Inductively Coupled Plasma RF Power Research Articles

Etch characteristics of cobalt thin films using high density plasma of halogen gas

Inductively coupled plasma (ICP) reaction ion etching of Co thin films patterned with SiO2 hard marks was performed using Cl2/Ar and Cl2/O2/Ar gas mixtures. The etch rate, etch selectivity, and etch profile of the cobalt thin films were investigated by varying the gas concentration in the Cl2/Ar and Cl2/O2/Ar gas mixtures. The etching parameters, including the ICP RF power, DC-bias voltage to the substrate, and process pressure, were varied to investigate the etch characteristics. The etch mechanisms in the Cl2/Ar and Cl2/O2/Ar gas mixtures were examined using X-ray photoelectron spectroscopy, scanning probe microscopy, and optical emission spectroscopy. Finally, the cobalt thin films with 300 nm line pattern were etched using a Cl2/O2/Ar gas mixture under the optimized etch conditions.

Fabrication of Ultra-Fine Micro-Vias in Non-Photosensitive Polyimide for High-Density Vertical Interconnects.

With the growing demands for transferring large amounts of data between components in a package, it is required for advanced packaging technologies to form smaller vertical vias in the insulators. Plasma etching is one of the most widely used micro-vias formation processes. This paper has developed a fabrication process for 5-10 µm residue-free micro-vias with 70° tapered angle in polyimide film based on O2/CHF3 inductively coupled plasma (ICP). The etch rate would monotonically increase with the ICP power, RF power, and gas flow rate. As for the gas ratio, there is an optimum range of CHF3 ratio, which could obtain the highest etch rate. The results have clearly shown that the enhancement of ion bombardment and prolongation of etching time would be beneficial to grass-like residue removal. In addition, during the etching of partially cured polyimide, the lateral etch rate would significantly increase in the region near the metal hard mask.

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.

Surface Chemical Reaction on HfO2 Thin Film Etched by High Density Plasma

In this work, we investigated the etching characteristics of HfO2 thin films and the selectivity of HfO2 to SiO2 in an O2/CF4/Ar inductively coupled plasma (ICP) system. The maximum etch rates of HfO2 thin films was 70 nm/min at a gas mixing ratio of O2/CF4/Ar (3:4:16 sccm). At the same time, the etch rate were measured as a function of the etching parameters, such as the ICP RF power, DC-bias voltage, and process pressure. 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. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the CF4-containing plasmas.

Inductively coupled plasma reactive ion etching of FePt magnetic thin films in a CH4/O2/Ar plasma

An inductively coupled plasma (ICP) reactive ion etching of FePt thin films masked with TiN films was carried out in CH4/O2/Ar plasma. As CH4 gas was added to Ar, the etch rates of the FePt thin films and TiN hard mask decreased gradually, and the etch profile of the FePt films improved slightly. The addition of O2 gas to the CH4/Ar gas mixture enhanced the etch profile due to an increase in the etch selectivity of the FePt film to the TiN hard mask. From optical emission spectroscopy (OES) for the CH4/O2/Ar gas mix, the increase in etch selectivity was attributed to the increase in [H] species as well as [O] species due to the addition of O2 gas.With increasing ICP rf power and dc-bias voltage to the substrate, the etch rates increased and the etch profiles improved with a higher degree of anisotropy. X-ray photoelectron spectroscopy (XPS) of the etched FePt films revealed the existence of Fe-containing compounds formed during etching in CH4/O2/Ar plasma. The etch characteristics, OES and XPS analysis of the film surface showed that the etching of FePt films in CH4/O2/Ar plasma follows mainly sputter etching with the assistance of chemical reactions with the films.

$\hbox{BCl}_{3}/\hbox{Cl}_{2}$-Based Inductively Coupled Plasma Etching of GaN/AlGaN Using Photoresist Mask

Gallium nitride/aluminium gallium nitride (GaN/AlGaN) etching in BCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Cl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based inductively coupled plasma (ICP) is investigated for high electron mobility transistor (HEMT) mesa etching using rarely preferred mask-photoresist. The critical issues related to photresist burning/deforming, resist removal, selectivity, mesa edge roughening, and nonuniform etching of GaN and AlGaN layers are discussed in detail using plasma of BCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> / Cl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gases. The effect of ICP process parameters like ICP power, RF power, pressure, and BCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Cl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> flow rate ratio on etch rate of GaN/AlGaN layers and mask is studied systematically for the optimization of a HEMT mesa etching process that results in smooth etched surface with sharp and highly anisotropic mesa edges. The photoresist mask selectivity is found to depend strongly on pressure and RF power, whereas the etched surface morphology changes significantly with the gas flow rate ratio and chamber pressure. The AlGaN etch rate and selectivity with respect to GaN is also characterized for different Al concentrations varying up to 33%. The etch process is finally applied to GaN/AlGaN HEMT mesa etching, where the mesa features with depth of ~ 1500 A° are etched successfully. The resultant process etch uniformity is found to be better than 5% over 2-in wafer.

