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.

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.

Micro-Mechanical Characterization of Tantalum Nitride Thin Films on Sapphire Substrates

1994 ◽  
Vol 343 ◽  
Author(s):  
Shankar K. Venkataraman ◽  
John C. Nelson ◽  
Neville R. Moody ◽  
David L. Kohlstedt ◽  
William W. Gerberich
Keyword(s):  
Thin Films ◽  
Fracture Toughness ◽  
Film Thickness ◽  
Film Surface ◽  
Interfacial Fracture ◽  
Tantalum Nitride ◽  
Interfacial Fracture Toughness ◽  
Sapphire Substrates ◽  
Thin Film Resistors ◽  
Sputter Deposited

ABSTRACTThe adhesion of Ta2N thin films – often used as thin film resistors – to sapphire substrates has been studied by continuous microindentation and microscratch techniques. Ta2N films, 0.1-0.63μm in thickness, were sputter deposited onto single crystal substrates. Continuous microscratch experiments were performed by driving a conical diamond indenter simultaneously into and across the film surface until stresses high enough to delaminate the film were developed. Continuous microindentation experiments were performed to induce film spallation by normal indentation. From both of these experiments, interfacial fracture toughness was determined as a function of film thickness. The interfacial fracture toughness obtained from continuous microscratch experiments is 0.53±0.17 MPa√m, independent of film thickness. This observation indicates that there is almost no plastic deformation in the film prior to fracture so that a ‘true’ interfacial fracture toughness is measured. For the 0.63 µm thick film, continuous microindentation data yielded a fracture toughness of 0.61 ±0.08 MPa√m, which matches closely the value obtained from the microscratch test. Hence, the continuous microscratch and microindentation techniques are viable methods for determining the interfacial fracture toughness in such bi-material systems.

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.

Adhesion Thin Ductile Films Using Stressed Overlayers and Nanoindentation

2002 ◽  
Vol 750 ◽  
Author(s):  
M. J. Cordill ◽  
N. R. Moody ◽  
D. F. Bahr
Keyword(s):  
Fracture Toughness ◽  
Silicon Dioxide ◽  
Energy Release Rate ◽  
Fracture Energy ◽  
Energy Release ◽  
Release Rate ◽  
Pure Shear ◽  
Interfacial Fracture ◽  
Shear Mode ◽  
Interfacial Fracture Toughness

ABSTRACTDifferently stressed films of tungsten on silicon dioxide have been studied to determine the interfacial fracture toughness and the Mode I fracture energy release rate of tungsten on glass. Tungsten films with a low compressive stress (less than 1GPa) had nanoindentation tests performed on them to induce buckling. Using mechanics based models and the dimensions of the buckles the fracture energy release rate and the phase angle of loading (Ψ) were calculated to be between 3.8 and 13 J/m2. By varying the residual stress in the film it was possible to examine regions of pure shear (Mode II) interfacial fracture as well as mixed mode interfacial fracture toughness of this system. A similar tungsten film was then used as stressed overlayer on sputtered Pt films on silicon dioxide to determine the fracture energy release rate. Nanoindentation was required to induce buckling, as the overlayer alone did not cause spontaneous buckling. The stressed overlayer method and nanoindentation were used to determine the interfacial toughness of the Pt/silica system to be 1.4 J/m2.

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.

Measurement of the Mode Mix Dependent Interfacial Fracture Toughness for a Ti/Si Interface Using a Modified Decohesion Test

2003 ◽  
Author(s):  
Mitul B. Modi ◽  
Suresh K. Sitaraman
Keyword(s):  
Fracture Toughness ◽  
Crack Surface ◽  
Unit Area ◽  
Interfacial Fracture ◽  
Analytical Models ◽  
Interfacial Fracture Toughness ◽  
Testing Methods ◽  
Available Energy ◽  
Test Parameters ◽  
Toughness Testing

The Modified Decohesion Test (MDT), developed by the authors, eliminates shortcomings of current interfacial fracture toughness testing methods. In this approach, a highly stressed super layer is used to drive delamination and create any mode mix at the crack tip. MDT uses the change in crack surface area to vary the available energy per unit area for crack growth and thus to bound the interfacial fracture toughness. Therefore, this technique uses a single sample to measure the interfacial fracture toughness, as opposed to the decohesion test that uses several samples to be able to bound the interfacial fracture toughness. 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. In this paper, the mechanics based solution used in the MDT to correlate test parameters to the fracture metrics is discussed and compared against other analytical models. Interfacial fracture toughness results are provided for a Ti/Si interface at several mode mixes.

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