Showing papers on "Etching (microfabrication) published in 1995"

Properties of Silicon Carbide

Abstract: Basic physical properties optical and paramagnetic properties carrier properties and band structure energy levels surface structure, metallization and oxidation etching diffusion of impurities and ion implantation bulk and epitaxial growth contacts and junctions Schottky diodes, transistors and optoelectronic devices.

Micromachining applications of a high resolution ultrathick photoresist

Abstract: This article describes a new negative‐tone photoresist, SU‐8, for ultrathick layer applications. An aspect ratio of 10:1 has been achieved using near‐ultraviolet lithography in a 200‐μm‐thick layer. The use of this resist for building tall micromechanical structures by deep silicon reactive‐ion etching and electroplating is demonstrated. Using SU‐8 stencils, etched depths of ≳200 μm in Si and electroplated 130‐μm‐thick Au structures with near‐vertical sidewalls have been achieved.

High brightness electroluminescent device emitting in the green to ultraviolet spectrum and method of making the same

Abstract: A green-blue to ultraviolet light-emitting optical device, e.g. a green-blue to ultraviolet emitting laser or a green-blue to ultraviolet emitting diode, comprising a green-blue to ultraviolet light emitting gallium nitride material on a base structure including a silicon carbide substrate, which preferably consists of 2H-SiC, 4H-SiC, or a-axis oriented 6H-SiC. The carrier mobility and the transparency of the silicon carbide substrate are optimized by the selection of orientation and polytype, thus enhancing device performance. The light-emitting diodes may incorporate a structural modification to increase the light output comprising a dielectric Bragg mirror beneath the LED structure, made of alternating layers of AlN, GaN, InN or their alloys. Methods for making such light-emitting diodes are provided, including a technique for defining individual devices by mesa etching which avoids possible damage to the active area during dicing.

Microchip electrophoresis with sample stacking

Abstract: A fused quartz microchip with a serpentine column geometry is fabricated to perform rapid microchip electrophoresis of dansylated amino acids. A 67 mm separation column is constructed in a 7 x 10 mm area on a quartz substrate using standard photolithographic, etching and deposition techniques. Buffer and sample flows within the channel manifold are precisely controlled through potentials applied to the reservoirs. To enhance the detection limits, a stacking injection technique is used to concentrate the sample at the inlet of the separation column. The stacked injections exhibit high reproducibility (2.1% relative standard deviation in peak area). Using a separation length of 67 mm and a separation field strength of 1100 V/cm, separations are performed in < or = 15 s generating approximately 40,000 theoretical plates.

Simplified dual damascene process for multilevel metallization and interconnection structure

Abstract: A semiconductor device containing an interconnection structure having a reduced interwiring spacing is produced by a modified dual damascene process An embodiment comprises the simultaneous formation of a via and trench in a single etching step

Advanced silicon etching using high-density plasmas

Abstract: High density plasmas are beginning to dominate the market for advanced anisotropic silicon etching for MEMS applications. This paper looks at the reasons behind this dominance for high etch rate, deep anisotropic etching. A discussion of anisotropic etch mechanisms highlights the need for sidewall passivation to meet these requirements. Results are presented of a novel room temperature advanced silicon etch process: >= 2 micrometers /min; >= 70:1 selectivity to resist (and >= 150:1 to oxide); up to 30:1 aspect ratio; 500 micrometers depth capability; using a non-toxic, non-corrosive environmentally acceptable fluorine-based chemistry.

Dry-etching method

Abstract: PURPOSE:To realize a good etching wherein etching residues are hard to be left in a material to be etched, by adding trialkyl-aluminium to a halogen-based etching gas. CONSTITUTION:The exhaust of a vacuum container 101 is so performed via a pressure regulating valve 113 by both high-vacuum exhaust turbo molecular pump 114 and low-vacuum exhaust backing pump 115 that a high-vacuum state is obtained. Also, in the vacuum container 101, an electrode 103 is provided, and on the electrode 103, a semiconductor substrate 100 of a material to be etched is put. In the dry-etching of a metallic film containing copper, a gas wherein such an aluminium component as halogen-based trialkyl-aluminium is included is used as an etching gas. Therefore, copper or copper chloride, etc., which are easy to be left as etching residues in the material to be etched for their low vapor pressure are easily subjected to desorptions from the material to be etched while they are changed into such metallic substances having high vapor pressures as copper-aluminium chloride. Thereby, a good etching leaving no residue is made possible.

