Fast Etch Rate Research Articles

Dry Etching of BST using Inductively Coupled Plasma

BST thin films were etched with inductively coupled CF<TEX>$_{4}$</TEX>/(Cl<TEX>$_{2}$</TEX>+Ar) plasmas. The etch characteristics of BST thin films as a function of CF<TEX>$_{4}$</TEX>/(Cl<TEX>$_{2}$</TEX>+Ar) gas mixtures were analyzed using optical emission spectroscopy (OES) and Langmuir probe. The BST films in CF<TEX>$_{4}$</TEX>/Cl<TEX>$_{2}$</TEX>/Ar plasma is mainly etched by the formation of metal chlorides which depends on the emission intensity of the atomic Cl and the bombarding ion energy. The maximum etch rate of the BST thin films was 53.6 nm/min because small addition of CF<TEX>$_{4}$</TEX> to the Cl<TEX>$_{2}$</TEX>/Ar mixture increased chemical and physical effect. A more fast etch rate of BST films can be obtained by increasing the DC bias and the RF power, and lowering the working pressure.

Design and fabrication of a hybrid nanofluidic channel

A hybrid micro-nanofluidic channel network is developed on a silicon wafer for bioanalytical applications, such as separation, concentration, and fractionation. The nanochannel is formed on the silicon wafer using surface micromachining techniques, while the microchannel is fabricated on the poly-di-methyl-siloxane utilizing soft lithography techniques. Microfluidic networks not only support the very thin wall of the nanofluidic channel, but also provide appropriate gateways for the fluid/sample flow. The thickness of the microchannels is kept below 10 µm by changing the spin rate and time during photolithography. On the other hand, nanochannel thickness is varied between 100 and 200 nm by controlling the sputtering time of the sacrificial copper layer. Electrochemical wet etching is employed to release the thin layer of copper from the silicon dioxide shell. Our etching technique demonstrates significant advantages over other existing methods, such as wet chemical etching and reactive ion etching, including relatively fast etching rate, good selectivity, less safety and environmental concerns, less monitoring and control issues, and low cost. The dimensions of our microfluidic channels are measured using a profilometer, while the nanochannel thickness is confirmed by the atomic force microscopy and scanning electron microscopy images.

A robust two-step etching process for large-scale microfabricated SiO 2 and Si 3N 4 MEMS membranes

The ability to reliably and controllably micromachine membranes by wet anisotropic etching of silicon is essential in microelectromechanical system (MEMS) device fabrication. This paper proposes an effective way to dependably microfabricate SiO 2 and Si 3N 4 membranes with little supervision. This two-step method takes full advantage of the different etching behaviors of both EDP (a solution of ethylene diamine, pyrocatechol, and water) and potassium hydroxide (KOH). First, EDP is used, which has almost no reaction with silicon nitride and a moderately fast silicon etching rate. Next, KOH is used, which has a negligible nitride etching rate and a significantly faster silicon etching rate. Using this method, fully etched membranes of large geometries can be consistently generated. The size of microfabricated membranes presented in this paper varies from 200 μm × 200 μm to 9000 μm × 9000 μm with a thickness variation from 100 nm to 1000 nm. High temperatures were used in both etchants to further increase the silicon etching rate.

ECR plasma etching of GaAs in CCl2F2/Ar/O2 discharge and IR studies of the etched surface

The etching of GaAs materials under electron cyclotron resonance conditions has been performed in an ECR etching system with rf biasing using the CCl2F2/Ar/O2 plasma chemistry. Etching experiments were carried out at a pressure between 0.015 and 0.020 mbar, rf power 0.39 W/cm2, and dc bias voltage 200 V. The surface morphology and etch depth were taken by scanning electron microscopy and Dektek Profilometry respectively. The use of ECR conditions with additional rf biasing provides the good etching of the surface and fast etch rates. Moreover, the surface of the GaAs material display smooth and stoichiometric surfaces at higher ECR powers. The surface damages on the GaAs samples after the plasma exposure have been studied using IR spectroscopy.

Nanometer-sized patterning of polysilicon thin films by high density plasma etching

Nanometer-sized patterning of polysilicon thin films was performed by a high density inductively coupled plasma (ICP) etching. The etch characteristics of polysilicon thin films with an e-beam resist mask were investigated using Cl 2, C 2F 6, and HBr-based gas mixes. The etch rate, the etch selectivity and the etch profile of polysilicon films were examined as a function of the concentration of each gas, using Ar as a diluent. The Cl 2 gas showed fast etch rate of polysilicon films, and the high selectivity of polysilicon films to resist was obtained in HBr and C 2F 6 gases. The effect of an etch gas on the etch profile of polysilicon thin films was observed using field emission scanning electron microscopy for nanometer-sized patterns. Good nanometer-sized patterning of polysilicon thin films with 60 and 95 nm wide lines has been achieved in HBr/Ar and C 2F 6/Ar plasmas.

