Etch Rate Of Films Research Articles

Magnetron Reactive Ion Etching of Polycrystalline 3C-SiC Thin Films

This paper describes the magnetron reactive ion etching (RIE) characteristics of polycrystalline (poly) 3C-SiC thin films grown on thermally oxidized Si substrates by using atmospheric pressure chemical vapor deposition (APCVD). The etch rate of the poly 3C-SiC thin films was varied from 20 ˚ to 400 ˚ depending on conditions, such as the gas flow rates, the chamber pressure, the RF power, and the electrode gap. The best vertical structures were obtained by the addition of 40 % O2, 16 % Ar and 44 % CHF3 reactive gas at a 40-mTorr chamber pressure. Stable etching was achieved at 70 W, and the poly 3C-SiC was undamaged. These results show that in a magnetron RIE system, it is possible to etch SiC with lower power than that of a commercial RIE system. Therefore, poly 3C-SiC etched by magnetron RIE has a potential for applications to be applied to micro/nano electromechanical systems (M/NEMS).

Fabrication of low-loss channel waveguides in Al2O3 and Y2O3 layers by inductively coupled plasma reactive ion etching

Etching of amorphous Al2O3 and polycrystalline Y2O3 films has been investigated using an inductively coupled reactive ion etch system. The etch behaviour has been studied by applying various common process gases and combinations of these gases, including CF4/O2, BCl3, BCl3/HBr, Cl2, Cl2/Ar and Ar. The observed etch rates of Al2O3 films were much higher than Y2O3 for all process gases except for Ar, indicating a much stronger chemical etching component for the Al2O3 layers. Based on analysis of the film etch rates and an investigation of the selectivity and patterning feasibility of possible mask materials, optimized optical channel-waveguide structures were fabricated in both materials. In Al2O3, channel waveguides were fabricated with BCl3/HBr plasma and using a standard resist mask, while in Y2O3, channel waveguides were fabricated with Ar and using either a resist or a sputter deposited Al2O3 mask layer. The etched structures in both materials exhibit straight sidewalls with minimal roughness and sufficient etch depths (up to 530 nm for Al2O3 and 250 nm for Y2O3) for defining waveguides with strong optical confinement. Using the developed etch processes, low additional optical propagation losses (on the order of 0.1 dB/cm) were demonstrated in single-mode ridge waveguides in both Al2O3 and Y2O3 layers at 1550 nm.

High etch rates of poly-crystalline 3C-SiC films in magnetron enhanced CHF 3 plasmas

Magnetron enhanced reactive ion etching (RIE) of poly-crystalline 3C-SiC thin films grown on thermally oxidised Si substrates has been investigated in CHF 3 plasmas. The magnetron enhanced RIE can stably etch the poly-crystalline 3C-SiC thin film at a lower ion energy (70 W) without any damage than can the commercial RIE system. The best vertical structure was improved by the addition of 40% O 2 and 16% Ar with the CHF 3 reactive gas.

Deposition of sacrificial silicon oxide layers by electron cyclotron resonance plasma

Electron cyclotron resonance plasmas with SiH4∕O2∕Ar mixtures were used for deposition of thin films of silicon oxide, to be employed as sacrificial layers in microelectromechanical system (MEMS) fabrication. The grown films were characterized by Fourier transform infrared and ellipsometry. Optical emission spectroscopy and Langmuir probe were used for plasma characterization. It has been shown that OH molecules generated in the plasma play an important role in formation of films suitable as sacrificial layers for MEMS fabrication. Extremely high etch rates of grown oxide films (up to 10μm∕min) were obtained, allowing fabrication of high quality poly-Si suspended structures.

