Electron Cyclotron Resonance Etching Research Articles

Boundary effect on mode transformation in an electron cyclotron resonance etching reactor

Etching apparatuses using electron cyclotron resonance (ECR) have been used by major ULSI manufacturers, and uniform plasma generation on a large wafer is realized. However, it is not well understood the reason for the uniform plasma generation, which is crucial for the industrial field. By using a simulation technique and a theoretical analysis of a plasma waveguide with an outer vacuum layer with imposed boundaries, we investigated the microwave distribution in the ECR reactor to understand the mechanism of the uniform plasma generation. Contrary to the usual understanding of the right-hand polarized wave (R wave) damping in the ECR plasma production scheme, we found that the introduced R wave is transformed into the extraordinary wave and the electrostatic wave of Trivelpiece–Gould wave by comparing the theoretical result considering the wall effect. Moreover, we found that surface wave is observed at the interface of the quartz window and the plasma.

Numerical Identification of Trivelpiece–Gould Waves in an Electron Cyclotron Resonance Etching Reactor

Electron cyclotron resonance (ECR) plasma sources have been widely used for ultra-large-scale integration manufacturing processes because of their wide operating range and excellent uniformity over 300- or 450-mm diameter wafer. However, microwave electromagnetic fields in magnetized plasma-filled reactors are not well understood because of the complexity of electromagnetic wave field analysis. We conducted microwave electromagnetic field analysis of an ECR plasma etcher by the finite-element method using a simulation platform. Complicated electric field patterns were clearly observed under some conditions. We investigated the patterns in detail to determine whether they were spurious or not. The patterns proved to be Trivelpiece–Gould waves according to their characteristics imposed by the dispersion relation of waves. This analysis approach is a powerful method because very fine-wave structures can be identified.

Spatial phase-resolved optical emission spectroscopy for understanding plasma etching uniformity

Plasma chemistry of an oxygen-argon discharge in an electron cyclotron resonance (ECR) plasma etcher with a SiO2 wafer is observed. The study involves: Phase-resolved optical emission spectroscopy (PROES) of neutral atomic argon (Ar I) and oxygen (O I) spectral lines, spectroscopic ellipsometry of the wafer and a magnetic-field measurement of the ECR etcher's electro-magnet. Spatial PROES results together with the ellipsometry and magnetic-field measurements are used to assess the plasma etching uniformity of the SiO2 wafer. To evaluate the cross-dependences of the measured outputs for a wide range of process parameters, a design-of-experiment approach is taken. Spatial PROES of the oxygen atom shows a different spectral radiation pattern for the oxygen from the gas phase and those from the solid phase due to surface etching.

Phase-resolved optical emission spectroscopy for an electron cyclotron resonance etcher

Phase-resolved optical emission spectroscopy (PROES) is used for the measurement of plasma products in a typical industrial electron cyclotron resonance (ECR) plasma etcher. In this paper, the PROES of oxygen and argon atoms spectral lines are investigated over a wide range of process parameters. The PROES shows a discrimination between the plasma species from gas phase and those which come from the solid phase due to surface etching. The relationship between the micro-wave and radio-frequency generators for plasma creation in the ECR can be better understood by the use of PROES.

Correlation between Electrical and Optical Properties of Tantalum Anodic Oxide and Electron Cyclotron Resonance Etching Studies of E-beam Deposited Ta2O5 Films

The anodicTa2O5 films were grown in 5ml/98%H2SO4 electrolyte. Discharge currents were collected immediately after growth. The optical properties were studied with a Spectroscopic Ellipsometer, over a wide range of frequencies from the UV to the IR. It was established that films for which the discharge current followed the known "~ -1" power dependence (characteristic of films that can sustain electric fields of MV/cm) have different optical properties as compared to films for which the discharge current is not represented by that function. Etching studies of the e-beam deposited Ta2O5 films, combined with reflectance measurements after each etch step, resulted in a shift in the reflectance spectrum as a function of film thickness, d. This empirical f versus d dependence (where f is the frequency corresponding to the reflectance minimum for each d) was used to calculate the energies of the 4d doublet of Ta+5 in Ta2O5.

