Reactive Ion Etching Of Si Research Articles

An examination of the performance of molecular dynamics force fields: Silicon and silicon dioxide reactive ion etching

Classical molecular dynamics (MD) simulations of plasma-surface interactions were performed of physical sputtering and reactive ion etching (RIE), with predictions based on several force fields. In this paper, we focus mainly on SiO2 but include some results for Si substrates as well. We compare predictions from these MD simulations to experimental studies of SiO2 physical sputtering (by Ar+ ions), RIE of Si, and RIE of SiO2 (both using F atoms and Ar+ ions). MD results using different published force fields are compared to reported yields from published vacuum beam experiments. The near-surface depth profiles predicted using different force fields are compared. One motivation for the present study is to document the nature and magnitude of differences in the predictions for selected systems and conditions of practical interest.

Specific Features of the Kinetics of the Reactive-Ion Etching of Si and SiO2 in a CF4 + O2 Mixture in a Low Power Supply Mode

Specific Features of the Kinetics of the Reactive-Ion Etching of Si and SiO2 in a CF4 + O2 Mixture in a Low Power Supply Mode

Molecular dynamics simulation for reactive ion etching of Si and SiO2 by SF5+ ions

Silicon (Si)-based materials such as Si and silicon dioxide (SiO2) are commonly used as basic components of advanced semiconductor devices. For example, alternating stacks of poly-Si and SiO2 layers are used in three-dimensional (3D) NAND flash memory devices. Fabrication of high-aspect-ratio deep holes through such stacked materials by plasma etching may be achieved by highly energetic and chemically reactive ion injections to the surface. Etching by sulfur hexafluoride (SF6) plasmas can produce ions carrying multiple fluorine (F) atoms and therefore exhibit high etch rates for both Si and SiO2. In this study, reactive ion etching of Si and SiO2 materials by SF5+ ions was examined with the use of molecular dynamics (MD) simulation. For this purpose, a simplified interatomic potential functions model for sulfur (S) was developed that approximately represents molecular moieties or molecules SFn (n≤6) based on density-functional-theory (DFT) calculations. The etching yields of Si and SiO2 by SF5+ ions evaluated by MD simulations with these new potential functions were found to be in good agreement with those obtained from multibeam injection system experiments, which implies that the etching process is essentially due to sputtering enhanced by chemical reactions of F atoms with the surface materials. Analyses of the depth profiles of atomic concentrations of etched surfaces and desorbed species obtained from MD simulations also indicate that the presence of excess F atoms on the surface enhances the etching yield of Si and SiO2 significantly over corresponding physical sputtering.

Kinetics of Reactive Ion Etching of Si, SiO2, and Si3N4 in C4F8 + O2 + Ar Plasma: Effect of the C4F8/O2 Mixing Ratio

Kinetics of Reactive Ion Etching of Si, SiO2, and Si3N4 in C4F8 + O2 + Ar Plasma: Effect of the C4F8/O2 Mixing Ratio

Abstract B26: A new way of fabricating high-porosity parylene membranes for high-throughput capturing of viable circulating and exfoliated tumor cells from large-volume bodily fluids

Abstract Liquid biopsy is a critical component in cancer precision medicine. The ability to capture rare cancer cells from liquid samples, such as circulating tumor cells (CTCs) from peripheral blood as well as exfoliated tumor cells (ETCs) from other body fluids, has shown great promises in cancer detection and prognosis, as well as understanding of cancer biology at different stages. Different ways have been developed for rare cancer cell capture, including biomarker-based immunocapture and capture through other physical processes, such as size, mechanical or dielectric properties, hydrodynamic fluids, etc. However, the throughputs of these techniques are limited to 0.2-2 mL/min. Recently, a high-porosity parylene membrane has been shown to be able to process sample at a fluid rate of > 100 mL/min, which would greatly extend the capability of CTC and ETC-based liquid biopsy. The high porosity of the membrane can also dramatically reduce the shear stress the tumor cells encountered during capture, which has been shown to be critical to maintain cell viability. However, the current parylene membrane fabrication involves deep Si reactive ion etching, which is an expensive process and not widely available. The release of the parylene membrane can also be challenging. We report here a new method to fabricate the parylene membrane using simple photolithography and reactive ion etching techniques. The fabricated parylene membranes and their capability of processing large volume sample for viable cell capture will be presented. Citation Format: Jian Gu, Inad Rabadi, Frederic Zenhausern, David Carpentieri, Jue Wang. A new way of fabricating high-porosity parylene membranes for high-throughput capturing of viable circulating and exfoliated tumor cells from large-volume bodily fluids [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B26.