Etching SiO2 with HF/pyridine-supercritical carbon dioxide solutions and resultant interfacial electronic properties

Silicon dioxide (SiO2) films grown on single crystal Si in high temperature O2 were etched using nonaqueous HF/pyridine solutions in supercritical CO2. The etch rate of SiO2 films were studied in the solutions with HF concentration up to 1000μM at 1.38×107Pa and at 35, 45, and 55°C. Capacitance versus voltage, conductance versus voltage, and leakage current measurements were performed on capacitor structures fabricated after SiO2 regrowth on completely etched Si surfaces. The electronic results revealed no systematic differences of etched and unetched samples with various etch times concentrations and that the Si–SiO2 interface of completely etched samples was comparable to the unetched control sample in terms of interface electronic charge and states and leakage current.

Silicon dioxide films by RF sputtering for microelectronic and MEMS applications

In the present work, we report low temperature (<285 °C) RF sputter deposition of silicon dioxide films for microelectronic and MEMS applications. The films were prepared by RF diode sputtering using a 3 inch diameter SiO2 target in argon atmosphere in the pressure range 5–20 mTorr and RF power from 100 to 300 W. The effect of deposition parameters (RF power and sputtering pressure) on various properties such as deposition rate, surface morphology, surface roughness, stress and etch rate of silicon dioxide films are investigated. The deposition parameters are optimized to obtain the films having low surface roughness and minimum stress. Due to the advantage of much lower thermal budget of the sputtering process compared to thermal oxidation, the application of RF-sputtered SiO2 films in IC fabrication is explored. Boron diffusion experiments are conducted using a sputtered SiO2 film as a masking layer. In order to investigate the application of RF-sputtered silicon dioxide films for MEMS, SiO2 microstructures such as bridges and cantilever beams were fabricated using bulk and surface micromachining processes. We also explore silicon wafer bonding using RF-sputtered silicon dioxide films as an intermediate layer.

Inductively Coupled Plasma Reactive Ion Etching of GeSbTe Thin Films in a HBr/Ar Gas

ABSTRACT Inductively coupled plasma reactive ion etching of GeSbTe (GST) thin films with a photoresist mask was performed using a HBr/Ar gas mixture. The etch rate of GST films increased up to 20% HBr concentration and began to decrease with further increase of HBr concentration. The etch profiles were improved with increasing HBr gas concentration. In particular, clean and vertical etch profiles were achieved at 80∼ 100% HBr gas concentrations. As the coil rf power and dc-bias voltage increased, the etch rates increased. The gas pressure had little influence on the etch rate. The good etch profiles were obtained at high coil power, low dc-bias and high gas pressure. The x-ray photoelectron spectroscopy analysis reveals that Te showed highest reactivity with HBr gas chemistry. A high degree of anisotropic etching of GST films was achieved using HBr/Ar gas mixture at the optimized etch conditions.

Nanolithographic patterning of transparent, conductive single-walled carbon nanotube films by inductively coupled plasma reactive ion etching

The authors report successful patterning of transparent, conductive single-walled carbon nanotube films down to 100nm lateral dimensions by photolithography or e-beam lithography and subsequent O2 plasma etching using an inductively coupled plasma reactive ion etching (ICP-RIE) system. They systematically study the effect of ICP-RIE etch parameters, such as substrate bias power, chamber pressure, and substrate cooling, on the nanotube film etch rate and etch selectivity. They also characterize the effect of the linewidth etched on the nanotube film etch rate for widths ranging from 50μm down to 100nm. Furthermore, by fabricating standard four point probe structures using the patterning capability developed, the authors investigate the effect of different resist processes on the resistivity of patterned single-walled carbon nanotube films and the effect of ICP reactive ion etching on the resistivity of partially etched nanotube films. In addition, they demonstrate that using an ICP-RIE system provides significant advantages, such as faster etch rates and better etch selectivity, over conventional parallel plate RIE plasma systems, making it possible to pattern lateral features as small as 100nm in nanotube films. The simple and efficient “top-down” patterning capability developed in this article could open up many opportunities for integrating single-walled nanotube films into a wide range of electronic and optoelectronic devices.