Visualization, velocimetry, and mass spectrometric analysis of engineered and laser-produced particles passing through inductively coupled plasma sources

Velocities of particles passing through the load coil region of an inductively coupled plasma (ICP) attached to a quadrupole mass spectrometer (MS) were measured by particle image velocimetry (PIV). Particles were produced either by laser ablation (LA) of solid targets or from drying analyte-spiked microdroplets ejected by a piezoelectrically actuated quartz capillary. For instance, velocities determined under conditions typically applied to LA-ICP-MS analyses were found to range between 10 and 20 m s−1, depending on the axial position. Our data, furthermore, evidence significant changes of the gas velocity upon modifications of the ICP operating conditions such as plasma power, gas flow rate, and torch injector diameter if helium is admixed in excess of >50% of the total gas flow passing through the injector. For instance, an increase of the ICP RF power from 800 to 1600 W resulted in particle velocity gradients up to 15 m s−1 kW−1 measured after the third turn of the RF-coil. Temporal changes in velocity, i.e. particle accelerations over the axis of the load coil region were specified to 300–1000 m s−2. In addition, ICP-MS analyses of laser-produced aerosols carried out at constant volumetric flow rates but reduced injector diameters made signal intensities of elements such as Y, Ce, or U drop by up to two orders of magnitude suggesting incomplete particle evaporation as well as notably different aerosol penetration depths. Sensitivities measured in this case turned out to correlate with boiling points of the respective oxides rather than the element-specific ionization potentials commonly observed. The mechanisms controlling gas velocity and sensitivity variations are discussed and consequences on LA-ICP-MS analyses are drawn.

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.

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 CH 3OH/Ar plasma. As the CH 3OH 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 CH 3OH/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 CH 3OH gas.

Optimization of inductively coupled plasma deep etching of GaN and etching damage analysis

Inductively coupled plasma (ICP) etching of GaN with an etching depth up to 4μm is systemically studied by varying ICP power, RF power and chamber pressure, respectively, which results in etch rates ranging from ∼370nm/min to 900nm/min. The surface morphology and damages of the etched surface are characterized by optical microscope, scanning electron microscope, atomic force microscopy, cathodoluminescence mapping and photoluminescence (PL) spectroscopy. Sub-micrometer-scale hexagonal pits and pillars originating from part of the structural defects within the original GaN layer are observed on the etched surface. The density of these surface features varies with etching conditions. Considerable reduction of PL band-edge emission from the etched GaN surface indicates that high-density non-radiative recombination centers are created by ICP etching. The density of these non-radiative recombination centers is found largely dependent on the degree of physical bombardments, which is a strong function of the RF power applied. Finally, a low-surface-damage etch recipe with high ICP power, low RF power, high chamber pressure is suggested.

Nano-crystalline silicon thin films grown by the inductively coupled plasma assisted CFUBM at low temperature

The hydrogenated nano-crystalline silicon thin films were deposited on glass substrates at low temperatures in an argon and hydrogen atmosphere using inductively coupled plasma (ICP) — assisted closed field unbalanced magnetron sputtering (CFUBM) system. A one-turn ICP coil was installed to dissociate the hydrogen molecules by the induced magnetic field inside the chamber. The emission intensity, I Hα (656.28 nm), was saturated at a magnetron RF (13.56 MHz) power of 400 W and increased with increasing ICP RF (13.56 MHz) power. The Raman peak of the silicon thin film shifted from 480 cm − 1 (amorphous phase) to 520 cm − 1 (crystalline phase) with increasing ICP power. The crystalline volume fraction of the silicon thin films was 65% at an ICP power of 400 W and the crystallite grain size was approximately 7 nm. X-ray diffraction and Fourier-transform infrared spectroscopy were used to examine the structural changes and chemical bonding state, respectively.

Optimization of inductively coupled plasma etching for low nanometer scale air-hole arrays in two-dimensional GaAs-based photonic crystals

This paper mainly describes fabrication of two-dimensional GaAs-based photonic crystals with low nanometer scale air-hole arrays using an inductively coupled plasma (ICP) etching system. The sidewall profile and surface characteristics of the photonic crystals are systematically investigated as a function of process parameters including ICP power, RF power and pressure. Various ICP powers have no significant effect on the verticality of air-hole sidewall and surface smoothness. In contrast, RF power and chamber pressure play a remarkable role in improving sidewall verticality and surface characteristics of photonic crystals indicating different etching mechanisms for low nanometer scale photonic crystals. The desired photonic crystals have been achieved with hole diameters as low as 130 nm with smooth and vertical profiles by developing a suitable ICP processes. The influence of the ICP parameters on this device system are analyzed mainly by scanning electron microscopy. This fabrication approach is not limited to GaAs material, and may be efficiently applied to the development of most two-dimensional photonic crystal slabs.

