Mechanical and Piezoresistive Properties of Graphite-Filled Polyimide Thin Films

1992 ◽  
Vol 276 ◽  
Author(s):  
A. Bruno Frazier ◽  
M. R. Khan ◽  
Mark G. Allen
Keyword(s):  
Thin Films ◽  
Film Stress ◽  
Polyimide Films ◽  
Film Properties ◽  
Piezoresistive Effect ◽  
Strong Function ◽  
Graphite Particles ◽  
Microelectronic Fabrication ◽  
Residual Film

ABSTRACTThe piezoresistive effect of materials is used as the basis for many types of microsensors. Polyimide, a material widely used in microelectronic fabrication, may be made to exhibit this effect by addition of small graphite particles to form a composite material. Polyimide / graphite based piezoresistive films have the advantage of being spin-castable, plasma-processable, highly chemically resistant, and thermally stable up to 400 °C in nitrogen atmospheres. In this work, piezoresistive polyimide films are formed by addition of various amounts (loadings) of graphite particles one micron in diameter or less to DuPont PI-2555 polyimide. Thin films of these materials are spin-cast on silicon wafers, and an in-situ load-deflection measurement technique is used to evaluate the following film properties: piezoresistive coefficient as a function of both strain and graphite loading; Young's modulus as a function of graphite loading; and residual film stress as a function of graphite loading. The observed piezoresistive coefficient is a strong function of graphite loading, with good piezoresistive properties exhibited in the loading range of 15–25 wt% graphite.

In-Situ TEM Study of Plastic Stress Relaxation Mechanisms and Interface Effects in Metallic Films

2005 ◽  
Vol 875 ◽  
Author(s):  
Marc Legros ◽  
Gerhard Dehm ◽  
T. John Balk
Keyword(s):  
Thin Films ◽  
High Strength ◽  
Dislocation Motion ◽  
Dislocation Nucleation ◽  
Film Stress ◽  
In Situ Tem ◽  
Metallic Films ◽  
Cross Sectional ◽  
Thin Foils

AbstractTo investigate the origin of the high strength of thin films, in-situ cross-sectional TEM deformation experiments have been performed on several metallic films attached to rigid substrates. Thermal cycles, comparable to those performed using laser reflectometry, were applied to thin foils inside the TEM and dislocation motion was recorded dynamically on video. These observations can be directly compared to the current models of dislocation hardening in thin films. As expected, the role of interfaces is crucial, but, depending on their nature, they can attract or repel dislocations. When the film/interface holds off dislocations, experimental values of film stress match those predicted by the Nix-Freund model. In contrast, the attracting case leads to higher stresses that are not explained by this model. Two possible hardening scenarios are explored here. The first one assumes that the dislocation/interface attraction reduces dislocation mobility and thus increases the yield stress of the film. The second one focuses on the lack of dislocation nucleation processes in the case of attracting interfaces, even though a few sources have been observed in-situ.

scholarly journals Thin film stress and microstructure analysis by energy-dispersive diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C724-C724
Author(s):  
Christoph Genzel
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Residual Stress ◽  
Film Growth ◽  
High Energy ◽  
Energy Dispersive ◽  
Film Stress ◽  
Ex Situ ◽  
Near Surface

The most important advantage of energy dispersive (ED) diffraction compared with angle dispersive methods is that the former provides complete diffraction patterns in fixed but arbitrarily selectable scattering directions. Furthermore, in experiments that are carried out in reflection geometry, the different photon energies E(hkl) of the diffraction lines in an ED diffraction pattern can be taken as an additional parameter to analyze depth gradients of structural properties in the materials near surface region. For data evaluation advantageous use can be made of whole pattern methods such as the Rietveld method, which allows for line profile analysis to study size and strain broadening [1] or for the refinement of models that describe the residual stress depth distribution [2]. Concerning polycrystalline thin films, the features of ED diffraction mentioned above can be applied to study residual stresses, texture and the microstructure either in ex-situ experiments or in-situ to monitor, for example, the chemical reaction pathway during film growth [3]. The main objective of this talk is to demonstrate that (contrary to a widespread opinion) high energy synchrotron radiation and thin film analysis may fit together. The corresponding experiments were performed on the materials science beamline EDDI at BESSY II which is one of the very few instruments worldwide that is especially dedicated to ED diffraction. On the basis of selected examples it will be shown that specially tailored experimental setups allow for residual stress depth profiling even in thin films and multilayer coatings as well as for fast in situ studies of film stress and microstructure evolution during film growth.