Etch damage evaluation on (Bi 4−xLa x)Ti 3O 12 thin films during the etch process using inductively coupled plasma sources

The etching mechanism of (Bi 4− x La x )Ti 3O 12 (BLT) thin films in Ar/Cl 2 inductively coupled plasma (ICP) and plasma-induced damages at the etched surfaces were investigated as a function of gas-mixing ratios. The maximum etch rate of BLT thin films was 50.8 nm/min of 80% Ar/20% Cl 2. From various experimental data, amorphous phases on the etched surface existed on both chemically and physically etched films, but the amorphous phase was thicker after the 80% Ar/20% Cl 2 process. Moreover, crystalline “breaking” appeared during the etching in Cl 2-containing plasma. Also the remnant polarization and fatigue resistances decreased more for the 80% Ar/20% Cl 2 etch than for pure Ar plasma etch.

Selective etching of (Ba,Sr)TiO 3 thin films over silicon in an inductively coupled plasma

In this work, we investigated etching characteristics of BST thin films and higher selectivity of BST over Si using inductive coupled O 2/Cl 2/Ar plasma (ICP) system. The maximum etch rate of BST thin films and selectivity of BST over Si were 61.5 nm/min at a O 2 addition of 1 sccm, 9.52 at a O 2 addition of 4 sccm into the Cl 2(30%)/Ar(70%) plasma, respectively. Plasma diagnostics was performed by Langmuir probe (LP), optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS). These results confirm that the increased etch rates at O 2 addition of 1 sccm is the result of the enhanced chemical reaction between BST and Cl radicals and an ion bombardment effect.

Plasma Etch Rates of Porous Silica Low-k Films with Different Dielectric Constants

The reactive ion etch rates of porous silica films with different dielectric constants (k-values) or film densities were measured by varying wafer bias and gas ratio for Ar/C5F8/O2 plasma. Both the etch rates of porous silica films and the optical emission intensities from the etching products (SiF) increased with wafer bias power. Etch rate increased with decreasing k-value of porous silica, whereas SiF emission intensity was maintained constant regardless of k-value, indicating that the amount of etching products escaping from the porous silica surface to the gas phase remained unchanged. From this result it is concluded that mass etch rate, defined as the weight of a porous silica film etched from a unit area per unit time, is constant for Ar/C5F8/O2 plasma.

Microstructural Evolution of ZnO by Wet-Etching Using Acidic Solutions

The characteristics of the wet-etching of ZnO thin films were investigated using hydrochloric and phosphoric acid solutions as etchants. The etch rate of ZnO films, using a highly diluted hydrochloric acid solutions at a concentration of 0.25% in deionized water, was determined to be about 120 nm/min, and linearly increased with increasing the acid concentration. The surface of ZnO(0001) etched by an HCl solution, observed by scanning electron microscopy, showed a rough morphology with a high density of hexagonal pyramids or cones with sidewall angles of about approximately 45 degrees. Moreover, the sidewall angles of the masked area were similar to those of the pyramids on the surface. In comparison, the surface of ZnO(0001) etched by a phosphoric acid had a smooth surface morphology. The origin of this difference is from the very initial stage of etching, indicating that the etch-mechanism is different for each solution. Furthermore, when H3PO4 was added to the HCl aqueous solution, the morphology of the etched surface was greatly enhanced and the sidewall angle was also increased to about 65 degrees.