Embedded micromechanical devices for the monolithic integration of MEMS with CMOS

Abstract: A flexible, modular manufacturing process for integrating micromechanical and microelectronic devices has been developed. This process embeds the micromechanical devices in an anisotropically etched trench below the surface of the wafer. Prior to microelectronic device fabrication, this trench is refilled with oxide, chemical-mechanically polished, and sealed with a nitride cap in order to embed the micromechanical devices below the surface of the planarized wafer. The feasibility of this technique in a manufacturing environment has been demonstrated by combining a variety of embedded micromechanical structures with a 2 /spl mu/m CMOS process on 6 inch wafers. A yield of 78% has been achieved on the first devices manufactured using this technique.

Nitride semiconductor light emitting element

Abstract: PROBLEM TO BE SOLVED: To enhance the luminous output of a semiconductor laser by a method, wherein first second and third N-type layers and an active layer having a multiple quantum well structure are laminated on an N-type contact layer, and the laminated material is formed into a double heterostructure. SOLUTION: A selective etching is performed from a P-type contact layer 11 of a wafer formed into a structure, wherein a buffer layer 2 and a contact layer 3 are grown on the surface of a sapphire substrate 1. A first n-type layer 4 consisting of an n-type InGaN layer, a second N-type layer 5 consisting of an n-type AlGaN layer, a third n-type layer 6 consisting of an n-type GaN layer, and an active layer 7 consisting of a multiple quantum well structure, are grown on the layer 3 and three layers of p-type nitride semiconductor layers 8, 9 and 10, the p-type contact layer 11 are laminated on the layer 7, the surface of the n-type contact layer 3 is made to expose, and stripped electrodes are respectively formed on the exposed surface of the layer 3 and the surface of the layer 11. The grown layers 3 to 7, the laminated layers 8, 9, 10 and 11 and the electrode on the layer 11 are etched from the direction intersecting orthogonally the layers 3 to 11, the electrode on the layer 11, vertical etched end surfaces are formed to form a reflecting mirror, and the reflecting mirror is used as a resonance surface.

Controlled etching of oxides via gas phase reactions.

Abstract: Oxides are etched with a halide-containing species and a low molecular weight organic molecule having a high vapor pressure at standard conditions, where etching is performed at preset wafer temperature in an enclosed chamber at a pressure such that all species present in the chamber, including water, are in the gas phase and condensation of species present on the etched surface is controlled. Thus all species involved remain in the gas phase even if trace water vapor appears in the process chamber. Preferably, etching is performed in a cluster dry tool apparatus.

Fabrication of nanometer‐scale side‐gated silicon field effect transistors with an atomic force microscope

Abstract: The fabrication of nanometer‐scale side‐gated silicon field effect transistors using an atomic force microscope is reported. The probe tip was used to define nanometer‐scale source, gate, and drain patterns by the local anodic oxidation of a passivated silicon (100) surface. These thin oxide patterns were used as etch masks for selective etching of the silicon to form the finished devices. Devices with critical features as small as 30 nm have been fabricated with this technique.

Wet chemical etching of AlN

Abstract: Single‐crystal AlN grown on Al2O3 is found to be wet etched by AZ400K photoresist developer solution, in which the active component is KOH. The etching is thermally activated with an activation energy of 15.5±0.4 kcal mol−1, and the etch rate is found to be strongly dependent on the crystalline quality of the AlN. There was no dependence of etch rate on solution agitation or any crystallographic dependence noted, and the etching is selective over other binary group III nitrides (GaN, InN) and substrate materials such as Al2O3 and GaAs.

Three dimensional microfabrication by localized electrodeposition and etching

Abstract: Embodiments of the present invention provide a new method for producing a three dimensional object, particularly suited to microfabrication applications. The method includes the steps of providing a substrate with a conducting interface, an electrode having a feature or features that are small relative to the substrate, and a solution. The solution has a reactant that will either etch the substrate or deposit a selected material in an electrochemical reaction. The electrode feature is placed close to but spaced from the interface. A current is passed between the electrode and the interface, through the solution, inducing a localized electrochemical reaction at the interface, resulting in either the deposition of material or the etching of the substrate. Relatively moving the electrode and the substrate along a selected trajectory, including motion normal to the interface, enables the fabrication of a three dimensional object. In an alternative embodiment, current is passed through an orifice placed close to but spaced from the substrate surface, and may be accompanied by forced convection through the orifice. The method provides the potential to fabricate using many materials, including metals, alloys, polymers and semiconductors in three dimensional forms and with sub-micrometer spatial resolution.

