally induced stresses imposed due to thermal mismatch, and/or extrinsically introduced forces. These stresses can reach upwards of 1 GPa and can easily exceed the strength of the metal thin film interface. Knowledge of the interfacial fracture toughness (Γ) is necessary to predict if delamination will occur. However, measuring Γ is a challenge for thin film interfaces. Typical testing methods such as bimaterial cantilever, microscratch, peel, bulge, or edge lift-off are limited to organic films, cause complex stress fields, can only measure a single mode mix, or cannot achieve the large energy release rates typical of metal thin film interfaces. A new approach based on the decohesion test, called the modified decohesion test (MDT), eliminates these shortcomings of current testing methods. In this approach, a highly stressed super layer is used to drive delamination and “tune-in” the mode mix at the crack tip. Since the deformations remain elastic, a mechanics-based solution can be used to correlate test parameters to the energy release rate. Common IC fabrication techniques are used to prepare the sample and execute the test, thereby making the test compatible with current microelectronic or MEMS facilities. Varying the crack surface area rather than the energy in the super layer allows the ability to bound Γ using a single test wafer providing a 90% savings in resources and 95% savings in time. Other modifications allow application of the method to highly chemically reactive metals and decrease the sample preparation time. Design, preparation, and execution of the MDT are presented. Results of finite element models are used to validate the approach. Results are shown for a Ti/Al2O3 interface.

Interfacial Fracture Characterization of Nano-Scale Thin Films Using Single-Strip Stress-Engineered Superlayer

2006 ◽  
Author(s):  
Jiantao Zheng ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Films ◽  
Crack Propagation ◽  
Interfacial Crack ◽  
Interfacial Fracture ◽  
Critical Energy ◽  
Test Method ◽  
Nano Scale ◽  
Available Energy ◽  
Fracture Parameters

Characterization of interfacial fracture parameters for nano-scale thin films continues to be challenging due to the difficulties associated with preparing samples, fixturing and loading the samples, and extracting and analyzing the experimental data. In this paper, we propose a stress-engineered superlayer test method that can be used to measure the interfacial fracture parameters of nano-scale (as well as micro-scale) thin films without the need for loading fixtures. The proposed test employs the residual stress in sputter-deposited metals to provide the energy for interfacial crack propagation. The innovative aspect of the test is the use of an etchable release layer that is deposited between the two interfacial materials of interest. The release layer is designed such that the available energy for interfacial crack propagation will continue to decrease as the crack propagates, and at the location where the crack ceases to propagate, the available energy for crack propagation will be the critical energy for crack propagation or the interfacial fracture toughness. The proposed test method has been successfully used to characterize Ti thin film on Si substrate.

Elasto-Plastic Analysis of the Peel Test for Thin Film Adhesion

1988 ◽  
Vol 110 (3) ◽  
pp. 266-273 ◽  
Author(s):  
Kyung-Suk Kim ◽  
Junglhl Kim
Keyword(s):  
Fracture Toughness ◽  
Interfacial Crack ◽  
Peel Test ◽  
Interfacial Fracture ◽  
Peel Strength ◽  
Interfacial Fracture Toughness ◽  
Cu Films ◽  
Film Adhesion ◽  
Thin Film Adhesion ◽  
Elastoplastic Bending

Analyses have been made to extract the objective interfacial fracture toughness from the peel strength of very thin metallic films. An elastoplastic bending model of the adherend film has been employed in the analyses applying the fracture mechanics concept of steady-state interfacial crack growth. The analytic result finally shown is a universal peel diagram where the objective interfacial fracture toughness is readily readable when the peel strength is known. Experimental results for Cu films on Si and polyimide substrate systems with a Cr interface are also presented.

scholarly journals Solutions and Discussions of thin film Undergoing the Nonlinear Peeling

2003 ◽  
Vol 795 ◽  
Author(s):  
Yueguang Wei ◽  
Siqi Shu ◽  
Ying Du LNM
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Effective Strain ◽  
Slope Angle ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Interfacial Fracture ◽  
Interfacial Fracture Toughness ◽  
Element Analysis ◽  
Von Mises

ABSTRACTBased on the bending model, three double-parameter criteria characterizing thin film peeling process are introduced and analyzed in detail. Three double-parameter criteria include: (1) the interfacial fracture toughness and the separation strength, (2) the interfacial fracture toughness and the interfacial crack tip slope angle of thin film, and (3) the interfacial fracture toughness and the critical von Mises effective strain of thin film at crack tip. Based on the three double-parameter criteria, the thin film nonlinear peeling problems are solved analytically for each case. The results show that the solutions of thin film nonlinear peeling based on the bending model are very sensitive to the model parameter selections. Through analyses and comparisons for different solutions, a connection between solutions based on the bending models and based on the two-dimensional elastic-plastic finite element analysis is obtained.

Interfacial Fracture Toughness Measurement of Thick Ceramic Coatings by Indentation

2005 ◽  
Vol 290 ◽  
pp. 183-190 ◽  
Author(s):  
Marion Bartsch ◽  
Iulian Mircea ◽  
Jens Suffner ◽  
Bernd Baufeld
Keyword(s):  
Fracture Toughness ◽  
Cross Sections ◽  
Interfacial Fracture ◽  
Ceramic Coatings ◽  
Test Method ◽  
Propagation Path ◽  
Material System ◽  
Coating System ◽  
Interfacial Fracture Toughness ◽  
Adhesive Properties

The basic requirement for the use of a ceramic coating is sufficient adhesion to its substrate. A measure of the adhesive properties of a coating is the interfacial fracture toughness. The test method applicable for interfacial fracture toughness measurements depends on the mechanical properties of the material system and the geometry of the test piece. In this work, indentation methods have been evaluated for the estimation of the fracture toughness of ceramic thermal barrier coatings on metallic substrates. Coatings of 100 to 300 µm thickness were applied by electron beam – physical vapour deposition. The performed test types were Vickers indentation at the interface of polished cross sections of the coating system and Rockwell indentation with a brale C indenter, penetrating the coating perpendicular to the surface. Both tests generate delamination, in which the delamination crack length corresponds to the interfacial fracture toughness. Fracture surfaces and cross sections of the fractured coatings were investigated by optical and scanning electron microscope. Determined fracture toughness values are discussed with respect to the loading conditions in the test and the fracture process – i.e. interaction between indenter and coating system and the crack propagation path.

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