Ion Etching Method Research Articles

Loss Reduction of Si Wire Waveguide Fabricated by Edge-Enhancement Writing for Electron Beam Lithography and Reactive Ion Etching Using Double Layered Resist Mask with C60

Loss reduction methods for single-mode photonic wire in silicon-on-insulator were investigated, with a Si core size of 200×440 nm2, fabricated with electron beam lithography and dry etching, using a double layer of electron beam (EB) resist mask. The transverse electric (TE) mode propagation loss measured at a wavelength of 1550 nm was 4.5 dB/cm, which is, to the best of our knowledge, the lowest value ever attained for a Si wire waveguide fabricated by the parallel plate reactive ion etching (RIE) method.

CdTe x-ray image sensor using a field emitter array

The authors have demonstrated the novel CdTe x-ray imaging device that consists of a Schottky CdTe diode and a 12×12 matrix-structured field emitter array (FEA). The Schottky CdTe diode was fabricated by depositing In on a Cl-doped p-type (π-type) CdTe substrate and Sb2S3 on the opposite side of the CdTe substrate. The matrix-structured FEA was fabricated by reactive ion etching and etch-back method. The output current was successfully detected by the recombination of holes with electrons from the FEA, and clearly depended on the x-ray intensity.

Research on Fabricating CVD Diamond Microstructures Using RIE Process

Diamond is one of the most important engineering materials for its extreme hardness, high thermal conductivity value and chemical inertness. Due to its high hardness and strength, it can be ideal candidates for AFM probe or micro-needle. In this research, micro cone-like shaped diamond tips with high aspect ratio formed using reactive ion etching (RIE) method. The scanning electron microscope (SEM), transmission electron microscope (TEM) and micro-Raman spectroscopy were used to study the surface morphology and sub-surface micro-structure before and after RIE process. The results showed that gold could be adopted as mask material during the RIE process. Different microstructures could be obtained using different RIE parameters such as etch duration and reactant gas. After RIE (O2 50sccm, 200W) for 5min the micro cone-like structures (aspect ratio~8) could be observed on the surface if a thin layer of gold was applied as mask. However, under the same RIE conditions, the irregular pillar-like microstructures started to emerge if the etching time was stretched longer.

Research on Fabricating CVD Diamond Microstructures Using RIE Process

Diamond is one of the most important engineering materials for its extreme hardness, high thermal conductivity value and chemical inertness. Due to its high hardness and strength, it can be ideal candidates for AFM probe or micro-needle. In this research, micro cone-like shaped diamond tips with high aspect ratio formed using reactive ion etching (RIE) method. The scanning electron microscope (SEM), transmission electron microscope (TEM) and micro-Raman spectroscopy were used to study the surface morphology and sub-surface micro-structure before and after RIE process. The results showed that gold could be adopted as mask material during the RIE process. Different microstructures could be obtained using different RIE parameters such as etch duration and reactant gas. After RIE (O2 50sccm, 200W) for 5min the micro cone-like structures (aspect ratio~8) could be observed on the surface if a thin layer of gold was applied as mask. However, under the same RIE conditions, the irregular pillar-like microstructures started to emerge if the etching time was stretched longer.

Cyclic, cryogenic, highly anisotropic plasma etching of silicon using SF6∕O2

The authors report on the development and characterization of a plasma etching method that utilizes process steps common to both the well-known Bosch and the cryogenic deep reactive ion etching methods for silicon. This hybrid process uses cyclical etch steps that alternate between etching and passivating chemistries as in the Bosch process, while still maintaining sample temperatures at −100°C on a cryogenically cooled stage. The advantages of this process are superior control of wall profiles for isolated features, minimization of grass formation, and the elimination of an expensive gas, c-C4F8, required in the Bosch passivation step. The authors show examples of x-ray optic elements deep etched to 100μm depth with the cyclic cryogenic process.

High aspect ratio copper through-silicon-vias for 3D integration

Three-dimensional (3D) integration, which uses through-silicon-vias (TSVs) to interconnect multiple layers of active circuits, offers significant improvements over planar integrated circuits (ICs) on performance, functionality, and integration density. To address a key issue in 3D integration, the fabrication of high aspect ratio TSVs, this paper presents the bottom-up copper electroplating technique to fill high aspect ratio vias with copper. Deep through-silicon holes with aspect ratio as high as 10:1 are etched using deep reactive ion etching (DRIE) method, and are completely filled with copper using bottom-up copper electroplating technique without forming any voids or seams. Based on this technique, a multi-layer 3D integration method is proposed. This method uses temporary transfer wafer to provide mechanical support to the device wafer during wafer thinning process and to provide the seed layer for copper electroplating. Then bottom-up electroplating is performed to fill the high aspect ratio vias with copper. Experimental results verify the feasibility of the proposed method.

