Measurement of Thin-Film Stress, Stiffness, and Strength Using an Enhanced Membrane Pressure-Bulge Technique

ABSTRACTAccurate mechanical properties of thin films are essential for viable design and fabrication of semiconductor devices and microelectromechanical systems. Relevant properties of thin films such as intrinsic stress, biaxial modulus, and fracture strength can be significantly different than their corresponding bulk values, and much more difficult to measure. However, such data can be obtained from the pressure-deflection response of clamped freestanding membranes, i.e., the so-called pressure-bulge test. Experimental challenges include membrane leakage prevention, ensuring proper structural boundary conditions, and accurately measuring applied pressure and transverse displacements simultaneously. In addition to these issues, most previously-developed pressure-bulge instruments rely on vacuum pump loadings. Such tools are limited by the one-atmosphere differential pressure over the membrane, which is inadequate for burst testing of high-strength films. Consequently, an enhanced pressure-bulge tool has been developed and will be described in this paper. It incorporates positive pressure to overcome the one-atmosphere load limitation, improved edge constraints, and the ability to test an array of membrane windows across a single substrate.

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Plastic Analysis of Metal Sheet Forming with SD Effects

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.299.216 ◽

2013 ◽

Vol 299 ◽

pp. 216-220

Author(s):

Zhen Yu Chen ◽

Chun Du Wu ◽

Zhong Xian Wang

Keyword(s):

Shear Stress ◽

Yield Criterion ◽

High Strength ◽

Sheet Forming ◽

Metal Sheet ◽

Film Stress ◽

Strength Differential ◽

Thin Film Stress ◽

Plastic Analysis ◽

Tension And Compression

Generally, many high-strength alloy materials used in aerospace, power and chemical industries have strength differential effect in tension and compression (SD effects). Usually, in mechanical calculations of sheet metal forming, Treasca yield criterion and Mises yield criterion are applied. Because the yield criterions don’t take SD effects into consideration, the calculation result may have errors for certain materials. However, generalized twin shear stress yield criterion, which takes into account the influence of the intermediate principal stress, is more suitable for most metal materials than Mohr-Coulomb strength theory. Therefore, this article has made plastic analysis on thin film stress issues of metal sheet forming with generalized twin shear stress yield criterion. We have obtained a unified plastic solution to the internal and external stretching issue of thin material with rounded holes and different tension and compression ratio. Providing a new result with wider applicability is very significant.

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In-Situ TEM Study of Plastic Stress Relaxation Mechanisms and Interface Effects in Metallic Films

MRS Proceedings ◽

10.1557/proc-875-o9.1 ◽

2005 ◽

Vol 875 ◽

Cited By ~ 6

Author(s):

Marc Legros ◽

Gerhard Dehm ◽

T. John Balk

Keyword(s):

Thin Films ◽

High Strength ◽

Dislocation Motion ◽

Dislocation Nucleation ◽

Film Stress ◽

In Situ Tem ◽

Metallic Films ◽

Cross Sectional ◽

Thin Foils

AbstractTo investigate the origin of the high strength of thin films, in-situ cross-sectional TEM deformation experiments have been performed on several metallic films attached to rigid substrates. Thermal cycles, comparable to those performed using laser reflectometry, were applied to thin foils inside the TEM and dislocation motion was recorded dynamically on video. These observations can be directly compared to the current models of dislocation hardening in thin films. As expected, the role of interfaces is crucial, but, depending on their nature, they can attract or repel dislocations. When the film/interface holds off dislocations, experimental values of film stress match those predicted by the Nix-Freund model. In contrast, the attracting case leads to higher stresses that are not explained by this model. Two possible hardening scenarios are explored here. The first one assumes that the dislocation/interface attraction reduces dislocation mobility and thus increases the yield stress of the film. The second one focuses on the lack of dislocation nucleation processes in the case of attracting interfaces, even though a few sources have been observed in-situ.

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Thin Film Polymer Stress Measurement Using Piezoresistive Anisotropically Etched Pressure Sensors

MRS Proceedings ◽

10.1557/proc-390-103 ◽

1995 ◽

Vol 390 ◽

Cited By ~ 3

Author(s):

David J. Monk ◽

Mahesh Shah

Keyword(s):

