Mechanisms of Stress-Induced and Electromigration-Induced Damage in Passivated Narrow Metallizations on Rigid Substrates

MRS Bulletin ◽  
1992 ◽  
Vol 17 (7) ◽  
pp. 61-69 ◽  
Author(s):  
M.A. Korhonen ◽  
P. Børgesen ◽  
Che-Yu Li
Keyword(s):  
Thermal Stress ◽  
Thermal Stresses ◽  
Elevated Temperatures ◽  
Semiconductor Industry ◽  
Pure Aluminum ◽  
Void Formation ◽  
Silicon Substrates ◽  
Thermal Expansion Coefficients ◽  
Hillock Formation ◽  
Current Densities

Narrow, passivated metal lines are generally used as interconnects in VLSI microcircuits at the chip level. In most metals, high electric current densities lead to a mass flow of constituent atoms accompanying the current of electrons. Electromigration (EM) has long been considered an important reliability concern in the semiconductor industry because the current-induced atomic fluxes can give rise to void formation and open circuits, or hillock formation and short circuits between nearby interconnects. The problem is exacerbated because of the continued trend of increasing the density of the devices on the chip. This means that the line widths of the interconnects have been reduced and are now in the submicron range; correspondingly, the current densities have increased and may be as high as 106 A/cm2. Recently, thermal-stress-induced damage in metallizations has also been recognized as an important reliability concern, perhaps of the same gravity as EM. Thermal stresses in the metallizations are caused by the different thermal expansion coefficients of the metal and the substrate. Stress-induced void and hillock formation are the main causes of in terconnect failures before service. More recently, concern has been growing that thermal stresses or thermal-stress-induced voids may enhance the subsequent electromigration damage during the service life of the microchips.For simplicity, this article addresses the case of pure aluminum metallizations on oxidized silicon substrates. However, much of what is said applies to other metal-rigid substrate systems as well, most notably to various aluminum and copper-based metallizations on ceramic substrates. The present treatment emphasizes void formation and growth in the metallizations during nd after cooldown from elevated temperatures, or those due to electromigration in service or testing conditions. Many of the mechanisms we explain are also applicable to hillock formation under compressive stresses, whether due to EM or thermal cycles during manufacturing.

Thermal Expansion Coefficients and Thermal Stresses in an Aligned Short Fiber Composite With Application to a Short Carbon Fiber/Aluminum

1985 ◽  
Vol 52 (4) ◽  
pp. 806-810 ◽  
Author(s):  
Y. Takao ◽  
M. Taya
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Carbon Fiber ◽  
Thermal Stresses ◽  
Short Fiber ◽  
Short Carbon Fiber ◽  
Thermal Expansion Coefficients ◽  
Equivalent Inclusion Method ◽  
Expansion Coefficients ◽  
Short Carbon

A formulation to compute the effective thermal expansion coefficients (αc) of an anisotropic short fiber-reinforced composite and the thermal stress (σ) induced in and around the fiber is developed. The formulation is based on the Eshelby’s equivalent inclusion method. Main emphasis is placed on short Carbon fiber/Aluminum. The thermal stress due to a uniform temperature rise ΔT is computed at points just outside the fiber. The effects of various parameters on αc and σ are also investigated.

Modelling of III-Nitride Epitaxial Layers Grown on Silicon Substrates with Low Dislocation-Densities

MRS Advances ◽  
2019 ◽  
Vol 4 (13) ◽  
pp. 755-760 ◽  
Author(s):  
Khaled H. Khafagy ◽  
Tarek M. Hatem ◽  
Salah M. Bedair
Keyword(s):  
Thermal Stresses ◽  
Life Time ◽  
Epitaxial Layers ◽  
Silicon Substrates ◽  
Thermal Expansion Coefficients ◽  
Dislocation Densities ◽  
Large Lattice ◽  
Expansion Coefficients ◽  
And Performance ◽  
Mesh Convergence

