Inductively Coupled Plasma Reactive Ion Etching Research Articles

Accurate Double-Height Micromolding Method for Three-Dimensional PolyDiMethylSiloxane Structures

A fabrication method for making accurate double-height micromolds is presented. Fine features of the micromold are transferred to a three-dimensional poly-dimethylsiloxane (PDMS) microfluidic membrane. The accuracy of features is within 1.55% and the maximum aspect ratio is 7. In this work, the first layer of the micromolds is made directly on silicon wafers by inductively coupled plasma reactive ion etching (ICP-RIE). The second layer is added by photolithography of SU-8 negative photoresist on top of the first layer. This method allows the fabrication of micromolds having wall dimensions as small as 3 µm that was not previously achievable. Such dimensions are required in biological microfluidic systems to reduce the amount of chemicals or to confine cells to a desired position.

SOI-based fabrication processes of the scanning mirror having vertical comb fingers

A 1500 μm ×1200 μm scanning mirror having vertical comb fingers has been fabricated by using silicon-on-insulator (SOI)-based fabrication processes. It is a vertically driven electrostatic scanner and composed of two structures having vertical comb fingers. The comb fingers are etched by deep inductively coupled plasma reactive ion etching (ICPRIE) and assembled by the flip chip aligner bonder. The buried oxide layer is used as an etch stop to acquire the uniform thickness of torsion bars of the upper structure. Using an oxide mask process, we acquired the uniform comb fingers at the lower structure without the planarization process. The handling difficulty of a thin silicon wafer is improved by using an anodic bonding and following mechanical polishing. This scanning mirror showed a linear actuating performance. It can be used for laser display as a galvanometric vertical scanner.

Bonding of silicon scanning mirror having vertical comb fingers

A 1500 μm × 1200 μm silicon scanning mirror has been fabricated by using anodic bonding and flip chip bonding. This scanning mirror is mainly composed of two structures having vertical comb fingers. By anodic bonding between the silicon wafer and the Pyrex glass substrate, and following deep inductively coupled plasma reactive ion etching (ICPRIE), isolated comb electrodes were fabricated at the lower structure. However, gold signal lines for electrical connection to the electrodes, which were inserted between silicon and Pyrex glass, were damaged during anodic bonding. This problem was solved by using the proposed processes and signal lines were successfully fabricated with the contact resistance below several tens of ohms. By flip chip bonding, the upper and lower structures having vertical comb fingers were assembled. Vertical comb fingers of two structures were aligned with a microscope and the frames of two structures were bonded at 300 °C for 20 s using the eutectic bonding material—electroplated AuSn. Finally, the scanning mirror was successfully fabricated and could be used for laser display as a galvanometric vertical scanner.

Low-Damage Etching of Silicon Carbide in Cl2-Based Plasmas

Fluorine-based plasmas have been extensively reported for etching SiC in inductively coupled plasma reactive ion etching (ICP-RIE) systems for device fabrication and via-hole formation. The primary advantage of fluorine-based plasmas for etching SiC is that they yield very high etch rates. However, while high etch rates are very suitable for via-hole formation into SiC, lower etch rates are desirable for SiC device fabrication. The etching of SiC using ICP-RIE in various -based mixtures is reported. It was found that in comparison with -based gas mixtures, -based gas mixtures induced less damage on etched SiC surfaces. Optimized etching conditions using gas mixtures that induce minimal surface damage on SiC are reported. Results of Auger electron spectroscopy showed that etching conditions produced negligible change in surface stoichiometry. © 2002 The Electrochemical Society. All rights reserved.

Fabrication of electrostatic micro-actuators for a hard disk drive application

Micro-actuators are developed for a hard disk drive application. The aim is to obtain a high density of data storage by positioning the read and write head element precisely. The desired specifications are a displacement of ±0.5 μm, operating voltage of 20 V and a structural resonance frequency of 15 kHz. We manufactured the metallic actuator by using thick photoresist lithography and nickel electroplating. The electrostatic gap between the mover and the stator has a high aspect ratio, in order to achieve low voltage operation. We deposited a copper layer by electroplating as a vertical sacrificial layer. Then we removed the copper layer at last process step to make the electrostatic gap with high aspect ratio. We utilize a photoresist which has a thickness of 10 μm as the first trial. We completed the process and operated the actuator successfully. We also developed a silicon actuator using the silicon deep etching and deposition technology. We use an Inductive Coupled Plasma-Reactive Ion Etching (ICP-RIE) machine for silicon etching and a Low Pressure Chemical Vapor Deposition (LPCVD) machine for deposition of the vertical sacrificial layer of SiO2 and the mover structure of polySi. We obtained an actuator which had thickness of 100 μm with the electrode gap having a aspect ratio of 50.