Chemical Free Room Temperature Wafer To Wafer Direct Bonding

Abstract: A limitation to the use of direct wafer bonding methods for micromachining and thin film device manufacturing has been the necessity for high temperature anneals to strengthen the bonded interface. Obviously, strong interface strength is needed to withstand backthinning processes and the rigors of device fabrication. Unfortunately, the elevated temperature exposure has a detrimental effect on implanted or diffused etch stop layers via diffusive broadening. Additionally, for many micromachined applications wafer bonding could be used as a final assembly step, replacing epoxies. However, the sensitive components of the device must be protected from thermal effects. This paper describes the use of oxygen plasmas to develop chemical free, room temperature, wafer to wafer bonding methods. The bond developed between plasma‐activated silicon wafers is virtually at full strength upon contact bonding and does not require further thermal strengthening. The results for silicon dioxide bonding show that full strength material is achieved with anneals below 300°C. This process has been applied to a number of wafer materials including sapphire, silicon dioxide, silicon nitride, and gallium arsenide. The data presented are the results of strength tests, interfacial defect etching, transmission electron microscopy analysis, initial interface reaction kinetics, and mechanisms studies. We also show preliminary results from a suggested model to explain the observed increases in kinetics compared to conventional aqueous solution processing of samples.

Anisotropic Reactive Ion Etching of Silicon Using SF 6 / O 2 / CHF 3 Gas Mixtures

Abstract: Reactive ion etching of silicon in an RF parallel plate system, using SF6/O2/CHF3, plasmas has been studied. Etchingbehavior was found to be a function of loading, the cathode material, and the mask material. Good results with respect toreproducibility and uniformity have been obtained by using silicon as the cathode material and silicon dioxide as themasking material for mask designs where most of the surface is etched. Etch rate, selectivity, anisotropy, and self-biasvoltage have been examined as a function of SF6 flow, O2 flow, CHF3 flow, pressure, and the RF power, using responsesurface methodology, in order to optimize anisotropic etching conditions. The effects of the variables on the measuredresponses are discussed. The anisotropic etch mechanism is based on ion-enhanced inhibitor etching. SF6 provides thereactive neutral etching species, O2 supplies the inhibitor film forming species, and SF6 and CHF3 generate ion species thatsuppress the formation of the inhibitor film at horizontal surfaces. Anisotropic etching of high aspect ratio structures withsmooth etch surfaces has been achieved. The technique is applied to the fabrication of three-dimensional micromechanicalstructures.

Method of etching silicon nitride film

Abstract: A method for etching a silicon nitride film, includes the steps of supplying a fluorine radical, a compound of fluorine and hydrogen, and an oxygen radical close to a substrate having the silicon nitride film, and selectively etching the silicon nitride film from the substrate with the fluorine radical, the compound of fluorine and hydrogen, and the oxygen radical. A method for etching a silicon nitride film, includes the steps of exciting gas containing fluorine and oxygen gas, thereby generating a fluorine radical and an oxygen radical, supplying the fluorine radical and the oxygen radical close to a substrate having the silicon nitride film and supplying gas of a compound containing a hydroxyl close to the substrate, reacting the fluorine radical, the oxygen radical and the compound containing the hydroxyl, thereby generating a compound of the fluorine radical, the oxygen radical and a compound of fluorine and hydrogen, and selectively etching the silicon nitride film from the substrate with the compound of the fluorine radical, the oxygen radical and the compound of fluorine and hydrogen.

Porous microfabricated polymer membrane structures

Abstract: Polymer membrane structures are microfabricated from polyimide film by lithography or etching. The microfabricated structures have systematically varied dimensions and geometries conducive to implanting in host tissue and the promotion, when implanted, of new vascular structures.

Substrate selectivity in the formation of microcrystalline silicon: Mechanisms and technological consequences

Abstract: We report the results of an in situ spectroscopic ellipsometry study concerning the substrate dependence of the evolution of microcrystalline silicon films deposited by alternating amorphous silicon deposition and hydrogen plasma treatment. The evolution of the composition of the films during growth, up to thicknesses of ∼100 nm, indicates that besides etching, the diffusion of atomic hydrogen efficiently promotes the growth (and/or nucleation) of buried crystallites. Moreover, the evolution of the films strongly depends on the nature of the substrate. This substrate selectivity is discussed in terms of initial growth processes. The effect of the hydrogen plasma well below the film surface, which produces the thickness‐dependent film composition, along with the substrate selectivity, may be of prime importance in technological applications of microcrystalline silicon.

Method of etching a trench into a semiconductor substrate

Abstract: Trench structures (12,32,35,46) are formed in single crystal silicon substrates (10,30) that have either a (110) or (112) orientation. A selective wet etch solution is used that removes only the exposed portions of the single crystal silicon substrates (10,30) that are in the (110) or (112) crystal planes. The trench structures (12,32,35,46) are defined by the {111} crystal planes in the single crystal silicon substrate (10,30) that are exposed during the selective wet etch process. Trench structures (32,35) can be formed on both sides of a single crystal silicon substrate (30) to form an opening (34). Opening (34) can be used as an alignment mark to align front side processing to backside and vice versa. Trench structures can also be use to form a microstructure (41,61) for a sensor (40,60).

