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.

Experimental Investigation on Contact Angle of Sintered Copper Powder Wick

2016 ◽  
Vol 819 ◽  
pp. 575-579 ◽  
Author(s):  
Nandy Putra ◽  
Iwan Setyawan ◽  
Dimas Raditya
Keyword(s):  
Contact Angle ◽  
Copper Powder ◽  
High Speed ◽  
Ambient Air ◽  
Video Camera ◽  
High Heat ◽  
High Heat Flux ◽  
Powder Particle Size ◽  
Air Exposure ◽  
Sintered Copper

Heat pipes are widely used in electronic cooling and other applications that require efficient transport or spreading of heat from local sources of high heat flux. One factor that most affect the performance of this device is the wetting properties of the wick material, whereby a hydrophilic wick material is required to transport the liquid from the evaporator to the condenser. The performance of heat pipe will decrease when the wick surface becomes hydrophobic as indicated by changes in its contact angle (CA). This study aims to determine the effect of ambient air exposure on the wettability of wick material. Wettability for a surface by a certain liquid can be shown by measuring the contact angle of liquid droplets on the surface. In this experiment, the contact angle was captured using a high speed video camera followed by image processing and then measured using Image J software. The surface of the sample/wick is a sintered copper powder which in this study through a process of forming or compaction by various parameters such as powder particle size, compacting pressure and sintering temperature. From the results of this study was found that the longer wicks were exposed in the ambient air, the contact angle of the liquid on the wick surface will be getting increased. After 7 days were contaminated on the ambient air, then all samples have been turned into hydrophobic, CA>90°.

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.

Integrated Titanium Silicide Processing

1990 ◽  
Vol 181 ◽  
Author(s):  
Jaim Nulman
Keyword(s):  
Sheet Resistance ◽  
Silicon Surface ◽  
Processing System ◽  
Ambient Air ◽  
Titanium Silicide ◽  
Air Exposure ◽  
Processing Window ◽  
Wafer Cleaning ◽  
Annealing Step ◽  
Cleaning Technology

ABSTRACTThe processing of titanium silicide in a multichamber processing system is described. Three processes are included: wafer cleaning, Ti deposition, and annealing. The results are compared to wafers processed in a conventional way with exposure to ambient air between Ti deposition and the annealing step. TEM, RBS and sheet resistance measurements indicate that the films processed without exposure to ambient air have thicker and purer TiN layers as compared to the films with air exposure. Furthermore, integration allows for a wider processing window for the first annealing step. The use of reactive cleaning chemistry prior to Ti deposition results in a smooth silicon surface and therefore uniform silicidation as compared to inert cleaning technology, where redeposit of etched material occurs.

A Nonlithographic Approach for Creating Unstable Hierarchical (Micro-Nano) Superhydrophobic Silicon Surfaces

2006 ◽  
Author(s):  
Ming-Fang Wang ◽  
Nithin Nraghuna ◽  
Babak Ziaie
Keyword(s):  
Contact Angle ◽  
Porous Silicon ◽  
High Current Density ◽  
Contact Angles ◽  
Wet Etching ◽  
Silicon Surfaces ◽  
Rolling Angle ◽  
Step Method ◽  
Shape Structure ◽  
P Type

In this paper, we report on an inexpensive non-lithographic approach to create superhydrophobic silicon surfaces using porous silicon technology. We have used a two-step method to create an unstable hierarchical (micro-nano) superhydrophobic silicon surface. Our technique is a unique combination of a high current density (170mA/cm2) porous silicon formation step followed by a wet etching step in BOE/HNO3. Porous silicon layers, of both n- and p-type wafers were used in these experiments. The contact and rolling angles were measured for: 1) regular porous silicon, 2) porous silicon with hierarchical fractal-shape structure, and 3) hierarchical fractal-shape porous silicon after the wet etching step. For both n- and p-type wafers, the contact angles of regular porous silicon (nonhierarchical) were around 120° with a rolling angle of 90°. With hierarchical structure, the contact angle increased to 135° and after addition wet etching, the contact angle approached 160° (superhydrophobic). Besides, after wet etching step the surface became extremely unstable showing a very low rolling angle (<1°).

Comparative Studies of Hydrogen Termination on Single-Crystal Silicon Surfaces by FT-IR and Contact-Angle Measurements

1997 ◽  
Vol 51 (12) ◽  
pp. 1905-1909 ◽  
Author(s):  
Oliver M. R. Chyan ◽  
Junjun Wu ◽  
Jin-Jian Chen
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Silicon Surface ◽  
Silicon Surfaces ◽  
Crystal Silicon ◽  
Water Contact ◽  
Angle Measurements ◽  
Contact Angle Measurements ◽  
Hydrogen Termination ◽  
Termination Process

The hydrogen termination process on a Si(100) surface has been studied by multiple internal reflection infrared spectroscopy (MIR-IS) and contact-angle measurements. Three main silicon hydride absorption peaks at 2087, 2104, and 2114 cm−1 were found to gradually increase with the hydrofluoric (HF) acid etching. Eventually, a constant peak height was reached as an indication of complete hydrogen termination. Integration of all the surface hydrides absorption peaks (2000 to 2200 cm−1) provides direct quantitative evaluation of the hydrogen termination process. On the other hand, water contact-angle data were shown to consistently lag behind the IR measurement in determining the extent of hydrogen termination on the silicon surface. Analysis of the surface free energy of HF-etched silicon surfaces indicates that the degree of the hydrogen termination determined by water contact-angle measurements is subjected to inaccuracies due to the preferential hydrogen-bonding interaction between the water and silicon surface oxide.

