Creep-controlled Diffusional Hillock Formation in Blanket Aluminum Thin Films as a Mechanism of Stress Relaxation

2000 ◽  
Vol 15 (8) ◽  
pp. 1709-1718 ◽  
Author(s):  
Deok-Kee Kim ◽  
William D. Nix ◽  
Michael D. Deal ◽  
James D. Plummer
Keyword(s):  
Thin Films ◽  
Grain Structure ◽  
Formation Model ◽  
Surrounding Area ◽  
Grain Sizes ◽  
Hillock Formation ◽  
Diffusional Relaxation ◽  
New Type ◽  
Columnar Grain ◽  
Sputter Deposited

Hillock formation, a stress-induced diffusional relaxation process, was studied in sputter-deposited Al films. The grain sizes in these films were small compared to those in other sputter-deposited Al films, and impurities (O, Ti, W) were incorporated during the preparation of the films. Stress and hardness measurements both indicate that the Al films were strengthened by the small grain size and incorporated impurities. We observed a new type of hillock in these Al thin films after annealing for 2 h at 450 °C in a forming gas ambient. The hillocks were composed of large Al grains created between the substrate and the original Al film with its columnar grain structure, apparently by diffusion from the surrounding area. By modifying the boundary conditions of Chaudhari's hillock formation model [P. Chaudhari, J. Appl. Phy. 45, 4339 (1974)], we have created a new model that can describe the experimentally observed hillocks. Our model seems to explain the experimentally observed abnormal hillock formation and may be applied to other types of hillock formation using different creep laws.

Diffusional Hillock Formation in Al Thin Films Controlled by Creep

1999 ◽  
Vol 594 ◽  
Author(s):  
Deok-kee Kim ◽  
William D. Nix ◽  
Eduard Arzt ◽  
Michael D. Deal ◽  
James D. Plummer
Keyword(s):  
Power Law ◽  
Original Film ◽  
Stress Measurement ◽  
Grain Structure ◽  
Surrounding Area ◽  
Hillock Formation ◽  
Columnar Grain ◽  
Sputter Deposited ◽  
Power Law Creep ◽  
Microstructural Studies

AbstractThermal hillocks in sputter-deposited Al films have been studied as a part of a broad study of stress-induced diffusional processes in Al. Trace amounts of the impurities Ti, W, and O were incorporated into the films during deposition, causing them to be much stronger than most sputter deposited Al films. Stress measurement during thermal cycling, using the wafer curvature method, showed that these Al films are very strong; this finding was corroborated by hardness measurements. Microstructural studies using TEM and FIB showed that the hillocks start to form at the Al/SiO2 interface and grow under the original Al film, with its columnar grain structure. In some cases, the film fails as hillocks grow completely through the original film. The Al film on top of the hillocks appears to inhibit hillock growth by creating a back pressure associated with power law creep of the film. We modeled this form of hillock formation by modifying the boundary conditions in Chaudhari's hillock model [1]. Our model describes hillock formation by diffusion of Al atoms from the surrounding area into isolated hillocks, assuming that the original Al film on top of hillocks deforms following power law creep. Our model can be applied to many different situations by using different creep laws for the top Al film.

TEM studies of solid-state reactions in sputter-deposited Nb/Al multilayer thin films

1996 ◽  
Vol 54 ◽  
pp. 1020-1021
Author(s):  
F. Ma ◽  
S. Vivekanand ◽  
K. Barmak ◽  
C. Michaelsen
Keyword(s):  
Thin Films ◽  
Solid State ◽  
Stoichiometric Composition ◽  
Analytical Electron Microscopy ◽  
Grain Structure ◽  
Solid State Reactions ◽  
Multilayer Thin Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sputter Deposited

Solid state reactions in sputter-deposited Nb/Al multilayer thin films have been studied by transmission and analytical electron microscopy (TEM/AEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The Nb/Al multilayer thin films for TEM studies were sputter-deposited on (1102)sapphire substrates. The periodicity of the films is in the range 10-500 nm. The overall composition of the films are 1/3, 2/1, and 3/1 Nb/Al, corresponding to the stoichiometric composition of the three intermetallic phases in this system.Figure 1 is a TEM micrograph of an as-deposited film with periodicity A = dA1 + dNb = 72 nm, where d's are layer thicknesses. The polycrystalline nature of the Al and Nb layers with their columnar grain structure is evident in the figure. Both Nb and Al layers exhibit crystallographic texture, with the electron diffraction pattern for this film showing stronger diffraction spots in the direction normal to the multilayer. The X-ray diffraction patterns of all films are dominated by the Al(l 11) and Nb(l 10) peaks and show a merging of these two peaks with decreasing periodicity.

