Inductively Coupled Plasma Process Research Articles

Deep Hole Fabrication Based on ICP Process

This paper presents deep-hole etching process by inductively coupled plasma (ICP),the hole is higher than 400um ,and its diameter is 200um wide. Etching process successfully used in anchor fabrication below 150 um deep in micro-inertial devices, is first used in deep-hole etching .The result is badly, the sidewall surface is coarse, and the sidewall perpendicularity is poor,the dimension difference between upper and down diameter is as large as 35um.Because with the depth increasing , deep-hole etching brings new problem, such as fluorine(F) radical and ions distributing very differently between in down and upper area, also extracting reactant and temperature distribution . To solve above problems, process parameters such as gas flow mass and time in one reaction cycle, source and substrate power, reaction pressure and temperature should be adjusted. Through several experiments, optimal process is applied and the result is satisfied .From SEM figure, The the sidewall surface is smoother, the sidewall perpendicularity is good, the dimension difference between upper and down diameter is controlled in 1.6um,the sidewall angle is 89.78°. The process has been used in deep-hole fabrication of micromachined filter, and the rate of device enhances largely at present.

Process induced mechanical stress in InP ridge waveguides fabricated by inductively coupled plasma etching

Inductively coupled plasma (ICP) etching is suitable for producing semiconductor structures with a high aspect ratio. While the morphology of the structures is very satisfactory, less is known about other aspects related to the process, but with potential influence in the optical performance of the devices. We present herein a study of the mechanical stresses produced by the ICP process in the fabrication of ridge waveguides in InP. Stresses purely induced by the process are revealed by the spectral analysis of the cathodoluminescence. A dependence of the stress distribution on the aspect ratio of the waveguides is demonstrated.

Fabrication of carbon nanotube arrays for field emission and sensor devices by nanoimprint lithography

This work brings forth the idea of incorporating insulation in the resist used for ultraviolet (UV) curing nanoimprint lithography (NIL). Carbon nanotubes (CNTs) are grown in the space between two insulated resist patterns on the conductive substrate to make CNTs arrays. Two imprinting processes, soft UV curing NIL with DRPPR process and novel NIL without cured residual resist, are presented to achieve the insulation patterns. First the fabricating process is performed using a polydimethylsiloxane (PDMS) stamp. Subsequently, inductively coupled plasma (ICP) is essential to wipe off the residual resist film. To avoid the ICP process, a novel UV curing NIL is presented. Its special hard quartz stamp with chrome shelter can protect the residual resist film out of curing during the UV exposure process, and the uncured resist can be easily removed by ultrasonic vibration in organic solutions. The CNT arrays are prepared on the patterned substrates by the pyrolysis of iron phthalocyanine (FePc). Field emission experiments reveal that the turn-on field of those CNTs arrays is low to 1.3 V/um.

Morphology of Inductively Coupled Plasma Processed HgCdTe Surfaces

Inductively coupled plasma (ICP) processing has become the industrial processing standard for HgCdTe and its related II–VI compounds. In this study ICP processes were developed that allow several microns of HgCdTe to be plasma etched while maintaining a low root-mean-square (RMS) roughness, and even improving the surface roughness in the case of HgCdTe-on-Si. These ICP processes are superior to older electron cyclotron resonance (ECR) plasma etches. The resulting ICP plasma processed surfaces are oxygen and carbon free, have a good reflection high-energy electron diffraction (RHEED) pattern, and have only a small amount of mercury depletion, x = 0.22 to 0.47 (where x is the ratio of Cd to␣Hg), in the first 25 A to 30 A of the HgCdTe. Nanofeatures of the as-grown HgCdTe are retained during the process and are believed to be indicative of the fundamental defect mechanisms in the different HgCdTe etched surfaces. Results from these experiments strongly suggest that ICP plasma processes can be used to delineate pixels, etch vias, clean surfaces, and even produce epi-ready surfaces that would allow HgCdTe to become much more manufacturable, and perhaps allow the replacement of wet processing in HgCdTe.