Correlation between Electrical and Optical Properties of Tantalum Anodic Oxide and Electron Cyclotron Resonance Etching Studies of E-beam Deposited Ta2O5 Films

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Correlation between Electrical and Optical Properties of Tantalum Anodic Oxide and Electron Cyclotron Resonance Etching Studies of E-Beam Deposited Ta2O5 Films

The anodic tantalum oxide films were grown in 5mL/98% H2SO4 electrolyte saturated with additional H2. Discharge currents were collected immediately after growth. The optical properties of these films were studied with a J. V. Woollam Co., Inc., Spectroscopic Ellipsometer, VASE, over a wide range of frequencies from the UV to the IR. It was established that films for which the discharge current followed the known “∼−1” power dependence (characteristic of films that can sustain large electric fields in the range of MV/cm) have different optical properties as compared to films for which the discharge current is not represented by that empirical function. Etching studies of the E-beam deposited Ta2O5 films, combined with reflectance measurements after each etch step, resulted in a shift in the reflectance spectrum as a function of film thickness. This empirical f versus d dependence (where f is the frequency corresponding to the reflectance minimum for each film thickness, d) was used to calculate the energies of the 4d doublet of Ta+5 in Ta2O5.

ChemInform Abstract: An Overview of Dry Etching Damage and Contamination Effects

Plasma or dry etching techniques, such as reactive ion etching, magnetron reactive ion etching, electron cyclotron resonance etching, ion beam etching, and plasma etching, can result in damage and contamination of the materials used in device structures and interconnects. The damage that can take place occurs because of ion bombardment, radiation‐induced bonding changes, and charge buildup. If not removed, damage can have effects which vary from gettering to creating traps in insulators and gap states in semiconductors. The contamination that can take place can have two forms: residue layers and permeation. The former are ultrathin layers of reaction products that can coat surfaces whereas the latter is the embedding or implantation, and perhaps subsequent diffusion, of impurities. These impurities can range from metals whose source is the processing chamber to hydrogen which is often found in the etch recipe or may even be found due to the presence of water in the processing chamber. If not removed, residues can interfere with subsequent processing such as oxidation and can cause series resistance in contacts. Impurities, if not removed, can have a range of effects from modifying carrier lifetimes to interfering with subsequent processing. Hydrogen, in particular, can affect materials in a number of ways including modifying doping activation.

Modeling of Silicon Carbide ECR Etching by Feed-Forward Neural Network and Its Physical Interpretations

The behavior of electron cyclotron resonance etching of 4H-SiC based on SF6 + O2 plasma is studied using a three-layered feed-forward neural network model trained by the Broyden, Fletcher, Goldfarb, and Shanno optimization algorithm. The etch rate of 4H-SiC is modeled as a function of microwave power, dc bias, process pressure, and O2/(SF6 + O2) flow ratio referred to as the O2 fraction. The results clearly reveal the interaction of the various process parameters and their resultant effects on the etch rate. It is found that, by varying the O2 fraction and process pressure, optimized etch rate peaks can be achieved. Increasing dc bias and microwave power is found to result in the optimized etch rate peaks occurring at higher O2 fraction and process pressure, respectively. In addition, increasing dc bias or microwave power will increase the etch rate. However, there is saturation in the etch rate at higher dc bias, which does not occur with microwave power. Based on these modeling results, detailed physical interpretations of the etching process are given in terms of the chemical reaction of 4H-SiC with F, O, positive ion bombardment, etc.

Temperature Facilitated ECR-Etching for Isotropic SiC Structuring

In order to realize complex three dimensional or free standing structures on SiC substrates, an undercut, i.e. a selective isotropic etching process of SiC, is required. This was realized using an electron cyclotron resonance etching set up with pure SF6 and a SF6/Ar gas composition at elevated substrate temperatures. Above 350°C a significant lateral etch component was observed, which rose to a value of 50-70 nm/min increasing the substrate temperature up to 570°C during the etching process. Depending on substrate temperature the etching profiles and surface roughness were studied. Based on an analysis of the influence of microwave power, working pressure, bias voltage, gas flow and gas mixture on the etching behavior a novel isotropic, high selective, residue free etch process for SiC was developed, which allows for example the fabrication of piezoelectric actuated AlGaN/GaN resonators grown on SiC substrates.

Comparison of CF4 and SF6 based plasmas for ECR etching of isotopically enriched 10boron films

Isotopically enriched 10boron films have been successfully etched in an Electron Cyclotron Resonance (ECR) etching tool using CF4 and SF6 based plasmas. Comparisons between the two are made with regard to etch rate, selectivity to the underlying Si device structure, and morphology of the 10boron post-etching. Our present film etching development is expected to be critical for the fabrication of next generation thermal neutron solid state detectors based on 10boron.