Photoluminescence studies of porous silicon carbide

Abstract: A detailed investigation of the dependence of the photoluminescence from porous silicon carbide on preparation conditions and starting material is presented. Porous silicon carbide prepared from different polytypes shows almost identical emission spectra, demonstrating a clear impedance of the band‐gap energy of a particular SiC polytype. Emission bands with peak energies of 2.43, 2.22, 2.07, and 1.93 eV were resolved with the use of selective excitation by tuning the excitation wavelength. The origin of luminescence is suggested to relate to defect states produced at the etched surface.

Method for hot wall reactive ion etching using a dielectric or metallic liner with temperature control to achieve process stability

Abstract: The present invention relates to a method and apparatus for etching semiconductor devices where the undesirable deposition of films on the internal surfaces of the apparatus are prevented during the etching process. The system for etching devices provides an etching chamber having a deposition resistant surface, a holder for holding the device to be etched, and a heater for heating the deposition resistant surface to a temperature between 100 C to 600 C to impede the formation of films on the walls of the chamber. The etching system may further include the deposition resistant surface surrounding the holder while not interfering with the plasma used to etch the substrate.

High quantum efficiency for a porous silicon light emitting diode under pulsed operation

Abstract: A high quantum efficiency for a porous silicon light emitting diode (LED) is demonstrated under pulsed operation. The LED is fabricated from a p+nn+ structure by anodic/hydrofluoric etching followed by deposition of a transparent gold contact. The LED shows a rectifying behavior and emits orange‐red light under forward bias with a spectral width significantly narrower than the corresponding photoluminescence spectrum. By calibrated measurements, we here demonstrate electroluminescence external quantum efficiencies of ∼0.2% under pulsed operation corresponding to internal quantum efficiencies of a few percent.

Gas-phase silicon micromachining with xenon difluoride

Abstract: Xenon difluoride is a gas phase, room temperature, isotropic silicon etchant with extremely high selectivity to many materials commonly used in microelectromechancial systems, including photoresists, aluminum, and silicon dioxide. Using a simple vacuum system, the effects of etch aperture and loading were explored for etches between 10 and 200 micrometers . Etch rates as high as 40 micrometers /minute were observed. Initial characteriation of wafer surface temperature during the etch indicates tens of degrees of self-heating, which is known to cause substantial decrease in etch rate.

Method for dry etching of transition metals

Abstract: A method for dry etching of transition metals. The method for dry etching of a transition metal (or a transition metal alloy such as a silicide) on a substrate comprises providing at least one nitrogen- or phosphorous-containing π-acceptor ligand in proximity to the transition metal, and etching the transition metal to form a volatile transition metal/π-acceptor ligand complex. The dry etching may be performed in a plasma etching system such as a reactive ion etching (RIE) system, a downstream plasma etching system (i.e. a plasma afterglow), a chemically-assisted ion beam etching (CAIBE) system or the like. The dry etching may also be performed by generating the π-acceptor ligands directly from a ligand source gas (e.g. nitrosyl ligands generated from nitric oxide), or from contact with energized particles such as photons, electrons, ions, atoms, or molecules. In some preferred embodiments of the present invention, an intermediary reactant species such as carbonyl or a halide ligand is used for an initial chemical reaction with the transition metal, with the intermediary reactant species being replaced at least in part by the π-acceptor ligand for forming the volatile transition metal/π-acceptor ligand complex.

Etching method for refractory materials

Abstract: A plasma-assisted dry etching process for etching of a metal containing material layer on a substrate to remove the metal containing material from the substrate, comprising (i) plasma etching the metal containing material and, (ii) contemporaneously with said plasma etching, contacting the metal containing material with an etch enhancing reactant in a sufficient amount and at a sufficient rate to enhance the etching removal of the metal containing material, in relation to a corresponding plasma etching of the metal containing material layer on the substrate in the absence of the etch enhancing reactant metal material being contacted with the etch enhancing reactant.

Controlled photon emission in porous silicon microcavities

Abstract: We demonstrate the preparation of narrow‐band porous‐silicon reflectors integrated on porous‐silicon layers by electrochemical etching. By carefully tuning the resulting photon cavity mode around the maximum of the porous silicon photoluminescence, we have obtained both a narrowing and enhancement of the emission line, and a highly concentrated radiation pattern. These results show that the porous silicon spontaneous emission is modified because of the coupling with the photon cavity mode.