Investigation of GaAs Dry Etching in a Planar Inductively Coupled BCl3 Plasma

We investigated dry etching of GaAs in a planar inductively coupled plasma (ICP) reactor with gas chemistry. The process parameters included planar ICP source power, chamber pressure, reactive ion etching (RIE) chuck power, and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure was changed from 5 to 20 mTorr. RIE chuck power was controlled from 0 to 150 W. The gas flow rate was varied from 10 to 40 sccm. We found that a process condition at 20 sccm 300 W ICP, 100 W RIE, and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature showed extremely smooth surface vertical sidewall, relatively fast etch rate (>3000 Å/min) and good selectivity to a photoresist (>3:1). X-ray photoelectron spectroscopy study on the surface of processed GaAs proved a very clean surface of the material after dry etching. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. These results indicate that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors. © 2004 The Electrochemical Society. All rights reserved.

Influence of Etch Gas on High Density Plasma Etching of Polysilicon Thin Films with Nanometer-Size Patterns

High density plasma etching of polysilicon thin films with nanometer-size patterns was performed in an inductively coupled plasma. The etch process of polysilicon films with a photoresist mask was characterized using Cl 2 , C 2 F 6 , and HBr gas chemistries in terms of etch rate, etch selectivity, and etch profile. The fast etch rate of polysilicon films was obtained in Cl 2 /Ar gas and the high selectivity of polysilicon to photoresist was found in HBr/Ar gas mixture. The etching of polysilicon films masked by photoresist with nanometer-size patterns was attempted with various etch gases, and an anisotropic etching of 60 nm sized pattern was achieved in HBr/Ar and C 2 F 6 /Ar plasmas.

Nanorings, Nanopillars and Nanospikes on Si(111) by Modified Nanosphere Lithography: Fabrication and Application

ABSTRACTUniform arrays of nanopillars, nanospikes, nanorings and rings atop nanopillars were fabricated using modified nanosphere lithography on the Si(111) surface and observed using AFM and SEM. A self-assembled monolayer mask which utilized 450±10nm polystyrene spheres were used as an etch mask during a fabrication process of physical Ar+ ion bombardment followed by SF6RIE to produce nanopillars with flat tops that could be as large as 210nm in height and 175nm in diameter. Nanospikes of approximately the same height were fabricated made with a FWHM of 250nm. The initial Ar+ion bombardment step was varied to achieve up to 4 times faster etch rates and narrowed widths in the nanospikes. Both types nanostructures systems were “self-wired” which is an intrinsic result of this fabrication process. Self-wired nanorings and rings atop nanopillar structures were also fabricated using a two step etching process along with sonication. The nanorings had inner and outer diameters of 225±5nm and 175±5 nm, respectively and were up to 20nm in height and their nanowire connectivity could be made optional by a judicious choice of solvent for sonication. The self-wired Si nanostructures were also “dressed” with self-assembled Ge quantum dots. These Ge/Si nano-architectured structures possess the basic framework for fabricating novel nanoelectronic and nano-optoelectronic devices in the foreseeable future.

The effect of solvent on the etching of ITO electrode

In this study, the effect of solvents, HCl and aqua regia at room temperature, on the etching behavior of ITO film was investigated. A higher etching rate was obtained in aqua regia than in HCl. However, via XPS analysis, it was found that there was more surface residual byproduct in aqua regia etchant than in HCl. The surface concentration (ratio of chlorine to indium) was 7.2 and 0.38 in aqua regia and HCl, respectively. It was also observed that the surface residual byproduct reduced the carrier mobility due to the ionized impurity scattering. As seen in the ITO pattern after the etching process, a serious undercut occurred with the aqua regia due to the fast etching rate. Thus, the 9 M HCl solution is more suitable as an etchant for ITO/OLED application.

Optimization of the fabrication of sealed capacitive transducers using surface micromachining

Processing issues for the fabrication of capacitive micromachined ultrasonic transducer (cMUT) arrays have been studied using surface micromachining. This work focuses on the critical steps of process fabrication such as membrane formation, sacrificial layer properties and vacuum sealing performance of cavity. We describe a four-mask process for the realization of sealed cMUT. We demonstrate that the use of a sacrificial layer with a columnar structure gives a fast etching rate (29 nm s−1) in a buffered hydrofluoric acid solution. The mechanical stress of LPCVD silicon nitride (SiNx), used as membrane, was evaluated. We compared the vacuum sealing performance of different materials in order to find the best material in terms of lateral deposition inside the cavity. Functional transducers have been obtained. We proposed an electrical test in order to evaluate the vacuum sealing of the cavity based on the collapse voltage determination. Laser interference measurements were used to characterize the dynamic displacement of the membrane.