Effect of ECR etching conditions of (100)Ib diamond substrates on homoepitaxial low boron doped diamond layer quality

AbstractThe effect of oxygen electron cyclotron resonance (ECR) microwave plasma etching on the crystallinity of low boron doped thin diamond films grown on Ib (100)‐oriented diamond substrates by MPCVD has been investigated with respect to the main experimental conditions: microwave power and O2 pressure at a constant DC bias. The substrates were exposed to ECR oxygen plasma to remove from 0.8 μm to 3.5 μm (depending on the value of the microwave power). The optimization of these two parameters has been performed in order to get the lowest surfaces roughness. This study aims also at demonstrating that oxygen ECR plasma etching is a powerful tool to remove surface and subsurface defects of diamond substrates as polishing grooves, subsurface damaged zone (polishing process induced defects) and various substrate roughness according to the observed growth sector. Low boron doped layers ([acceptors] = 4 × 1016 atoms/cm3) were grown by MPCVD on either O2 ECR plasma etched or merely chemically prepared (100) Ib diamond substrates. Cathodoluminescence analysis showed, for specific substrate etching conditions, a decrease of the band A emission (2.8 eV) in a low boron doped layer deposited on an etched substrate compared to a layer grown on a chemically prepared one. The FWHM of the FETO excitonic line of all theses layers is comprised between 16 meV and 13 meV for the best ones at 5 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

NiCr etching in a reactive gas

The authors have etched NiCr through a resist mask using Cl∕Ar based chemistry in an electron cyclotron resonance etch system. The optimum gas mixture and etch parameters were found for various ratios of Ni to Cr, based on the etch rate, redeposits, and the etch ratio to the mask. The introduction of O2 into the chamber, which is often used in the etching of Cr, served to both increase and decrease the etch rate depending explicitly on the etching parameters. Etch rates of >50nmmin−1 and ratios of >1 (NiCr:Mask) were achieved for NiCr (80:20). Pattern transfer from the mask into the NiCr was achieved with a high fidelity and without redeposits for a Cl∕Ar mix of 10% Ar (90%Cl2) at an etch rate of ≈50nmmin−1 and a ratio of 0.42 (NiCr:ZEP 7000 e-beam mask).

Dry etching of N‐face GaN using two high‐density plasma etch techniques

This paper describes processing of GaN on the on the (000I) N-face surface, using two different high-density plasma etch techniques, inductively coupled plasma (ICP) etch, and electron cyclotron resonance (ECR) etching. ICP experiments used several different conditions employing Cl2-Ar-BCl3 or Cl2-Ar plasmas. The resulting maximum etch rates of 370-390 nm/min are approximately twice as high as etch rates for Ga-face (0001) GaN with the same recipes. ECR etching employed a Cl2-CH4-Ar recipe, which produced an average etch rate of 55 nm/min in a 20-minute etch process on N-face GaN. Both etch techniques increased the roughness of N-face GaN, but could produce surfaces with average roughness values below 3 nm. Selection of conditions with a dominant chemical etch contribution is important to maintain smooth surfaces. The use of both ICP and ECR etching in sequence is advantageous in situations where a GaN substrate several tens of microns in thickness must be thinned from the backside, stopping the etch in a suitable marker layer.

Experimental and theoretical studies of d-dot

We propose the idea of d-dot, where a d-wave superconducting dot is embedded in s-wave matrix. Spontaneous half vortices should appear in the four corners of the d-dot [M. Kato, M. Ako, M. Machida, T. Koyama, T. Ishida, Physica C 412–414 (2004) 352; M. Ako, M. Kato, M. Machida, T. Koyama, T. Ishida, Physica C 412–414 (2004) 544; M. Fujii, T. Abe, H. Yoshikawa, S. Miki, S. Kawamata, K. Satoh, T. Yotsuya, M. Kato, M. Machida, T. Koyama, T. Terashima, S. Tsukui, M. Adachi, T. Ishida, Physica C 426–431 (2005) 104]. Symmetric geometry and the fourfold symmetry of the d-dot would be suitable as a building block for constructing the novel physical systems. The phase dynamics of a closed 0–π junction, which can be realized in a small dx2-y2-dot, is mapped on a quantum two-level system when the system size is small enough. Using two-component Ginzburg–Landau equation, we study the physical properties of d-dots systematically. We prepare epitaxial YBa2Cu3O7 (YBCO) films of thickness 100nm on SrTiO3 substrates using a laser ablation apparatus. The d-dot is fabricated by a photolithography, electron beam lithography EB and an electron cyclotron resonance (ECR) etching, a focused ion beam microscope, and a lift-off technique. Local vortex profile is investigated using a SQUID microscope when d-dot is cooled in zero field.

