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.     

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 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.     

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.     

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.     

The dry etching property of TiO2 thin films using metal-insulator-metal capacitor in inductively coupled plasma system

In this work, we investigated the etching characteristics of TiO₂ thin films and the selectivity of TiO₂ to SiO₂ in a BCl₃/Ar inductively coupled plasma (ICP) system. The maximum etch rate of 84.68 nm/min was obtained for TiO₂ thin films at a gas mixture ratio of BCl₃/Ar (25:75%). In addition, etch rates were measured as a function of etching parameters, such as the RF power, DC-bias voltage and process pressure. Using the X-ray photoelectron spectroscopy analysis the accumulation of chemical reaction on the etched surface was investigated. Based on these data, the ion-assisted physical sputtering was proposed as the main etch mechanism for the BCl₃-containing plasmas.     

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.     

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.     

Etch characteristics of silver by inductively coupled fluorine-based plasmas

In this study, thin films of Ag deposited onto glass substrates were etched using inductively coupled fluorine-based plasmas. The effects of various process conditions on the Ag etch characteristics were evaluated to ascertain whether it would be possible to etch patterned Ag films with high etch rates and smooth sidewalls free of involatile etch products. It was found that involatile etch products remained on the substrate when films were etched in CF₄-based gas mixtures possessing either O₂ or N₂ as an additive. However, when Ar was added to either NF₃ or CF₄, a residue-free etch was obtained provided the partial pressure of Ar was no less than 50%. It is proposed that the residue-free Ag etch mechanism involves the formation of silver fluoride, which is physically sputtered by Ar⁺ ions. A Ag etch rate of 160 nm/min with a Ag to photoresist etch selectivity exceeding 1.1 was achieved with an inductive power of 1500 W, a d.c. bias voltage of −180 V and a chamber pressure of 0.8 Pa with 50-50 CF₄/Ar partial pressures obtained with 60 sccm CF₄/60 sccm Ar flows. In addition, these conditions produced smooth Ag sidewall etch profiles.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Characteristics of GaN thin films by inductively coupled plasma etching with Cl2/BCl3 and Cl2/Ar

GaN thin films were etched by inductively coupled plasma (ICP). The effects of BCl₃ and Ar with different Cl₂ fraction are studied and compared. The ICP power and RF power are also altered to investigate the different effects by using Cl₂/BCl₃ or Cl₂/Ar as etching gases. The etch rate and surface morphology of the etched surface are characterized by using surface profiler, scanning electron microscopy and atomic force microscopy. The root-mean-square roughness values are systematically compared. It is found that the etch rates of Cl₂/Ar are higher than that of the Cl₂/BCl₃ in the Cl₂ fraction ranging from 10 to 90%. When the ICP power is increased, the RMS roughness of GaN surface after ICP etching shows reverse trend between Cl₂/BCl₃ and Cl₂/Ar gas mixture. The results indicate quite different features using Cl₂/BCl₃ and Cl₂/Ar for GaN ICP etcing under the same conditions.     

Plasma etching of high-k and metal gate materials

Etching characteristics of high-k dielectric materials (HfO₂) and metal electrode materials (Pt, TaN) have been studied in high-density chlorine-containing plasmas at pressures around 10 mTorr. The etching of HfO₂ was performed in BCl₃ without rf biasing, giving an etch rate of about 5 nm/min with a high selectivity of >10 over Si and SiO₂. The etching of Pt and TaN was performed in Ar/O₂ with high rf biasing and in Ar/Cl₂ with low rf biasing, respectively, giving a Pt etch rate of about several tens nm/min and a TaN etch rate of about 200 nm/min with a high selectivity of >8 over HfO₂ and SiO₂. The etched profiles were outwardly tapered for Pt, owing to the redeposition of etch or sputter products on feature sidewalls, while the TaN profiles were almost anisotropic, probably owing to the ion-enhanced etching that occurred.     

Etch characteristics of indium zinc oxide thin films in a C2F6/Ar plasma

Dry etching of indium zinc oxide (IZO) thin films was performed using inductively coupled plasma reactive ion etching in a C₂F₆/Ar gas. The etch characteristics of IZO films were investigated as a function of gas concentration, coil rf power, dc-bias voltage to substrate, and gas pressure. As the C₂F₆ concentration was increased, the etch rate of the IZO films decreased and the degree of anisotropy in the etch profile also decreased. The etch profile was improved with increasing coil rf power and dc-bias voltage, and decreasing gas pressure. An X-ray photoelectron spectroscopy analysis confirmed the formation of InF₃ and ZnF₂ compounds on the etched surface due to the chemical reaction of IZO films with fluorine radicals. In addition, the film surfaces etched at different conditions were examined by atomic force microscopy. These results demonstrated that the etch mechanism of IZO thin films followed sputter etching with the assistance of chemical reaction.     

A study on the etch characteristics of HfAlO3 dielectric thin film in Cl2/Ar gas chemistry using inductively coupled plasma system

Thin films of HfAlO₃, a high-k material, were etched using inductively-coupled plasma. The dry etching mechanism of the HfAlO₃ thin film was studied by varying the Cl₂/Ar gas mixing ratio, RF power, direct current bias voltage, and process pressure. The maximum etch rate of the HfAlO₃ thin film was 16.9 nm/min at a C1₂/(C1₂ + Ar) ratio of 80%. Our results showed that the highest etch rate of the HfAlO₃ thin films was achieved by reactive ion etching using Cl radicals, due to the high volatility of the metal-chlorides. Consequently, the increased chemical effect caused an increase in the etch rate of the HfAlO₃ thin film. Surface analysis by x-ray photoelectron spectroscopy showed evidence that Hf, Al and O reacted with Cl and formed nonvolatile metal-oxide compounds and volatile metal-chlorides. This effect may be related to the concurrence of chemical and physical pathways in the ion-assisted chemical reaction.