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Application of UV-Vis Spectroscopy to the Monitoring, Characterization and Analysis of Chemical Equilibria of Copper Etching Baths

Description: The continuously increasing demand for innovation in the miniaturization of microelectronics has driven the need for ever more precise fabrication strategies for device packaging, especially for printed circuit boards (PCBs). Subtractive copper etching is a fundamental step in the fabrication process, requiring very precise control of etch rate and etch factor. Changes in the etching chemical equilibrium have significant effects on etching behavior, and CuCl2 / HCl etching baths are typically monitored with several parameters including oxidation-reduction potential, conductivity, and specific gravity. However, the etch rate and etch factor can be difficult to control even under strict engineering controls of those monitoring parameters. The mechanism of acidic cupric chloride etching, regeneration and recovery is complex, and the current monitoring strategies can have difficulty controlling the interlocking chemical equilibria. A complimentary tool, thin-film UV-Vis spectroscopy, can be utilized to improve the current monitoring strategies, as UV-Vis is capable of identifying and predicting etching behavior that the current standard methodologies have difficulty predicting. Furthermore, as a chemically-sensitive probe, UV-Vis can investigate the complex changes to the chemical equilibrium and speciation of the etch bath, and can contribute overall to significant improvements in the control of the copper etching system in order to meet the demands of next-level design strategies.
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Date: August 2017
Creator: Lambert, Alexander S
Partner: UNT Libraries

Modification of Graphene Properties: Electron Induced Reversible Hydrogenation, Oxidative Etching and Layer-by-layer Thinning

Description: In this dissertation, I present the mechanism of graphene hydrogenation via three different electron sources: scanning electron microscopy, e-beam irradiation and H2 and He plasma irradiation. in each case, hydrogenation occurs due to electron impact fragmentation of adsorbed water vapor from the sample preparation process. in the proposed model, secondary and backscattered electrons generated from incident electron interactions with the underlying silicon substrate are responsible for the dissociation of water vapor. Chemisorbed H species from the dissociation are responsible for converting graphene into hydrogenated graphene, graphane. These results may lead to higher quality graphane films having a larger band gap than currently reported. in addition, the dissertation presents a novel and scalable method of controllably removing single atomic planes from multi-layer graphene using electron irradiation from an intense He plasma under a positive sample bias. As the electronic properties or multi-layer graphene are highly dependent on the number of layers, n, reducing n in certain regions has many benefits. for example, a mask in conjunction with this thinning method could be used for device applications.
Date: May 2012
Creator: Jones, Jason David
Partner: UNT Libraries

Inductively Coupled Plasma Etching of III-V Semiconductors in BCl(3)-Based Chemistries: Part 1: GaAs, GaN, GaP, GaSb and AlGaAs

Description: BC13, with addition of Nz, Ar or Hz, is found to provide smooth anisotropic pattern transfer in GaAs, GaN, GaP, GaSb and AIGriAs under Inductively Coupled Plasma conditions, Maxima in the etch rates for these materials are observed at 33% N2 or 87$'40 Hz (by flow) addition to BC13, whereas Ar addition does not show this behavior. Maximum etch rates are typically much higher for GaAs, Gap, GaSb and AIGaAs (-1,2 @rein) than for GaN (-0.3 ymu'min) due to the higher bond energies of the iatter. The rates decrease at higher pressure, saturate with source power (ion flux) and tend to show maxima with chuck power (ion energy). The etched surfaces remain stoichiometric over abroad range of plasma conditions.
Date: December 4, 1998
Creator: Abernathy, C.R,; Han, J.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Lee, J.W. et al.
Partner: UNT Libraries Government Documents Department

Group-III Nitride Etch Selectivity in BCl(3)/Cl(2) ICP Plasmas

Description: Patterning the group-IH nitrides has been challenging due to their strong bond energies and relatively inert chemical nature as compared to other compound semiconductors. Plasma etch processes have been used almost exclusively to pattern these films. The use of high-density plasma etch systems, including inductively coupled plasmas (ICP), has resulted in relatively high etch rates (often greater than 1.0 pmhnin) with anisotropic profiles and smooth etch morphologies. However, the etch mechanism is often dominated by high ion bombardment energies which can minimize etch selectivity. The use of an ICP-generated BCl~/C12 pkyma has yielded a highly versatile GaN etch process with rates ranging from 100 to 8000 A/rnin making this plasma chemistry a prime candidate for optimization of etch selectivity. In this study, we will report ICP etch rates and selectivities for GaN, AIN, and InN as a function of BCl~/Clz flow ratios, cathode rf-power, and ICP-source power. GaN:InN and GaN:AIN etch selectivities were typically less than 7:1 and showed the strongest dependence on flow ratio. This trend maybe attributed to faster GaN etch rates observed at higher concentrations of atomic Cl which was monitored using optical emission spectroscopy (OES). ~E~~~~f:~ INTRODUCTION DEC j 4898 Etch selectivi
Date: December 9, 1998
Creator: Abernathy, C.R.; Han, J.; Hong, J.; Lester, L.F.; Pearton, S.J.; Shul, R.J. et al.
Partner: UNT Libraries Government Documents Department