Thin Film ◽

Thin Films ◽

Pressure Sensor ◽

Stress Measurement ◽

Applied Pressure ◽

Pressure Sensors ◽

Film Stress ◽

Polymeric Coating ◽

Stress Effect ◽

Parylene C

ABSTRACTStresses in thin polymer films have been studied for some time by using wafer bowing, bending beams, microstructure release, and laser holographic techniques. An alternative technique for measuring stresses in thin films is discussed in the following paper. Piezoresistive anisotropically etched single crystal silicon pressure sensors are sensitive not only to applied pressure, but also to applied package stress. Deposited passivation materials, like silicone gels and polyimides, have been observed to change the sensitivity of the pressure sensor. In the current work, a thin, conformal polymeric coating (parylene C) is being developed for these pressure sensors. This thin film has been observed to reduce the sensitivity of the device as a function of the film thickness and modulus and the silicon thickness and modulus. The parylene C thin films exhibit a consistent change in film stress during annealing indicating a modification to polymer crystallinity and a corresponding change in material properties. Qualitatively, the electrical output on the pressure sensor compares favorably with measurements taken using wafer bowing. Experimental DMA and TMA work has been performed to determine the modulus (7.84 × 105 psi) and CTE (39 ppm/°C at 25 °C) of the material. However, literature values of modulus (4.1 × 105 psi) have been used with finite element analysis to model the stress effect more accurately for the thin conformal coating on the pressure sensor device. These results indicate that the sensitivity of the pressure sensor will be reduced approximately quadratically as a function of the polymer coating thickness. An empirical function has been derived to estimate sensitivity loss as a function of substrate (i.e., initial diaphragm material) modulus and thickness and coating modulus and thickness.

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Deposition Of BaTiO3 Thin Films And MgO Buffer Layers On Patterned GaAs Substrates For Integrated Optics Applications

MRS Proceedings ◽

10.1557/proc-784-c11.23 ◽

2003 ◽

Vol 784 ◽

Author(s):

Ding-Yuan Chen ◽

Timothy E. Murphy ◽

Jamie D. Phillips

Keyword(s):

Thin Films ◽

Integrated Optics ◽

Deposition Process ◽

Buffer Layers ◽

Film Stress ◽

Thin Film Stress ◽

Heating And Cooling ◽

Gaas Substrates ◽

Electro Optic ◽

Optic Waveguide

ABSTRACTThis work addresses the need for thick layers of ferroelectric thin films on semiconductors for integrated optics applications. The deposition of BaTiO3 thin films with MgO buffers on patterned GaAs substrates is presented as an approach to achieve crack-free optical waveguiding structures. Cracking and peeling of the thin films are observed on patterns with lateral dimensions exceeding 60 microns and nearly crack-free thin films for patterns with lateral dimensions of a few microns. The cracking and peeling of the thin films is attributed to thermal expansion mismatch during the heating and cooling steps of the deposition process. A thin film stress and fracture model is used to analyze the phenomenon. Reduced cracking and peeling on the patterned features are attributed to strain relief on the patterned features. The inclusion of thick AlxOy buffer layers obtained through wet-oxidation of AlGaAs prior to BaTiO3/MgO deposition are presented as a means of obtaining electro-optic waveguide structures on GaAs.

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Deviation in Nano-Mechanical Properties of Ceramic Nano Composite Thin Films

Material Science Research India ◽

10.13005/msri/140101 ◽

2017 ◽

Vol 14 (1) ◽

pp. 01-04

Author(s):

A. S. Bhattacharyya ◽

R. P. Kumar

Keyword(s):

Thin Film ◽

Thin Films ◽

Mechanical Properties ◽

Magnetron Sputtering ◽

Strain Hardening ◽

Hard Coatings ◽

Film Stress ◽

Nano Composite ◽

Thin Film Stress ◽

Morphological Patterns

Ceramic hard Coatings based on Si, C , N, Ti and B were developed using magnetron sputtering, applicable for protecting the underlying substrate. Different morphological patterns were observed on the coating surface due to sputtering. Nanoindentation was used to determine the hardness and modulus of the coatings. The deviations in H and E values were attributed to indentation positions, thin film stress and anisotropy. Evidence of strain hardening was found during loading.

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Correlation between Processing, Composition, and Mechanical Properties of PECVD-SiN, Thin Films

MRS Proceedings ◽

10.1557/proc-188-79 ◽

1990 ◽

Vol 188 ◽

Cited By ~ 7

Author(s):

D. C. H. Yu ◽

J. A. Taylor

Keyword(s):

Thin Films ◽

Mechanical Properties ◽

Silicon Substrate ◽

Lattice Distortion ◽

High Stress ◽

Index Of Refraction ◽

The Other ◽

Film Stress ◽

Intrinsic Stress ◽

Bond Density

ABSTRACTThe inter-relationship between plasma processing, composition, and mechanical properties of PECVD-SiNx, thin films was investigated. Results showed that by varying the gas feeding ratio of NH3/SiH4N2, one can obtain PECVD-SiNx, films of different composition and streu levels. For high stress films, the deposition rate is low, values of index of refraction and Si/N ratio are small. On the other hand, film density of such films is high; values of Young's modulus and N-H/Si-H relative bond density are large. A model which correlates film stress to that contributed by (1) lattice distortion induced by Si-H and NH bondings, (2) ion bombardment, (3) thermal mismatch between PECVD-SiNx films and silicon substrate, and (4) intrinsic stress introduced during the formation of covalent Si-N bonding is proposed and examined in this work.

