Hillock Formation in Platinum Films

1992 ◽  
Vol 260 ◽  
Author(s):  
Philip D. Hren ◽  
H. Al-Shareef ◽  
S. H. Rou ◽  
A. I. Kingon ◽  
P. Buaud ◽  
...  
Keyword(s):  
Room Temperature ◽  
Ion Beam ◽  
Metal Films ◽  
Film Stress ◽  
Beam Deflection ◽  
Platinum Surface ◽  
Cross Sectional ◽  
Compressive Stresses ◽  
Hillock Formation ◽  
Ion Beam Sputter Deposition

ABSTRACTHillocks, surface protrusions from thin metal films, have been observed in Al, Al/Cu, Pb, and other materials. Platinum films are widely used as substrates for the deposition of ferroelectric thin films because of their superior oxidation resistance. However, hillock formation in platinum films has not been reported in the literature. In this work, we report the appearance of hillocks in platinum in Pt/Ti bilayers on oxidized silicon wafers. Platinum films 250 to 300 nra were deposited by ion beam sputter deposition at 25°C and 300°C onto a 70 nm Ti film on oxidized Si wafers. The wafers were then heated in flowing argon to 600°C, held 1 hr at 600°C, and cooled to room temperature while the wafer curvature (and hence the film stress) was measured with a laser beam deflection technique. At 600°C, compressive stresses of 0.1 to 0.4 GPa, due to thermal expansion mismatch, developed in the metal films. The platinum surface, initially flat, showed strong hillocking after the anneal. Cross-sectional TEM revealed that severe Ti/Pt interdiffusion occurred, in one case leading to a Ti layer on the top surface.

Initial hillock formation and changes in overall stress in Al–Cu films and pure Al films during heating

1999 ◽  
Vol 14 (10) ◽  
pp. 4087-4092 ◽  
Author(s):  
C. Kylner ◽  
L. Mattsson
Keyword(s):  
Film Surface ◽  
Film Stress ◽  
Beam Deflection ◽  
Strengthening Effect ◽  
Cu Films ◽  
Force Microscopy ◽  
Compressive Stresses ◽  
Atomic Force ◽  
Hillock Formation ◽  
Measurement Principle

The effect of adding a few percent (3 at.%) Cu to Al films on the initial hillock formation and the changes in overall film stress were studied. Al films were evaporated by an electron-beam gun onto Si wafers in an ultrahigh vacuum deposition system and Al–Cu films were coevaporated with a thermally heated source used for the Cu. The as-deposited samples were radiatively heated at 3 °C/s in an air environment. During heating, the initial hillocking and the changes in overall stress were measured simultaneously and in real time with a specially designed optical instrument. The measurement principle of this instrument is based on laser beam deflection, caused by wafer bending due to film stress, and collection of the laser light scattered off from the hillocks appearing on the film surface. The experimental results show that Cu alloying has a strengthening effect on Al films, resulting in delayed and considerably reduced hillock formation. Before heating, the as-deposited Al–Cu samples were investigated by total integrated scattering and atomic force microscopy. These investigations showed that Al–Cu films are considerably smoother and have smaller grains than Al films of similar thickness (340 nm). It was found that the small grains of Al–Cu films contribute to increasing the tensile stress–temperature slope. In addition, Al–Cu films can withstand higher compressive stresses than Al films.

Effects of Ionized Cluster Beam Bombardment on Epitaxial Metal Film Deposition on Silicon Substrates

1988 ◽  
Vol 128 ◽  
Author(s):  
Isao Yamada
Keyword(s):  
Room Temperature ◽  
Lattice Mismatch ◽  
Ion Beam ◽  
Substrate Surface ◽  
Metal Films ◽  
Epitaxial Films ◽  
Film Structure ◽  
Film Deposition ◽  
Cluster Beam ◽  
Tem Analysis

ABSTRACTThe effects of ion beam bombardment during ionized cluster beam (ICB) deposition of metal films on Si(111) and Si(100) substrates have been discussed. In the case of Al deposition, films have been epitaxially deposited on Si(lll) and Si(100) substrates at near room temperature. On Si(111) substrates, nearly perfect Al single crystal films could be formed. On Si(100) substrates, Al bicrystals have been grown epitaxially. A remarkable fact concerning these results is that the epitaxial films could be formed at nearly room temperature and on a large lattice mismatch (25%) substrate surface. Atomic resolution TEM analysis suggests that the epitaxy of Al occurs not only on Si surfaces but also at Al/Al grain boundaries. These epitaxial films exhibit extremely high thermal stability and long electromigration life time. To understand the deposition features and film characteristics, the effects of ICB bombardment on the film growth at the initial stage of the deposition and the resultant film structure have been studied. The results show that the role of very low energy ion bombardment is especially important in forming epitaxial metal films. Depositions of Au and Cu on Si substrates have also been made to understand whether ICB deposition may improve the characteristics of other metal films. Preliminary results of these film depositions are also obtained.