Concerning the Effect of Type of Fluorocarbon Gas on the Output Characteristics of the Reactive-Ion Etching Process

The comparative research of the parameters, steady-state composition, and the effects of heterogeneous interaction in the plasma of fluorocarbon gases CxHyFz with various z/x relations in conditions of an induction RF (13.56 MHz) discharge is carried out. The binary systems CxHyFz + Ar based on CF4 (z/x = 4), CHF3 (z/x = 3), and C4F8 (z/x = 2) are used as the subjects of research. Through the methods of diagnostics and simulation of plasma we found (a) the reasons of the differences in the physical parameters (temperature and density of electrons, energy of ion bombardment) of the plasma in the studied systems; (b) the special characteristics of the kinetics of the plasma-chemical processes determining the steady state concentrations of fluorine atoms and polymer-forming radicals; and (c) the special characteristics of the kinetics of the heterogeneous process forming the output parameters (rate, selectivity, anisotropy) of the reactive ion etching of Si and SiO2.

Observation of Geometry Induced Doping in Thin Si Nano-grating Layers

We fabricate Si nano-grating layers and measure their electrical characteristics to monitor geometry induced doping. SOI device layer was thinned down by thermal oxidizing and subsequent wet etching of the oxide. Grating was fabricated using laser interference lithography (375nm laser) followed by reactive ion etching of Si. Next, large square island (0.5x0.5mm) was shaped in the device layer and four Si\\Ti\\Ag ohmic contacts were formed to measure electrical characteristics. The I-V characteristics were recorded using both 4 wire and 2 wire methods. Resistance-temperature dependences (T= 4-300K) were recorded as well. For all 12 samples, nano-grating layers show 2-3 order reduction of resistivity. Resistivity anisotropy was in the range 0.2-1 at 300K. Obtained geometry induced doping level corresponds to “effective impurity” concentration of 3x1018 cm-3. The dependence is in agreement with G-doping theory only below T=150K.

High-Performance Vertical Gate-All-Around Silicon Nanowire FET With High-<inline-formula> <tex-math notation="TeX">$\kappa $ </tex-math></inline-formula>/Metal Gate

We present a vertical gate-all-around Si nanowire (SiNW) metal–oxide–semiconductor field-effect transistor with high- \(\kappa \) dielectric and TiN metal gate. The process flow is fully compatible with CMOS technologies. SiNWs are fabricated by deep Si reactive ion etching, gate-stack is formed by atomic layer deposition, and metal salicide is utilized as drain contact. The fabricated p-type gate-all-around SiNW metal–oxide–semiconductor field-effect transistors that have a gate length of 320 nm exhibit excellent characteristics with \(I_\mathrm{{\scriptstyle ON}}\) /I \(_\mathrm{{\scriptstyle OFF}}\) > \(10^{4}\) , subthreshold slope of 87 mV/decade, and 25 mV/V of drain-induced barrier lowering. Low-temperature characteristics are also presented. The demonstrated devices have potential applications in novel low-power logic circuits and as selection transistors for \(4F^{2}\) cross-point memory cells.