Absolute Intensities of the Vacuum Ultraviolet Spectra in a Metal-Etch Plasma Processing Discharge

Description: In this paper we report absolute intensities of vacuum ultraviolet and near ultraviolet emission lines (4.8 eV to 18 eV ) for aluminum etching discharges in an inductively coupled plasma reactor. We report line intensities as a function of wafer type, pressure, gas mixture and rf excitation level. IrI a standard aluminum etching mixture containing C12 and BC13 almost all the light emitted at energies exceeding 8.8 eV was due to neutral atomic chlorine. Optical trapping of the WV radiation in the discharge complicates calculations of VUV fluxes to the wafer. However, we see total photon fluxes to the wailer at energies above 8.8 eV on the order of 4 x 1014 photons/cm2sec with anon- reactive wafer and 0.7 x 10 `4 photons/cm2sec with a reactive wtier. The maj ority of the radiation observed was between 8.9 and 9.3 eV. At these energies, the photons have enough energy to create electron-hole pairs in Si02, but may penetrate up to a micron into the Si02 before being absorbed. Relevance of these measurements to vacuum-W photon-induced darnage of Si02 during etching is discussed.
Date: December 9, 1998
Creator: Aragon, B.P.; Blain, M.G.; Hamilton, T.W.; Jarecki, R.L. & Woodworth, J.R.
Partner: UNT Libraries Government Documents Department

Stable, free-standing Ge nanocrystals

Description: Free-standing Ge nanocrystals that are stable under ambient conditions have been synthesized in a two-step process. First, nanocrystals with a mean diameter of 5 nm are grown in amorphous SiO{sub 2} by ion implantation followed by thermal annealing. The oxide matrix is then removed by selective etching in diluted HF to obtain free-standing nanocrystals on a Si wafer. After etching, nanocrystals are retained on the surface and the size distribution is not significantly altered. Free-standing nanocrystals are stable under ambient atmospheric conditions, suggesting formation of a self-limiting native oxide layer. For free-standing as opposed to embedded Ge nanocrystals, an additional amorphous-like contribution to the Raman spectrum is observed and is assigned to surface reconstruction-induced disordering of near-surface atoms.
Date: January 28, 2005
Creator: Sharp, I.D.; Xu, Q.; Liao, C.Y.; Yi, D.O.; Beeman, J.W.; Liliental-Weber, Z. et al.
Partner: UNT Libraries Government Documents Department

Triode cathodic vacuum etcher for the low-voltage polishing and etching of metallographic specimens

Description: From international metallography society symposium on specimen preparation for metallography; Los Angeles. California, USA (23 Sep 1973). A triode cathodic vacuum etcher has been developed that has a number of advantages over conventional diode etchers. The triode etcher can be operated at specimen voltages well below 1000 V(dc) to minimize mount deterioration and the danger of arcing to the etched surface. Etching voltage and current density can be independently varied so that high current densities can be used with low voltages to provide rapid etching rates while minimizing heating of the specimen. Also. redeposition of sputtered material on the etched surface is reduced because of the low operating pressure (<3 millitorr) of the triode system. At very low voltages (75 to 125 V(dc)) the etching rate is relatively insensitive to crystalline orientation and a polishing action is obtained. This permits the removal of deformed surface layers and even such gross surface defects as the scratches from 600-grit paper without producing significant surface relief. This ion polishing capability has been used to reveal the pore structure of UO/sub 2/ and UO/sub 2/-PuO/sub -specimens by removing surface flow material without enlarging the pores. Details of the design and operation of a simple, inexpensive triode eathodic vacuum etcher are presented and its ion polishing and etching capabilities are illustrated for a variety of materials including copper, plutonium, samarium, and uranium oxide. (auth)
Date: September 13, 1973
Creator: Arrowsmith, H. W. & Allen, R. P.
Partner: UNT Libraries Government Documents Department

Inductively Coupled Plasma Etching of III-V Semiconductors in BCl(3)-Based Chemistries: Part II: InP, InGaAs, InGaAsP, InAs and AllnAs

Description: A parametric study of etch rates and surface morphologies of In-containing compound semiconductors (InP, InGaAs, InGaAsP, InAs and AlInAs) obtained by BClj-based Inductively Coupled Plasmas is reported. Etch rates in the range 1,500-3,000 &min. are obtained for all the materials at moderate source powers (500 W), with the rates being a strong function of discharge composition, rf chuck power and pressure. Typical root-mean-square surface roughness of-5 nm were obtained for InP, which is worse than the values obtained for Ga-based materials under the same conditions (-1 run). The near surface of etched samples is typically slightly deficient in the group V element, but the depth of this deficiency is small (a few tens of angstroms).
Date: December 2, 1998
Creator: Abernathy, C.R.; Han, J.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Lee, J.W. et al.
Partner: UNT Libraries Government Documents Department

