Surface Engineering of Polycrystalline Silicon Microelectromechanical Systems for Fatigue Resistance

2002 ◽  
Vol 729 ◽  
Author(s):  
C.L. Muhlstein ◽  
W.R. Ashurst ◽  
E.A. Stach ◽  
R. aboudian ◽  
R.O. Ritchie
Keyword(s):  
Stress Corrosion ◽  
Fatigue Resistance ◽  
Reaction Layer ◽  
Polycrystalline Silicon ◽  
Microelectromechanical Systems ◽  
Fatigue Behavior ◽  
Ambient Air ◽  
Degradation Process ◽  
Native Oxide ◽  
Premature Failure

AbstractRecent research has established that for silicon structural films used in microelectromechanical systems (MEMS), the susceptibility to premature failure under cyclic fatigue loading originates from a degradation process that is confined to the surface oxide. In ambient air environments, a sequential, stress-assisted oxidation and stress-corrosion cracking process can occur within the native oxide on polycrystalline silicon (referred to as reaction-layer fatigue); for the structural films of micron-scale dimensions, such incipient cracking in the oxide can lead to catastrophic failure of the entire silicon component. Since the degradation process is intimately linked to the thin reaction layer on the silicon, modification of this surface and the access of the environment to it can dramatically alter the fatigue resistance of the material. The purpose of this paper is to evaluate the efficacy of modifying the fatigue behavior of polycrystalline silicon with alkene-based monolayers. Specifically, 2-μm thick polysilicon fatigue structures were coated with a monolayer film based on 1-octadecene and cyclically tested to failure in laboratory air. By applying the coating, the formation of the native oxide was prevented. Compared to the fatigue behavior of untreated polysilicon, the lives of the coated samples ranged from 105 to >1010 cycles at stress amplitudes greater than ∼90% of the ultimate strength of the film. The dramatic improvement in fatigue resistance was attributed to the monolayer inhibiting the formation of the native oxide and stress corrosion of the surface. It is concluded that the surprising susceptibility of thin structural silicon films to premature fatigue failure can be inhibited by such monolayer coatings.

Interfacial Effects on the Premature Failure of Polycrystalline Silicon Structural Films

2002 ◽  
Vol 741 ◽  
Author(s):  
C.L. Muhlstein ◽  
E.A. Stach ◽  
R.O. Ritchie
Keyword(s):  
Thin Films ◽  
Reaction Layer ◽  
Polycrystalline Silicon ◽  
Ambient Air ◽  
Native Oxide ◽  
Small Scale ◽  
Native Oxide Layer ◽  
Silica Layer ◽  
Premature Failure ◽  
Structural Applications

ABSTRACTAlthough bulk silicon is not known to be susceptible to cyclic fatigue, micron-scale structures made from mono and polycrystalline silicon films are vulnerable to degradation by fatigue in ambient air environments. Such silicon thin films are used in small-scale structural applications, including microelectromechanical systems (MEMS), and display “metal-like” stress-life (S/N) fatigue behavior in room temperature air environments. Previously, the authors have observed fatigue lives in excess of 1011 cycles at high frequency (∼40 kHz), fully-reversed stress amplitudes as low as half the fracture strength using a surface micromachined, resonant-loaded, fatigue characterization structures. Stress-life fatigue, transmission electron microscopy, infrared microscopy, and numerical models were used to establish that the mechanism of the fatigue failure of thin-film silicon involves the sequential oxidation and environmentally-assisted crack growth solely within the native silica layer, a process that we term “reaction-layer fatigue”. Only thin films are susceptible to such a failure mechanism because the critical crack size for catastrophic failure of the entire silicon structure can be exceeded by a crack solely within the native oxide layer. The importance of the interfacial geometry on the mechanics of the reaction-layer fatigue mechanism is described.