Introduction of defects during the dry etching of InP photonic structures: a cathodo-luminescence study

Introduction of point defects during the dry etching process of InP-based photonic structures has been investigated using the spectroscopic cathodo-luminescence (CL) technique. The measurements were performed on cleaved cross-sections from standard passive waveguides with rectangular shape, different widths, etched in bulk InP using either reactive ion etching (RIE) with CH4/H2 as the etching gases, or high density—inductively coupled plasma (ICP) etching with SiCl4. Etched depths up to 4 μm were reached. In the case of the ICP process, a defect-related band appears in the CL spectra, which is tentatively attributed to some kind of complex defect involving indium vacancies, because of its energy measured at low temperature. This band does not appear for the RIE process. In addition, local stress also occurs in the etched ridges (identified from the spectral shift of the band to band transitions), which seems to arise from the occurrence of the defects. The features on the spectroscopic CL images (both in terms of the defect band and the changes in intensity related to non-radiative recombination centers) are discussed based on the nature of the hard mask material used for the etching process and the local temperature reached during processing, especially with the high density ICP process.

Investigation of point defect generation in dry etched InP ridge waveguide structures

Waveguides engraved in InP by dry etching, reactive ion etching and inductively coupled plasma (ICP), were studied by cathodoluminescence. The dry etching processes were found to induce nonradiative recombination centers, which reduce the luminescence emission from the ridge structures. In addition, the ICP process introduced intrinsic defects, probably In vacancy related defects, which were generated at the dielectric cap/InP interface at the ridge top.

The effects of capacitor termination at an internal ICP antenna on the power coupling, plasma parameters and impurity incorporation

During the ICP (inductively coupled plasma) process, a very high self-bias voltage is induced along the coil, which can cause sputtering of dielectric materials covering the coil. This problem can be solved by installing a capacitor between the coil end and ground. The effect of the capacitance termination was investigated by measuring the voltages at both of coil ends, plasma parameters and the impurity contents on the Si substrate after Ar plasma treatment at different ICP powers. The voltages at the coil ends decreased by half and the induced self-bias voltage approached zero under resonance conditions. The capacitance was approximately 200 pF, with both coil inlet and outlet voltages the same. In the range of this critical capacitance of 200 pF, the harmonics between coil and plasma decreased and the plasma density increased to 120–250% by controlling pressure and power compared to that with the grounded coil end. When the pressure was 1 and 5 mTorr, the plasma density doubly increased. Impurity concentrations were also suppressed drastically by the capacitance termination.

Inductively coupled plasma etching of Si1−xGex in CF4∕Ar and Cl2∕Ar discharges

In this article, we report the experimental realization of SiGe∕Si materials using CF4∕Ar and Cl2∕Ar mixed-gas inductively coupled plasma (ICP) etching process. The effects of process parameters such as gas combination and gas species on etch rates and selectivities were investigated. It was found that samples in CF4 gas result in a faster etching rate than those obtained in Cl2 gas, which are responsible for a lower boiling point for Si-based fluoride. The lower boiling point provides more chemically active Si and SiGe materials. Moreover, the selectivity of 1.5 between Si0.3Ge0.7∕Si by ICP technology was found and higher than that obtained previously by reactive ion etching reported in the literature. Based on these etch characteristics, the application of the ICP process to the device fabrication of SiGe doped-channel field-effect transistors was conducted. The devices using ICP mesa have excellent pinch-off characteristics with relatively low leakage current, small output conduction in the saturated region, and low knee voltage.

Optimization of an inductively coupled plasma etching process of GaInP∕GaAs based material for photonic band gap applications

In this article, we investigate the dry etching of GaInP∕GaAs based material system using an inductively coupled plasma (ICP) etching system. In a view to develop a suitable ICP process for the etching of aluminum-free material, ridge waveguides have been fabricated and the effects of the ICP parameters have been assessed. The coil power and the platen power have been varied at constant pressure and temperature for a chlorine-based process. The surface quality, sidewall profile, and selectivity have been reported. We also demonstrate the optimization of the chlorine-based process for deep etching and its subsequent implementation in photonic band gap device fabrication for 1.55μm optical applications. The optimized process has been shown to provide a high aspect ratio and a good selectivity for 250nm diam holes with a depth of 3μm in the GaInP∕GaAs material system. The influence of the ICP parameters on this material system have been analyzed mainly by scanning electron microscopy with particular attention drawn to the ways of reducing trenching, an effect commonly associated with ICP etching.