ICP Etching of SiC

Description: A number of different plasma chemistries, including NF{sub 3}/O{sub 2}, SF{sub 6}/O{sub 2}, SF{sub 6}/Ar, ICl, IBr, Cl{sub 2}/Ar, BCl{sub 3}/Ar and CH{sub 4}/H{sub 2}/Ar, have been investigated for dry etching of 6H and 3C-SiC in a Inductively Coupled Plasma tool. Rates above 2,000 {angstrom} cm{sup {minus}1} are found with fluorine-based chemistries at high ion currents. Surprisingly, Cl{sub 2}-based etching does not provide high rates, even though the potential etch products (SiCi{sub 4} and CCl{sub 4}) are volatile. Photoresist masks have poor selectivity over SiC in F{sub 2}-based plasmas under normal conditions, and ITO or Ni are preferred.
Date: February 4, 1999
Creator: Grow, J.M.; Lambers, E.S.; Ostling, M.; Pearton, S.J.; Ren, F.; Shul, R.J. et al.
Partner: UNT Libraries Government Documents Department

Final Report: Free Standing Quantum Wells, August 15, 1996 - May 31, 1999

Description: Recent advances in microfabrication techniques in conjunction with the precise growth of layers of single crystalline materials by epitaxial growth techniques allow the creation of new electro-optic microstructures. We have selectively etched compositionally modulated 111-v heterostructures to produce quantum wells (QW's) which are confined on both sides by air or vacuum. The material is patterned so to have the QW's suspended horizontally between vertical support posts. This structure is ideal for probing the local properties of solids, e.g., the interaction of quantum confined states with surface or interface states.
Date: October 11, 1999
Creator: Williams, M.D.; Lee, H.W.H. & Collins, J.
Partner: UNT Libraries Government Documents Department

High-Density Plasma-Induced Etch Damage of GaN

Description: Anisotropic, smooth etching of the group-III nitrides has been reported at relatively high rates in high-density plasma etch systems. However, such etch results are often obtained under high de-bias andlor high plasma flux conditions where plasma induced damage can be significant. Despite the fact that the group-III nitrides have higher bonding energies than more conventional III-V compounds, plasma-induced etch damage is still a concern. Attempts to minimize such damage by reducing the ion energy or increasing the chemical activity in the plasma often result in a loss of etch rate or anisotropy which significantly limits critical dimensions and reduces the utility of the process for device applications requiring vertical etch profiles. It is therefore necessary to develop plasma etch processes which couple anisotropy for critical dimension and sidewall profile control and high etch rates with low-damage for optimum device performance. In this study we report changes in sheet resistance and contact resistance for n- and p-type GaN samples exposed to an Ar inductively coupled plasma (ICP). In general, plasma-induced damage was more sensitive to ion bombardment energies as compared to plasma flux. In addition, p-GaN was typically more sensitive to plasma-induced damage as compared to n-GaN.
Date: April 29, 1999
Creator: Baca, A.G.; Han, J.; Lester, L.F.; Pearton, S.J.; Ren, F.; Shul, R.J. et al.
Partner: UNT Libraries Government Documents Department

Effect of Inert Gas Additive Species on Cl(2) High Density Plasma Etching of Compound Semiconductors: Part 1. GaAs and GaSb

Description: The role of the inert gas additive (He, Ar, Xe) to C12 Inductively Coupled Plasmas for dry etching of GaAs and GaSb was examined through the effect on etch rate, surface roughness and near-surface stoichiometry. The etch rates for both materials go through a maximum with Clz 0/0 in each type of discharge (C12/'He, C12/Ar, C12/Xc), reflecting the need to have efficient ion-assisted resorption of the etch products. Etch yields initially increase strongly with source power as the chlorine neutral density increases, but decrease again at high powers as the etching becomes reactant-limited. The etched surfaces are generally smoother with Ax or Xe addition, and maintain their stoichiometry.
Date: December 23, 1998
Creator: Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Jung, K.B.; Pearton, S.J. et al.
Partner: UNT Libraries Government Documents Department

Inductively Coupled Plasma and Electron Cyclotron Resonance Plasma Etching of InGaAlP Compound Semiconductor System

