Sputter Etching Research Articles

Formation of Fine Holes by Sputter Etching of Ti-15V-3Cr-3Al-3Sn Alloy and Commercially Pure Titanium

Formation of Fine Holes by Sputter Etching of Ti-15V-3Cr-3Al-3Sn Alloy and Commercially Pure Titanium

Fabrication of micro-ignition sequence based on electronics safety and arming unit

This paper describes an ignition circuit consisted of one micro igniter and one electronic security microswitch that could realize the intelligent function of micro-ignition sequence. The micro-ignition sequence, integrated with ignition circuit, chamber, nanothermite and B/KNO3, was fabricated on the same silicon chip by mechanical engraving and classic micro mechanical systems (MEMS) technology including magnetron sputtering and plasma etching steps. In addition, the size of micro-ignition sequence was less than 0.15 cm3. The electronic security microswitch based on energetic film Al/MoO3 can implement the function of circuit switch conversion under 1.5 A during 3 ms. The paper presents the design, fabrication and test of the micro-ignition sequence integrating of electronics safety and arming unit.

High-Cycle Mechanical Fatigue Performance of Sputtered Nitinol

This paper investigates the fatigue performance of Nitinol thin-film devices used in medical applications. Freestanding films are fabricated and structured by microsystem technology processes (magnetron sputtering, UV lithography and wet chemical etching). A test rig is developed to address the requirements of Nitinol thin-film samples in terms of force, stroke and precision and also allows the multiplication of test rigs due to its inexpensive components. Hence, several samples can be tested simultaneously at different parameters in order to obtain a thorough characterization within reasonable test duration. Finite element analysis (FEA) is used to derive maximum principle strains of test specimen during cycling loading. Therefore, a superelastic, multiaxial material model with two different kinetic transformation mechanisms being capable of considering tension/compression asymmetry and temperature effects is realized and implemented using the FEA software Comsol Multiphysics. Good agreement between simulation and experimental tensile tests is shown. An excellent fatigue resistance with a high fatigue safety limit of 1.75% pulsatile strain amplitude for mean strains up to 2.5% with sputtered Nitinol diamond specimen is observed.

Superhydrophobic Polydimethylsiloxane via Nanocontact Molding of Solvent Crystallized Polycarbonate: Optimized Fabrication, Mechanistic Investigation, and Application Potential.

Herein, we describe a benchtop protocol to create superhydrophobic polydimethylsiloxane (PDMS) via nanocontact molding of polycarbonate (PC) that was crystallized by controlled solvent treatment. The crystallized PC chains rearrange into a network of spherulites (spherical semicrystalline domains); the overall surface is rough on the micrometer-scale, while the spherulites themselves consist of nanoscale features. It was confirmed via conventional spectroscopic and high-resolution microscopic investigation that such hierarchical roughness is key to the development of superhydrophobic PC and the substantial enhancement upon PDMS molding. Thus, the prepared PDMS surface has excellent superhydrophobicity with an optimized contact angle of 172 ± 1° and a sliding angle of <1°, superior to those prepared from more elaborate techniques, such as plasma sputtering and laser etching. More importantly, the knowledge acquired regarding the structural transition and superhydrophobicity development would be beneficial to engineering and evaluating templates for many other polymeric nanostructures and functional surfaces.

3-D SRIM Simulation of Focused Ion Beam Sputtering with an Application-Oriented Incident Beam Model

Ion beam sputter etching has been widely used in material surface modification and transmission electron microscope (TEM) sample preparation. Due to the complexity of the ion beam etching process, the quantitative simulation of ion beam sputtering is necessary to guarantee precision in surface treatment and sculpting under different energies and beam currents. In this paper, an application-oriented incident ion beam model was first built with aberrations and Coulomb repulsion forces being considered from the Ga ion source to the sample. The sputtering process of this model on the sample was then analyzed and simulated with an improved stopping and range of ions in matter (SRIM) program. The sputtering performance of this model, the point-like incident beam and the typical Gaussian incident beam was given in the end. Results show that the penetration depth of Ga ions having 30 keV energy in silicon is 28 nm and the radial range is 29.6 nm with 50 pA beam current. The application-oriented model has been verified by our focused ion beam-scanning electron microscopy (FIB-SEM) milling experiment and it will be a potential thermal source in simulating the process of FIB bombarding organic samples.