ABSTRACTLarge lattice and thermal expansion coefficients mismatches between III-Nitride (III N) epitaxial layers and their substrates inevitably generate defects on the interfaces. Such defects as dislocations affect the reliability, life time, and performance of photovoltaic (PV) devices. High dislocation densities in epitaxial layer generate higher v-shaped pits densities on the layer top surface that also directly affect the device performance. Therefore, using an approach such as the embedded void approach (EVA) for defects reduction in the epitaxial layers is essential. EVA relies on the generation of high densities of embedded microvoids (∼108/cm2), with ellipsoidal shapes. These tremendous number of microvoids are etched near the interface between the III N thin-film and its substrate where the dislocation densities present with higher values.This article used a 3-D constitutive model that accounts the crystal plasticity formulas and specialized finite element (FE) formulas to model the EVA in multi-junction PV and therefore to study the effect of the embedded void approach on the defects reduction. Mesh convergence and 2-D analytical solution validation is conducted with accounting thermal stresses. Several aspect and volume ratios of the embedded microvoids are used to optimize the microvoid dimensions.

Thermal Stress Effects of Thin Superconducting Films

1968 ◽  
Vol 26 ◽  
pp. 386-387
Author(s):  
M. Connella ◽  
R. J. Deck ◽  
R. H. Morriss
Keyword(s):  
Thermal Stress ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
Superconducting Films ◽  
Temperature Cycle ◽  
Superconducting Properties ◽  
Replication Method ◽  
Thermal Expansion Coefficients ◽  
Before And After ◽  
The Difference

In order to completely understand the role of microstructural defects in superconductivity, it is very desirable to have quantitative correlations between superconducting properties and structural properties. This research is part of a study to correlate grain-sizes with “flux creep phenomena” which occur in the mixed state of Type II superconducting films. Since the superconducting properties in our study must be observed at liquid helium temperatures, whereas the films are evaporated at elevated temperatures, the structural changes produced in some films by cycling to 4.2°K have been investigated.As the temperature of a film is lowered, the difference in thermal expansion coefficients of a film and its substrate results in thermal stress. This stress can produce structural changes. Films have been examined by electron microscopy techniques before and after a temperature cycle down to 4.2°K and back to room temperature. All temperature cycles were carried out in approximately 20 minutes. Both transmission and replication techniques have been employed. The direct replication method was employed using carbon. The carbon replica was separated from the film and post-shadowed with Pt-C.

Thermal Stress in a Coated Short Fiber Composite

1987 ◽  
Vol 109 (1) ◽  
pp. 59-63 ◽  
Author(s):  
Hiroshi Hatta ◽  
Minoru Taya
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Stress Field ◽  
Thermal Stresses ◽  
Fiber Composite ◽  
Short Fiber ◽  
Critical Parameters ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Short Fiber Composite

When a coated short fiber composite is subject to temperature change, thermal stresses in and around the coated fibers are induced due to the mismatch of thermal expansion coefficients of the constituents. The problem of the above thermal stresses in a coated short fiber composite is solved by using the Eshelby’s equivalent inclusion method under the assumption of thin coating. A parametric study is then conducted to examine the effect of thermo-mechanical properties of the coating on the stress field in an and around a coated short fiber. It is found in this study that critical parameters influencing the thermal stress field are the thermal expansion coefficients of the fiber and coating.

Thermal Stress Analysis of a Bi-Material Layered Structure

2010 ◽  
Vol 450 ◽  
pp. 161-164 ◽  
Author(s):  
Shiuh Chuan Her ◽  
Chin Hsien Lin ◽  
Shun Wen Yeh
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Dissimilar Materials ◽  
Beam Theory ◽  
Layered Systems ◽  
Thermal Expansion Coefficients ◽  
Parametric Studies ◽  
Expansion Coefficients ◽  
Good Agreement

Thermal stress induced by the mismatch of the thermal expansion coefficients between dissimilar materials becomes an important issue in many bi-layered systems, such as composites and micro-electronic devices. It is useful to provide a simple and efficient analytical model, so that the stress level in the layers can be accurately estimated. Basing on the Bernoulli beam theory, a simple but accurate analytical formulation is proposed to evaluate the thermal stresses in a bi-material beam. The analytical results are compared with finite element results. Good agreement demonstrates that the proposed approach is able to provide an efficient way for the calculation of the thermal stresses. It is shown that thermal stresses are linear proportion to the ratio of thermal expansion coefficients between the two materials. Parametric studies reveal that thermal stresses in each layer are decreasing with the increase of thickness, and are increasing with the increase of Young’s modulus ratio between the two materials.