Accurate Reactive Ion Etching of Si, Ge and P Doped Ge in an SF6-O2 Radio-Frequency Plasma

The effect of reactive ion etching (RIE) of Silicon (Si), Germanium (Ge) and highly phosphorous doped Germanium (Ge:P) in an SF6-O2 plasma has been studied. We find that the etch characteristics of etch rate and sidewall profile are greatly affected by the O2 content. Etching rates of Ge and Ge:P depend on the O2 content with a significant reduction up to 20% of O2. We also find that an anisotropic sidewall etching mechanism exists and is dependent on the percentage of O2 (%O2) in the plasma. Sidewall angles range from a minimum of 66° to a maximum of 166°, where a critical concentration for etching angle exists where the etching angle can alternate from below 90° to above 90°. In combination, both features allow for precision plasma etching of Si, Ge and Ge:P.

Accurate Reactive Ion Etching of Si, Ge and P Doped Ge in an SF6-O2 Radio-Frequency Plasma

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Concept of Spatially Divided Deep Reactive Ion Etching of Si using Oxide Atomic Layer Deposition in the Passivation Cycle

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Multiple-Height Microstructure Fabricated by Deep Reactive Ion Etching and Selective Ashing of Resist Layer Combined with Ultraviolet Curing

UV-cured photoresist is applied to the delay masking process to realize a multiple-height microstructure for the first time. Although the UV-cured photoresist is a soft mask, its material property becomes stable against resist thinner and UV exposure. A layered resist pattern can be realized by stacking normal photoresist on the UV-cured photoresist. The UV curing increases the glass transition temperature from 120 to 160 °C. By controlling the temperature, the normal photoresist can be ashed twice as fast as the UV-cured photoresist. This selectivity can be combined with the deep reactive ion etching of Si, and a microstructure having three different etching depths is realized, thus forming a micromirror. The multiple-height structure is advantageous for reducing the inertia of the mirror plate. For the same rotational spring constant, the micromirror has a higher resonant frequency, which is required for realizing higher-resolution laser displays.

Multiple-Height Microstructure Fabricated by Deep Reactive Ion Etching and Selective Ashing of Resist Layer Combined with Ultraviolet Curing

UV-cured photoresist is applied to the delay masking process to realize a multiple-height microstructure for the first time. Although the UV-cured photoresist is a soft mask, its material property becomes stable against resist thinner and UV exposure. A layered resist pattern can be realized by stacking normal photoresist on the UV-cured photoresist. The UV curing increases the glass transition temperature from 120 to 160 °C. By controlling the temperature, the normal photoresist can be ashed twice as fast as the UV-cured photoresist. This selectivity can be combined with the deep reactive ion etching of Si, and a microstructure having three different etching depths is realized, thus forming a micromirror. The multiple-height structure is advantageous for reducing the inertia of the mirror plate. For the same rotational spring constant, the micromirror has a higher resonant frequency, which is required for realizing higher-resolution laser displays.

Cu-plated through-wafer vias for AlGaN∕GaN high electron mobility transistors on Si

A robust method for creating Cu-plated through-wafer vias for AlGaN∕GaN high electron mobility transistors on Si is reported. The initial 70μm deep vias with diameters of 50μm are created by deep Si reactive ion etching, followed by pulsed Cu electroplating and mechanical polishing to planarize the metal. This is an attractive approach for increasing the effective thermal conductivity of the composite substrate for very high power device applications.

Electrochemical Synthesis and Application of NF3

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Measuring of Low Contact Resistivities of CoSi<tex>$_2$</tex>on Shallow B-Junctions

The active boron concentration, which affects contact resistivity, was profiled by stepwise four-point probing and Si reactive ion etching. The maximum concentration of 1.6/spl times/10/sup 20/ cm/sup -3/ remained constant up to a depth, which depends on the boron annealing temperature. This depth should be larger than the CoSi/sub 2/ penetration depth in Si. Conductance profiling of the silicide indicated an undesired layer on top of the CoSi/sub 2/. This upper layer influences contact resistivity. It is shown that the removal of this layer may reduce the contact resistivity down to 3 /spl Omega//spl mu/m/sup 2/.

