Quantitative analysis of strengthening mechanisms in thin Cu films: Effects of film thickness, grain size, and passivation

1998 ◽  
Vol 13 (5) ◽  
pp. 1307-1317 ◽  
Author(s):  
R-M. Keller ◽  
S. P. Baker ◽  
E. Arzt
Keyword(s):  
Grain Size ◽  
Film Thickness ◽  
Thermal Stresses ◽  
Native Oxide ◽  
Silicon Substrates ◽  
Native Oxide Layer ◽  
X Ray Diffraction ◽  
Cu Films ◽  
Order Of Magnitude ◽  
Constraint Model

Thermal stresses in thin Cu films on silicon substrates were examined as a function of film thickness and presence of a silicon nitride passivation layer. At room temperature, tensile stresses increased with decreasing film thickness in qualitative agreement with a dislocation constraint model. However, in order to predict the stress levels, grain-size strengthening, which is shown to follow a Hall–Petch relation, must be superimposed. An alternative explanation is strain-hardening due to the increase in dislocation density, which was measured by x-ray diffraction. At 600 °C, the passivation increases the stress by an order of magnitude; this leads to a substantially different shape of the stress-temperature curves, which now resemble those of aluminum with only a native oxide layer. The effect of passivation is shown to be very sensitive to the deposition and test conditions.

Mechanical Properties of Electroplated Copper Thin Films

1999 ◽  
Vol 594 ◽  
Author(s):  
R. Spolenak ◽  
C. A. Volkert ◽  
K. Takahashi ◽  
S. Fiorillo ◽  
J. Miner ◽  
...  
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Grain Size ◽  
Film Thickness ◽  
Yield Stress ◽  
Laser Scanning ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Cu Films ◽  
Electroplated Copper

AbstractIt is well known that the mechanical properties of thin films depend critically on film thickness However, the contributions from film thickness and grain size are difficult to separate, because they typically scale with each other. In one study by Venkatraman and Bravman, Al films, which were thinned using anodic oxidation to reduce film thickness without changing grain size, showed a clear increase in yield stress with decreasing film thickness.We have performed a similar study on both electroplated and sputtered Cu films by using chemical-mechanical polishing (CMP) to reduce the film thickness without changing the grain size. Stress-temperature curves were measured for both the electroplated and sputtered Cu films with thicknesses between 0.1 and 1.8 microns using a laser scanning wafer curvature technique. The yield stress at room temperature was found to increase with decreasing film thickness for both sets of samples. The sputtered films, however, showed higher yield stresses in comparison to the electroplated films. Most of these differences can be attributed to the different microstructures of the films, which were determined by focused ion beam (FIB) microscopy and x-ray diffraction.

Heteroepitaxial Metal Oxides on Silicon by Laser Ablation

1990 ◽  
Vol 191 ◽  
Author(s):  
D. B. Fenner ◽  
D. K. Fork ◽  
G. A. N. Connell ◽  
J. B. Boyce ◽  
F. A. Ponce ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Single Crystal Silicon ◽  
Native Oxide ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Crystal Silicon ◽  
Ybco Films ◽  
Zero Resistance ◽  
High Degree

ABSTRACTThin epitaxial films of cubic - fluorite structured PrO2 and YSZ (yttria- stabilized zirconia) were grown on single crystal silicon substrates using the laser ablation - deposition technique. X-ray diffraction theta two - theta, omega rocking and phi scans indicate a high degree of epitaxial orientation of the films to the Si lattice. The highest quality of epitaxy was obtained with the PrO2 [111] oriented normal to Si(111) surfaces and the cubic YSZ [100] normal to Si(100) surfaces. For both PrO2 and YSZ, high epitaxial quality required the removal of the Si native oxide prior to deposition and careful control of the deposition environment. It was further found that the YSZ films on Si(100) were an excellent surface for subsequent laser ablation of YBCO films by the usual in situ process. The resistivity of this YBCO was ≈ 250 micro-ohm-cm at 300 K, extrapolated to the resistivity -temperature origin, showed a sharp transition to zero resistance at ≈ 85 K and was nearly identical to high quality YBCO films deposited on (bulk) YSZ substrates.

