Etch Rate Measurements Research Articles

New architecture of 3D graphene with enhanced properties obtained by cold rolling

Previously, we reported 3D Shaped 3D Graphene (3D2G) with controlled structural design. In this work, we introduced cold rolling as a post-processing technique to obtain compressed 3D2G, referred here as C3D2G, and investigated the relationship between its microstructure and properties. The performed comprehensive materials characterization of C3D2G revealed the micro-motion of the graphene flakes from their random orientations into a stacked and aligned structure along with the extrusion of bulk material into the structural pores which acted as stress-relief spaces. The obtained new bulk morphology significantly enhanced its properties. The achieved gravimetric density, electrical conductivity, and tensile strength of C3D2G were higher than 3D2G by 37.3, 53.4, and 24.9 times, respectively. A new process was demonstrated based on the observed extrusion enabling the welding of multiple pieces of 3D2G into one structure via cold rolling, thus showing potential for dimensional scaling up. The conducted tensile and electrical conductivity studies across the welded region revealed the presence of a mechanical bond within the joined area with a higher strength than the initial pieces involved in welding. Further, a unique application of this material was explored as a reusable, etch-resistant hard mask for patterning silicon wafers, and as a protective barrier against fluorine plasma environment. The etch rate measurements showed a higher etching resistance of C3D2G compared to Si and SiO2 when exposed to a fluorine plasma Reactive Ion Etching (RIE).

Control of silicon dioxide etching rate in hydrogen microwave plasma by addition of oxygen

Hydrogen plasma treatment of thin films and bulk silica is important process for surface cleaning, smoothing and patterning. We studied etching of SiO2 plates in H2 + O2 microwave plasma at moderate pressures at high temperatures in the range of 790–1300 °C. A low-coherent optical interferometer was used for simultaneous in situ measurement of etch rate (ER) and the SiO2 temperature. We show that even a small addition of O2 (<1%) in microwave H2 plasma can effectively reduce the SiO2 ER due to redox reaction. Using an optical profilometry and atomic force microscopy we observed not only a strong etching inhibition by O2 addition in gas, but a significantly smoother etched surface as well. The activation energies Ea = 128 ± 8 kJ/mol and 276 ± 23 kJ/mol are found for the etching in pure H2 and H2 + 0.4 %O2 plasmas, respectively. An exponential dependence of ER on O2 content in gas is established, particularly, the O2 concentration as small as 2.6 % is sufficient to reduce the ER by 100 times. The effect of oxygen induced etching slow-down is supported by thermodynamic consideration of the surface reactions involved. The experiments were complimented with the plasma diagnostics by optical emission plasma spectroscopy to detect volatile etching products, and other species such as OH, and correlate the Si emission intensity with the measured ER. Our results confirm the efficiency of oxygen to control in a wide range the etch rate and surface topography upon atomic hydrogen etching in a microwave plasma.

Effect of Dissolved Oxygen on Removal of Benzotriazole from Co during a Post-Co CMP Cleaning

A systematic study of the adsorption of benzotriazole on Co surface and its removal in aqueous solutions was carried out for post-CMP cleaning application. Static etch rate (SER) measurements and electrochemical impedance spectroscopy (EIS) were employed. The experimental results show that BTA adsorbed well on Co surface when it exposed to BTA solution at neutral and alkaline pH. BTA did not adsorb due to active Co dissolution at acidic pH. The effect of dissolved oxygen (DO) concentration in de-ionized (DI) water on the removal of Co-BTA complex layer was investigated. At DI water rinse process after BTA treatment, Co-BTA layer was maintained on Co surface when DO concentration of DI water was low. Interestingly, BTA was removed by DI water with high DO concentration.

