Mechanical Stress as a Function of Temperature in Thin Aluminum Films and its Alloys

1988 ◽  
Vol 130 ◽  
Author(s):  
Donald S. Gardner ◽  
Paul A. Flinn
Keyword(s):  
Aluminum Alloys ◽  
Thermal Cycling ◽  
Mechanical Stress ◽  
Film Stress ◽  
Solid State Reactions ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Aluminum Films ◽  
Thin Aluminum ◽  
Stress Changes

AbstractAluminum alloys have virtually replaced aluminum for interconnections in VLSI because of their improved reliability. Mechanical stress is a problem of growing importance in these interconnections. Stress as a function of temperature was measured for thin aluminum films and several aluminum alloys and layered films consisting of silicon, copper, titanium, tungsten, tantalum, vanadium, and TiSi2. Solid-state reactions of the aluminum with the additives and with the ambient during thermal cycling will occur and depending on what compounds have formed and at what temperature, this will determine the morphology and reliability of the metallization. The measurement technique, based on determination of wafer curvature with a laser scanning device, directly measures the total film stress and reflectivity in situ during thermal cycling. Changes in stress were detected when film composition and structure varied and were correlated using x-ray diffraction with the formation of aluminides. Other phenomena that contribute to stress changes including elastic behavior, recrystallization, grain growth, plastic behavior, yield strength, and film hardening from precipitates.

Correlation between texture and mechanical stress durability of thin aluminum films

2014 ◽  
Vol 556 ◽  
pp. 376-380 ◽  
Author(s):  
R. Nüssl ◽  
T. Jewula ◽  
W. Ruile ◽  
T. Sulima ◽  
W. Hansch
Keyword(s):  
Mechanical Stress ◽  
Aluminum Films ◽  
Thin Aluminum

Parallel Glide: A Fundamentally Different Type of Dislocation Motion in Ultrathin Metal Films

2003 ◽  
Vol 779 ◽  
Author(s):  
T. John Balk ◽  
Gerhard Dehm ◽  
Eduard Arzt
Keyword(s):  
Thermal Cycling ◽  
Grain Boundaries ◽  
Film Surface ◽  
Metal Films ◽  
Geometric Constraints ◽  
Film Stress ◽  
Diffusional Creep ◽  
Creep Model ◽  
Substrate Interface ◽  
Film Substrate

AbstractWhen confronted by severe geometric constraints, dislocations may respond in unforeseen ways. One example of such unexpected behavior is parallel glide in unpassivated, ultrathin (200 nm and thinner) metal films. This involves the glide of dislocations parallel to and very near the film/substrate interface, following their emission from grain boundaries. In situ transmission electron microscopy reveals that this mechanism dominates the thermomechanical behavior of ultrathin, unpassivated copper films. However, according to Schmid's law, the biaxial film stress that evolves during thermal cycling does not generate a resolved shear stress parallel to the film/substrate interface and therefore should not drive such motion. Instead, it is proposed that the observed dislocations are generated as a result of atomic diffusion into the grain boundaries. This provides experimental support for the constrained diffusional creep model of Gao et al.[1], in which they described the diffusional exchange of atoms between the unpassivated film surface and grain boundaries at high temperatures, a process that can locally relax the film stress near those boundaries. In the grains where it is observed, parallel glide can account for the plastic strain generated within a film during thermal cycling. One feature of this mechanism at the nanoscale is that, as grain size decreases, eventually a single dislocation suffices to mediate plasticity in an entire grain during thermal cycling. Parallel glide is a new example of the interactions between dislocations and the surface/interface, which are likely to increase in importance during the persistent miniaturization of thin film geometries.

Time-Resolved, Laser-Induced Phase Transformation in Aluminum

1984 ◽  
Vol 35 ◽  
Author(s):  
S. Williamson ◽  
G. Mourou ◽  
J.C.M. Li
Keyword(s):  
Point Defect ◽  
Long Range ◽  
Rapid Heating ◽  
Range Order ◽  
Nucleation Theory ◽  
Long Range Order ◽  
Time Resolved ◽  
Aluminum Films ◽  
Thin Aluminum ◽  
Initial Nucleus

ABSTRACTThe technique of picosecond electron diffraction is used to time resolve the laser-induced melting of thin aluminum films. It is observed that under rapid heating conditions, the long range order of the lattice subsists for lattice temperatures well above the equilibrium point, indicative of superheating. This superheating can be verified by directly measuring the lattice temperature. The collapse time of the long range order is measured and found to vary from 20 ps to several nanoseconds according to the degree of superheating. Two interpretations of the delayed melting are offered, based on the conventional nucleation and point defect theories. While the nucleation theory provides an initial nucleus size and concentration for melting to occur, the point defect theory offers a possible explanation for how the nuclei are originally formed.

scholarly journals Mechanical Stress Changes the Movements and Organization of Biofilm-Associated Bacteria

2015 ◽  
Vol 108 (2) ◽  
pp. 601a
Author(s):  
David J. Lemon ◽  
Xingbo Yang ◽  
Pragya Srivastava ◽  
M. Cristina Marchetti ◽  
Anthony Garza
Keyword(s):  
Mechanical Stress ◽  
Associated Bacteria ◽  
Stress Changes

scholarly journals Superlayer Residual Stress Effect on the Indentation Adhesion Measurements

1999 ◽  
Vol 594 ◽  
Author(s):  
Alex A. Volinsky ◽  
Neville R. Moody ◽  
William W. Gerberich
Keyword(s):  
Residual Stress ◽  
Sputter Deposition ◽  
Work Of Adhesion ◽  
Stress Effect ◽  
Aluminum Films ◽  
Nanoindentation Testing ◽  
Deposition Parameters ◽  
Thin Aluminum ◽  
Residual Stress Effect ◽  
Sputter Deposited

AbstractThe practical work of adhesion has been measured in thin aluminum films as a function of film thickness and residual stress. These films were sputter deposited onto thermally oxidized silicon wafers followed by sputter deposition of a one micron thick W superlayer. The superlayer deposition parameters were controlled to produce either a compressive residual stress of 1 GPa or a tensile residual stress of 100 MPa. Nanoindentation testing was then used to induce delamination and a mechanics based model for circular blister formation was used to determine practical works of adhesion. The resulting measured works of adhesion for all films between 100 nm and 1 μm thick was 30 J/m2 regardless of superlayer stress. However, films with the compressively stressed superlayers produced larger blisters than films with tensile stressed superlayers. In addition, these films were susceptible to radial cracking producing a high variability in average adhesion values.