DC and microwave performance of recessed-gate GaN MESFETs using ICP-RIE

The fabrication and characterization of GaN MESFETs grown on sapphire recessed using inductively-coupled-plasma reactive ion etching (ICP-RIE) are reported for the first time. The MESFETs were recessed using a Cl 2/Ar plasma in ICP-RIE, and the drain current was monitored during recess. The devices with a gate length of 0.25 μm exhibited a peak extrinsic transconductance of 36 mS/mm and a threshold voltage of −3.7 V. The unity current gain cutoff frequency f T and maximum frequency of oscillation f max were measured to be 28 and 55 GHz, respectively at room temperature. This recessed-gate process produced high extrinsic transconductances and lower threshold voltages compared with those of unrecessed GaN MESFETs. Also, the values of f T and f max are at least twice the highest frequency data ever reported for GaN MESFETs. The influence of substrate temperature on the DC and microwave characteristics is also reported.

Reactive ion etching of SiC using C2F6/O2 inductively coupled plasma

The inductively coupled plasma-reactive ion etching (ICP-RIE) of SiC single crystals using the C2F6/O2 gas mixture was investigated. It was observed that the etch rate increased as the ICP power and bias power increased. With increasing sample-coil distance, O2 concentration, and chamber pressure, the etch rate initially increased, reached a maximum, and then decreased. Mesas with smooth surfaces (roughness ≤1 nm) and vertical sidewalls (∼85°) were obtained at low bias conditions with a reasonable etch rate of about 100 nm/min. A maximum etch rate of 300 nm/min could be obtained by etching at high bias conditions (≥300 V), in which case rough surfaces and the trenched sidewall base were observed. The trenching effect could be suppressed by etching the samples on anodized Al plates, although mesas with sloped (60–70°) sidewalls were obtained. Results of various surface characterization indicated little contamination and damage on the etched SiC surfaces.

Design and fabrication of scanning mirror for laser display

A 1500mm � 1200 mm silicon scanning mirror for laser display has been designed and fabricated by deep inductively coupled plasma reactive ion etching (ICPRIE) and flip chip bonding technology. It is a vertically driven electrostatic scanner and composed of two structures having vertical comb fingers. The upper structure is composed of a scanning mirror plate, two torsion bars, a supporting frame and vertical comb fingers. The lower structure is composed of vertical comb fingers, a supporting frame, gold signal lines and pads on the Pyrex glass substrate. The comb fingers are etched by ICPRIE and assembled by flip chip aligner bonder. This scanning mirror can be used for laser display as a galvanometric vertical scanner. # 2002 Elsevier Science B.V. All rights reserved.

Recessed 0.25 µm gate AlGaN/GaN HEMTs onSiC with high gate-drainbreakdown voltage using ICP-RIE

Using inductively coupled plasma reactive ion etching (ICP-RIE), recessed 0.25 µm gate-length AlGaN/GaN high electron mobility transistors (HEMTs) have been fabricated. A post-etch anneal eliminated the plasma-induced damage resulting in an improvement of the gate-drain breakdown voltage from –27 V for the as-etched to over –90 V for the annealed devices. The gate leakage current reduced from 91 to 4 µA at Vgd = –25 V, after annealing. These devices exhibited maximum drain current density of 770 mA/mm, unity gain cutoff frequency (fT) of 48 GHz, and maximum frequency of oscillation (fmax) of 108 GHz.

Antireflection microstructures fabricated upon fluorine-doped SiO_2 films

Two-dimensional periodic structures were fabricated upon a fluorine-doped SiO(2) film in which the fluorine content changed gradually in the direction of film thickness. The films were deposited by plasma-enhanced chemical-vapor deposition. The film was periodically patterned into a 1-mum period and an ~1-mum -groove depth by inductive coupled plasma reactive-ion etching followed by chemical etching in a diluted HF solution. A surface reflectance of 0.7% was attained at 1.85-mum wavelength, a value that is one fifth as large as the 3.5% Fresnel reflection of a SiO(2) substrate with a flat surface.