Nanometer-sized patterning of polysilicon thin films by high density plasma etching using Cl2 and hbr gases

High density plasma etching of polysilicon thin films was carried out in an inductively coupled plasma (ICP) for the formation of nanometer-sized patterns. The etch rate and etch selectivity of polysilicon films were investigated as a function of the concentration of Cl2 and HBr etch gases. The fast etch rate of polysilicon films was obtained in Cl2/Ar gas, and the high selectivity of polysilicon to photoresist was found in HBr/Ar gas. Finally, the etching of polysilicon films masked with photoresists was attempted in HBr/Ar and Cl2/Ar gases. The good pattern profile of polysilicon films with 60 nm lines was achieved in an HBr/Ar plasma.

Surface characterization of cast Ti-6Al-4V in hydrofluoric-nitric pickling solutions

Hydrofluoric acid offers a fast etching rate for removing 200 μm-thick alpha-cases from the surfaces of cast Ti-6Al-4V. The acid picks up hydrogen gas into substrate of the cast, which can be limited by introducing an oxidizing acid. This study proposes the optimal ratios of hydrofluoric/nitric acid as the pickling solutions. The cast Ti-6Al-4V in these solutions is monitored with chemical etching and electrochemical polarization. The mechanisms of etching procedures are initiated by generating oxygen vacancies that lead to several products from a series of quasi-chemical steps. The final product of the reactions may deduce as the form of H 2TiF 6 that is peeled out by the evolution of produced gases. Polarized curves are performed to illustrate passive behaviors of the alpha-case removed Ti-6Al-4V. The amounts of charge transference increase with increasing hydrofluoric acid concentrations. The newly formed passive film was estimated to be 20 nm in thickness with non-stoichiometric arrangements in the 4% HF electrolyte.

Dry Etching of GaAs in a Planar Inductively Coupled BCI3 Plasma

We studied BCl<TEX>$_3$</TEX> dry etching of GaAs in a planar inductively coupled plasma system. The investigated process parameters were planar ICP source power, chamber pressure, RIE chuck power and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure, RIE chuck power and gas flow rate were controlled from 5 to 15 mTorr, 0 to 150 W and 10 to 40 sccm, respectively. We found that a process condition at 20 sccm <TEX>$BCl_3$</TEX> 300 W ICP, 100 W RIE and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature depicted extremely smooth surface (RMS roughness < 1 nm), vertical sidewall, relatively fast etch rate (> <TEX>$3000\AA$</TEX>/min) and good selectivity to a photoresist (> 3 : 1). XPS study indicated a very clean surface of the material after dry etching of GaAs. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. It demonstrated that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors.

Effect of Etch Gas on Dry Etching of Ferroelectric Bi3.25La0.75Ti3O12 Thin Films

The etch study of ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films has been performed using C2F6, Cl2 and HBr gases in an inductively coupled plasma (ICP). The etch rate and etch selectivity of BLT films were investigated as a function of gas concentration for each gas. The etch rates in the range of 700–900 Å/min were obtained for C2F6 gas while the etch rates by Cl2 and HBr gases were in the range of 700–1100 Å/min under the etch conditions used in this study. The etch profiles of BLT films by each gas were observed using field emission scanning electron microscopy (FESEM). Cl2 gas was more effective in obtaining a fast etch rate and clean etch profile than C2F6 and HBr gases. The surface chemistry of BLT films etched in a Cl2 plasma was analyzed by X-ray photoelectron spectroscopy (XPS).

Use of high temperature hydrogen annealing to remove sub-surface damage in bulk GaN

The results of a study to use atmospheric pressure annealing in hydrogen for etching GaN to remove damage from mechanical polishing is reported. Annealing in hydrogen ambient can achieve high removal rates. However, the highest removal rates at a given temperature result in an unacceptably rough surface morphology, possibly related to surface accumulation of Ga during the etching. Lower GaN removal rates maintained smooth surfaces for unpolished GaN. Faster etch rates are always observed for damaged material, with results suggesting that such differential etching may be suppressed at higher temperatures. Both photoluminescence and optical microscopy indicate mechanical polishing damage can extend as far as 2 μm into the sample, and could be removed by hydrogen annealing.