Thermomechanical Stresses in Copper Films at Elevated Temperature

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000129-000135 ◽  
Author(s):  
Martin Lederer ◽  
Javad Zarbakhsh ◽  
Rui Huang ◽  
Thomas Detzel ◽  
Brigitte Weiss
Keyword(s):  
Elevated Temperature ◽  
Thermal Cycling ◽  
Copper Film ◽  
Film Stress ◽  
Elastic Response ◽  
Copper Films ◽  
Thermomechanical Stress ◽  
Wafer Curvature ◽  
Electronic Parts ◽  
Stoney Formula

Thermomechanical stresses in metallic films are a root cause for material fatigue which limits the lifetime of electronic devices. Since the yield stress of metals is temperature dependent, plastic deformations during thermal cycling are increased at elevated temperature. This effect reduces the reliability of electronic parts. In order to investigate this problem, a 20μm thick copper film was deposited on a silicon wafer. After annealing at 400°C, the sample was exposed to thermal cycles in the temperature range between room temperature and 600°C. The different values for the CTE of copper and silicon lead to a curvature of the sample. The wafer curvature was measured by a multi-laser beam method. On the basis of the experimental results, a new theoretical model was developed, which describes the stress evolution in the film during thermal cycling. In this investigation, the relation between wafer curvature and film stress is calculated by analogy to a model by Freund [1] which is an improvement to the well known Stoney formula. In addition to the elastic response, the new model considers plasticity of the copper film as well as temperature dependence of creep. It is demonstrated that the model can well describe the experiment and thus thermomechanical stress in copper films.

Isothermal Stress Relaxation in Al, Alcu and A1vpd Films

1996 ◽  
Vol 436 ◽  
Author(s):  
J. P. Lokker ◽  
J. F. Jongste ◽  
G. C. A. M. Janssen ◽  
S. Radelaar
Keyword(s):  
Stress Relaxation ◽  
Integrated Circuits ◽  
Tensile Stress ◽  
Thermal Cycling ◽  
Mechanical Behavior ◽  
Mechanical Stress ◽  
Plasma Etching ◽  
Isothermal Treatment ◽  
Aluminum Metallization ◽  
Curvature Measurements

AbstractMechanical stress and its relaxation in aluminum metallization in integrated circuits (IC) are a major concern for the reliability of the material. It is known that adding Cu improves the reliability but complicates plasma etching and increases corrosion sensitivity. The mechanical behavior of AlVPd, AlCu and Al blanket films is investigated by wafer curvature measurements. During thermal cycling between 50°C and 400°C the highest tensile stress is found in AlVPd. In a subsequent experiment, the cooling was interrupted at several temperatures to investigate the stress behavior during an eight hour isothermal treatment. Isothermal stress relaxation has been observed in the three types of films and is discussed.

Stress-Strain Equations for Some Near-Eutectic Tin-Lead Solders

1991 ◽  
Vol 113 (4) ◽  
pp. 475-484 ◽  
Author(s):  
K. P. Jen ◽  
J. N. Majerus
Keyword(s):  
Strain Rate ◽  
Printed Circuit Boards ◽  
Volume Fraction ◽  
Total Error ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Strain Rates ◽  
Stress Strain ◽  
Engineering Strain

This paper presents the evaluation of the stress-strain behavior, as a function of strain-rate, for three tin-lead solders at room temperature. This behavior is critically needed for reliability analysis of printed circuit boards (PCB) since handbooks list minimal mechanical properties for the eutectic solder used in PCBs. Furthermore, most handbook data are for stable eutectic microstructure whereas PCB solder has a metastable microstructure. All three materials were purchased as “eutectics.” However, chemical analysis, volume fraction determination, and microhardness tests show some major variations between the three materials. Two of the materials have a eutectic composition, and one does not. The true stress-strain equations of one eutectic and the one noneutectic material are determined from compressive tests at engineering strain-rates between 0.0002/s and 0.2/s. The second eutectic material is evaluated using tensile tests with strain-rates between 0.00017/s and 0.042/s. The materials appear to exhibit linear elastic behavior only at extremely small strains, i.e., less than 0.0005. However, this “elastic” behavior showed considerable variation, and depended upon the strain rate. In both tension and compression the eutectic alloy exhibits nonlinear plastic behavior, i.e., strain-softening followed by strain-hardening, which depends upon the strain rate. A quadratic equation σy = σy(ε˚/ε˚0) + A(ε˚/ε˚0)ε + B(ε˚/ε˚0)ε2 fit to the data gives correlation coefficients R2 > 0.91. The coefficients σy(ε˚/ε˚0), A(ε˚/ε˚0), B(ε˚/ε˚0) are fitted functions of the normalized engineering strain rate ε˚/ε˚0. Replicated experiments are used at each strain-rate so that a measure of the statistical variation could be estimated. Measures of error associated with the regression analysis are also obtained so that an estimate of the total error in the stress-strain relations can be made.

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