Cell Placement and Neural Guidance Using a Three-Dimensional Microfluidic Array

Several fabrication techniques for making three-dimensional arrays of micro-wells for biological cell patterning and single-neuron guidance are presented. Methods for making complex 3d high-aspect-ratio structures in poly-dimethylsiloxane (PDMS) membrane are explored. In this work, three-dimensional micro-molds are made directly on silicon wafers though inductively coupled plasma reactive ion etching (ICP-RIE), and also using SU-8 negative photoresist. Cell placement is achieved through an array of 50-µm square holes in a 150–100 µm thick PDMS membrane, which is placed on a glass substrate. Vertical holes in the membrane are linked by horizontal tunnels on the glass side of the membrane, for use in neural guidance or delivery of drugs or nutrients. The effectiveness of the membrane for cell placement, growth and guidance was tested using fluorescent yeast cells and PC12 neuronal cells.

Multiple-height Microstructures Fabricated by ICP-RIE and Embedded Masking Layers

Due to the processing limitation of photolithography, only width and length have been controllable parameters for designing mechanical characteristics of silicon micromachined structures, while thickness has been left pre-determined by the thickness of layers. The range of electromechanical properties have been, therefore, strongly limited by the practical range of these tunable parameters. In this paper, we present a universally applicable fabrication technique to realize multiple-height microstructures by locally controlling the etching depth of ICP-RIE (inductively coupled plasma reactive ion etching). Several layers of etching masks of different materials have been prepared on the initial surface of substrate to avoid repeating photolithography on the etched surfaces. This technique enables us to have one more degree of freedom in designing MEMS structures.

Production method for aluminum beam leads on ceramic substrates : R. E. McMahon, F. J. Bachner, R. A. Cohen, W. S. Franklin and J. D. Impey. Proc. 21st Electronic Components Conf., Washington DC, USA, 10–12 May (1971), p. 96

Chalcogenide glasses are good candidate materials for ultra-fast non-linear optic devices. In this work, we present the photolithographic process and the plasma etching of arsenic tri-sulphide (As2S3) film. The films were deposited on thermally oxidized silicon substrates by ultra-fast pulsed laser deposition. To protect As2S3 film from photo-resist developer, thin resist layer ∼100–200 nm was remained on the UV exposed area by controlling resist development time. After removing the protective layer in oxygen plasma, As2S3 waveguides were patterned in inductively coupled plasma reactive ion etching (ICP-RIE) system using CF4–O2 gas mixture. We investigated the etch rate and the etch selectivity to photo-resist of As2S3 as a function of bias power, induction power, operating pressure, and gas flow rate ratio of CF4 and O2. The film is mainly etched by the chemical reaction with fluorine radicals. The content of oxygen in the plasma determines the etched sidewall profiles and nearly vertical profile was obtained at high oxygen content plasma.

Charge-coupled devices—a new approach to MIS device structures : W. S. Boyle and G. E. Smith. IEEE Spectrum, July (1971), p. 18

Chalcogenide glasses are good candidate materials for ultra-fast non-linear optic devices. In this work, we present the photolithographic process and the plasma etching of arsenic tri-sulphide (As2S3) film. The films were deposited on thermally oxidized silicon substrates by ultra-fast pulsed laser deposition. To protect As2S3 film from photo-resist developer, thin resist layer ∼100–200 nm was remained on the UV exposed area by controlling resist development time. After removing the protective layer in oxygen plasma, As2S3 waveguides were patterned in inductively coupled plasma reactive ion etching (ICP-RIE) system using CF4–O2 gas mixture. We investigated the etch rate and the etch selectivity to photo-resist of As2S3 as a function of bias power, induction power, operating pressure, and gas flow rate ratio of CF4 and O2. The film is mainly etched by the chemical reaction with fluorine radicals. The content of oxygen in the plasma determines the etched sidewall profiles and nearly vertical profile was obtained at high oxygen content plasma.