Utilizing On-Chip Testing and Electron Microscopy to Study Fatigue and Wear in Polysilicon Structural Films

2004 ◽  
Vol 821 ◽  
Author(s):  
D.H. Alsem ◽  
E.A. Stach ◽  
C.L. Muhlstein ◽  
M.T. Dugger ◽  
R.O. Ritchie
Keyword(s):  
Electron Microscopy ◽  
Failure Modes ◽  
Microelectromechanical Systems ◽  
Fatigue Behavior ◽  
Side Wall ◽  
Ambient Air ◽  
Wall Friction ◽  
Native Oxide ◽  
Chip Testing ◽  
On Chip

AbstractWear and fatigue are important factors in determining the reliability of microelectromechanical systems (MEMS). While the reliability of MEMS has received extensive attention, the physical mechanisms responsible for these failure modes have yet to be conclusively determined. In our work, we use a combination of on-chip testing methodologies and electron microscopy observations to investigate these mechanisms. Our previous studies have shown that fatigue in polysilicon structural thin films is a result of a ‘reaction-layer’ process, whereby high stresses induce a room-temperature mechanical thickening of the native oxide at the root of a notched cantilever beam, which subsequently undergoes moisture-assisted cracking. Devices from a more recent fabrication run are fatigued in ambient air to show that the post-release oxide layer thicknesses that were observed in our earlier experiments were not an artifact of that particular batch of polysilicon. New in vacuo data show that these silicon films do not display fatigue behavior when the post release oxide is prevented from growing, because of the absence of oxygen. Additionally, we are using polysilicon MEMS side-wall friction test specimens to study active mechanisms in sliding wear at the microscale. In particular, we have developed in vacuo and in situ experiments in the scanning electron microscope, with the objective of eventually determining the mechanisms causing both wear development and debris generation.

Investigation of Pre-Tungsten Silicide Deposition Wet Chemical Processing

1995 ◽  
Vol 386 ◽  
Author(s):  
A. Philipossian ◽  
M. Moinpour ◽  
R. Wilkinson ◽  
V. H. C. Watt
Keyword(s):  
Contact Angle ◽  
Polycrystalline Silicon ◽  
Silicon Surface ◽  
Morphological Characteristics ◽  
Ambient Air ◽  
Contact Angles ◽  
Silicon Surfaces ◽  
Native Oxide ◽  
Initial Contact ◽  
Air Exposure

ABSTRACTRemoving the native oxide from the poly-Si surface prior to WSix deposition is essential for achieving high quality silicides as well as sufficient film adhesion, particularly after high temperature anneal or oxidation. Contact angle studies have been used to determine initial and time-dependent surface characteristics of several types of silicon surfaces following immersions in HF-based etchants for varying amounts of time. The morphological characteristics of the surfaces before and after exposure to etchants, as well as the relative etch rates and wetting capabilities of the etchants have been used to explain the following results: With respect to initial contact angle studies, the implanted & annealed polycrystalline silicon surface has the lowest contact angle followed by polycrystalline and monocrystalline surfaces. Longer immersion times yield lower initial contact angles. The 0.1% lightly-buffered HF solution results in the highest contact angle followed by the 1% buffered HF solution with surfactant, and the 1% HF solution. With respect to contact angle changes during ambient air exposure time, the asdeposited polycrystalline silicon surface is most stable followed by monocrystalline, and implanted & annealed polycrystalline silicon surfaces. Longer immersion times improve surface stability while the 0.1% lightly-buffered HF solution results in the most stable surface followed by the 1% buffered HF solution with surfactant, and the 1% HF solution.

On The Mechanism of Fatigue in Micron-Scale Structural Films of Polycrystalline Silicon

2001 ◽  
Vol 697 ◽  
Author(s):  
C. L. Muhlstein ◽  
E. A. Stach ◽  
R. O. Ritchie
Keyword(s):  
Thin Film ◽  
Polycrystalline Silicon ◽  
Fatigue Behavior ◽  
Crack Size ◽  
Native Oxide ◽  
Self Assembled Monolayer ◽  
Critical Crack ◽  
Thin Film Silicon ◽  
Transmission Electron ◽  
Critical Crack Size