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Stress and Stability of Sputter Deposited A-15 and BCC Crystal Structure Tungsten Thin Films

MRS Proceedings ◽

10.1557/proc-472-233 ◽

1997 ◽

Vol 472 ◽

Cited By ~ 3

Author(s):

M. J. O'keefe ◽

C. E. Stutz

Keyword(s):

Crystal Structure ◽

Thin Films ◽

Stress Measurement ◽

Thermal Studies ◽

Film Stress ◽

Thin Film Stress ◽

Deposition Parameters ◽

Magnetron Sputter Deposition ◽

Series Of Experiments ◽

Sputter Deposited

ABSTRACTMagnetron sputter deposition was used to fabricate body centered cubic (bec) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bec phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bec phase between 500°C and 650°C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bec tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperature cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was ∼ 1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bec film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bec phase resulted in ≥ 1 GPa tensile increase in film stress.

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Growth, Structure, and Thin Film Stress in TiAl AND Ti3Al FILMS

MRS Proceedings ◽

10.1557/proc-317-503 ◽

1993 ◽

Vol 317 ◽

Cited By ~ 3

Author(s):

M. Chinmulgund ◽

R. B. Inturi ◽

J. A. Barnard

Keyword(s):

Thin Film ◽

Thin Films ◽

Mechanical Properties ◽

Magnetron Sputtering ◽

Hexagonal Structure ◽

Film Stress ◽

Dc Magnetron Sputtering ◽

Bulk Materials ◽

Growth Structure ◽

Thin Film Stress

ABSTRACTThin films of Ti, Al, TiAl and Ti3Al were deposited by dc magnetron sputtering onto 2” dia. oxidized Si<111> wafers and their mechanical properties were studied by measuring the internal stress in the films. Ti and Ti3Al films show hexagonal structure with preferred orientation in the (0002) direction. TiAl is tetragonal, nanocrystalline, and (111) oriented; Al is random fee polycrystalline in nature. Young's Modulii of thin films of these materials were calculated from the stress temperature plots. The E values of TiAI and Ti3Al thin films were found to be significantly higher than those of the bulk Materials.

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Residual Stress Reduction in Sputter Deposited Thin Films by Density Modulation

MRS Proceedings ◽

10.1557/proc-1224-ff05-22 ◽

2009 ◽

Vol 1224 ◽

Cited By ~ 5

Author(s):

Arif Sinan Alagoz ◽

Jan-Dirk Kamminga ◽

Sergey Yu Grachev ◽

Toh-Ming Lu ◽

Tansel Karabacak

Keyword(s):

Electron Microscopy ◽

Thin Films ◽

Residual Stress ◽

Stress Reduction ◽

Mechanical Stability ◽

Film Stress ◽

Radius Of Curvature ◽

Thin Film Stress ◽

Order Of Magnitude ◽

Sputter Deposited

AbstractControl of residual stress in thin films is critical in obtaining high mechanical quality coatings without cracking, buckling, or delamination. In this work, we present a simple and effective method of residual stress reduction in sputter deposited thin films by stacking low and high material density layers of the same material. This multilayer density modulated film is formed by successively changing working gas pressure between high and low values, which results in columnar nanostructured and dense continuous layers, respectively. In order to investigate the evolution of residual stress in density modulated thin films, we deposited ruthenium (Ru) films using a DC magnetron sputtering system at alternating argon (Ar) pressures of 20 and 2 mTorr. Wafer’s radius of curvature was measured to calculate the intrinsic thin film stress of multilayer Ru coatings as a function of total film thickness by changing the number of high density and low density layers. By engineering the film density, we were able to reduce film stress more than one order of magnitude compared to the conventional dense films produced at low working gas pressures. Due to their low stress and enhanced mechanical stability, we were able to grow these density modulated films to much higher thicknesses without suffering from buckling. Morphology and crystal structure of the thin films were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A previously proposed model for stress reduction by means of relatively rough and compliant sublayers was used to explain the unusually low stress in the specimens investigated.

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