Effects of Processing Parameters on the Excimer Laser Deposition of Yba2Cu3O7-δ Thin Films

1989 ◽  
Vol 169 ◽  
Author(s):  
R. E. Muenchausen ◽  
X. D. Wu ◽  
R. C. Dye ◽  
K. M. Hubbard ◽  
R. C. Estler ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Energy ◽  
Processing Parameters ◽  
Spot Size ◽  
Laser Deposition ◽  
Angular Distributions ◽  
Superconducting Thin Films ◽  
Film Properties ◽  
Optimized Conditions

AbstractSystematic studies of the effects of pulsed laser deposition processing parameters on plume dynamics and resultant film properties have been performed. Plume angular distributions, cosm(θ), were observed to be variable between 1 > m > 15 depending on laser energy density and spot size. Under optimized conditions, epitaxial, superconducting thin films could be grown in‐situ on a variety of single‐crystal substrates. High quality, 2000 Å  ss thick films were obtained at deposition rates approaching 150 Å/sec.

Processing and morphology of permeable polycrystalline silicon thin films

2002 ◽  
Vol 17 (9) ◽  
pp. 2235-2242 ◽  
Author(s):  
G. G. Dougherty ◽  
A. A. Pisano ◽  
T. Sands
Keyword(s):  
Thin Films ◽  
Polycrystalline Silicon ◽  
Film Growth ◽  
Film Stress ◽  
Silicon Thin Films ◽  
Residual Film ◽  
Simple Kinetic Model ◽  
Free Films ◽  
The Right ◽  
The Relationship

It is known that thin films of polycrystalline silicon, deposited under the right conditions, can be permeable to HF-based etching solutions. While these films offer unique capabilities for microfabrication, both the poor reproducibility of the permeable film properties and the lack of a detailed physical understanding of the material have limited their application. This work provides a methodical study of the relationship between process, microstructure, and properties of permeable polycrystalline silicon thin films. It is shown that the permeability is a result of small pores, on the order of 10 nm, between the 100–200-nm hemispherical grains characteristic of the permeable film morphology. This morphology occurs only in nearly stress-free films grown in a narrow temperature range corresponding to the transition between tensile and compressive film growth regimes. This result strongly suggests that the monitoring of residual film stress can provide the process control needed to reliably produce permeable films. A simple kinetic model is proposed to explain the evolution of the morphology of the permeable films.

Ion beam sputter deposition of YBa2Cu3O7−δ thin films

1993 ◽  
Vol 8 (12) ◽  
pp. 3032-3042 ◽  
Author(s):  
B.J. Kellett ◽  
J.H. James
Keyword(s):  
Thin Films ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Ion Beam ◽  
High Oxygen ◽  
Ion Beam Sputtering ◽  
Film Properties ◽  
High Oxygen Partial Pressure ◽  
Beam Sputtering

This article addresses issues associated with in situ growth of superconducting YBa2Cu3O7−δ thin films by ion beam sputtering. High oxygen partial pressure during ion beam deposition can cause significant beam broadening and oxidation of filaments and grids. Also, many of the targets used for processing YBCO are unstable when sputtered in a high oxygen partial pressure. It is shown that ion beam sputtering can produce YBCO films of comparable quality to those produced by laser ablation or dc magnetron sputtering. Typical film properties are Tco = 91 K and Jc (77 K) = 106 A cm−2. It appears that the oxygen gas pressure during the postdeposition cooldown has a more important influence on film properties than the oxygen partial pressure during deposition.

Viscoelastic Behavior of Polymer Thin‐Films Under Thermal Stresses

1996 ◽  
Vol 445 ◽  
Author(s):  
Stephen D. Bluestein ◽  
Dewi P. Y. Bramono ◽  
Ioannis N. Miaoulis ◽  
Peter Y. Wong
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Thermal Loading ◽  
Thermal Stresses ◽  
Viscoelastic Behavior ◽  
Polymer Materials ◽  
Microelectronic Packaging ◽  
Polyimide Films ◽  
Different Temperatures

AbstractStresses and deformation in microelectronic packaging are affected by the viscoelastic behavior of polymer materials during manufacture or operation. Predicting and measuring these thermo‐mechanical effects is important for new devices, components, and materials. The viscoelastic response of Nycoa 851 polyimide thin‐films during thermal loading is investigated. The time‐dependent relaxation of polyimide films was measured in‐situ, focusing on the change in thermo‐mechanical properties based on the thickness of the polyimide layer. The curvature change of the multilayer structure (silver‐polyimide‐quartz heterostructure) was obtained for different temperatures and polymer film thicknesses. The polyimide relaxation time constant and activation energy were determined. Results indicate that the thermo‐mechanical properties of polyimide thin films are dependent on the thickness of the polymer layer.