Low-k SiOCH Film Etching Process and Its Diagnostics Employing Ar/C5F10O/N2 Plasma

We proposed an environmental harmonic etching gas of C5F10O (CF3CF2CF2OCFCF2), and demonstrated the etching of low-k SiOCH films employing a dual-frequency capacitively coupled etching system. Dissociative ionization cross sections for the electron impact ionizations of C5F10O and c-C4F8 gases have been measured by quadrupole mass spectroscopy (QMS). The dissociative ionization cross section of CF3+ from C5F10O gas was much higher than those of other ionic species, and 10 times higher than that of CF3+ from C4F8 gas. CF3+ is effective for increasing the etching rate of SiO2. As a result, the etching rate of SiOCH films using Ar/C5F10O/N2 plasma was about 1000 nm/min, which is much higher than that using Ar/C4F8/N2 plasma. The behaviours of fluorocarbon radicals in Ar/C5F10O/N2 plasma, which were measured by infrared diode laser absorption spectroscopy, were similar to those in Ar/C4F8/N2 plasma. The densities of CF and CF3 radicals were markedly decreased with increasing N2 flow rate. Etching rate was controlled by N2 flow rate. A vertical profile of SiOCH with a high etching rate and less microloading was realized using Ar/C5F10O/N2 plasma chemistry.

Etching characteristics of LaNiO3 thin films in BCl3∕Ar gas chemistry

La Ni O 3 (LNO) electrode was intensively studied as electrodes because LNO has a pseudocubic perovskite crystal structure with a lattice parameter of 3.84Å. But the etching process of LNO thin films must be developed in order to realize highly integrated ferroelectric random access memories. In this work, we investigated etching characteristics and mechanisms of LNO thin films using inductively coupled BCl3∕Ar plasma (ICP) system. The maximum etch rate of LNO thin films was 41.1nm∕min at a BCl3(20)∕Ar(80) gas mixing ratio. The positive ions and the ion energy distributions were measured with a quadrupole mass spectrometer (QMS). As rf power and dc bias voltage increased and working pressure decreased, the ion energy and etch rates of LNO thin films were increased. A chemically assisted physical etch of LNO was experimentally confirmed by ICP system and QMS measurements.

Surface etching mechanism of Bi4−xLaxTi3O12 thin films using quadrupole mass spectroscopy

The etching mechanism of (Bi4−xLax)Ti3O12 (BLT) thin films in Ar∕Cl2 inductively coupled plasma (ICP) was investigated as a function of gas mixing ratios, process pressure, and ICP powers at fixed other conditions. Etch rates were measured by using an α-step surface profiler. The maximum etch rate of BLT thin films was 117nm at 0.8 Ar∕(Ar+Cl2) gas mixing ratios with following conditions: process pressure of 15mTorr, gas flow rate of 20sccm, ICP power of 700W, and dc bias of −150V. The etch rate was increased as decreasing the process pressure. For a detailed investigation of etching mechanisms of BLT thin films, the ion energy distributions of each positive species were measured using quadrupole mass spectrometer and analyzed those data. Also the electron energy distribution was measured as a function of Ar∕Cl2 gas mixing ratios.

Application of polysilazane to etch mask in pattern transfer processes for deep and vacuum ultraviolet lithography

A polysilazane is investigated for a spin-on glass (SOG) used for a middle layer in a trilevel resist system. Higher film density is required for the middle layer to obtain higher etch resistance during the underlayer etching. The compositions of the polysilazane baked at 200°C and 300°C are Si0.42O0.34C0.40N0.20 and Si0.29O0.65C0.10N0.05, respectively, which are determined by x-ray photoelectron spectroscopy. The polysilazane is converted to silicon-oxide-like compositions by baking at 300°C. The film density and etch rate of SOG made from polysilazane are compared with that of polysiloxsane on condition that both films are baked at 300°C. The film density of the SOG made from the polysilazane is 2.07 g/cm3, which is higher than 1.87 g/cm3 of the conventional SOG made from a polysiloxsan. The etch resistance of the SOG made from the polysilazane is improved by 90% compared with that of the SOG made from the polysiloxsane due to the increased film density.