Fluorine-doped SiO 2 and fluorocarbon low- k dielectrics investigated by SIMS

In this work, we present secondary ion mass spectrometry (SIMS) investigations of the incorporation of fluorine into thin SiO 2 films adapted as low- k dielectrics in the metal-oxide-semiconductor (MOS) devices. The insulating SiOF oxides with the thickness ranging from 1 up to 15 nm have been prepared by plasma-enhanced chemical vapor deposition (PECVD) and/or by reactive ion etching (RIE) methods on 〈1 0 0〉 oriented p-Si substrates with the use of either CF 4 or CHF 3 source of the plasma. SIMS experiments were performed using ultra-low energy (1 keV) argon ion beam and quadrupole mass analyzer. Depth profiles of the resulting dielectric films illustrate: (i) the incorporation of F into the SiO 2 matrix is accomplished by either the CHF 3 or CF 4 plasmas; (ii) no etching of SiO 2 matrix is observed by using of CHF 3; (iii) CHF 3 is a source of fluorocarbon film deposition on top of the SiO 2 that prevents the SiO 2 etching; and (iv) fluorine quantifications done based on implantation criteria give the maximum concentrations within the films from 6.0 × 10 18 to 2.4 × 10 20 atoms/cm 3 depending on the different fluoridation conditions. The F concentration in SiO 2 increases with the r.f. power of CF 4 or with decreasing a gas pressure of CHF 3 plasma.

Ion etching methods for depth profiling of complex three-dimensional samples in combination with scanning Auger electron microscopy

Ion etching of surfaces combined with detection of secondary events (particles or radiation emitted) are used for depth profiling of samples with interesting features at-, near-, or somewhat below the surface. These methods are destructive and relatively slow, and compete with non-destructive methods like Rutherford backscattering spectroscopy, energy-dispersive X-ray spectroscopy in the scanning electron microscope or angle-resolved photoemission spectroscopy, which are non-destructive and relatively faster methods. In this work we have concentrated on the use of noble gas ion sputtering with low-energy beams in combination with electron excited Auger electron spectroscopy and imaging for analysis of nanostructured and microstructured samples. No attempt will be made here to justify this method over the other methods, as their relative merits depend on the nature of the sample and the problem at hand. We have thus chosen to study samples and problems for which this technique would be obvious to use. This work is also aimed at providing practical standards and guidelines (“metrology”) for the use of the technique in the context of industrial nanotechnology. The use of Auger electron spectroscopy instead of photoemission spectroscopy is preferred for laterally non-uniform samples due to the presently better resolution capabilities of electron beams and narrower information depths of typical Auger electron transitions. The use of Auger electrons for concentration sampling, and low-energy beams of noble gas ions for sputtering, reduces the adverse influence of atomic mixing. In this report two systems are intensively studied with sputter profiling in combination with Auger electron spectroscopy and scanning electron imaging: a hard disk and a surface of a stainless-steel sample.

Fabrication and evaluation of a wideband multilayer laminar-type holographic grating for use with a soft-x-ray flat-field spectrograph in the region of 17 keV

A multilayer laminar-type holographic grating having an average groove density of 2400 lines/mm is designed and fabricated for use with a soft-x-ray flat-field spectrograph covering the 0.70-0.75 nm region. A varied-line-spaced groove pattern is generated by the use of an aspheric wavefront recording system, and laminar-type grooves are formed by a reactive ion-etching method. Mo/SiO2 multilayers optimized for the emission lines of Hf-M, Si-K, and W-M are deposited on one of the three designated areas on the grating surface in tandem. The measured first-order diffraction efficiencies at the respective centers of the areas are 18%-20%. The flat-field spectrograph equipped with the grating indicates a spectral linewidth of 8-14 eV for the emission spectra generated from electron-impact x-ray sources.

Ultrafast laser micromachining of 3C-SiC thin films for MEMS device fabrication

Femtosecond pulsed laser (800 nm, 120 fs) micromachining of thin films of 3C-SiC (β-SiC) semiconductor deposited on silicon substrate was investigated as a function of pulse energy (0.5 μJ to 750 μJ). The purpose is to establish suitable laser parametric regime for the fabrication of high accuracy, high spatial resolution and thin diaphragms for high-temperature MEMS pressure sensor applications. Etch rate, ablation threshold and quality of micromachined features were evaluated. The governing ablation mechanisms, such as thermal vaporization, phase explosion, Coulomb explosion and photomechanical fragmentation, were correlated with the effects of pulse energy. The results show that the etch rate is higher and the ablation threshold is lower than those obtained with nanosecond pulsed excimer laser ablation, suggesting femtosecond laser’s potential for rapid manufacturing. In addition, the etch rates were substantially higher than those achievable in various reactive ion and electrochemical etching methods. Excellent quality of machined features with little collateral thermal damage was obtained in the pulse energy range (1–10 μJ). The leading material removal mechanisms under these conditions were photomechanical fragmentation, ultrafast melting and vaporization. At very low pulse energies (<1 μJ), nanoscale material removal has occurred with the formation of nanoparticles that is attributed to Coulomb explosion mechanism. The effect of assist gas on the process performance at low and high energy fluences is also presented.