Fabrication and Characterization of Freestanding NiTi Based Thin Film Materials for Shape Memory Micro-actuator Applications

Thin film shape memory actuators fabricated by micro-system technology processes are of particular interest in micro-actuator applications due to their high work output, large displacements, and a comparably easy and compact system setup. Micro-system technology processes allow to deposit and structure ultra-precise parts from a wide range of alloys, among them alloys that are difficult to process with conventional fabrication techniques. However, sputtered NiTi based thin films are seldom deposited with thicknesses > 10 µm, which limits their range of application as well as makes the handling of freestanding films difficult. In this work, freestanding NiTi, NiTiCu, and NiTiHf shape memory structures were fabricated by means of sputtering, lithography, and wet etching, with a process that allows for thicknesses up to 80 µm. Their high cycle actuation behavior and microstructure were characterized. NiTiCu actuators show an excellent cyclic stability, resulting in high fatigue lives of > 108 cycles at 1.5% strain, even for stresses as high as 550 MPa. A distinct martensite/austenite interface is observed during transformation, in contrast to NiTi exhibiting a rather homogeneous transformation during heating and cooling throughout the sample volume. Sputtered NiTiHf actuators tested in air can reach fatigue lives as high as 1.5 × 106 cycles at 1% strain.

Measurements of phase shifts in YBCO transmission lines for evaluation of kinetic inductance change

We fabricated a coplanar waveguide (CPW) using high temperature superconductor YBa2Cu3O7-δ (YBCO) and evaluated its characteristics for the realization of a superconducting parametric amplifier. A YBCO thin film with a film thickness of 200 nm was formed by the PLD method using a YAG laser on a 10 × 10 mm MgO substrate. The YBCO thin films were processed into the CPW shape with a line width of 8 μm, a gap width of 8 μm and a line length of 5 mm by photolithography and sputter etching. Using a network analyzer, phase differences of microwave were measured at dc current bias from 0 mA to 14 mA. From the measurement results, it was found that the phase difference decreased with increasing temperature. In addition, it was found that the phase shifts greatly varied near the superconducting transition temperature at each current bias. We observed a maximum phase difference Δθ of -0.08 rad at a bias current of 14.0 mA, which is the closest to the transition temperature. A parametric gain was estimated to be 0.15 dB from the measured maximum phase difference.

The Hybrid Fabrication Process of Metal/Silicon Composite Structure for MEMS S&A Device.

The micro-electromechanical system (MEMS) safety-and-arming (S&A) device has the features of integration and miniaturization, which is one of the important directions of weapon development. Confined by the fabrication process, the silicon-based devices are too fragile, and the metal-based devices are low precision. In order to solve the contradiction between high precision and high structure strength, a metal/silicon composite structure is proposed in this paper, and a hybrid fabrication process is introduced. This new method mainly consists of metal sputtering, electroplating, and (inductively–coupled-plasma) ICP etching. As the resolution of the thick dry film is limited, the process of a femtosecond laser is applied to refine the structure, and the Ni plate (a block of 1 mm × 3 mm × 0.3 mm with a cavity of ϕ 0.85 mm × 0.3 mm in the center) is fabricated on the silicon-on-insulator (SOI) wafer successfully. After the double sides are etched by ICP, the SOI wafer is immersed in a buffered-oxide-etch (BOE) etchant to remove the buried layer. The cover plate acts as the encapsulation and is bonded with the SOI wafer by the epoxy glue. Then, the temporary support beam of the device is broken by the probe, and the suspended composite structure can be fully released. The hybrid process is the integration of the silicon-based process and the metal-based process, which can combine the advantages of both high precision and a high structure strength. The process proposed here is suitable for the application of weapon miniaturization.