Ionic Conductivities of Doped CeO2 Thin Films as Related to Their Microstructure

1995 ◽  
Vol 411 ◽  
Author(s):  
Chunyan Tian ◽  
Siu-Wai Chan
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Ionic Conductivities ◽  
Dielectric Constants ◽  
Grain Structure ◽  
X Ray Diffraction ◽  
Fine Grain ◽  
Brick Layer Model ◽  
Columnar Grain ◽  
Beam Deposition

ABSTRACTThin films of 4% Y2O3 doped CeO2/Pd film/(001)LaA103 with a very low pinhole density were successfully prepared using electron-beam deposition technique. The microstructure of the films was characterized by x-ray diffraction and the electrical properties were studied as a function of temperature with AC impedance spectroscopy. A brick layer model was adopted to correlate the electrical properties to the microstructure of the films, which can be simplified as either a series or a parallel equivalent circuit associated with either a fine grain or a columnar grain structure, respectively. The conductivities of the films fell between the conductivities derived from the two circuit models, suggesting that the films are of a mixed fine grain and columnar grain structure. The measured dielectric constants of the films were found smaller than that of the bulk.

Nucleation and Growth of the First Phase in Sputter-Deposited Nb/Al Multilayer Thin Films

1995 ◽  
Vol 398 ◽  
Author(s):  
K. Barmak ◽  
S. Vivekanand ◽  
F. Ma ◽  
C. Michaelsen
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Nucleation And Growth ◽  
Grain Structure ◽  
Multilayer Thin Films ◽  
Product Phase ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Sputter Deposited

ABSTRACTThe formation of the first phase in the reaction of sputter-deposited Nb/Al multilayer thin films has been studied by power-compensated and heat-flux differential scanning calorimetry, x-ray diffraction and transmission electron microscopy. The modulation periods of the films are in the range of 10-500 nm. Both types of calorimetrie measurements, performed at a constant heating rate, show the presence of two peaks (A and B) for the formation of the single product phase, NbAl3. Isothermal calorimetrie scans show that peak A is associated with a nucleation and growth type transformation. The formation of NbAl3 is thus interpreted as a two-stage process of nucleation and lateral growth to coalescence (peak A) followed by normal growth until the consumption of one or both reactants (peak B). Transmission electron microscopy investigations of samples annealed into the first stage of NbAl3 formation show the presence of this phase at the Nb/Al interface and its preferential growth along the grain boundaries of the Al layer. The latter highlights the role of reactant phase grain structure in product phase formation.

Hillocks on half-micron aluminum lines

1991 ◽  
Vol 6 (9) ◽  
pp. 1817-1819 ◽  
Author(s):  
Carey A. Pico ◽  
Tom D. Bonifield
Keyword(s):  
Grain Boundary ◽  
Large Scale ◽  
Boundary Diffusion ◽  
Al Alloy ◽  
Grain Sizes ◽  
Integrated Devices ◽  
Hillock Formation ◽  
New Type ◽  
Hillock Growth ◽  
Bamboo Structure

A new regime of hillock growth has been observed in patterned Al98.5 W.%Si1.0 Wt.%-Cuo0.5 wt.% films. The “surface” hillock and “side” hillock, which have been seen previously, form on patterned metal lines having linewidths greater than the larger Al alloy grain sizes (∼3 μm). None is seen on the fabricated lines having linewidths between 0.9 and 2 μm where long-range grain boundary diffusion cannot occur because of its bamboo structure. However, a new type of hillock, the “line hillock”, occurs in structures having linewidths of 0.6 μm. The presence of this last type of hillock is inconsistent with the current understanding of hillock formation and may present severe restrictions on the down-sizing of ultra–large–scale integrated devices.

Deposition and characterization of ZrO2 thin films on silicon substrate by MOCVD

1993 ◽  
Vol 8 (6) ◽  
pp. 1361-1367 ◽  
Author(s):  
Cheol Seong Hwang ◽  
Hyeong Joon Kim
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Substrate Surface ◽  
Relative Dielectric Constant ◽  
Grain Structure ◽  
Breakdown Field ◽  
Electrical Characteristics ◽  
Dielectric Thin Film ◽  
Si Substrates ◽  
Columnar Grain

ZrO2 thin films were deposited at 1 atm on Si substrates by oxidation-assisted thermal decomposition of zirconium-trifluoroacetylacetonate in the temperature range of 300–615 °C. Above a deposition temperature of 400 °C, the deposited thin films have a columnar grain structure, where each grain is perpendicular to the substrate surface with a c-axis preferred crystallographic orientation, and have poor electrical characteristics as a dielectric thin film. But the thin film deposited at 350 °C has a fine equiaxed microcrystalline structure and has superior electrical characteristics of a breakdown field of 1 MV/cm and a relative dielectric constant of 27.