High-density plasma etching of CoFeSiB magnetic films with hard mask

High-density plasma etching of amorphous CoFeSiB magnetic films was carried out in a Cl 2/Ar and Cl 2/O 2/Ar gas mixes. In a Cl 2/Ar gas, as the Cl 2 concentration increased, the etch rate of CoFeSiB films decreased, and etch residues decreased but the etch slope was slanted. However, in Cl 2/O 2/Ar gas mix, the etch characteristics of CoFeSiB films with TiN hard mask was enhanced. The etch rate and selectivity of CoFeSiB films were investigated as a function of O 2 concentration. The use of TiN hard mask gave rise to high etch selectivity of CoFeSiB to TiN mask due to large decrease in etch rate of TiN in Cl 2/O 2/Ar chemistry. The addition of O 2 into the gas mix led to the anisotropic etching of CoFeSiB films without the etch residues.

Wet-etch characteristics of ZnO using acidic solutions

The characteristics of the wet-etching of ZnO thin films were investigated using hydrochloric and phosphoric acid solutions as etchants. The etch rate of ZnO films, using highly diluted hydrochloric acid solutions at a concentration of 0.25% in deionized water, was determined to be about 120 nm/min, and linearly increased with increasing the acid concentration, resulting in <TEX>$1.17{\mu}m/min$</TEX> when a 2% HCl solution was used. The surface of ZnO etched by an HCl solution, observed by scanning electron microscopy, showed a rough morphology with a high density of hexagonal pyramids or cones with sidewall angles of about <TEX>${\sim}45^{\circ}C$</TEX>. Moreover, the sidewall angles of the masked area were similar to those of the pyramids on the surface. In comparison, the surface of ZnO etched by a phosphoric acid had a smooth surface morphology. The origin of this difference is from the very initial stage of etching, indicating that the etch-mechanism is different for each solution. Furthermore, when <TEX>$H_3PO_4$</TEX> was added to the HCl aqueous solution, the morphology of the etched surface was greatly enhanced and the sidewall angle was also increased to about <TEX>$65^{\circ}C$</TEX>.

Wet etching mechanisms of ITO films in oxalic acid

This study examines how oxalic acid solutions affect indium tin oxide (ITO) etching. Experimental results show that the etching rate of ITO films increased linearly with the concentration of C 2 O 4 2 - . The open circuit potentials included in the potential–pH diagrams for indium and tin in aqueous oxalic acid systems helped determine that ITO films was dissolved by the formation of In ( C 2 O 4 ) 2 - in oxalic acid. However, the tin oxide in ITO films was difficult to dissolve, but could be removed by stripping. The EDS analysis and optical microscopic images indicate that the removal rate of SnO 2 in oxalic acid etchants was slower than that of In 2O 3, and many residues were distributed around the ITO bars after the etching process. Moreover, kinetic experiments reveal the high activation energy of ITO etching, and it was found stirring or ultrasonic vibration of the etchants had no influence on the dissolution rate of ITO films at all. Therefore, the rate-determining step should be the chemical reaction on ITO surface. A mechanism including protonation and ligand adsorption was proposed to explain the observed results.

Organic Acid Mixing to Improve ITO Film Etching in Flat Panel Display Manufacturing

This study examines how oxalic acid mixed with tartaric acid affect indium tin oxide (ITO) etching. When the ITO films were etched with the mixed solutions of oxalic acid and tartaric acid, the dissociation of tartaric acid impeded the formation of oxalate ion and decreased the etching rate of ITO films. Furthermore, the potential–pH diagrams for indium and tin in oxalic acid and tartaric acid systems reveal that indium oxide could be dissolved to form in oxalic acid etchants, and that indium oxide and tin oxide were both soluble in the mixed etchants of oxalic acid and tartaric acid. Additionally, the X-ray photoelectron spectroscopy results demonstrate that the removal rate of was slower than that of in oxalic acid etchants, which induced many residues after the etching process. However, adding tartaric acid to oxalic acid increased the dissolution rate of tin oxide and decreased the level of residues. Consequently, the ITO etching by oxalic acid with tartaric acid shows a more uniform pattern than that by only oxalic acid.