Facile and precise fabrication of 10-nm nanostructures on soft and hard substrates

One of the major challenges in the field of nanotechnology is the facile and inexpensive fabrication of <10-nm nanostructures with a defect-free and precise pattern over a large area. Nanoimprint lithography (NIL) is a nanopatterning method that allows low-cost, fast production, and large-scale fabrication, but it needs improvement with regard to achieving a high resolution over a large area, processing on soft substrates, and nanomaterial patterning. Herein, it is demonstrated 10-nm patterning on soft and hard substrates via an advanced nanoimprint process. With a 100-nm master mold, both soft and hard molds with reduced pattern sizes (50, 20, 10, and 5 nm) are first fabricated using atomic layer deposition (ALD) of Al2O3. After surface functionalization of the mold, nanoscale patterns are imprinted on both hard (Si) and soft polyethylene terephthalate substrates, which result in structures with a pattern size of 10 nm. Using a hybrid supporting layer poly(methyl methacrylate) (PMMA)/poly(vinyl alcohol) (PVA) and ion sputter etching, a well-defined and clean sub-10 nm nanostructure is achieved for the nanomaterial on the substrate after lift-off and thermal annealing processes. Using this method, a graphene nanoribbon 10 nm wide is fabricated. Our approach is suitable for the fabrication of devices and structures with a 10-nm-scale pattern over a large area.

Thickness dependence of Al0.88Sc0.12N thin films grown on silicon

The thickening behavior of aluminum scandium nitride (Al0.88Sc0.12N) films grown on Si(111) substrates has been investigated experimentally using X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, and residual stress measurement. Al0.88Sc0.12N films were grown with thicknesses spanning 14 nm to 1.1 μm. TEM analysis shows that the argon sputter etch used to remove the native oxide prior to deposition produced an amorphous, oxygen-rich surface, preventing epitaxial growth. XRD analysis of the films show that the AlScN(002) orientation improves as the films thicken and the XRD AlScN(002) rocking curve full width half maximum decreases to 1.34° for the 1.1 μm thick film. XRD analysis shows that the unit cell is expanded in both the a- and c-axes by Sc doping; the a-axis lattice parameter was measured to be 3.172 ± 0.007 Å and the c-axis lattice parameter was measured to be 5.000 ± 0.001 Å, representing 1.96% and 0.44% expansions over aluminum nitride lattice parameters, respectively. The grain size and roughness increase as the film thickness increases. A stress gradient forms through the film; the residual stress grows more tensile as the film thickens, from −1.24 GPa to +8.5 MPa.

Progress in Understanding Initiation of Intergranular Corrosion on AA6005 Aluminum Alloy with Low Copper Content

As part of an extensive research program to study recent, unexpected intergranular corrosion (IGC) on 6xxx series aluminum alloys (AlMgSi), this paper investigates the mechanism of initiation and early propagation of IGC on the extruded AA6005-T5 alloy with small Cu content (0.1 wt%) by use of advanced electron microscopy techniques applied for near surface characterization. Corrosion testing was restricted to the accelerated IGC test according to the standard BS ISO 11846, involving exposure to acidified chloride solution. The effect of modifying the as-received extruded surface by metallographic polishing, argon sputtering, and alkaline etching was investigated. Initiation of IGC was delayed on the as-received surface compared to the modified surface, caused by the presence of an approximately 8 nm thick crystalline oxide layer formed during extrusion. IGC initiated at the primary α-Al(Fe,Cu,Mn)Si particles for all types of surfaces. However, these particles corroded rapidly in the test solution forming a residue of Cu and Si on the exposed particle surface. This phenomenon, as well as enrichment of Cu on the Al matrix surface by dealloying, contributed increasingly to the formation of new effective cathodic sites and continuing propagation of IGC. The AlMgSiCu (Q) phase, present as primary and secondary particles, was relatively inert against both oxidation and reduction.

Monte Carlo simulation of nanoscale material focused ion beam gas-assisted etching: Ga+ and Ne+ etching of SiO2 in the presence of a XeF2 precursor gas.

Elucidating energetic particle-precursor gas–solid interactions is critical to many atomic and nanoscale synthesis approaches. Focused ion beam sputtering and gas-assisted etching are among the more commonly used direct-write nanomachining techniques that have been developed. Here, we demonstrate a method to simulate gas-assisted focused ion beam (FIB) induced etching for editing/machining materials at the nanoscale. The method consists of an ion–solid Monte Carlo simulation, to which we have added additional routines to emulate detailed gas precursor–solid interactions, including the gas flux, adsorption, and desorption. Furthermore, for the reactive etching component, a model is presented by which energetic ions/target atoms, and secondary electrons, transfer energy to adsorbed gas molecules. The simulation is described in detail, and is validated using analytical and experimental data for surface gas adsorption, and etching yields. The method is used to study XeF2 assisted FIB induced etching of nanoscale vias, using both a 35 keV Ga+, and a 10 keV Ne+ beam. Remarkable agreement between experimental and simulated nanoscale vias is demonstrated over a range of experimental conditions. Importantly, we demonstrate that the resolution depends strongly on the XeF2 gas flux, with optimal resolution obtained for either pure sputtering, or saturated gas coverage; saturated gas coverage has the clear advantage of lower overall dose, and thus lower implant damage, and much faster processing.