Inductively coupled plasma etching of Pb(ZrxTi1-x)O3 thin films in Cl2/C2F6/Ar and HBr/Ar plasmas

Pb(ZrxTi1-x)O3 thin films were etched in an inductively coupled plasma by using various etch gases such as Cl2/Ar, C2F6/Ar, Cl2/C2F6/Ar and HBr/Ar. The etch rates and etch profiles for each etch gas were investigated. Fast etch rates were obtained in chlorine-containing etch gases (e.g., Cl2/Ar and Cl2/C2F6/Ar), and clean and steep etch profiles were achieved in Cl2/Cv2F6/Ar or HBr/Ar gases. The gas mixture of Cl2 and C2F6 was proposed to give a fast etch rate and a steep sidewall angle of etched patterns. The optimum gas mixture of Cl2C2F6/Ar was found by varying the gas ratio of Cl2 to C2F6. On the other hand, HBr/Ar gas as an alternative for etching of the Pb(ZrxTi1-x)O3 films was examined. Cl2/C2F6/Ar and HBr/Ar etch gases were compared with respect to etch rate, etch profile and electrical properties.

Heat transfer between wafer and electrode in a high density plasma etcher

Heat transfer between a wafer and electrode has been studied in a planar-type inductively coupled plasma reactor in terms of temperatures of wafer, chamber wall and electrode. A substantial increase in the wafer temperature was attributed mainly to bombardment of incident ions onto the wafer surface. The decrease in the wafer temperature at a higher pressure was attributed to the decrease in plasma density and a resistance to heat transfer in a micro gap formed between the wafer and the electrode. Compared to the case of no rf-chuck power applied, the wafer temperature when the electrode was biased with 13.56 MHz if power showed a greater increase mainly due to increased ion bombardment. Since the electrode having a water-cooled-backside geometry gains heat from the bulk plasma, it may lead to fast etch rates of hard materials whose etch products are less volatile at low temperatures, but not be good for photoresist materials.

자성 박막의 습식 식각 특성

The wet etching characteristics of magnetic materials such as NiFe and CoFe were investigated in terms of etch rate and etch profile by using variouus etching solutions (etchants). Among the various etching solutions, HNO<TEX>$_3$</TEX>, HCl, and H<TEX>$_2$</TEX>SO<TEX>$_4$</TEX>were selected for the etching of magnetic materials and showed distinct results. In the case of NiFe films, faster etch rate were obtained with HNO<TEX>$_3$</TEX>solution. When NiFe films ere etched with HCl solution, white etch residues were found on the surface of etched films. From FEAES analysis of these etch residues, they were proved to be by-product from the reaction of NiFe with Cl element. CoFe thin films showed the similar trend to the case of NiFe films. They were etched fast in HNO<TEX>$_3$</TEX> solution while Chl solution represented slow etching. The etch profiles of CoFe films showed smooth etch profile but revealed the partial etching around the patterns in HNO<TEX>$_3$</TEX>solution of relatively high concentration. It was observed that the etched surface was clean and smooth, and that white etch residues were also remained on the etched films.

Dry etch chemistries for TiO 2 thin films

Several different plasma chemistries were investigated for dry etching of TiO 2 thin films. Fluorine-based discharges produced the fastest etch rates (∼2000 Å min −1) and selectivities >1 for Si over TiO 2. Chlorine-based discharges also showed a chemical enhancement over pure Ar sputtering and had selectivities <1 for Si over TiO 2 for a range of plasma conditions. Methane–hydrogen discharges produced very slow etch rates, below those obtained with Ar sputtering. The etched surface morphologies of TiO 2 were excellent in all three types of plasma chemistry. Small concentrations (2 at.%) of chlorine- or fluorine-containing residues were identified on the TiO 2 surface after Cl 2/Ar or SF 6/Ar etching, but these residues were water soluble.

MR fluids workpiece holding apparatus

The ability to reliably and controllably micromachine membranes by wet anisotropic etching of silicon is essential in microelectromechanical system (MEMS) device fabrication. This paper proposes an effective way to dependably microfabricate SiO2 and Si3N4 membranes with little supervision. This two-step method takes full advantage of the different etching behaviors of both EDP (a solution of ethylene diamine, pyrocatechol, and water) and potassium hydroxide (KOH). First, EDP is used, which has almost no reaction with silicon nitride and a moderately fast silicon etching rate. Next, KOH is used, which has a negligible nitride etching rate and a significantly faster silicon etching rate. Using this method, fully etched membranes of large geometries can be consistently generated. The size of microfabricated membranes presented in this paper varies from 200 μm × 200 μm to 9000 μm × 9000 μm with a thickness variation from 100 nm to 1000 nm. High temperatures were used in both etchants to further increase the silicon etching rate.