Growth of TiO2 Thin Films by Pulsed Laser Evaporation

1990 ◽  
Vol 191 ◽  
Author(s):  
Ming Y. Chen ◽  
P. Terrence Murray
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Pulsed Laser ◽  
Grazing Incidence ◽  
Ex Situ ◽  
Laser Evaporation ◽  
Tio2 Thin Films ◽  
Film Properties ◽  
X Ray

ABSTRACTThin films of TiO2 have been grown by pulsed laser evaporation. The films were analyzed by in-situ Auger and x-ray photoelectron spectroscopy as well as by ex-situ grazing incidence xray diffraction. Films grown at room temperature and at a pressure of 5×10minus; 3 Torr were oxygen deficient. Films grown at 500°C and higher were found to be stoichiometric TiO2.The effect of substrate temperature and evaporation conditions on film properties will be discussed.

Stress in evaporated films used in GaAs processing

1991 ◽  
Vol 6 (3) ◽  
pp. 548-552 ◽  
Author(s):  
W.A. Strifler ◽  
C.W. Bates
Keyword(s):  
Thin Films ◽  
Practical Method ◽  
Optical Microscope ◽  
Metal Films ◽  
Film Stress ◽  
Cantilever Beams ◽  
Vertical Deflection ◽  
Thermal Component ◽  
Residual Film ◽  
Micro Cantilever

A simple and practical method is described for determining the residual stress in vapor deposited thin films that are less than 1000 Å in thickness. The method relies on the evaporation of thin films onto prefabricated micro-cantilever beams of SiO2. The vertical deflection at the end of the beam is measured using an optical microscope to determine the average film stress with a resolution of 25 MPa. Calculations show that the vapor deposition of metal films onto these beams does not induce significant heating, so the thermal component of residual film stress is minimal. The micro-cantilever technique is used to measure the film stress in 500 Å films of Al, Ti, Pt, Au, Ni, and Ge. These measured values are compared to similar measurements reported in the literature.

Evaluation on Stress and Optical Property of Thin Films Used in Optical MEMS Device

2003 ◽  
Vol 795 ◽  
Author(s):  
Lianchao Sun ◽  
Ping Hou
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Optical Property ◽  
Film Stress ◽  
Mems Devices ◽  
Film Properties ◽  
Optical Mems ◽  
Micro Electro Mechanical Systems ◽  
Index Changes ◽  
Mems Device

ABSTRACTControl of the film stress and optical property has long been considered as an issue in the tunable optical MEMS (Micro-Electro-Mechanical Systems) devices. In this paper, the atmospheric evolution of Titanium Dioxide (TiO2) and Silicon Dioxide (SiO2) thin films for the optical MEMS devices were studied. These films were prepared by ion-assisted e-beam evaporation. It is found that as-deposited SiO2 films exhibit compressive stress; whereas, it is tensile in the TiO2 films under present processing conditions. When annealed at 150 °C, both SiO2 and TiO2 films show slight changes in stress with annealing time. However, increasing the anneal temperature to 250°C caused an apparent change of film stresses with time, in which SiO2 film turns into less compressive and TiO2 film appears to be more tensile. The optical properties after annealing were also investigated by measuring the thickness and the refractive index changes using the spectroscopic ellipsometry technique. At both experimental temperatures, the film thickness increases slightly and the refractive index at 1550 nm decreases a little at the initial annealing stage for SiO2 films. For TiO2 films, it is found that the refractive index increases after annealing at 250°C. This might be caused by the TiO2 film densification process during amorphous-to-crystalline phase transformation. Because most of the significant film evolutions occur during the initial 12 hours of annealing, a practical way of stabilizing the film properties in a MEMS device is to pre-anneal the as-deposited thin films.

Nucleation and Early Growth of Sputtered thin Films

1970 ◽  
Vol 28 ◽  
pp. 516-517
Author(s):  
Dudley M. Sherman ◽  
Thos. E. Hutchinson
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
Ion Beam ◽  
Ion Source ◽  
Water Cooling ◽  
Stages Of Growth ◽  
Lens Assembly ◽  
Microscope Technique ◽  
Ion Beam Sputter Deposition

The in situ electron microscope technique has been shown to be a powerful method for investigating the nucleation and growth of thin films formed by vacuum vapor deposition. The nucleation and early stages of growth of metal deposits formed by ion beam sputter-deposition are now being studied by the in situ technique.A duoplasmatron ion source and lens assembly has been attached to one side of the universal chamber of an RCA EMU-4 microscope and a sputtering target inserted into the chamber from the opposite side. The material to be deposited, in disc form, is bonded to the end of an electrically isolated copper rod that has provisions for target water cooling. The ion beam is normal to the microscope electron beam and the target is placed adjacent to the electron beam above the specimen hot stage, as shown in Figure 1.

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