Showing papers on "Isotropic etching published in 1994"

Inductive plasma reactor

Abstract: A plasma reactor and methods for processing semiconductor wafers are described. Gases are introduced into a reactor chamber. An induction coil surrounds the reactor chamber. RF power is applied to the induction coil and is inductively coupled into the reactor chamber causing a plasma to form. A split Faraday shield is interposed between the induction coil and the reactor chamber to substantially block the capacitive coupling of energy into the reactor chamber which may modulate the plasma potential. The configuration of the split Faraday shield may be selected to control the level of modulation of the plasma potential. For etch processes, a separate powered electrode may be used to accelerate ions toward a wafer surface. For isotropic etching processes, charged particles may be filtered from the gas flow, while a neutral activated species passes unimpeded to a wafer surface.

Influence of the surface chemistry on the wettability of stainless steel

Abstract: Degreasing with solvents, chemical etching, polishing, oxygen and argon plasma treatment and heating and drying produce stainless-steel surfaces with different amounts of organic contamination and ‘bonded water’. The hydroxide/oxide layer of the passive film formed on stainless-steel foils is also affected by surface pretreatment. Electron spectroscopy for chemical analysis (ESCA) has been used to analyze the composition of the surface film formed after different cleaning procedures. Organic contamination on 304 stainless-steel foils can be reduced by a factor of five using various cleaning treatments. Wettability or surface energy measurements have been performed on the treated surfaces and it was found that the surface energy of the metal decays with the inverse of the contamination layer thickness. As these cleaning treatments lead to different oxide layers, it is concluded that the nature of the oxide layer is not the main parameter that determines the surface free energy of metals.

Method for anisotropic plasma etching of substrates

Abstract: A method for anisotropic plasma etching of silicon substrates, a plasma etching apparatus for implementing the method, and an electronic device manufactured according to the method, which method includes the steps of positioning a substrate having a surface to be depleted by etching within a processing chamber and in communication with an electrode; introducing a gas mixture including an etching gas and a passivating gas which are essentially free of chlorine, bromine or iodine into the processing chamber, the etching gas including at least one halogen or halogen compound and the passivating gas including at least one polymer-generating monomer; exciting the gas mixture with electromagnetic radiation effective to produce a plasma containing ions; and applying a voltage to one of the substrate or the electrode to accelerate the ions toward the substrate and provide the ions with an energy ranging from about 1 to about 40 eV, preferably from about 10 to about 30 eV, when the ions impinge on the surface of the substrate.

Nanolithography with an atomic force microscope for integrated fabrication of quantum electronic devices

Abstract: We describe a novel technique using an atomic force microscope (AFM) for integrated nanometer‐scale lithography on various mask materials such as photoresist or gold covering a mesa‐etched GaAs‐AlGaAs heterostructure at ambient conditions. The generated patterns can be transferred to the two‐dimensional electron gas by wet chemical etching or by ion beam irradiation. We succeed in fabricating hole arrays with a periodicity down to 35 nm and a hole diameter of only a few nanometers. In magnetoresistance studies on so‐called antidot devices with 95 nm period at T=4.2 K we can clearly observe commensurability oscillations, demonstrating the successful pattern transfer to the electron system. With the AFM we can also pattern lines of varying width and depth into prefabricated devices.

Applications of fluorocarbon polymers in micromechanics and micromachining

Abstract: Several thin-film deposition and etching techniques of the polymer fluorocarbon are investigated and the resulting thin-film properties will be compared with those of commercially available bulk polytetrafluoroethylene. The most promising deposition technique is performed in a conventional reactive ion etcher using a carbonhydrotrifluoride (CHF3) plasma. By changing the deposition parameters, control of the properties and step coverage of the deposited thin films within a certain range is possible, eg., uni-directional and conformal step coverage of deposited thin films can be obtained. Etching is performed with the help of an evaporated aluminium oxide mask using an oxygen, nitrogen, or sulfurhexafluoride plasma for isotropic etching, or a CHF3 plasma giving a directional etch profile. The combination of the unique properties, deposition and etching techniques make fluorocarbon thin films a promising tool for micromachining; a number of applications will be discussed and demonstrated.