Electroplated Cu Recrystallization in Damascene Structures at Elevated Temperatures

1999 ◽  
Vol 564 ◽  
Author(s):  
Qing-Tang Jiang ◽  
Michael E. Thomas ◽  
Gennadi Bersuker ◽  
Brendan Foran ◽  
Robert Mikkola ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Grain Size ◽  
Film Thickness ◽  
Grain Growth ◽  
Elevated Temperatures ◽  
Retardation Effect ◽  
Cu Films ◽  
Grain Sizes ◽  
Geometrical Constraints ◽  
The Difference

AbstractTransformations in electroplated Cu films from a fine to course grain crystal structure (average grain sizes went from ∼0.1 µm to several microns) were observed to strongly depend on film thickness and geometry. Thinner films underwent much slower transformations than thicker ones. A model is proposed which explains the difference in transformation rates in terms of the physical constraint experienced by the film since grain growth in thinner films is limited by film thickness. Geometrical constraints imposed by trench and via structures appear to have an even greater retardation effect on the grain growth. Experimental observations indicate that it takes much longer for Cu in damascene structures to go through grain size transformations than blanket films.

MOCVD ZnS:Mn Films: Grain Size Distribution and Crystal Structure as a Function of the Growth Parameters

2001 ◽  
Vol 672 ◽  
Author(s):  
Kathleen A. Dunn ◽  
Katharine Dovidenko ◽  
Anna W. Topol ◽  
Serge R. Oktyabrsky ◽  
Alain E. Kaloyeros
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Grain Size ◽  
Low Temperature ◽  
Film Thickness ◽  
Growth Parameters ◽  
X Ray Diffraction ◽  
Direction Parallel ◽  
X Ray ◽  
Average Grain Size

ABSTRACTZinc sulfide doped with manganese is extensively used for thin film electroluminescent device applications. In order to assess the key material and process challenges, ZnS:Mn layers were fabricated by metalorganic chemical vapor deposition in the 250°-500°C range on an AlTiO/InSnO/glass stack. The microstructure of the ZnS:Mn films was examined by Transmission Electron Microscopy (TEM) as part of a larger study which fully characterizes these films by a variety of structural and chemical characterization techniques, including Rutherford Backscattering, Secondary Ion Mass Spectroscopy, Atomic Force Microscopy, Scanning Electron Microscopy and X-ray Diffraction. For all the growth conditions, the films were found to be polycrystalline having predominantly 2H hexagonal ZnS structure. The ZnS grains are found to grow columnar as the film thickness increases, also widening in the direction parallel to the substrate surface and reaching the 100 - 200 nm average lateral size at the 650 nm film thickness. The presence of the 8H ZnS polytype was detected in the low-temperature ZnS:Mn films by TEM selected area electron diffraction and confirmed by X-ray diffraction analysis. Dark field TEM imaging correlated this 8H ring with very small (∼2.5 nm) grains present throughout the low temperature film with a slightly higher density at the film/substrate interface. The 700°C post-deposition annealing was found to initiate a solid state transformation to the cubic (3C) ZnS crystal structure, and resulted in an average grain size of ∼250 nm at the surface of the annealed film.

A Semiconductor Nano-Patterning Approach Using AFM-Scratching Through Oxide Thin Layers

2002 ◽  
Vol 740 ◽  
Author(s):  
L. Santinacci ◽  
T. Djenizian ◽  
P. Schmuki
Keyword(s):  
Oxide Layer ◽  
Electrochemical Deposition ◽  
Thin Layers ◽  
Native Oxide ◽  
Silicon Substrates ◽  
Native Oxide Layer ◽  
Thermal Oxide ◽  
P Type ◽  
Insulating Properties ◽  
Nano Patterning

ABSTRACTAFM-scratching was performed through thin oxide layer which was either a native oxide layer (1.5 – 2 nm thick) or a thermal oxide layer (10 nm thick). Due to their insulating properties, the SiO2 films act as masks for the metal electrochemical deposition. In the scratched openings copper deposition can take place selectively and thus nano-scale metal lines could be successfully plated onto the p-type silicon substrates. Using particularly, if sufficiently thick thermal oxide has advantages over the native oxide, it allows a H-termination of the Si within the grooves (HF treatment) without eliminating the oxide layer on the rest of the surface.

An Anodic Process for the Determination of Grain Boundary and Film Thickness Strengthening Effects in Aluminum Films on Oxidized Silicon.

1991 ◽  
Vol 239 ◽  
Author(s):  
Ramnath Venkatraman ◽  
John C. Bravman
Keyword(s):  
Grain Size ◽  
Film Thickness ◽  
Anodic Oxide ◽  
Film Stress ◽  
Anodic Process ◽  
Aluminum Films ◽  
Cu Films ◽  
Si Substrates ◽  
Tension And Compression ◽  
Stress Variations

ABSTRACTWe have measured stress variations with temperature as a function of film thickness and a given grain size in pure Al and AI-0.5%Cu films on Si substrates. The variation in thickness for a given grain size is brought about by using the same film and the repeated controlled growth and dissolution of a barrier anodic oxide which can be grown uniformly on the film. Stress measurements were made as a function of temperature by measuring wafer curvature after successively removing each 0. Iμm of Al film. The components of strengthening due to the film thickness and the presence of grain boundaries were separated by assuming that the flow stress of the film is simply the sum of these two components. The observations are consistent with results obtained using lascr-rcflowed films in an earlier work. The variations of these two components with temperature, and under tension and compression is discussed.