Microstructure and Reliability of Sputter Deposited Cr-Crcu-Cu thin Films for Flip-Chip Applications

1996 ◽  
Vol 445 ◽  
Author(s):  
Na Zhang ◽  
Mark Mcnicholas ◽  
Neil Colvin
Keyword(s):  
Cross Sections ◽  
Thermal Cycle ◽  
Flip Chip ◽  
Grain Structure ◽  
Transmission Electron ◽  
Alloy Solder ◽  
Solder Balls ◽  
Columnar Grain ◽  
Sputter Deposited ◽  
Bond Pads

AbstractThe Cr‐CrCu‐Cu metal scheme, as a terminal multistructure metallization for flip chip applications, has been investigated utilizing PVD sputter deposition varying the conditions of deposition power and temperature, and film thickness. A modified Controlled Collapse Chip Connection (C4) process was utilized in order to evaluate the aforementioned deposition of the Cr‐CrCu‐Cu multilayers and the effect of film microstructure on the parameters of shear strength and thermal cycle reliability. Thermal cycle reliability results proved to be a function of both the CrCu alloy and the Cu overlayer thickness. Transmission electron microscopy (TEM) cross‐sections of the Cr‐CrCu‐Cu multilayers suggests that the columnar grain structure of the CrCu layer may provide a sacrificial thermal diffusion barrier between the PbSn alloy solder balls and the Al bond pads during the thermal‐cycle tests.

Stress Gradient and Relaxation Measurements in Al and Oxygen-Implanted al Films.

1993 ◽  
Vol 309 ◽  
Author(s):  
Paul R. Besser ◽  
Stefan Bader ◽  
Ramnath Venkatraman ◽  
John C. Bravman
Keyword(s):  
Stress Gradient ◽  
Film Surface ◽  
Grazing Incidence ◽  
Incidence Geometry ◽  
Film Stress ◽  
Grain Structure ◽  
Relaxation Measurements ◽  
Diffusional Relaxation ◽  
Columnar Grain ◽  
Grazing Incidence Geometry

AbstractSynchrotron radiation has been used in the grazing incidence geometry to determine the stress gradients and stress relaxation in 0.6 μm thick Al uniform films. We have examined both pure Al and Al implanted with 3 at% oxygen. The films were cycled between 23°C and 400°C. The surface of the pure Al films was more highly stressed, on average, than the film as a whole, both in tension and in compression. In contrast, the surface of the oxygen-implanted film was relaxed relative to the average film stress in compression but was more stressed in tension. The larger gradient in stress in the implanted films reduces during subsequent thermal cycling. These differences are attributed to the microstructures of the films. The 0-implanted film develops a small, non-columnar grain structure and forms small AI2O3 particles during annealing. The small grain size allows diffusional relaxation to occur in compression, relieving the stress in areas close to the film surface.

Image processing to delineate defect structures in HREM images of vapor-deposited thin films

1989 ◽  
Vol 47 ◽  
pp. 128-129
Author(s):  
R.M. Fisher ◽  
J.Z. Duan ◽  
Crispin J. Hetherington ◽  
Norman Fowler
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Cross Sections ◽  
Failure Modes ◽  
Grain Structure ◽  
Intrinsic Stress ◽  
Plan View ◽  
Transmission Electron ◽  
Columnar Grain ◽  
Chromium Films

The resistance of deposited thin films to cracking or delamination from substrates during production or service, crucial to the long term reliability of IC devices, is under study as part of a broad program on interfacial bonding and adhesion. Chromium films, of particular interest because of their widespread use in microelectronics, are especially prone to mechanical failure due to the high residual stresses that are generally present and their low fracture toughness. Transmission and scanning electron microscopy are being used to define the columnar grain structure and failure modes and x-ray diffraction is being employed to determine the nature of through-thickness stress gradients that occur in such films.The intrinsic stress, as distinguished from the extrinsic stress caused by differential contraction between film and substrate during cooling from the deposition temperature, results from the presence of vacancies and diffuse “voids” trapped between the columns during deposition. Transmission electron microscopy of plan-view and cross-sections is being used in efforts to observe and define the structure of the inter-columnar regions.

EFFECTS OF PLASTIC ANISOTROPY AND HARDENING ON INDENTATION MODULUS OF THIN FILMS

2010 ◽  
Vol 24 (01n02) ◽  
pp. 247-255
Author(s):  
SALMON M. KALKHORAN ◽  
NUWONG CHOLLACOOP ◽  
ANDREW GOULDSTONE
Keyword(s):  
Thin Films ◽  
Plastic Anisotropy ◽  
Grain Structure ◽  
Plastic Behavior ◽  
Indentation Modulus ◽  
Plastic Substrates ◽  
Elastic Plastic ◽  
Nickel Thin Films ◽  
Columnar Grain ◽  
Steel Substrates

In this study we have modeled the Berkovich indentation response of elastic-plastic thin films on elastic-plastic substrates, the modulus of film and substrate being equivalent, using FEM. The stimulus for this investigation was experimental indentation data of rapidly quenched nickel thin films on stainless steel substrates, for which depth-dependent, significantly low (>50% decrease) moduli were extracted via the Oliver-Pharr method. This was notable because both film and substrate had the same elastic modulus. Previous studies showed that differences in plastic behavior could elicit such a modulus drop, for extremely hard films on substrates. In this study, we performed further FEM models to explore the modulus decrease, using aspects of continuum plastic behavior that could be hypothesized from microstructural observations. Specifically, we used plastic anisotropy and significant delayed hardening that would be expected from the nano-scale, highly columnar grain structure as input, and results showed a significant modulus decrease for reasonable values of hardness.

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