PLASMA PARAMETERS AND SiO2 ETCHING KINETICS IN C4F8 + Ar + O2 GAS MIXTURE

The effect of Ar/O2 mixing ratio on plasma parameters, steady-state densities of active species and SiO2 etching kinetics in the three-component C4F8+Ar+O2 gas mixture was studied under typical conditions of reactive ion etching process (inductive 13.56 MHz RF discharge, total gas pressure of 6 mTorr, input power of 700 W and bias power of 200 W). The investigation combined etching rate measurements, plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling in order to determine steady-state densities and fluxes of plasma active species. It was found that the full substitution of Ar for O2 at constant fraction of fluorocarbon gas (in fact, the transition from 50% C4F8 + 50% Ar to 50% C4F8 + 50% O2 gas system): 1) results in weakly non-monotonic (with a maximum) SiO2 etching rate with close values for both O2-free and Ar-free plasmas; 2) causes the monotonic decrease in both F atom flux and ion energy flux; and 3) suppresses the formation of the fluorocarbon polymer film on the etched surface through its oxidative destruction pathway. The model-based analysis of SiO2 etching kinetics allowed one to conclude that an increase in effective probability for SiO2 + F reaction contradicts with the behavior ion energy flux as well as demonstrate the agreement with the change in gas-phase parameters characterizing the fluorocarbon film thickness. Therefore, an increase in O2 content in a feed gas influences the effective reaction probability by decreasing fluorocarbon film thickness and providing better access of F atoms to the etched surface.

(Invited) Top-Down Etching of III-Nitride Nanostructures

Chemical etch processes for III-nitride (AlGaInN) materials and devices are significantly underdeveloped due to its apparent inertness to common wet etchants. To fully realize the potential of the III-nitrides in new electronic and photonic nano and micro device concepts, a more complete knowledge and development of anisotropic and three-dimensional top-down etch techniques are needed. Here, we explore the etch characteristics of GaN and AlGaN based materials using the general geometric principles of crystallographic dissolution processes to enable the prediction of facet-determined etch structures, including high aspect ratio nanowires and nanowalls. We perform the first complete nonpolar orientation-dependent etch rate measurements for GaN, and use them to predict the faceting of pillar structures with good agreement with experiment. We use these developments in wet etching to fabricate functional III-nitride-based optical nanowire and microcavity structures with control over the cross-sectional shape, where faceting enables sidewalls with near atomic-smoothness. Finally, we discuss a new fabrication method, quantum-size controlled photoelectrochemical etching, for the etching of InGaN quantum dots with high size uniformity from planar InGaN films.

193\xa0nm ArF laser ablation and patterning of chitosan thin films

This paper reports laser ablation studies on spin-coated biopolymer chitosan films, β-l,4-1inked 2-amino-2-deoxy-d-glucopyranose. Chitosan has been irradiated using an ArF laser emitting at 193 nm. An ablation threshold of FT = 85±8 mJ cm−2 has been determined from etch rate measurements. Laser-ablated chitosan is characterised using white light interferometry, scanning electron microscopy, and thermo-gravimetric analysis. Laser ablation of chitosan is discussed in terms of thermal and photoacoustic mechanisms. Heat transfer is simulated to assist in the understanding of laser-irradiated chitosan using a finite-element method and the software package COMSOL Multi-Physics™. As a demonstrator, a micro-array of square structures in the form of a crossed grating has been fabricated by laser ablation using a mask projection scanning method. The initial investigations show no evidence of thermal damage occurring to the adjacent chitosan when operating at a moderately low laser fluence of 110 mJ cm−2.

Characterization of saturation of CR-39 detector at high alpha-particle fluence

Abstract The occurrence of saturation in the CR-39 detector reduces and limits its detection dynamic range; nevertheless, this range could be extended using spectroscopic techniques and by measuring the net bulk rate of the saturated CR-39 detector surface. CR-39 detectors were irradiated by 1.5 MeV high alpha-particle fluence varying from 0.06 × 108 to 7.36 × 108 alphas/cm2 from Am-241 source; thereafter, they were etched in a 6.25N NaOH solution at a temperature of 70°C for different durations. Net bulk etch rate measurement of the 1.5 MeV alpha-irradiated CR-39 detector surface revealed that rate increases with increasing etching time and reaches its maximum value at the end of the alpha-particle range. It is also correlated with the alpha-particle fluence. The measurements of UV–Visible (UV–Vis) absorbance at 500 and 600 nm reveal that the absorbance is linearly correlated with the fluence of alpha particles at the etching times of 2 and 4 hour. For extended etching times of 6, 10, and 14.5 hour, the absorbance is saturated for fluence values of 4.05 × 108, 5.30 × 108, and 7.36 × 108 alphas/cm2. These new methods pave the way to extend the dynamic range of polymer-based solid state nuclear track detectors (SSNTDs) in measurement of high fluence of heavy ions as well as in radiation dosimetry.

