Dry etch properties of IZO thin films in a CF4/Ar adaptively coupled plasma system

In this study, we investigated to the etch characteristics of indium zinc oxide (IZO) thin films in a CF₄/Ar plasma, namely, etch rate and selectivity toward SiO₂. A maximum etch rate of 76.6 nm/min was obtained for IZO thin films at a gas mixture ratio of CF₄/Ar (25:75%). In addition, etch rates were measured as a function of etching parameters, including adaptively coupled plasma chamber pressure. X-ray photoelectron spectroscopy analysis showed efficient destruction of the oxide bonds by ion bombardment, as well as accumulation of low volatile reaction products on the surface of the etched IZO thin films. Field emission Auger electron spectroscopy analysis was used to examine the efficiency of ion-stimulated desorption of the reaction products.     

Etch characteristics of HfO2 thin films by using CF4/Ar inductively coupled plasma

In this study, we carried out an investigation of the etching characteristics (etch rate, selectivity) of HfO₂ thin films in the CF₄/Ar inductively coupled plasma (ICP). The maximum etch rate of 54.48 nm/min for HfO₂ thin films was obtained at CF₄/Ar (=20:80%) gas mixing ratio. At the same time, the etch rate was measured as function of the etching parameters such as ICP RF power, DC-bias voltage, and process pressure. The X-ray photoelectron spectroscopy analysis showed an efficient destruction of the oxide bonds by the ion bombardment as well as an accumulation of low volatile reaction products on the etched surface. Based on these data, the chemical reaction was proposed as the main etch mechanism for the CF₄-containing plasmas.     

Etching characteristics and mechanism of Pb(Zr,Ti)O3 thin films in CF4/Ar inductively coupled plasma

The effect of the CF₄/Ar mixing ratio on the etching behaviour and mechanisms for Pb(Zr,Ti)O₃ (PZT) thin films in an inductively coupled plasma was carried out. It was found that an increase of Ar mixing ratio causes non-monotonic behaviour of the PZT etch rate, which reaches a maximum of 2.38 nm/s at 80% Ar. Investigating the plasma parameters, we found a weak sensitivity of both electron temperature and electron density to the change of CF₄/Ar mixing ratio. A combination of zero-dimensional plasma model with the model of surface kinetics shows the possibility of a non-monotonic etch rate behaviour due to the concurrence of physical and chemical pathways in the ion-assisted chemical reaction.     

Dry etching properties of TiO2 thin films in O2/CF4/Ar plasma

In this work, the etching properties of titanium dioxide (TiO₂) thin film in additions of O₂ at CF₄/Ar plasma were investigated. The maximum etch rate of 179.4 nm/min and selectivity of TiO₂ of 0.6 were obtained at an O₂/CF₄/Ar (=3:16:4 sccm) gas mixing ratio. In addition, the etch rate and selectivity were measured as a function of the etching parameters, such as the RF power, DC-bias voltage, and process pressure. The efficient destruction of the oxide bonds by ion bombardment, which was produced from the chemical reaction of the etched TiO₂ thin film, was investigated by X-ray photoelectron spectroscopy. To determine the re-deposition of sputter products and reorganization of such residues on the surface, the surface roughness of TiO₂ thin film were examined using atomic force microscopy.     

The dry etching of a sol-gel deposited ZnO thin film in a high density BCl3/Ar plasma

The etching characteristics of zinc oxide (ZnO) including the etch rate and the selectivity of ZnO in a BCl₃/Ar plasma were investigated. It was found that the ZnO etch rate showed a non-monotonic behavior with an increasing BCl₃ fraction in the BCl₃/Ar plasma, along with the RF power, and gas pressure. At a BCl₃ (80%)/Ar (20%) gas mixture, the maximum ZnO etch rate of 50.3 nm/min and the maximum etch selectivity of 0.75 for ZnO/Si were obtained. Plasma diagnostics done with a quadrupole mass spectrometer delivered the data on the ionic species composition in plasma. Due to the relatively high volatility of the by-products formed during the etching by the BCl₃/Ar plasma, ion bombardment in addition to physical sputtering was required to obtain the high ZnO etch rates. The chemical state of the etched surfaces was investigated with X-ray Photoelectron Spectroscopy (XPS). Inferred from this data, it was suggested that the ZnO etch mechanism was due to ion enhanced chemical etching.     