Abstract2-μm thick structural films of polycrystalline silicon are shown to display “metal-like” stress-life fatigue behavior in room air, with failures occurring after > 1011 cycles at stresses as low as half the fracture strength. Using in situ measurements of the specimen compliance and transmission electron microscopy to characterize such damage, the mechanism of thin-film silicon fatigue is deduced to be sequential oxidation and moisture-assisted cracking in the native SiO2 layer. This mechanism can also occur in bulk silicon but it is only relevant in thin films where the critical crack size for catastrophic failure can be exceeded within the oxide layer. The fatigue susceptibility of thin-film silicon is shown to be suppressed by alkene-based self-assembled monolayer coatings that prevent the formation of the native oxide.

On the Mechanism of Fatigue in Micron-Scale Structural Films of Polycrystalline Silicon

2001 ◽  
Vol 687 ◽  
Author(s):  
C. L. Muhlstein ◽  
E. A. Stach ◽  
R. O. Ritchie
Keyword(s):  
Thin Film ◽  
Polycrystalline Silicon ◽  
Fatigue Behavior ◽  
Crack Size ◽  
Native Oxide ◽  
Self Assembled Monolayer ◽  
Critical Crack ◽  
Thin Film Silicon ◽  
Transmission Electron ◽  
Critical Crack Size

Abstract2-νm thick structural films of polycrystalline silicon are shown to display “metal-like” stress- life fatigue behavior in room air, with failures occurring after >1011 cycles at stresses as low as half the fracture strength. Using in situ measurements of the specimen compliance and transmission electron microscopy to characterize such damage, the mechanism of thin-film silicon fatigue is deduced to be sequential oxidation and moisture-assisted cracking in the native SiO2 layer. This mechanism can also occur in bulk silicon but it is only relevant in thin films where the critical crack size for catastrophic failure can be exceeded within the oxide layer. The fatigue susceptibility of thin-film silicon is shown to be suppressed by alkene-based self- assembled monolayer coatings that prevent the formation of the native oxide.

scholarly journals Tension-Tension Fatigue Behavior of High-Toughness Zr61Ti2Cu25Al12 Bulk Metallic Glass

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2815
Author(s):  
Yu Hang Yang ◽  
Jun Yi ◽  
Na Yang ◽  
Wen Liang ◽  
Hao Ran Huang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Shear Band ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Fatigue Resistance ◽  
Metallic Glasses ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Bulk Metallic Glasses ◽  
High Toughness

Bulk metallic glasses have application potential in engineering structures due to their exceptional strength and fracture toughness. Their fatigue resistance is very important for the application as well. We report the tension-tension fatigue damage behavior of a Zr61Ti2Cu25Al12 bulk metallic glass, which has the highest fracture toughness among BMGs. The Zr61Ti2Cu25Al12 glass exhibits a tension-tension fatigue endurance limit of 195 MPa, which is higher than that of high-toughness steels. The fracture morphology of the specimens depends on the applied stress amplitude. We found flocks of shear bands, which were perpendicular to the loading direction, on the surface of the fatigue test specimens with stress amplitude higher than the fatigue limit of the glass. The fatigue cracking of the glass initiated from a shear band in a shear band flock. Our work demonstrated that the Zr61Ti2Cu25Al12 glass is a competitive structural material and shed light on improving the fatigue resistance of bulk metallic glasses.

Interfacial Delamination in Plastic Encapsulated Integrated Circuits (Pics)

1996 ◽  
Vol 445 ◽  
Author(s):  
Nickolaos Strifas ◽  
Aris Christou
Keyword(s):  
Integrated Circuits ◽  
Failure Analysis ◽  
Stress Corrosion ◽  
Integrated Circuit ◽  
Point Of View ◽  
Acoustic Microscopy ◽  
Electrical Performance ◽  
Premature Failure ◽  
Interfacial Delamination ◽  
Die Surface