The role of oxygen in electron cyclotron resonance etching of silicon carbide

The electron cyclotron resonance (ECR) etching of silicon carbide (SiC) was studied using SF 6 + O 2 based plasma. The role of O 2 was studied by varying the O 2 flow rate while keeping the total gas flow constant. It was found that oxygen enhances the etch rate at low O 2 fraction through releasing more fluorine atoms, while lowers the etch rate at high O 2 fraction by diluting fluorine atoms and forming an oxide-like layer. The etched surface roughness was found to be affected by the surface oxidation and oxygen ion related physical ion bombardment. The role of oxygen in chemical etching of carbon was found to be insignificant. In general, the etched surface is smooth and free of micromasking effect that can arise from Al contamination and C rich layer.

Fabrication of superconducting d-wave dot embedded in an s-wave matrix

When a d-wave superconducting dot (d-dot) is embedded in an s-wave superconductor matrix, a half flux quantum vortex is expected to appear spontaneously at four corners of the d-dot without applying an external magnetic field. First, we have prepared c-axis oriented YBa 2Cu 3O 7 (d-wave superconductor) thin films by pulsed-laser ablation deposition on c-axis oriented SrTiO 3 single-crystal substrates. We have fabricated resist-coated YBa 2Cu 3O 7 square islands by using an electron beam lithography and an electron cyclotron resonance etching. Then, we have deposited Pb (s-wave superconductor) film on the fabricated YBa 2Cu 3O 7 thin film, and removed extra Pb and resist films on the YBa 2Cu 3O 7 islands by a lift-off technique. Magnetic field distribution on superconducting d-dot has been measured by using a SQUID microscope in zero fields.

Determination of the ion angular distribution for electron cyclotron resonance, plasma-etched HgCdTe trenches

Ion angular distribution (IAD) affects the width and aspect ratio in electron cyclotron resonance (ECR)-etched HgCdTe trenches. The IAD was determined by etching studies together with scanning electron microscopy (SEM) analysis. The results confirm that low-energy, large-angle ions contribute to the etching of the photoresist, while higher-energy, low-angle ions are responsible for HgCdTe etching. The HgCdTe ECR etching was further elucidated by sputter-bombardment theory. This model correctly predicts the nature and depth of the damage region in ECR-etched HgCdTe as well as the distribution and composition of the ejected material.

Lithography factors that determine the aspect ratio of electron cyclotron resonance plasma etched HgCdTe trenches

Factors that affect width and aspect ratio in electron cyclotron resonance (ECR) etched HgCdTe trenches are investigated. The ECR etch bias and anisotropy are determined by photoresist feature erosion rate. The physical characteristics of the trenches are attributed to a combination of photoresist feature geometry and ECR plasma etch chemistry. This knowledge has led to production of trenches suitable for two-color, 20 µm pitch detectors.

Fabrication of Josephson junctions with as-grown MgB/sub 2/ thin films

We report on the fabrication of as-grown MgB/sub 2/ thin films and MgB/sub 2//AlN/NbN thin film heterostructures having as-grown MgB/sub 2/ thin films. The MgB/sub 2/ thin films deposited by using a carousel-type sputtering system at substrate temperatures T/sub s/ of 252/spl deg/C typically showed a critical temperature of 28 K. The results of XRD measurements of the thin films indicated a c-axis orientation. The surface morphology of the films fabricated at T/sub s/=252/spl deg/C was determined to be very flat and smooth from SEM images. The MgB/sub 2//AlN/NbN trilayer was continuously deposited on sapphire [001] substrates in a single vacuum run. The AlN-barrier and NbN-counter layers were deposited by using DC-reactive magnetron sputtering at ambient substrate temperatures. The junctions were fabricated by using conventional photolithography, reactive ion etching, and electron cyclotron resonance etching techniques. The junctions demonstrated excellent quasiparticle tunneling characteristics having ideal dependence of the normal resistance on the junction area and on the AlN-barrier thickness. Also, the DC magnetic field and temperature dependences of the supercurrent I/sub c/ were measured to investigate the Josephson tunneling behavior in the MgB/sub 2//AlN/NbN junctions. The junction I/sub c/-H curve showed the ideal Fraunhofer pattern.