Thermal expansion and pore pressure generation in oil sands

1986 ◽  
Vol 23 (3) ◽  
pp. 327-333 ◽  
Author(s):  
J. G. Agar ◽  
N. R. Morgenstern ◽  
J. D. Scott
Keyword(s):  
Thermal Expansion ◽  
Pore Pressure ◽  
Oil Sands ◽  
Thermal Stresses ◽  
Elevated Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Oil Sand ◽  
Thermal Expansion Coefficients ◽  
Stress Changes ◽  
Expansion Coefficients

The prediction of stress changes and deformations arising from ground heating requires the coupled solution of the heat transfer and consolidation equations. Heat consolidation as a class of problems is distinct from other thermally induced consolidation problems involving processes such as frost heave and thaw consolidation in that it involves heating to elevated temperatures well above normal ground temperatures. Two of the important parameters required in analyses of heat consolidation problems are thermal expansion coefficients and a coefficient of thermal pore pressure generation.Relationships describing thermal expansion behaviour and thermal pore pressure generation in oil sands are presented. Both drained and undrained thermal expansion coefficients for Athabasca oil sand were determined by means of heating experiments in the temperature range 20–300 °C. The thermal pore pressure generation coefficient was evaluated in undrained heating experiments under constant total confining stresses and under constant effective confining stresses. The equipment and experimental methods developed during this study are appropriate for determination of thermal expansion and pore pressure generation properties of oil sands and other unconsolidated geologic materials. Key words: thermal expansion, oil sand, tar sand, thermal pore pressure generation, heat consolidation, thermal consolidation, coefficient of thermal expansion, thermal stresses, ground heating, thermally enhanced oil recovery, thermoelasticity, undrained heating.

scholarly journals Control of Thermophysical Properties of Langasite-Type La3Ta0.5Ga5.5O14 Crystals for Pressure Sensors

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 936
Author(s):  
Haruki Usui ◽  
Makoto Tokuda ◽  
Kazumasa Sugiyama ◽  
Takuya Hoshina ◽  
Takaaki Tsurumi ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Temperatures ◽  
Thermal Stresses ◽  
Pressure Sensors ◽  
Czochralski Method ◽  
Order Type ◽  
Cation Site ◽  
Young’S Moduli ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

We present a possible method to reduce the anisotropy of the thermal stress generated on langasite-type La3Ta0.5Ga5.5O14 (LTG) piezoelectric crystals arising from the mismatch of the thermal expansion coefficients and Young’s moduli of the crystals and metals at high temperatures. To formulate this method, the thermal stresses of order-type langasite crystals, in which each cation site is occupied by one element only, were calculated and compared to each other. Our results suggest that the largest cation site affects the thermal stress. We attempted to replace La3+ in LTG by a larger ion and considered Sr2+. Single crystals of strontium-substituted LTG (Sr-LTG) were grown using the Czochralski method. The thermal stress along the crystallographic c-axis decreased but that perpendicular to the c-axis increased by strontium substitution into the LTG crystal. The anisotropic thermal stress was reduced effectively. The Sr-LTG single crystal is a superior candidate material for pressure sensors usable at high temperatures.