Dopant induced polarity inversion in polar ZnO nanorods

Highly oriented and polarity controlled ZnO nanorod thin films are deposited by chemical bath deposition where the preferred polarity depends on the anionic nature of the Zn salt. Significant differences are noticed in magnesium (Mg) doping concentration on Zn- and O-polar ZnO nanorods. Higher doping concentration is achieved in Zn polar nanorods, which is characterized with different spectroscopic techniques. A noteworthy contribution in morphological changes is noted upon by Mg doping on both Zn- and O-polar ZnO nanorods. Polarity inversion of the individual nanorods are found at certain doping condition, characterized by chemical etching rate measurements and Schottky Barrier Height determination of the individual nanorod.

Nonlinear photooxidation of diamond surface exposed to femtosecond laser pulses

We present an experimental investigation of photooxidation of a diamond surface exposed to femtosecond laser pulses that induce transient high concentrations of free carriers (>1022cm−3) while the lattice stays cold. Etching rate measurements and a laser-induced plasma study indicated that the rate of desorption of carbon species is proportional to the square of the induced plasma density, which contrasts with previous investigations of diamond etching by nanosecond pulses. We discuss how laser-induced ionization of diamond occurs and how it affects the photoreaction mechanism.

Measurements and modeling of the impact of weak magnetic fields on the plasma properties of a planar slot antenna driven plasma source

The radial line slot antenna plasma source is a type of surface wave plasma source driven by a planar slot antenna. Microwave power is transmitted through a slot antenna structure and dielectric window to a plasma characterized by a generation zone adjacent to the window and a diffusion zone that contacts a substrate. The diffusion zone is characterized by a very low electron temperature. This renders the source useful for soft etch applications and thin film deposition processes requiring low ion energy. Another property of the diffusion zone is that the plasma density tends to decrease from the axis to the walls under the action of ambipolar diffusion at distances far from where the plasma is generated. A previous simulation study [Yoshikawa and. Ventzek, J. Vac. Sci. Technol. A 31, 031306 (2013)] predicted that the anisotropy in transport parameters due to weak static magnetic fields less than 50 G could be leveraged to manipulate the plasma profile in the radial direction. These simulations motivated experimental tests in which weak magnetic fields were applied to a radial line slot antenna source. Plasma absorption probe measurements of electron density and etch rate showed that the magnetic fields remote from the wafer were able to manipulate both parameters. A summary of these results is presented in this paper. Argon plasma simulation trends are compared with experimental plasma and etch rate measurements. A test of the impact of magnetic fields on charge up damage showed no perceptible negative effect.

Bulk Etch Rate Measurement of Cr-39 Detector at Constant Normality Using The Diameters and The Lengths of The Tracks of Α-Particles

The aim of this paper is to determine the bulk etch rate of Nuclear Track Detector (type CR-39) using the track’s diameter-length (Le-D) measurement method by irradiating the detector with different energies of alpha particles from 241Am source. Constant normality (6.25) N of the chemical solution NaoH at a temperature of (70±1) oC is used in etching the detectors to measure the track’s lengths and it’s diameter at different etching times corresponding to the energy of the incident’s particles. The bulk etch rate VB values of CR-39 detector have been found by using Le-D method are (1.4228, 1.2563, 1.5098, 1.438) µm.hr-1 and they showed good agreement with the values measured by the removed layer method which were (0.944-1.831) µm.hr-1.

Decrease in reflectance of vertically-aligned carbon nanotubes after oxygen plasma treatment

Oxygen plasma treatment was used to lower the reflectance of multiwall vertically-aligned carbon nanotubes (VACNT). Specular reflectance measurements at an incident angle of 65° from normal show a decrease in reflectance over the wavelength range of 250-2500 nm, with up to 5 times lower reflectance at long wavelengths. Total hemispherical reflectance measurements show a decrease in reflectance from 300-2400 nm, with up to 8 times lower reflectance at short wavelengths. Etch rate measurements and helium ion microscopy reveal that the oxygen plasma reduces the reflectance of VACNT by modifying the surface morphology, characterized by etching away the top layer and inducing agglomeration of nanotube tips.