Characteristics of Palladium Thin Films Deposited by the Ionized Cluster Beam Technique

1991 ◽  
Vol 239 ◽  
Author(s):  
Maria Huffman ◽  
T. S. Kalkur ◽  
L. Kammerdiner ◽  
R. Kwor ◽  
L. L. Levenson ◽  
...  
Keyword(s):  
Grain Size ◽  
Substrate Temperature ◽  
Substrate Surface ◽  
Silicon Substrates ◽  
Cluster Beam ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Neutral Mode ◽  
Almost All ◽  
Substrate Temperatures

ABSTRACTAn ionized cluster beam (ICB) source was used to deposit Pd onto oxidized silicon substrates. The ICB source was operated in both the neutral mode (no ionization and no acceleration) and in the ICB mode with ionization and acceleration voltages at 3 kV and 6 k.V. Also, substrate temperatures were varied between 100°C and 400°C. The Pd film thicknesses were generally between 1, 200Å and 1, 800Å, with one film thickness about 500Å. The films were examined by transmission electron microscopy (TEM), transmission electron diffraction (TED), and x-ray diffraction (XRD). Grain size measurements by TEM and XRD showed that ionization and acceleration of Pd resulted in a slight increase in grain size compared to films deposited without ionization or acceleration at any substrate temperature. However, the grain size increased significantly as the substrate temperature rose. XRD showed that all ICB deposited Pd films have significant (111) texturing as determined by comparison to XRD data for Pd powder. For Pd films deposited at 400°C, almost all grains were oriented with the (111) planes parallel to the substrate surface. The electrical conductivity of all Pd films was comparable to that of bulk Pd.

Plasticity, Microstructure and the Thermal Dependence of Flow Stresses in Aluminum Thin Film Interconnects

1994 ◽  
Vol 338 ◽  
Author(s):  
Ramnath Venkatraman
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Film Thickness ◽  
Thermal Cycling ◽  
Thermal Stresses ◽  
Film Flow ◽  
Thermal Strain ◽  
Free Standing ◽  
Thermal Dependence ◽  
Theoretical Considerations

ABSTRACTA study was conducted towards fundamentally understanding the nature and magnitude of thermal stresses in aluminum thin films on silicon and correlating them with deformation mechanisms that serve to relax the stresses imposed by the thermal strain. A number of experiments and theoretical considerations are described in order to describe the sources of strengthening and stress relaxation in such films. It is shown that the flow stress of an aluminum film corresponds to the critical stress required to drive dislocation glide events. This mechanism entails an inverse flow stress dependence on the film thickness and grain size. A novel set of experiments in which the effects of strengthening due to finite film thickness and the grain size were separated and quantified is described. The variation of these strengthening components with temperature during heating and cooling were noted. Theoretical considerations of diffusional relaxation combined with the results of grazing incidence X-ray scattering (GIXS) experiments suggest that grain boundary diffusion is much less effective in limiting film flow stress than would be expected from the strain rate relation derived for a free-standing film. Line broadening observations in the GIXS experiments suggested large changes in dislocation density in the tested films during thermal cycling. The nature of these variations are qualitatively consistent with those of the film flow stress, suggesting that strain hardening could be an additional strengthening mechanism in Al films during thermal cycling.

The Mechanical Properties of Electroplated Cu Thin Films Measured by means of the Bulge Test Technique

2001 ◽  
Vol 695 ◽  
Author(s):  
Yong Xiang ◽  
Xi Chen ◽  
Joost J. Vlassak
Keyword(s):  
Mechanical Properties ◽  
Film Thickness ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Bulge Test ◽  
X Ray Diffraction ◽  
Test Technique ◽  
Cu Films ◽  
Analytical Formulae

ABSTRACTThe mechanical properties of freestanding electroplated Cu films were determined by measuring the deflection of Si-framed, pressurized membranes. The films were deformed under plane-strain conditions. The pressure-deflection data are converted into stress-strain curves by means of simple analytical formulae. The microstructure of the Cu films was characterized using scanning electron microscopy and x-ray diffraction. The yield stress, Young's modulus, and residual stress were determined as a function of film thickness and microstructure. Both yield stress and Young's modulus increase with decreasing film thickness and correlate well with changes in the microstructure and texture of the films.

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