Modeling Thermal Stress Behavior in Microelectronic Components

1990 ◽  
Vol 112 (1) ◽  
pp. 35-40 ◽  
Author(s):  
G. C. Scott ◽  
G. Astfalk
Keyword(s):  
Mechanical Properties ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Elevated Temperatures ◽  
Underlying Mechanism ◽  
Mechanical Failure ◽  
Computational Techniques ◽  
Thermal And Mechanical Properties ◽  
Stress Cracking ◽  
Microelectronic Components

Thermal stress cracking is a significant mechanical failure mode in microelectronic components. This failure results from elevated stresses in components exposed to elevated temperatures due to the mismatch of thermal and mechanical properties of the constituent materials. The underlying mechanism responsible for these elevated stresses is not well understood. Therefore, we developed general mathematical and computational techniques for modeling the evolution of these stresses. As a test vehicle, we applied these techniques to thermal stress evolution in multilayer ceramic capacitors (MLCC). Thermal stress cracking has been implicated in significant, industry-wide problems associated with the cracking of these components. The model is used to solve for the transient development of thermal and mechanical gradients across the two spatial dimensions of the MLCC mid-plane. Material types with different thermal and mechanical properties and the interfaces between the material types are specifically included in the model. The stress field solutions are used to indicate when and where mechanical failure is expected to occur. The solutions of the model equations have been obtained using special partial differential equation solvers implemented on a CONVEX C120/220 supercomputer. The model is used to investigate the effects of MLCC termination geometry and material properties on the evolution of thermal stresses.

Stress-Assisted Atomic Migration in Thin Copper Films

2007 ◽  
Vol 353-358 ◽  
pp. 671-674
Author(s):  
Hanabusa Takao ◽  
Kazuya Kusaka ◽  
Kenta Kaneko ◽  
Osamu Sakata ◽  
Nishida Masayuki
Keyword(s):  
Thermal Stress ◽  
Thick Film ◽  
Thermal Stresses ◽  
Copper Film ◽  
Passivation Layer ◽  
Copper Films ◽  
Cooling Stage ◽  
Stress Development ◽  
Aln Film ◽  
Hillock Formation

Stress-assisted atomic migration occurs in thin films due to thermal stress development, followed by hillock and void formation on a film surface. Relation between thermal stresses and hillock formation was investigated on copper films with and without passivation layer. Copper films with a thickness of 10, 50 and 100 nm on oxidized silicon wafer were prepared for investigating thermal stress and hillock formation. In-situ thermal stress observation by X-ray measurement revealed that compressive stresses develop in an early stage of heating followed by a sudden decrease in the temperature region between 100 and 200 deg. In a cooling stage, stresses in a film linearly changed with decreasing temperature to form a tensile residual stress state. Surface morphology is observed by optical microscope and SEM after the heat cycle as well as at elevated temperatures in a vacuum chamber. Dome-like swells were formed on an AlN passivation layer. Almost of all of the swells on 100 nm thick film collapsed after the heat treatment up to 350 deg whereas the swells on 10 nm thick film had no collapse excepting a few case. Comparing with the film without passivation, the swell is considered to be the result of atomic migration of copper film to form hillocks in the interface between copper film and AlN passivation film during heating. Atoms are considered to migrate reversibly into the copper film in the cooling stage, resulting to make vacant hall in the swell of AlN film and then collapse due to tensile stress development.

Three Turnaround Heat Treating Studies

2003 ◽  
Author(s):  
Jaan Taagepera ◽  
Marty Clift ◽  
D. Mike DeHart ◽  
Keneth Marden
Keyword(s):  
Heat Treatment ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Heat Treating ◽  
Element Analysis ◽  
Stress Profiles ◽  
Insight Into

Three vessel modifications requiring heat treatment were analyzed prior to and during a planned turnaround at a refinery. One was a thick nozzle that required weld build up. This nozzle had been in hydrogen service and required bake-out to reduce the potential for cracking during the weld build up. Finite element analysis was used to study the thermal stresses involved in the bake-out. Another heat treatment studied was a PWHT of a nozzle replacement. The heat treatment band and temperature were varied with location in order to minimize cost and reduction in remaining strength of the vessel. Again, FEA was used to provide insight into the thermal stress profiles during heat treatment. The fmal heat treatment study was for inserting a new nozzle in a 1-1/4Cr-1/2Mo reactor. While this material would ordinarily require PWHT, the alteration was proposed to be installed without PWHT. Though accepted by the Jurisdiction, this nozzle installation was ultimately cancelled.

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