Growth Stress of Thin Ti-, Al- and TiAlx-Films Deposited Under UHV-conditions and its Dependence on Substrate Temperature

1999 ◽  
Vol 580 ◽  
Author(s):  
St. Lackner ◽  
R. Abermann
Keyword(s):  
Substrate Temperature ◽  
Room Temperature ◽  
Metal Films ◽  
Growth Stress ◽  
Layer Growth ◽  
Film Stress ◽  
Layer By Layer ◽  
Island Growth ◽  
Aluminum Films ◽  
Beam Technique

AbstractThe growth stress of metal films was measured continuously both during as well as after their deposition under UHV-conditions with a cantilever beam technique. The metal films were deposited onto 10 rim thick alumina substrate films prepared by reactive evaporation of Al in an oxygen atmosphere. The substrate temperature for the metal deposition was varied from -20°C to 500°C.The growth stress of both titanium and aluminum films deposited at room temperature and above is characteristic of island growth and the formation of a polycrystalline film. The film stress built up in these films decreases with increasing substrate temperature. Below RT the growth stress of titanium films indicates a transition from island growth to layer by layer growth due to a reduced adatom mobility. The temperature range in which this transition in the growth mode occurs is strongly affected by impurities in the Ti-evaporation source material and gas ambient.In the last part of this paper we present results of experiments in which the above metals were evaporated simultaneously from separate sources to form alloy films with TiAl3-stoichiometry. Sudden changes in the incremental film stress are tentatively attributed to segregation and phase formation phenomena.

Microstructure Control for Thin Film Metallization

1996 ◽  
Vol 441 ◽  
Author(s):  
G. S. Was ◽  
D. J. Srolovitz ◽  
Z. Ma ◽  
D. Liang
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Surface Roughness ◽  
Ion Beam ◽  
Metal Films ◽  
Fiber Texture ◽  
Thin Metal ◽  
Thin Metal Films ◽  
Ion Beam Assisted Deposition ◽  
Hillock Formation

AbstractA strategy was developed for controlling hillock formation in thin metal films by controlling the fiber texture to be of a relatively “weak” orientation. Two-dimensional molecular dynamics (MD) simulations were performed to determine the parameter dependencies of texturing under ion beam assisted deposition. Simulations showed that even for film orientations that have a lower number of nearest neighbor surface bonds, the reduction in sputtering rate by ion channeling will favor the growth of the grains aligned with their channeling direction in the direction of the ion beam. Higher energies should result in greater sputtering and a higher surface roughness. Confirmatory experiments were performed by growing Al films using ion beam assisted deposition in which the Ne ion beam was normal to the substrate surface. For all energies above 0 eV/atom, the fiber texture contained a (220) component and, at high normalized energies, the fiber texture was heavily (220) dominated. Subsequent annealing at 450°C for 30 min. resulted in hillock formation in the PVD (physical vapor deposition) condition, a reduction in the hillock density by two orders of magnitude in the 120 eV/atom condition and complete elimination of hillocking above 800 eV/atom. Although the surface roughness increased with ion beam energy as modeled by MD, the surface became smoother during annealing. These results show that the fiber texture can be controlled in a thin metal film in such a way as to eliminate hillock formation, that molecular dynamics simulation is a valuable predictive tool for guiding experiments in the development of thin film microstructures and that ion beam assisted deposition is an effective, practical tool for controlling microstructures of thin metal films.

Microstructure and Residual Stresses in Al2O3 Prepared by Ion Beam Assisted Deposition

1993 ◽  
Vol 316 ◽  
Author(s):  
M. G. Goldiner ◽  
G. S. Was ◽  
L. J. Parfitt ◽  
J. W. Jones
Keyword(s):  
Residual Stress ◽  
Ion Beam ◽  
Arrival Rate ◽  
Film Stress ◽  
Amorphous Phases ◽  
Alumina Films ◽  
Compressive Stresses ◽  
Ion Beam Assisted Deposition ◽  
Rapid Transition ◽  
Film Porosity

ABSTRACTAlumina films synthesized by ion beam assisted deposition (EBAD) were characterized in terms of their microstructure and residual stress. Normalized energy per deposited atom, En, ranged from 0 to 130 eV/atom. The microstructure of PVD films (En=0) is a mixture of crystalline (γ-Al2O3) and amorphous phases and IBAD films are amorphous. Density and stoichiometry vary between 2.6 and 3.1 g/cm3 and 1.3 and 1.6, respectively. Neither are dependent on either ion-to-atom arrival rate ratio, R, or En. The film porosity is in the form of small (4-6 nm) voids of density 1017 - 1018 cm-3. Bombarding gas is incorporated with 80% efficiency to levels of 4-5 at. %. A tensile residual stress of 0.3 GPa exists in PVD films. A rapid transition to high compressive stresses occurs with increased En, with a saturation of -0.4 GPa occurring at high En There is a strong correlation between gas incorporation and residual film stress. However, no existing models are capable of providing a quantitative explanation of the results.