Surface characteristics of parylene-C films in an inductively coupled O2/CF4 gas plasma

In this article, we report the results obtained from a study carried out on the inductively coupled plasma (ICP) etching of poly-monochloro-para-xylylene (parylene-C) thin films using an O₂/CF₄ gas mixture. The effects of adding CF₄ to the O₂ plasma on the etch rates were investigated. As the CF₄ gas fraction increases up to approximately 16%, the polymer etch rate increases in the range of 277-373 nm/min. In this work, the atomic force microscopy (AFM) analysis indicated that the surface roughness was reduced by the addition of CF₄ to the O₂ plasma. Contact angle measurements showed that the surface energy decreases with increasing CF₄ fraction. At the same time, X-ray photoelectron spectroscopy (XPS) demonstrated the increase in the relative F atomic content on the surface.     

Etch characteristics of TiN/Al2O3 thin film by using a Cl2/Ar adaptive coupled plasma

In this study, we carried out an investigation in the etching characteristics of TiN thin films in a C1₂/Ar adaptive coupled plasma. The maximum etch rate of the TiN thin films was 768 nm/min at a gas mixing ratio of C1₂ (75%)/Ar (25%). At the same time, the etch rate was measured as functions of the various etching parameters. The X-ray photoelectron spectroscopy analysis showed the efficient destruction of the oxide bonds by the ion bombardment as well as the accumulation of low volatile reaction products on the etched surface. Field emission Auger electron spectroscopy analysis was used to examine the efficiency of the ion-stimulated desorption of the reaction products.     

Dry etching of TaN thin film using CH4/Ar inductively coupled plasma

In this research, we investigated the TaN etch rate and selectivity with under layer (HfO₂) and mask material (SiO₂) in inductively coupled CH₄/Ar plasma. As the CH₄ content increased from 0% to 80% in CH₄/Ar plasma, the TaN etch rate was increased from 11.9 to 22.8 nm/min. From optical emission spectroscopy (OES), the intensities for CH [431 nm] and H [434 nm] were increased with the increasing CH₄ content from 0% to 100% in CH₄/Ar plasma. The results of x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) showed no accumulation of etch by-products from the etched surface of TaN thin film. As a result of OES, AES and XPS analysis, we observed the etch by-products from the surfaces, such as Ta-N-CH and N-CH bonds. Based on the experimental results, the TaN etch was dominated by the chemical etching with the assistance of Ar sputtering in reactive ion etching mechanism.     

Effect of etching on dielectric constant and surface composition of SiCOH low-k films in inductively coupled fluorocarbon plasmas

SiCOH low-k (k = 2.8) film etched in fluorocarbon (CF₄ and CHF₃) inductively coupled plasmas was characterized in this work. The surface composition and molecular structures of the low-k films after etching in the CF₄, CHF₃, CF₄/Ar, and CHF₃/Ar plasmas were characterized. A higher etch rate was observed with the CF₄ plasmas than with the CHF₃ plasmas. The etch rate of the low-k film in the CF₄ plasmas was decreased and the etch rate in the CHF₃ plasmas was increased by the Ar addition. After etching the low-k films, a decrease in the dielectric constant of up to 0.19 was observed. The thickness of the fluorocarbon (CF_x) layer and CF_x (x = 1, 2, 3)-to-carbon ratio obtained from the XPS C 1s peak increased with decreasing etch rate. The k-value was correlated with amount of Si-CH₃ and Si-O related groups determined from the Fourier transform infrared (FT-IR) spectrum. The Si-O related peaks were markedly decreased after etching in the CF₄ and CF₄/Ar plasmas. The lower k-value was attributed to the increase of the Si-CH₃/Si-O ratio after etching low-k film.     

A study of the surface reaction on the etched ITO thin films by using inductively coupled plasma

In this study, we investigated the etching characteristics of indium tin oxide (ITO) thin films at CF₄/Ar plasma. The maximum etch rate of 29.8 nm/min for the ITO thin films was obtained at CF₄/Ar (=80/20) gas mixing ratio. The standard conditions were the RF power of 800 W, the DC-bias voltage of −150 V, the process pressure of 2 Pa, and the substrate temperature of 40 °C. Corresponding to these etching conditions, chemical reaction of the etched ITO surface has been studied by X-ray photoelectron spectroscopy measurement to investigate the chemical reactions between the surfaces of ITO thin film and etch species. The preferential losses on the etched surfaces were investigated using atomic force microscopy.     