Durability of aminosilane-silica hybrid gas-barrier coatings on polymers

Aminosilane solutions with pH equal to 8 and to 11 were applied and cured on SiO 2-coated poly(ethylene terephthalate) (PET) films. The permeability of the silane–silica hybrid coating on PET was reduced twofold compared to that of the SiO 2/PET film, at solution concentrations as low as 1 wt.%, irrespective of the pH. This concentration level led to a dense silane monolayer crosslinked to the silica surface. The oxygen transport mechanisms in the hybrid coatings were determined based on the thermally activated rate theory. Permeation experiments were also performed under tensile loading, and the critical strain for loss of barrier performance was found to be improved by a factor of two, only in case of basic pH. The defect population and morphology of the hybrid coating subjected to hydrothermal aging were analyzed using a reactive ion etching method and atomic force microscopy, respectively. These experiments confirmed the defect healing action of the aminosilane at low concentrations in solution, through the formation of a densely crosslinked polysiloxane layer at the silane–silica interface for both pH8 and pH11. The influence of the silane treatment was emphasized in case of basic pH due to the dissolution of superficial oxide layers.

Two-chamber integrated multichannel narrowband filter prepared by a multistep etching method

A new, to the best of our knowledge, method, which combines the multistep ion-etching method with a traditional narrowband filter coating technique, is developed to prepare a two-chamber integrated multichannel filter. The influence of film deposition and etch technique on the shape and height of the narrow transmittance peaks is analyzed. A 32-channel narrowband integrated filter is fabricated with a homemade ion-etching machine and a coating machine. Every channel is distinctly separated and the FWHM is 1% of its central wavelength. The feasibility of the technique will be useful in the fabrication of a higher integrated multichannel narrowband filter.

Fabrication of Integrated Vertical Mirror Surfaces and Transparent Window for Packaging MEMS Devices

A scheme for creating metal-coated vertical mirrors in silicon, along with an integrated transparent package lid for assembling, packaging, and testing microelectromechanical systems (MEMS) devices is presented. Deep reaction ion etching (DRIE) method described here reduces the loading effect and maintains a uniform etch rate resulting in highly vertical structures. A novel self-masking lithography and liftoff process was developed to ensure that the vertical mirrors undergo uniform metallization while leaving a transparent window for optical probing. Front side of a Si wafer was shallow-etched using DRIE to define an eventual optical window. This surface was then anodically bonded to a Pyrex wafer. Backside Si was then patterned to define thin channels around the optical window. These channels were vertically etched using DRIE, after which the unattached portions of the window region were removed. Negative photoresist was spun on the remaining vertical structures and the stack was exposed from the Pyrex side using Si structures as a self-mask. Subsequent metal sputtering and liftoff results in the metallized top and mirror sidewalls while leaving a clear window. These integrated mirrors and lids are then bonded to the active MEMS mirrors. Various processes and results are illustrated with an example of packaged corner cube retroreflectors (CCRs)

第一原理計算に基づく反応性イオンエッチングプロセスの設計〜始めの一歩〜

We propose an intricate method of Reactive Ion Etching (RIE) process design for transition-metal (TM) materials using ab-initio calculations. The TM materials are inert in dry etching processes since volatile etching by-products cannot be formed easily. However, to achieve new high-performance memories based on the TM materials, a selective dry etching technique such as RIE is eagerly required instead of the conventional ion milling method. In this work, we would like to introduce our scenario of the RIE design for TM materials using the results of CoFe as an example.

High-Q micromachined three-dimensional integrated inductors for high-frequency applications

Three-dimensional micromachined inductors are fabricated on high-resistivity (10kΩcm) and low-resistivity (10Ωcm) Si substrates using a stressed metal technology. On high-resistivity Si substrate with low-k dielectric material (SU-8™), this technology achieves a quality factor Q of 75 for a 1nH inductor at frequencies around 4GHz and a self-resonant frequency fsr above 20GHz. Using Si bulk micromachining to etch away the low-resistivity Si substrate with a combination of deep reactive ion etching and tetramethyl ammonium hydroxide etching methods, a 1.2nH inductor achieves a peak quality factor Q of 140 at a frequency of 12GHz with a self-resonant frequency fsr above 40GHz. The dependence of high-frequency performance on the inductor’s variables, such as the number of turns, turn-to-turn gap, and substrate type, has been investigated. Excellent performance is achieved by removing the substrate due to the complete elimination of substrate losses and the reduction of the parasitic capacitance. This technology is simple and provides high performance integrated inductors on Si or compound-semiconductor platforms.