Ion Channel Sensor on a Silicon Support

AbstractWe are building a biosensor based on ion channels inserted into lipid bilayers that are suspended across an aperture in silicon. The process flow only involves conventional optical lithography and deep Si reactive ion etching to create micromachined apertures in a silicon wafer. In order to provide surface properties for lipid bilayer attachment that are similar to those of the fluorocarbon films that are currently used, we coated the silicon surface with a fluoropolymer using plasma-assisted chemical vapor deposition. When compared with the surface treatment methods using self-assembled monolayers of fluorocarbon chemicals, this novel approach towards modifying the wettability of a silicon dioxide surface provides an easy and fast method for subsequent lipid bilayer formation. Current-Voltage measurements on OmpF ion channels incorporated into these membranes show the voltage dependent gating action expected from a working porin ion channel.

Molecular dynamics simulations of Si etching with energetic F+: Sensitivity of results to the interatomic potential

Comparative analyses of molecular dynamics (MD) simulation studies of reactive ion etching of Si are presented. A recently developed empirical potential is used to model the Si–F system, and applied to the simulation of Si etching with energetic F+ at 10, 25 and 50 eV. These results are compared to those of a similar study using the Stillinger-Weber Si–F potential. This analysis leads to the expected result that different potentials lead to quantitatively different results with regard to Si etch yield, surface structure and composition, etching mechanisms, and product distributions. More importantly, however, it attests to the robustness of the qualitative nature of these results. The degree of qualitative agreement between systems studied with the two potentials is high enough for us to conclude that MD simulations have revealed valuable qualitative insights into the complicated system of reactive ion etching of Si.

Reactive ion etching of Si by Cl and Cl2 ions: Molecular dynamics simulations with comparisons to experiment

We present results of molecular dynamics simulations of reactive ion etching (RIE) of a reconstructed Si(100)(2×1) surface. The existing Stillinger–Weber interatomic potential for Si/Cl of Feil et al. has been modified by correcting the Si–Si bond strength for a SiCln moiety bound to a Si surface and the Si–Cl bond strength in SiClm molecules. This potential has been used to study RIE of Si by Cl and Cl2 ions. The calculated properties such as the Si yield, product stoichiometry, stoichiometry of the chlorosilyl surface, and Cl content of the chlorosilyl layer are in reasonable agreement with experiment. The dissociative chemisorption probability of Cl2 on Si(100)(2×1) as a function of energy has been simulated and the results are in reasonable agreement with experiment.

Fabrication of field emission Si-tip array using reduced submicron masks generated by isotropic etching of mask patterns

We have developed a novel technique for fabricating submicron size mask patterns using a wet etching technique of SiO 2 . The overetching of the SiO 2 mask layer would present reduction of the diameters of the mask. The reduction of 2 μm SiO 2 mask down to 0.5 μm diameter will be presented and utilized for the fabrication of nano-size Si-tip array. The 4 inch Si (100) wafer was thermally oxidized and followed by the pattern transfer of original mask patterns on the thermally grown oxide using conventional photographic contact printing method. The coated photoresist (PR) layer with 2 μm thickness was exploited as an etch mask layer for following mask reduction procedure. The mask reduction procedure was performed using 7:1 buffered hydrofluoric acid (BHF). Initially, the patterned PR mask layer was dipped into BHF solution for about 300 seconds in order to remove the SiO 2 layer until the Si substrate would be exposed. Additional ∼ 300 second extra-dipping in BHF solution created considerable overetching and resulted in the smaller diameter than that of the original one. The repetition of the dipping process with precise control provided proper size of mask layers. The shape of the mask layer is found to have smaller diameter at the top and greater diameter at the bottom of the mask layer. Further experiments resulted in the various submicron size SiO 2 mask patterns. The diameters of the reduced masks were measured by scanning electron microscopy (SEM) and observed, for example, to be 0.3, ∼ 0.2 μm on the top and 0.7, 0.5 μm at the bottom, respectively. The isotropic and anisotropic Si reactive ion etching (RIE) was performed with this patterned wafer in order to provide sharp Si tip on the ∼ 2 μm height Si-post arrays with the post diameter down to ∼ 0.2 μm. The sharpening oxidation followed by oxide etching resulted in the successful fabrication of the nanosize Si-tip arrays.