Etch characteristics of TiN/Al2O3 thin film by using a Cl2/Ar adaptive coupled plasma

In this study, we carried out an investigation in the etching characteristics of TiN thin films in a C1₂/Ar adaptive coupled plasma. The maximum etch rate of the TiN thin films was 768 nm/min at a gas mixing ratio of C1₂ (75%)/Ar (25%). At the same time, the etch rate was measured as functions of the various etching parameters. The X-ray photoelectron spectroscopy analysis showed the efficient destruction of the oxide bonds by the ion bombardment as well as the accumulation of low volatile reaction products on the etched surface. Field emission Auger electron spectroscopy analysis was used to examine the efficiency of the ion-stimulated desorption of the reaction products.     

Dry etching of TaN thin film using CH4/Ar inductively coupled plasma

In this research, we investigated the TaN etch rate and selectivity with under layer (HfO₂) and mask material (SiO₂) in inductively coupled CH₄/Ar plasma. As the CH₄ content increased from 0% to 80% in CH₄/Ar plasma, the TaN etch rate was increased from 11.9 to 22.8 nm/min. From optical emission spectroscopy (OES), the intensities for CH [431 nm] and H [434 nm] were increased with the increasing CH₄ content from 0% to 100% in CH₄/Ar plasma. The results of x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) showed no accumulation of etch by-products from the etched surface of TaN thin film. As a result of OES, AES and XPS analysis, we observed the etch by-products from the surfaces, such as Ta–N–CH and N–CH bonds. Based on the experimental results, the TaN etch was dominated by the chemical etching with the assistance of Ar sputtering in reactive ion etching mechanism.     

Effects of various additive gases on chemical dry etching rate enhancement of low-k SiOCH layer in F2/Ar remote plasmas

N₂ and NO gas addition to F₂/Ar remote plasmas during chemical dry etching (CDE) of low-k SiOCH layer was effective in increasing the etch rate, but the addition of O₂ decreased the etch rate. And, the injection of NO gas directly into the reactor increased the SiOCH etch rate most significantly. The addition of N₂ or NO gas contributes to an effective removal of oxygen in the SiOCH layer, by forming NO₂ and HNO₃ by-products, and of carbon species in the SiOCH layer by forming CF₄ by-product, which leads to enhancement of SiF₄ formation and in turn increase in the SiOCH etch rate.     

High density plasma etching of amorphous CoZrNb films for thin film magnetic devices

Inductively coupled plasma reactive ion etching of CoZrNb magnetic thin films was studied using a TiN hard mask in a Cl₂/O₂/Ar gas mix. The etch rates of CoZrNb films and TiN hard mask gradually decreased with increasing Cl₂ or O₂ gas concentrations. When O₂ gas was added in the Cl₂/Ar gas mix, the etch rate of TiN hard mask was suppressed effectively so that the etch selectivity of CoZrNb film to TiN hard mask was enhanced. The addition of O₂ into the gas mix also led to the anisotropic etching of the CoZrNb films and it was confirmed by Auger electron spectroscopy that there were no redeposited materials on the sidewall of the etched films. Highly anisotropic etching of CoZrNb films was achieved at room temperature under the optimized etching conditions.     

Inductively coupled plasma reactive ion etching of titanium thin films using a Cl2/Ar gas

Inductively coupled plasma reactive ion etching of titanium thin films patterned with a photoresist using Cl₂/Ar gas was examined. The etch rates of the titanium thin films increased with increasing the Cl₂ concentration but the etch profiles varied. In addition, the effects of the coil rf power, dc-bias voltage and gas pressure on the etch rate and etch profile were investigated. The etch rate increased with increasing coil rf power, dc-bias voltage and gas pressure. The degree of anisotropy in the etched titanium films improved with increasing coil rf power and dc-bias voltage and decreasing gas pressure. X-ray photoelectron spectroscopy revealed the formation of titanium compounds during etching, indicating that Ti films etching proceeds by a reactive ion etching mechanism.     

HfO2 etching mechanism in inductively-coupled Cl2/Ar plasma

Etching characteristics and the mechanism of HfO₂ thin films in Cl₂/Ar inductively-coupled plasma were investigated. The etch rate of HfO₂ was measured as a function of the Cl₂/Ar mixing ratio in the range of 0 to 100% Ar at a fixed gas pressure (6 mTorr), input power (700 W), and bias power (300 W). We found that an increase in the Ar mixing ratio resulted in a monotonic decrease in the HfO₂ etch rate in the range of 10.3 to 0.7 nm/min while the etch rate of the photoresist increased from 152.1 to 375.0 nm/min for 0 to 100% Ar. To examine the etching mechanism of HfO₂ films, we combined plasma diagnostics using Langmuir probes and quadrupole mass spectrometry with global (zero-dimensional) plasma modeling. We found that the HfO₂ etching process was not controlled by ion-surface interaction kinetics and formally corresponds to the reaction rate-limited etch regime.     