Hillock Formation in Tensile Loaded Films

1995 ◽  
Vol 391 ◽  
Author(s):  
Karen E. Harris ◽  
Alexander H. King
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Room Temperature ◽  
Large Single Crystal ◽  
Free Standing ◽  
Boundary Area ◽  
Compressive Stresses ◽  
Transmission Electron ◽  
Nominal Thickness ◽  
Hillock Formation

AbstractWhile hillocks usually form to relieve compressive stresses in thin films resulting from electromigration or a difference in thermal expansion in the film and substrate, we have observed hillock formation in tensile-loaded films. We have used transmission electron microscopy to study hillocks which formed in free-standing gold thin films of 25nm nominal thickness. Grain growth during 150°C anneals reduced the grain boundary area and associated free volume, placing the films under tensile stress. While hillock formation could only increase this stress, large single crystal or polycrystalline hillocks with thicknesses up to three times the film thickness are observed after 400°C annealing, after long room temperature anneals, and during TEM observation. These observations suggest the operation of a hillock formation mechanism not explained by any existing hillock formation theories.

scholarly journals Growth of Cu2O Nanopyramids by Ion Beam Sputter Deposition

2019 ◽  
Vol 2019 ◽  
pp. 1-5
Author(s):  
Assamen Ayalew Ejigu
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Ion Beam ◽  
Linear Sweep Voltammetry ◽  
Sputter Deposition ◽  
Exciton Luminescence ◽  
X Ray Diffraction ◽  
Linear Sweep ◽  
X Ray ◽  
Ion Beam Sputter Deposition

In this study, we have successfully deposited n-type Cu2O triangular nanopyramids on Si by employing ion beam sputter deposition with an Ar : O2 ratio of 9 : 1 at a substrate temperature of 450°C. Scanning electron microscopy measurements showed attractively triangular nanopyramids of ∼500 nm edge and height lengths. Both X-ray diffraction and Raman spectroscopy characterizations showed the structures were single-phase polycrystalline Cu2O, and the room-temperature photoluminescence investigation showed interestingly green and blue exciton luminescence emissions. All Mott—Schottky, linear sweep voltammetry, and photocurrent measurements indicated that the conductivity of the Cu2O pyramids is of n-type.

Temperature Dependence of Stress Relaxation at the Copper/Polyimide Interface

1986 ◽  
Vol 79 ◽  
Author(s):  
S. T. Chen ◽  
C. H. Yang ◽  
H. M. Tong ◽  
P. S. Ho
Keyword(s):  
Thin Film ◽  
Stress Relaxation ◽  
Thermal Cycling ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Copper Film ◽  
Interfacial Stress ◽  
Film Stress ◽  
Cross Sectional ◽  
Cu Film

AbstractA Cu/polyimide thin film couple prepared on a thin quartz reed has been used to study interfacial stress relaxation during thermal cycling between room temperature and 400 °C. The polyimide thickness varies from 0 (no polyimide at all) to 10.5μm while the Cu thickness was fixed at 0.53μm. The average copper film stress has been calculated from the curvature of the quartz reed. The information clarifies the relation between the polyimide thickness and the average Cu film stress. The Cu/polyimide interfacial morphology after thermal cycling has also been examined using the cross sectional TEM technique. The results suggest that the interfacial stress is partially released through the deformation of polyimide near the Cu/polyimide interface.

Simultaneous real-time study of initial hillocking and changes in overall stress in evaporated Al films during heating

1998 ◽  
Vol 13 (6) ◽  
pp. 1666-1671 ◽  
Author(s):  
C. Kylner ◽  
L. Mattsson
Keyword(s):  
Real Time ◽  
Optical Quality ◽  
Film Stress ◽  
Beam Deflection ◽  
Vacuum System ◽  
Surface Roughening ◽  
Time Study ◽  
Maximum Change ◽  
Hillock Formation ◽  
Physical Principles

Optical quality Al films were evaporated by an electron beam onto Si wafers in an ultrahigh vacuum system. The as-deposited samples were radiative heated at a rate of 3 °C/s in air environment. During heating, measurements of initial hillocking and changes in overall film stress were performed simultaneously and in real time as a function of time and temperature with a specially designed optical instrument. The physical principles of this instrument are based on laser beam deflection caused by film stress induced wafer bending and partial integrated light scattering from surface roughening. The experimental results show how the initial hillocking is accompanied by changes in the overall stress and yield a very good correlation between the onset of hillock formation and the maximum change in overall stress.

Sign in / Sign up

Export Citation Format

Share Document