Description: Current and future generations of sophisticated compound semiconductor devices require the ability for submicron scale patterning. The situation is being complicated since some of the new devices are based on a wider diversity of materials to be etched. Conventional IUE (Reactive Ion Etching) has been prevalent across the industry so far, but has limitations for materials with high bond strengths or multiple elements. IrI this paper, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma), for the etching of ternary compound semiconductors (InGaP, AIInP, AlGaP) which are employed for electronic devices like heterojunction bipolar transistors (HBTs) or high electron mobility transistors (HEMTs), and photonic devices such as light-emitting diodes (LEDs) and lasers. High density plasma sources, opeiating at lower pressure, are expected to meet target goals determined in terms of etch rate, surface morphology, surface stoichiometry, selectivity, etc. The etching mechanisms, which are described in this paper, can also be applied to other III-V (GaAs-based, InP-based) as well as III-Nitride since the InGaAIP system shares many of the same properties.
Date: November 4, 1998
Creator: Abernathy, C.R.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Pearton, S.J. & Shul, R.J.
Partner: UNT Libraries Government Documents Department

Minotauromachy

Description: No Description Available.
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: 1935
Creator: Picasso, Pablo, 1881-1973
Partner: UNT College of Visual Arts + Design

Inductively Coupled Plasma Reactive Ion Etching of AlGaAsSb and InGaAsSb for Quaternary Antimonide MIM Thermophotovoltaics

Description: In this letter we report on the inductively coupled plasma reactive ion etching (ICP-RIE) of InGaAsSb and AlGaAsSb for the fabrication of quaternary monolithic interconnected module (MIM) thermophotovoltaic (TPV) devices. A rapid dry etch process is described that produces smooth surfaces using BCl[sub]3 for AlGaAsSb and InGaAsSb capped with GaSb. Uncapped InGaAsSb was etched by adding an H[sub]2 plasma preclean to reduce surface oxides. InGaAsSb etch rate was studied as a function of accelerating voltage, RF power, temperature and pressure. The etch conditions found for InGaAsSb were used for AlGaAsSb etching to determine the effectiveness for isolation of the MIM cells.
Date: October 2002
Creator: Palmisiano, M. N.; Peake, G. M.; Shul, R. J.; Ashby, C. I.; Cederberg, J. G.; Hafich, M. J. et al.
Partner: UNT Libraries Government Documents Department

WSi2/Si Multilayer Sectioning by Reactive Ion Etching for Multilayer Laue Lens Fabrication

Description: SPIE Conference paper/talk presentation: Introduction: Reactive ion etching (RIE) has been employed in a wide range of fields such as semiconductor fabrication, MEMS (microelectromechanical systems), and refractive x-ray optics with a large investment put towards the development of deep RIE. Due to the intrinsic differing chemistries related to reactivity, ion bombardment, and passivation of materials, the development of recipes for new materials or material systems can require intense effort and resources. For silicon in particular, methods have been developed to provide reliable anisotropic profiles with good dimensional control and high aspect ratios1,2,3, high etch rates, and excellent material to mask etch selectivity...
Date: August 1, 2010
Creator: Bouet, N.; Conley, R.; Biancarosaa, J.; Divanc, R. & Macrander, A. T.
Partner: UNT Libraries Government Documents Department

Electrical Characterization of Etched Grain-Boundary Properties from As-Processed px-CdTe Based Solar Cells

Description: An ability to lift off or separate the thin-film polycrystalline CdTe from the CdS, without the use of chemical etches, has enabled direct electrical characterization of the as-processed CdTe near the CdTe/CdS heterointerface. We use this ability to understand how a back-contact, nitric-phosphoric (NP) etch affects the grain boundaries throughout the film. Quantitative determination of the grain-boundary barrier potentials and estimates of doping density near the grain perimeter are determined from theoretical fits to measurements of the current vs. temperature. Estimates of the bulk doping are determined from high-frequency resistivity measurements. Also, a variable doping density within the grains of non-etched material has been determined. These results allow a semi-quantitative grain-boundary band diagram to be drawn that should aid in determining more-accurate two-dimensional models for polycrystalline CdTe solar cells.
Date: October 22, 1998
Creator: Woods, L. M.; Robinson, G. Y. (Colorado State University, Ft. Collins, CO) & Levi, D. H. (National Renewable Energy Laboratory) Kaydanov, V. (Colorado School of Mines, Golden, CO)
Partner: UNT Libraries Government Documents Department

A structure zone diagram including plasma based deposition and ion etching

Description: An extended structure zone diagram is proposed that includes energetic deposition, characterized by a large flux of ions typical for deposition by filtered cathodic arcs and high power impulse magnetron sputtering. The axes are comprised of a generalized homologous temperature, the normalized kinetic energy flux, and the net film thickness, which can be negative due to ion etching. It is stressed that the number of primary physical parameters affecting growth by far exceeds the number of available axes in such a diagram and therefore it can only provide an approximate and simplified illustration of the growth condition?structure relationships.
Date: October 14, 2009
Creator: Anders, Andre
Partner: UNT Libraries Government Documents Department