Etch Control and SiGe Surface Composition Modulation by Low Temperature Plasma Process for Si/SiGe Dual Channel Fin Application

In this study, we discuss Si-SiGe etch characteristics as well as SiGe surface composition modification. It is required to etch Si and SiGe simultaneously for Si/SiGe dual channel Fin-FETs. Therefore, etch control of these two materials is desired. However, not only halogen chemistries but also physical sputtering etch SiGe selective to Si. We found that Si can be etched faster than SiGe by hydrogen plasma. Our analysis presents that hydrogen bonds selectively with Si rather than Ge, which leads to Si selective removal. As for SiGe surface modification, realizing Si-rich surface in SiGe is known to improve SiGe/high-k interface quality in advanced CMOS. It is also presented that the low-temperature hydrogen plasma induces Si-surface segregation (i.e., Si-rich surface) in SiGe, which is confined near the top-surface region. We proposed this may be caused by ion-energy-driven surface reaction. Our study also shows that Ge/Si ratio increases with plasma exposure time, which has correlation with surface roughness. Using the hydrogen plasma and conventional halogen plasma, we successfully demonstrate to etch Si/SiGe dual channel fins with depth and CD value control.

Multiple spin waves excitation modes observed in the Py film with antidots-like structure

A 2D antidots-like structure on 27.6 nm permalloy (Py) was fabricated by magnetic sputtering, photolithography and ion beam etching technology. By means of the ferromagnetic resonance (FMR) technique and micromagnetic simulation, we investigate the spin excitation in the antidots-like structure. The experimental results show that multiple resonance peaks were observed above the FMR peak, and the resonance frequencies show an unremarkable variation in the plane of the antidots-like structure. Micromagnetic simulation results verify the experiment results and further reveal the amplitude and phase of the resonance peaks. Remarkably, in this case, a well pronounced quantization spin wave mode can be excited. Meanwhile, based on the change of the phase of the spin wave, the propagate direction of the spin waves can be obtained.

Plasma nitriding of cone-shaped protrusions formed by sputter etching of AISI 420 stainless steel and their application to impression punch to form micro-holes on polymer sheets

Argon ion sputter-etching was applied to disk specimens of AISI type 420 martensitic stainless steel using a radio-frequency magnetron sputter-apparatus, and sharp cone-shaped protrusions with vertex angle of about 40° and base diameters less than 35 μm were formed. In order to increase compressive strength of protrusion tips without loss of sharpness, plasma-nitriding was applied to the as-sputter-etched specimens using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50 W for 1.8 ks. When the plasma-nitrided (PN-) and as-sputter-etched (AS-) specimens were statically impressed on polyethylene (PE) and polyvinylchloride (PVC) sheets by increasing the nominal stress step by step from 0.624 to 12.5 MPa, the protrusion tips of PN-specimen did not show bending deformation even at 12.5 MPa whereas those of AS-specimen revealed bending already at 2.2 MPa. When the PN-protrusions were impressed statically on a polycarbonate (PC) sheet, a part of tall protrusion tips were flattened, but the shape of the holes on the sheet was not distorted. The maximum hole-diameter on the PVC sheet is smaller than that of the PE and PC sheets due to a larger viscoelastic recovery of the PVC sheet. When the PN-protrusions were impressed repeatedly on the PE and PVC sheets one thousand times with nominal impression stress of 0.078 MPa, the tips did not show bending and very dense micro-holes were formed. On the other hand, a large bending of the AS-protrusion tips occurred by the repeated impression on the PVC sheet. Thus, the PN-specimen can be applied to an impression punch to form fine and dense holes on polymer sheets.