Micro-track structure analysis for 100 MeV Si ions in CR-39 by using atomic force microscopy

To analyze the micro-track structure of heavy ions in a polymer material, parameters including bulk etch rate, track etch rate, etch rate ratio, and track core size were measured. The pieces of CR-39 were exposed to 100 MeV Si ions with normal incidence and were etched in 6.25N NaOH solution at 70 °C. Bulk etch rate was read out by a profilemeter after several hours of etching. The other parameters were obtained by using an atomic force microscope (AFM) after a short time of etching. We have measured the second etch pits and minute etch pits to obtain the track growth curve and three dimension track structures to track the core size and etch rate measurements. The local dose of the track core was calculated by the δ-ray theory. In our study, we figure out that the bulk etch rate Vb = (1.58 ± 0.022) μm/h, the track etch rate Vt = (2.90 ± 0.529) μ.m/h, the etch rate ratio V = 1.84 ± 0.031, and the track core radii r ≍ 4.65 nm. In the meantime, we find that the micro-track development violates the traditional track-growth model. For this reason, a scenario is carried out to provide an explanation.

Excimer laser ablation of thick SiOx-films: Etch rate measurements and simulation of the ablation threshold

Excimer laser ablation of 4.5 μm thick SiOx-films with x ≈ 1 is investigated at 193 nm, 248 nm, and 308 nm. Strong absorption enables precisely tunable removal depths. The ablation rates correlate with laser penetration depths calculated from low level absorption coefficients. The experimental ablation thresholds are in agreement with numerical simulations on the basis of linear absorption and one-dimensional heat flow. This behaviour is similar to that of strongly UV-absorbing polymers, leading to well controllable micro machining prospects. After laser processing, SiOx can be converted to SiO2, opening a route to laser based fabrication of micro optical components.

Comparison between different models for alpha-particle range determination and a new approach to CR-39 detector

An extensive study was carried out to compare different models and a new approach for measuring the alpha-particle range in the CR-39 detector. The CR-39 samples were exposed perpendicularly to alpha particles with energies ranging from 2.5 MeV to 5.5 MeV emitted from 241Am. The CR-39 samples were etched in 7.25 N NaOH at (70 ± 0.5) °C for different durations. Both the track diameters and the track cone lengths were measured under an optical microscope. The new approach is based on measurement of the track etch rate along the particle’s trajectory as a function of the removal thickness (h). A correlation was found to exist between the removal thickness at the maximum track etch rate (V Tmax ) and the range of alpha particles in the CR-39 detector. The track etch rate data were fitted using the function V T (h) = a 1 + [a 2 − a 3 h]exp[a 4 h]. The ranges of alpha particles were determined by setting the first order derivative of the fitting function equal to zero, where h is equal to the range of the alpha particles (R) in the CR-39 detector. Furthermore, the range of the alpha particle in the CR-39 detector was measured using the over-etched track diameter and the track cone length. The theoretical predictions of the alpha-particle ranges were calculated using the SRIM software. A well-known function, R(E) = b 1 E b2, was used to fit the experimental results and the theoretical predictions. Experiments showed that the determination of the alpha-particle range based on the cone length model was in a good agreement with the theoretical calculations, where the discrepancy was less than that for the over-etched track diameter and the maximum track etch rate models.

Effect of Alkaline pH on Polishing and Etching of Single and Polycrystalline Silicon

In this paper, the polishing and etching behavior of single and polycrystalline silicon were studied. Prior to chemical mechanical polishing (CMP) process, the surfaces were treated with dilute hydrofluoric acid (DHF) to remove native oxides. The surface analysis shows that the poly contains trace amount of oxygen even after DHF treatment. The static and dynamic etch rates, and removal rates were measured as a function of slurry pH. The single silicon showed a higher static etch rate than the poly. After static etch rate measurements, poly showed higher surface roughness and more hydrophilic which indicates that the surface of poly is different from single crystal silicon. The friction force between pad and substrate and pad temperature was also measured as a function of pH during polishing in order to get more understanding of polishing process. At all the pH values being investigated, poly showed lower dynamic and removal rates, higher friction force and higher temperature. This indicates that the removal of poly in CMP is predominantly by mechanical actions. Also, these results, suggest a mechanism in which the oxygen present in the poly grain boundaries strongly influences the etching and removal mechanism.