AbstractThe reliability of plastic packaged integrated circuits was assessed from the point of view of interfacial mechanical integrity. It is shown that the effect of structural weaknesses caused by poor bonding, voids, microcracks or delamination may not be evident in the electrical performance characteristics, but may cause premature failure. Acoustic microscopy (C-SAM) was selected for nondestructive failure analysis of the plastic integrated circuit (IC) packages. Integrated circuits in plastic dual in line packages were initially subjected to temperature (25 °C to 85 °C) and humidity cycling (50 to 85 %) where each cycle was of one hour duration and for over 100 cycles and then analyzed. Delamination at the interfaces between the different materials within the package, which is a major cause of moisture ingress and subsequent premature package failure, was measured. The principal areas of delamination were found along the leads extending from the chip to the edge of the molded body and along the die surface itself. Images of the 3-D internal structure were produced that were used to determine the mechanism for a package failure. The evidence of corrosion and stress corrosion cracks in the regions of delamination was identified.

A study into the ability of SPD to restore the buckling strength and modes of rib stiffened panels with simulated stress corrosion cracks

2017 ◽  
Vol 8 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Rhys Jones ◽  
Neil Matthews ◽  
Daren Peng ◽  
Nicholas Orchowski
Keyword(s):  
Experimental Study ◽  
Stress Corrosion ◽  
Carrying Capacity ◽  
Particle Deposition ◽  
Load Carrying Capacity ◽  
Load Path ◽  
Premature Failure ◽  
Content Type ◽  
Buckling Strength ◽  
Load Carrying

Purpose The purpose of this paper is to describe the results of a combined numerical and experimental study into the ability of supersonic particle deposition (SPD) to restore the load carrying capacity of rib stiffened wing planks with simulated stress corrosion cracking (SCC). Design/methodology/approach In this context the experimental results reveal that SCC can result in a dramatic reduction in the load carrying capacity of the structure and catastrophic failure via cracking that tears the length of the structure through buckling. A combined numerical and experimental study then reveals how this reduction, in the load carrying capacity can be overcome by using SPD. Findings This paper is the first to show that SPD can be used to restore the load carrying capacity of rib stiffened structures with SCC. It also shows that SPD repairs can be designed to have only a minimal effect on the local stiffness and hence on the load path. However, care should be taken to ensure that the design is such that premature failure of the SPD does not occur. Originality/value This is the first paper to show that a thin layer of SPD deposited 7,075 aluminium alloy powder on either side of the SCC-simulated stiffener has the potential to restore the load carrying capability of a rib stiffened structure. As such it represents an important first step into establishing the potential for SPD to restore the buckling strength of rib stiffened wing panels containing SCC.

Observations on the Interaction of High Mean Stress and Type II Hot Corrosion on the Fatigue Behavior of a Nickel Base Superalloy

1985 ◽  
Vol 107 (1) ◽  
pp. 220-224 ◽  
Author(s):  
J. M. Allen ◽  
G. A. Whitlow
Keyword(s):  
Stress Corrosion ◽  
Maximum Stress ◽  
Rupture Strength ◽  
Fatigue Behavior ◽  
Nickel Base Superalloy ◽  
Chloride Salt ◽  
Mean Stress ◽  
R Ratio ◽  
Nickel Base ◽  
Udimet 720

A study measuring the effects of a molten sulfate/chloride salt on the creep/fatigue behavior of a nickel base turbine blade superalloy, Udimet 720, at 1300°F (704°C) is described. Cyclic stress–cycles to failure (S-N) curves were generated at high mean stress levels, with mean stress, maximum stress, or the ratio of minimum to maximum stress (R ratio) held constant. In salt, it was found that when maximum stress is above the yield, with the cyclic component 20 percent of the maximum, failure occurs by stress corrosion fatigue in orders of magnitude less time than for corresponding loading conditions in air. It is significant, from a failure analysis point of view, that fatigue fracture is intergranular in these circumstances. Similar fatigue behavior may be expected for other nickel base alloys, however, at substantially lower maximum stresses in as much as Udimet 720 exhibits superior short time rupture strength, i.e., resistance to this form of stress corrosion, over the other blade alloys evaluated in this environment.

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