Modification of photonic band structure in an ordered polystyrene particle layer by controlling interparticle light-mode interaction

Optical spectra of self-assembled monolayers of polystyrene particles (LATEX) which possess quasi-two-dimensional photonic band (PB) structure are investigated in case of the variation of the ratio of the particle diameter to the interparticle distance by reducing the particle size in the layer with use of a reactive ion etching (RIE) method. The transmission spectra of oblique incidence with an s- or p-polarized light beam clearly show that the resonance of PB at k=0 is blue-shifted and the PB width gradually decreases as the particle size decreases down to a certain size. The characteristic behavior of the PB is qualitatively explained in the framework of tight-binding approximation where the interparticle light-mode interaction can be controlled by the magnitude of the overlapping of surface near-fields of Mie resonance modes for the individual particles. Further reduction of the particle size causes anomalous change in the PB branches around the crossing points with a folded optical branch in hexagonal empty lattice.

Human erythrocytes possess a cytoplasmic endoskeleton containing .BETA.-actin and neurofilament protein

The biconcave disc shape of mammalian erythrocytes has been considered to be maintained only with a membrane underlain by a membranous cytoskeleton. Our improved ion-etching/scanning electron microscopy and saponin-ethanol treatment combined with immunocytochemistry in the human red blood cell revealed the three-dimensional structure of this cytoplasmic endoskeleton apart from the classical membranous cytoskeleton. The endoskeletal meshwork images obtained by the saponin-ethanol treatment corresponded to those by the repeated ion-etching method. The actin-rich endoskeleton was divided into two layers, one superficial and the other deep. The superficial filaments were perpendicularly connected to the membranous cytoskeleton, while the deep filaments formed an irregularly directed complicated meshwork. In the transitional hillside region between the convex periphery and concave center, the endoskeletal filaments containing a neurofilament protein ran parallel to the hillside slope toward the concave center. The endoskeleton of the erythrocyte associating with the membranous cytoskeleton may serve to keep its unique biconcave disc shape deformable, pliable, and restorable against external circumstances.

Fabrication and Characterization of Hydrogenated Amorphous Silicon Bipolar Thin Film Transistor (B-TFT)

ABSTRACTThe conventional a-Si:H thin film transistor (TFT) is a field effect transistor (FET), which has disadvantages of a low operation speed and a small current driving capability. To achieve a higher speed and larger current driving capability, a potential solution is to fabricate the a-Si:H-based bipolar thin film transistor (B-TFT). In this study, a-Si:H p-i-n junctions were prepared and studied in order to determine the proper layer thickness for good junction behaviors. B-TFTs composed of a stacked structure of n+/i/p/i/n+ were then fabricated. The complete B-TFT was made using plasma enhanced chemical vapor deposition (PECVD) to deposit all doped and undoped a-Si:H layers and SiNx dielectrics at 250°C. Reactive ion etching (RIE) and wet etching methods were used to define base and emitter regions and contacts. The I-V characteristics of the complete B-TFT were investigated. The common-emitter current gain is 3∼6, which is larger than the literature report of 2∼3. In addition, a collector current larger than the literature value was obtained. A significant current noise was observed, which may be contributed to the high series resistance of the base layer and defective junction interfaces. In this paper, process and structure influences on the a-Si:H junction and B-TFT performances are discussed.

‘Nano-rods’ of single crystalline diamond

We have developed a novel microfabrication method by combining a microwave plasma treatment with a reactive ion etching (RIE) method. First, the RIE system was used for fabricating whiskers of single crystalline diamond. Then, the whiskers were exposed to microwave plasma of hydrogen gas. As a result, we have successfully fabricated a nano-scale diamond rod of the single crystal, which has the crystalline facets. The sizes of the ‘nano-rods’ were 50–200 nm in thickness and several microns in height. Morphology of the nano-rods could be controlled by changing the crystal orientation of the diamond substrate.

A concave-type structure of a Ru electrode capacitor fabricated by the reactive ion etching method

We have developed a concave-type Ru electrode capacitor to overcome the limitation of conventional stack-type capacitor in a small critical-dimension (CD) pattern. We have deposited a Ru layer on the concave-type structure made by patterning of SiO 2 and subsequently we separated the adjacent nodes by an etch-back process with hydrogen silsesquioxane (HSQ) as a protecting layer. We have summarized the issues regarding the patterning in the reactive ion etching system for fabricating the concave-type capacitor.