Inductively coupled plasma etching for large format HgCdTe focal plane array fabrication

Inductively coupled plasma (ICP) using hydrogen-based gas chemistry has been developed to meet requirements for deep HgCdTe mesa etching and shallow CdTe passivation etching in large format HgCdTe infrared focal plane array (FPA) fabrication. Large format 2048×2048, 20-µm unit-cell short wavelength infrared (SWIR) and 2560×512, 25-µm unit-cell midwavelength infrared (MWIR) double-layer heterojunction (DLHJ) p-on-n HgCdTe FPAs fabricated using ICP processing exhibit >99% pixel operability. The HgCdTe FPAs are grown by molecular beam epitaxy (MBE) on Si substrates with suitable buffer layers. Midwavelength infrared detectors fabricated from 4-in. MBE-grown HgCdTe/Si substrates using ICP for mesa delineation and CdTe passivation etching demonstrate measured spectral characteristics, RoA product, and quantum efficiency comparable to detectors fabricated using wet chemical processes. Mechanical samples prepared to examine physical characteristics of ICP reveal plasma with high energy and low ion angle distribution, which is necessary for fine definition, high-aspect ratio mesa etching with accurate replication of photolithographic mask dimensions.

Etch mechanism and etch-induced effects in the inductively coupled plasma etching of GaN

The inductively coupled plasma (ICP) processing of gallium nitride (GaN) using SF6/N2 and Cl2/Ar gas mixtures has been compared. ICP processing of GaN using SF6 and N2 mixture of 1:1 produces an optimized etch rate of 67 nm/min while five times higher etch rate of 314 nm/min is achieved using Cl2 and Ar mixture of 1:3. Etch mechanism studies indicate an ion-induced, coupled with a large chemical enhancement component for both SF6/N2 and Cl2/Ar inductively coupled plasma etching. From electrical diode characterization, an increase in electrical degradation with increasing dc bias in Cl2/Ar plasma is observed, while an improvement of diode characteristics is evident after etching in SF6/N2 plasma. X-ray photoelectron spectroscopy results indicate the presence of a significantly Ga deficient surface after etching GaN in Cl2 and Cl2/Ar plasmas. Correlation between etch mechanism and etch-induced damage results strongly indicates the existence of ion-induced chemical damage in the ICP etching of GaN in Cl2 and Cl2/Ar plasmas.

Application of inductively coupled plasma to super-hard and decorative coatings

An inductively coupled plasma (ICP) assisted technique is expected to be the next generation deposition technique due to its many beneficial properties. In this paper, an internal type r.f. ICP process is presented. The core of this technology is the efficient production and control of self-depositing ions and reactive gas ions by an induced electric field. The properties of the immersed ICP can be tuned between the capacitively coupled and inductively coupled state by changing the antenna materials, the tuning network design, the driving frequency and the external magnetic field. Examples of applications of ICP to super-hard and decorative TiN and CrN coatings, which were produced by ICP magnetron sputtering and ICP evaporation, respectively, are presented.

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.

Cr absorber etch process for extreme ultraviolet lithography mask fabrication

Reactive ion etching (RIE) and inductively coupled plasma (ICP) Cr etch processes have been evaluated for fabrication of extreme ultraviolet lithography masks on 200 mm substrates. Experiments were completed to optimize the Cr etch rate, etch rate uniformity, and Cr to resist selectivity for both etch processes. The best ICP process was found to have superior etch rate, etch rate uniformity, and comparable Cr to resist selectivity to the RIE process. The effect of exposed Cr area on the Cr to resist selectivity, critical dimension (CD) bias, and CD bias 3σ was also investigated. A decrease in exposed Cr area from 95% to 7% was found to dramatically increase the Cr etch rate, leading to an increase in the Cr to resist selectivity. Lower Cr loading was also found to decrease the CD bias and CD bias 3σ. The average CD bias was very high for both processes, with the ICP etch process having a higher CD bias (143 nm) than the RIE process (89 nm). The CD bias uniformity was significantly lower for the ICP process (32 nm, 3σ) when compared to the RIE process (71 nm, 3σ).