Etch characteristics of indium zinc oxide thin films using inductively coupled plasma of a Cl2/Ar gas

Inductively coupled plasma reactive ion etching of indium zinc oxide (IZO) thin films masked with a photoresist was performed using a Cl₂/Ar gas. The etch rate of the IZO thin films increased as Cl₂ gas was added to Ar gas, reaching a maximum at 60% Cl₂ and decreasing thereafter. The degree of anisotropy in the etch profile improved with increasing coil rf power and dc-bias voltage. Changes in pressure had little effect on the etch profile. X-ray photoelectron spectroscopy confirmed the formation of InCl₃ and ZnCl₂ on the etched surface. The surface morphology of the films etched at high Cl₂ concentrations was smoother than that of the films etched at low Cl₂ concentrations. These results suggest that the dry etching of IZO thin films in a Cl₂/Ar gas occurs according to a reactive ion etching mechanism involving ion sputtering and a surface reaction.     

Fabrication of epitaxial III-nitride cantilevers on silicon (1 1 1) substrates

The molecular beam epitaxy of AlGaN/GaN epilayers on silicon (1 1 1) using an aluminum nitride buffer layer, and subsequent fabrication of free standing III-nitride cantilevers on Si(1 1 1) has been investigated. Transmission electron microscopy (TEM) of cross-section samples reveals a columnar structure consisting of the hexagonal gallium nitride polytype. Selected area diffraction indicates an epitaxial relationship between the gallium nitride and silicon substrate which is described by GaN[0 0 0 1]//Si[1 1 1] and GaN(1 1 0 0)//Si(1 1 1). Imaging of the electronic structure of an AlGaN/GaN interface has been investigated by mapping the variation in the plasmon frequency using an electron energy loss spectrometer on a dedicated scanning transmission electron microscope. Cantilevers were fabricated using a combination of etching processes. Nitride etch rates during inductively coupled plasma dry etch processing using a Cl₂/Ar plasma etchant were obtained by monitoring the optical reflectivity of the nitride films in situ. A peak GaN etch rate of 250 nm/min was measured, the etch rate was found to be strongly dependent on the d.c. self-bias. Thin beams of GaN having a length of 7 μm and 0.7 μm thickness, were fabricated and mechanically released from Si(1 1 1) substrates using a combination of two dry ICP etch processes, using Cl₂/Ar and CF₄/Ar/O₂ chemistries, and a potassium hydroxide (KOH) aqueous wet etch.     

Etch characteristics of FePt magnetic thin films using inductively coupled plasma reactive ion etching

Etch characteristics of L10 FePt thin films masked with TiN films were investigated using an inductively coupled plasma (ICP) reactive ion etching in a CH₃OH/Ar plasma. As the CH₃OH gas was added to Ar, the etch rates of FePt thin films and TiN hard mask gradually decreased, and the etch profile of FePt films improved with high degree of anisotropy. With increasing ICP rf power and dc-bias voltage to substrate and decreasing gas pressure, the etch rate increased and the etch profile becomes vertical without any redepositions or etch residues. Based on the etch characteristics and surface analysis of the films by X-ray photoelectron spectroscopy, it can be concluded that the etch mechanism of FePt thin films in a CH₃OH/Ar gas does not follow the reactive ion etch mechanism but the chemically assisted sputter etching mechanism, due to the chemical reaction of FePt film with CH₃OH gas.     

Etching characteristics of LiNbO3 crystal by fluorine gas plasma reactive ion etching

The etching characteristics of a LiNbO₃ single crystal have been investigated using plasma reactive ion etching (RIE) with a mixture of CF₄/Ar/H₂. The etching rate of LiNbO₃ with the mixture of CF₄/Ar/H₂ gases was evaluated. The etching surface was evaluated by atomic force microscopy, X-ray diffraction and X-ray photoelectron spectroscopy methods. The rate-determining process of RIE is the supply of F radicals in RIE. The surface morphology of the etched LiNbO₃ changed with the increase in the H₂ gas flow ratio. The surface profile became flat, on optimizing the etching conditions, similar to the surface of non-etched LiNbO₃. The X-ray diffraction peakfor etched LiNbO₃ using the mixture of CF₄ and Ar gases did not appear, because a non-crystalline layer was formed. It was found that the crystallinity of the surface is dependent on both, the flow rate of H₂ gas and the etching time. F atoms exist in the contamination layer of the sample etched, using the mixture of CF₄, Ar and H₂ gases. Optimum etching conditions, considering both the surface flatness and the crystallinity, were determined.