Superhard tantalum-nitride films formed by inductively coupled plasma-assisted sputtering

The effect of inductively coupled plasma (ICP) power on the mechanical properties of tantalum-nitride films was investigated. TaN films were grown on an Si (001) substrate using ICP assisted magnetron sputter deposition in a mixed Ar/N 2 discharges at 20 mTorr (2.67 Pa) and 350 °C. For the structural analysis, X-ray diffraction, auger electron scanning and atomic force microscopy were used and the hardness was measured using a micro indentation tester. The structure of the TaN films changed as the ICP power (100–400 W) and nitrogen fraction f N 2 (0.1–0.15) were varied. When the ICP RF power was increased from 100 to 400 W, hexagonal ε-TaN appeared in the existing compound of hexagonal γ-Ta 2N ( f N 2 = 0.1) or cubic δ-TaN ( f N 2 = 0.125 and 0.15). When the ICP power was increased from 100 W to 400 W, the hardness also increased from 25–35 GPa to around 70 GPa. It is supposed that the significant increase in the hardness was contributed to by the dense microstructure with very small grains and also by the multi-phase structure of the film.

MgO deposition using reactive ionized sputtering

We have developed a reactive ionized sputtering system, which composed of a conventional planar magnetron (PM) discharge and inductively coupled plasma (ICP), produced with an internal coil antenna. From the investigation on its discharge properties, we have confirmed that: (1) high density ICP of 10 11–10 12 cm −3 was successfully produced, (2) the target input power used for sputtering and ICP RF power were independently controllable, (3) the simultaneous operation of PM and ICP were effective for enhancing the ionization, and further excitation of sputtered magnesium atoms. In addition, from the hysteresis observation of reactive sputtering mode, we have confirmed that, the metallic mode sputtering was maintained even for large oxygen flow rate. Preliminary deposition results indicated for the first time that, high crystalline MgO films were deposited at almost the same deposition rate as that of Mg films, under the reactive ionized sputtering condition.

Inductively coupled plasma etching of GaN using Cl 2/He gases

We investigated n-GaN etched by an inductively coupled plasma (ICP) etcher using Cl 2/Ar and Cl 2/He as the etching gases. A detailed study on the samples etched in different ICP power, RF power, process pressure and Cl 2/Ar(He) mixing ratio was performed. It was found that n-GaN could be successfully etched by both Cl 2/Ar and Cl 2/He. The maximum etching rate could reach 8000 Å min −1 for n-GaN etched in Cl 2/Ar and 8400 Å min −1 for n-GaN etched in Cl 2/He. Furthermore, it was found that the specific contact resistance is 4.2×10 −4 and 1.37×10 −6 Ω-cm 2 for n-GaN etched by Cl 2/Ar and Cl 2/He, respectively. The smaller contact resistance is probably due to the lighter He which induce smaller plasma damages during ICP etching.

The effect of N 2 plasma damage on AlGaAs/InGaAs/GaAs high electron mobility transistors. I. DC characteristics

0.25 μm gate length AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors were exposed to inductively coupled plasma (ICP) N 2 discharges at varied source power and rf chuck power. The plasma damage was characterized by evaluating device extrinsic transconductance and saturated drain–source current, as well as Schottky gate ideality factor and reverse breakdown voltage as a function of both ICP source power and rf chuck power. Auger and atomic force microscopy were also used to characterize the atomic ratio and roughness of plasma damaged surface, respectively. At a lower range of ICP source power (between 100 and 300 W) with a constant rf power of 10 W, the device performance was barely changed. But at higher ICP source power (greater than 400 W) and rf power (greater than 20 W), device characteristics including gate ideality factor, reverse breakdown voltage and saturated drain–source current were seriously degraded. In this plasma damage study, two device degradation mechanisms were identified. The first was ion bombardment induced lattice disorder that created generation–recombination centers and reduced the free carrier concentration. The second was preferential loss of As from GaAs surface and this also created deep level states, which gave rise to gate leakage current.

Evaluation of halogenated polyimide etching for optical waveguide fabrication by using inductively coupled plasma

Oxygen plasma etching of a series of halogenated polyimides was carried out for low-loss waveguide fabrication by using inductively coupled plasma (ICP). The effects of etching parameters such as ICP power, rf power, and O2 flow rate on the etching rate and etching profile of polymer films were investigated. The increase in the etch rate with the ICP power and the rf power was observed. Both the vertical profile and sidewall roughness were found to be related to the ion energy (dc bias). By optimizing these parameters, a vertical profile and a smooth sidewall were obtained by 500 W of ICP power, 150 W of rf power, 5 mTorr of chamber pressure, and 40 sccm of the O2 flow rate. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 176–182, 2001

An array of inductively coupled plasma sources for large area plasma

An array of 2×2 inductively coupled plasma (ICP) sources has been built by modifying the conventional reactive ion etching (RIE) type LCD etcher. Each ICP has its own planar circular antenna and quartz dielectric window to the process chamber. One RF power supply and only one impedance matching network are used for delivering the power to all four ICP sources. Distribution of ion and electron densities and electron temperature are measured in terms of the number of acting ICP sources, chamber pressure and RF power. An uniform oxygen plasma density in the order of 1015 m−3 can be obtained at RF power of 600 W in process chamber of 620×620 mm2 cross-section, which is higher than that of RIE plasma. By adjusting the power distribution among the four ICP units, uniformity of the plasma can be improved to 10% on substrate stage. Photoresist etching by the oxygen plasma is performed on 320×400 mm glass plates.