Low damage dry etching of III–V materials for heterojunction bipolar transistor applications using a chlorinated inductively coupled plasma

Etching of InGaAs and InP in inductively coupled plasma (ICP) using SiCl4 was studied for heterojunction bipolar transistor (HBT) applications. Low sample temperature was used to minimize etching isotropy and to reduce group V element desorption. The low ion energy etching process results in a damaged layer thickness of a few Å. Auger electron spectroscopy results on InP demonstrate a very thin layer of nonstoichiometric material. The nature of the etching mask impacts the surface contamination: local contamination effects due to sputtering are observed. For such low ion energy process, the sample preparation before ICP etching is shown to be very important for surface roughness, as observed by atomic force microscopy. Various preparation schemes have been investigated, before ICP etching, for reduction of the surface degradation resulting from ICP etching. It is shown that the best results in terms of roughness and etch-rate are obtained with a silicon nitride mask and surface oxidation by ultraviolet ozonization before a wet desoxidation immediately preceding the ICP etching. An ICP process was used successfully for partly etching the base mesa of HBT structures. No significant difference with wet etching was observed in terms of induced damage and HBT current gain.

Characterization of carbon nitride films grown using an inductively-coupled plasma with adamantane as the source hydrocarbon

The films addressed here were grown using adamantane (C10H16) vapour in flowing argon/nitrogen mixtures in an inductively-coupled plasma processing (ICP) vacuum rig. The films were characterized by XPS, AES, infrared spectroscopy (Fourier transform infrared (FTIR) in transmission) and atomic force microscopy. The x-ray photoelectron data showed typically high nitrogen contents, and deconvolution of the observed C 1s band confirmed the presence of the chemical states identified by FTIR. Further XPS-quantified data established the changes observed in the relative carbon and nitrogen concentrations as a function of deposition regime. Evidence of a structural transformation in the films over time was established from the FTIR spectra, which exhibited significant changes in the relative intensities of the C≡N, CN/CC, NH and CH bands identified attendant on the deposition parameters. Analysis by AES revealed additionally an increasing carbon/nitrogen ratio, suggesting the transformation of sp3 to sp3 carbon was taking place in the film, with some nitrogen lost from the films during data acquisition. These data indicated clearly that the electron beam-stimulating production of the Auger spectra contributed to the transformation of the chemical states present initially. Finally, atomic force microscopy of the surfaces showed that the surface morphology of the film changes during Auger analysis. © 1998 John Wiley & Sons, Ltd.

Analysis of electrical arc furnace flue dusts by spark ablation inductively coupled plasma atomic emission spectrometry

A medium-voltage spark was used for the direct nebulization of electric arc furnace (EAF) flue dust. In order to attain the necessary sample conductivity, powder pellets are briquetted after mixing the sample 1 + 1 with graphite. The elutriated material was excited in an argon inductively coupled plasma (ICP). The use of cellulose as binder provides better results in terms of reproducibility. After optimization of the spark parameters (voltage, 500 V; repetition rate, 400 s–1; and resistance, 2.2 Ω), the carrier gas flow rate (2.1 l min–1 of argon) and the operating power of the ICP (1.2 kW), precisions (relative standard deviation) for zinc, lead, cadmium and iron range from 0.8 to 2.0%. The stability of the spark sampling, during a complete spark ablation (SA) ICP process (≈90 s) was tested by plotting emission intensity versus time profiles. The similarity between the amounts of analyte obtained from different pellets was proven by collecting the spark-eroded particles and analysing their carbon contents. Five steelmaking EAF flue dusts were selected for this study, using the two samples with extreme contents of the elements considered, for calibration. The results obtained by SA-ICP matched the results obtained by ICP from nebulized solutions.