Development of PVDF-TrFE/SiO2 composite film bulk acoustic resonator

This paper reports a film bulk acoustic resonator (FBAR) using polyvinylidene fluoride- trifluoroethylene (PVDF-TrFE)/SiO2 composite. The PVDF-TrFE/SiO2 composite FBAR was designed, simulated and developed. A Micro Electro Mechanical Systems (MEMS) process including xenon difluoride (XeF2) release etching was adopted with some tuning for PVDF-TrFE. The influences of the process on the surface morphology and crystal orientation of PVDF-TrFE were evaluated for RIE, gold sputtering and XeF2 etching. After poling PVDF-TrFE, the thickness expansion mode was observed at 387–398 MHz. Impedance characteristics was evaluated using a modified Butterworth-Van Dyke (MBVD) model for a lossy piezoelectric transducer. Impedance ratio, coupling coefficient (k2), mechanical quality factor (Qm) and figure of merit increase with the radius of the device. The maximum Qm is 33 for 80 μm radius of the device. The residual film stress of PVDF-TrFE was estimated as 34.8 MPa in tensile mean stress and −79.7 kPa in gradient stress. Elastic stiffness constants c33D and c33E at electrical displacement D = 0 and electric field E = 0 were obtained as 4.45 GPa and 4.46 GPa, respectively.

Molecular dynamic simulation of orientation-dependent effect on silicon crystalline during sputtering process of focused ion beam

In this paper, experiments and molecular dynamic simulation are performed to investigate the crystal orientation-dependent effects in a focused ion beam (FIB) sputtering etching process on silicon crystal planes. The experimental results indicate that different silicon orientation planes have different etched profiles, aspect ratios on microstructures, and sputtering yields under the same process conditions, which brings difficulty in deciding the process parameters for the fabrication of high-resolution nanostructures. Molecular dynamic simulation based on empirical potential is carried out to explain this effect on an atomic scale. The sputtered profiles of different silicon crystal planes after hundreds of impacts by Ga+ ions are analyzed. Both the simulation and experimental results show that with the same FIB etching conditions, structures on an Si (111) plane have the maximum opening width and minimum depth. Compared with the etched profile on an Si (100) plane, trenches on Si (110) have a smaller width, but greater depth. The Si (111) plane has the minimum sputtering yield. Furthermore, simulation results on the distribution of Ga+ ions remaining inside the substrate, number of ions sputtered out of the surface, and common neighbor analysis (CNA) can explain the orientation-dependent effect during FIB sputtering etching.

Fabrication of microchannels in single crystal diamond for microfluidic systems

A growth of single crystal diamond (SCD) microchannels on HPHT diamond substrate has been carried out successfully by a simple and novel method. Firstly, aluminum film was patterned on SCD diamond substrate surface by magnetron sputtering, photolithography and dry etching techniques. Secondly, the aluminum patterns were transferred onto diamond substrate via inductively coupled plasma etching to form grooves on diamond surface. Finally, microchannels were achieved by epitaxial lateral overgrowth of SCD on the surface of prepared substrate by microwave plasma chemical vapor deposition system. After that, fluorescent liquid was introduced to check hollowness of the microchannels. This work provides a simple and time saving method to fabricate SCD microchannels for microfluidic system, which offers a great potential for hard environment applications.

Formation of Multiscale Protrusions on Commercially Pure Titanium and Stainless Steel by Two-Stage Sputter Etching Using Different Cathode Disks

Formation of Multiscale Protrusions on Commercially Pure Titanium and Stainless Steel by Two-Stage Sputter Etching Using Different Cathode Disks

Experimental Study of SiO2 Sputter Etching Process in 13.56 MHz rf-Biased Inductively Coupled Plasma

Inductively coupled plasma (ICP) has been widely used in semiconductor manufacturing, especially in nanoscale etching and deposition process. It is important to understand the relationship among the 13.56[Formula: see text]MHz rf-biased power and the etching process. In this study, the effect of dual rf power on the SiO2 sputter etching is investigated by measuring the ion energy distributions (IEDs), ion flux and sputter etching rate. The results show that the IEDs transforms from uni-modal towards bi-modal distribution when rf-biased power is applied to electrode. The influence of source power, bias power, discharge pressure and current ratio on the ion flux, IEDs are investigated in detail. The energy separations measured by RFEA are in good agreement with analytical model. The ion flux can be modulated by the 13.56[Formula: see text]MHz rf-biased power. Moreover, the coil current ratio expands the control window of the ion bombardment energy for the ICP etch equipment while. Finally, an ion-enhanced etching model is introduced to obtain the sputter etching rate and reveals the influence of discharge conditions on the etch rate.