On the Fate of Tritium in Nickel

Uptake, distribution, and release behavior of tritium in Ni was investigated by chemical etching and thermal release rate measurements. Liberated tritium was found to consist almost exclusively of tritiated water. The chronic release rate of tritium from Ni was significantly larger than that from type 316 stainless steel. Depth profiles in specimens that partially lost tritium due to its chronic release into vacuum, air or a stream of argon could be reproduced by a one-dimensional diffusion model using best fit diffusion coefficients. Values of the best-fit diffusion coefficients at 298 K were found to be independent from the ambient into which tritium was released. The average diffusion coefficient from all measurements at 298 K, i.e. (2.7 ± 1.3) × 10-10 [cm2/s] was in line with diffusion coefficients calculated from literature data at the same temperature. Hence, the diffusion model constitutes a useful tool for the prediction of tritium bulk depth profiles in Ni during chronic release (CR).

Method of analyzing silicon groove damage using QSS‐PC, PL imaging, silicon etch rate, and visual microscopy for solar cell fabrication

AbstractThis work uses a variety of tools to investigate damage caused by laser and dicing saw grooving in silicon. The tools comprise quasi steady state photoconductance decay, photoluminescence imaging, measurement of silicon etch rate in anisotropic etch solution, and visual microscopy. Shallow grooves were formed using a 532 nm Q‐switched Nd:YLF frequency doubled solid state laser and a high speed spindle dicing saw. Combined analysis of the characterization tools enabled determination of the damage radius of the grooves within the bulk of the wafer, the radius of damage in the dielectric layer laterally along the surface of the wafer, as well as the groove etching requirements to fully recover the minority carrier lifetime in the vicinity of the groove. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Automatic real-time guidance of laser machining with inline coherent imaging

Optical coherence imaging can measure hole depth in real-time (&amp;gt;20 kHz) during laser drilling without being blinded by intense machining light or incoherent plasma emissions. Rapid measurement of etch rate and stochastic melt relaxation makes these images useful for process development and quality control in a variety of materials including metals, semiconductors, and dielectrics. The ability to image through the ablation crater in materials transparent to imaging light allows the guidance of blind hole cutting even with limited a priori knowledge of the sample. Significant improvement in hole depth accuracy with the application of manual feedback from this imaging has been previously demonstrated [P. J. L. Webster et al., Opt. Lett. 35, 646 (2010)]. However, the large quantity of raw data and computing overhead are obstacles for the application of coherent imaging as a truly automatic feedback mechanism. Additionally, the high performance components of coherent imaging systems designed for their traditional application in biological imaging are costly and may be unnecessary for materials processing. In this work, we present a coherent imaging system design that costs less than a fifth of comparable commercial products. We also demonstrate streamlined image processing suited for automated feedback that increases processing speed by two orders of magnitude.

RF sputtering of epitaxial lead chalcogenide films in argon and krypton plasma

The measurements of sputtering etch rates for monocrystalline (1 1 1)-oriented epitaxial films of semiconductor binary compounds PbTe, PbSe, PbS in RF high-density low-pressure inductively coupled argon and krypton plasma were performed. Films with 1–5 µm thickness were grown on Si(1 1 1) and BaF2(1 1 1) substrates using molecular beam epitaxy. Sputtering was carried out with the energy of Ar+ and Kr+ ions of 20–400 eV. The sputtering etch rates of the binary lead chalcogenides are demonstrated to have abnormally high values in comparison with the basic semiconductor materials of microelectronics. The sputtering yield values for PbTe, PbSe, PbS for the average energy of the argon ions of 200 eV are practically equal (0.46 ± 0.05 molecule/ion) and vary linearly with the variation of the ion energy. Substitution of the plasma discharge gas from the argon to krypton does not result in a significant change in the sputtering yield of lead chalcogenides. The physical principles of the observed phenomena are discussed.