Superhydrophobicity of Silicon-Based Microstructured Surfaces

2014 ◽  
Vol 989-994 ◽  
pp. 267-269 ◽  
Author(s):  
Gang Li
Keyword(s):  
Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Silicon Surfaces ◽  
Silicon Substrates ◽  
Optical Contact ◽  
Simple Method ◽  
Femtosecond Laser Micromachining ◽  
Microstructured Surfaces ◽  
Silicon Based

Here, a simple method was presented for fabricating superhydrophobic silicon surfaces. Square-pillar-array samples were fabricated on silicon substrates by using the femtosecond laser micromachining technology. We measured the static and dynamic contact angles for water on these surfaces. The contact angles and the rolling angles on the silicon surfaces were measured through an optical contact angle meter. Wettability studies revealed the films exhibited a superhydrophobic behaviour with a higher contact angle and lower rolling angle-a water droplet moved easily on the surface.

Wetting Behaviors of an Underwater Oil Droplet on Structured Surfaces

MRS Advances ◽  
2016 ◽  
Vol 1 (10) ◽  
pp. 667-673 ◽  
Author(s):  
Shuai Chen ◽  
Jiadao Wang ◽  
Darong Chen
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Contact Angles ◽  
Silicon Surfaces ◽  
Water Contact ◽  
Structured Surfaces ◽  
Oil Droplet ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Wetting Behaviors

ABSTRACTIn this study, the wetting behaviors of an underwater oil droplet on structured surfaces were investigated using molecular dynamics simulations and experiments. The wetting states and contact angles of the underwater oil droplet on different hydrophobic surfaces were simulated. The simulation results showed that there were three kinds of equilibrium states on the pillar surfaces: the Wenzel, cross, and Cassie states. Moreover, the equilibrium state of the underwater oil droplet transformed from a Wenzel to Cassie state when the water contact angle decreased. The contact angle of the underwater oil droplet increased as the water contact angle decreased. Furthermore, the wetting behaviors of the underwater oil droplet on rough polytetrafluoroethylene and silicon surfaces were studied in experiments. The experimental results also indicated that the contact angle of the underwater oil droplet increased as the water contact angle decreased, which corresponded well with the simulation results.

scholarly journals Time-Dependent Anisotropic Wetting Behavior of Deterministic Structures of Different Strut Widths on Ti6Al4V

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 938 ◽  
Author(s):  
Georg Schnell ◽  
Christopher Jagow ◽  
Armin Springer ◽  
Marcus Frank ◽  
Hermann Seitz
Keyword(s):  
Contact Angle ◽  
Sessile Drop ◽  
Ambient Air ◽  
Laser Wavelength ◽  
Contact Angles ◽  
Femtosecond Laser Irradiation ◽  
Ultrapure Water ◽  
Wetting Behavior ◽  
Maximum Contact ◽  
Deterministic Structures

This study investigated the wetting behavior of Ti6Al4V surfaces that were groove-structured by means of femtosecond laser irradiation. The material was treated under ambient air conditions by use of a laser wavelength of 1030 nm and a pulse duration of 300 fs. Highly accurate structures with a gap width of 20 µm, a gap depth of 10 µm, and varying strut widths (1–300 µm) were generated and the contact angles in parallel and perpendicular direction were determined using sessile drop method with ultrapure water 1, 8, and 15 days after irradiation. All deterministic surfaces exhibited a pronounced contact angle change over time. The structures showed a strong anisotropic wetting behavior with a maximum contact angle aspect ratio of 2.47 at a strut width of 40 µm and a maximum difference between the parallel and perpendicular contact angle of 47.9° after 1 day.

Water–propylene glycol sessile droplet shapes and migration: Marangoni mixing and separation of scales

2022 ◽  
Vol 933 ◽  
Author(s):  
J. Charlier ◽  
A.Y. Rednikov ◽  
S. Dehaeck ◽  
P. Colinet ◽  
D. Terwagne
Keyword(s):  
Contact Angle ◽  
Propylene Glycol ◽  
Ambient Air ◽  
Contact Angles ◽  
Apparent Contact Angle ◽  
Sessile Droplet ◽  
Convective Mixing ◽  
Separation Of Scales ◽  
And Migration

New light is shed on morphological features of water–propylene glycol sessile droplets evaporating into ambient air at not too high relative humidity. Such droplets adopt a Marangoni-contracted shape even on perfectly wetting substrates, an effect well known since Cira et al. (Nature, 519, 2015). We here highlight a strong separation of scales normally occurring for such droplets. Namely, there is a narrow high-curvature zone localized at the foot of the droplet, where the apparent contact angle is formed, while the core of the droplet merely adheres to the classical (capillary–gravity) static shape. Experimentally, we rely upon interferometry to discern such fine key details. We detect a maximum of the droplet slope profile in the foot region, which amounts to the apparent contact angle. Theoretically, a local description of the foot region is devised. We indicate a crucial role of convective mixing by the solutal Marangoni flow, here accounted for by the Taylor dispersion, which proves to underlie the separation of scales and ensure self-consistency of the local model. Migration of such droplets in a humidity gradient is also approached within the same experimental and theoretical framework. It is considered that the resulting back–front asymmetry of the apparent contact angles drives the motion similarly to a wettability gradient, although the drag (‘Cox–Voinov’) factor is here found to be different. The predictions, comparing well with the measurements (our own and from the literature), are based on rigorous models, isothermal and as reduced as possible, without any fitting parameters or microphysics effects.

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