Radiation Damage of SiO2 Surface Induced by Vacuum Ultraviolet Photons of High-Density Plasma

Abstract: The formation of a surface-damaged layer of gate SiO2 induced by exposure to plasma for gate etching led to the increase in etch rate of SiO2 during HF wet treatment. The effects of vacuum ultraviolet (VUV) photons from various gas plasmas generated by an electron cyclotron resonance (ECR) plasma system and a helicon plasma system were evaluated. It was found that the depth of the damaged layer depends on the energy and penetration depth of VUV radiation. The damaged layer grew exponentially with distance from the surface and was extremely disordered, making it more susceptible to the HF etchant.

Simulation of anisotropic chemical etching of crystalline silicon using a cellular automata model

Abstract: Anisotropic chemical etching of crystalline silicon in aqueous KOH is simulated at the atomic level using a cellular automata model. Experimental etch-rate ratios as well as the influence of temperature and concentration of the etchant are taken into account by introducing a stochastic component. With the help of two examples, the underetching of a convex mask corner and mask-corner compensation for mesa-type corners, the capabilities of this model are demonstrated.

Random surface protrusions on an implantable device

Abstract: An attachment surface for an implantable device has a random irregular pattern formed through a repetitive masking and chemical milling process. Surface material is removed from the implant surface without stress on the adjoining material and the process provides fully dimensional fillet radii at the base of the surface irregularities. This irregular surface is adapted to receive the ingrowth of bone material and to provide a strong anchor for that bone material. The unitary nature of the substrate and surface features provides a strong anchoring surface with is resistant to cracking or breaking. The surface is prepared through an etching process which utilizes the random application of a maskant and subsequent etching of the metallic substrate in areas unprotected by the maskant. This chemical etching process is repeated a number of times as necessitated by the nature of the irregularities required in the surface. The etching characteristics are controlled by the time, temperature and number of repetitions utilized in the etching process.

Processing method and apparatus using focused energy beam

Abstract: A processing method and apparatus using a focused energy beam for conducting local energy beam processing in a focused energy beam irradiating area by irradiating a sample with a focused energy beam such as an ion beam or an electron beam in an etching gas atmosphere. As the etching gas, a mixed gas different in composition from any conventional one is employed and the gas is uniformly supplied to an etching area and at least one of the components of such a mixed gas is a spontaneous reactive gas for use in etching the sample spontaneously and isotropically. With this arrangement, it is possible to subject to local etching a material for which the local etching has been impossible to provide since a single etching gas causes a reaction too fierce or causes almost nearly no reaction.

Control of etch selectivity

Abstract: Selective etching of separate materials in a manufacture of a device, such as a layer of silicon dioxide on a substrate of silicon in a semiconductor device, is accomplished in a reaction chamber having an RF electromagnetic field which interacts with plural etchants in gaseous phase to produce ions for etching the materials. The ratio of the concentration of etchants affect the relative rates of etching the respective materials. By pulsing the rf excitation waveform, intervals of deenergization of the field are produced repetitively wherein, during any one of these intervals, there is a decay in the concentration of each ionized etchant. Rates of decay and the resulting lifetimes differ for each of the etchants. Thereby, by adjustment of the duration of the deenergization interval, the average concentration of one etchant relative to the average concentration of a second etchant can be varied to attain selective etching of the materials. Continuous monitoring of etchant concentrations, as by ultraviolet absorption spectroscopy, permits automatic control of the modulation to attain a desired etch selectivity in real time.

Surface modification of UHMWPE fibers

Abstract: Ultrahigh molecular weight polyethylene (UHMWPE) fibers have a high specific strength, high specific modulus, and outstanding toughness, but their poor adhesive properties has limited their use for composite material applications. In this research, the effects of chemical etching on the surface chemistry and topography have been explored using chromic acid, potassium permanganate, and hydrogen peroxide etching. The smooth surface observed on the as-received fiber was rich in ether and/or hydroxyl oxygen. This smooth surface resulted from the presence of an outer layer, a weak boundary layer, that was removed by all the etchants. A fibrillar structural hierarchy was revealed beneath this outer layer and the fiber was relatively unchanged by further etching. Chromic acid, the strongest etchant studied, produced a rough and oxidized UHMWPE surface with both ether and carbonyl oxygen. The combination of outer layer removal, roughness, and changes in oxygen bonding helps explain the improved adhesion on chromic acid etching in spite of the reduction in surface oxygen. Neither hydrogen peroxide nor potassium permanganate etching roughened or oxidized the surface to a great extent and neither yielded improved adhesion. © 1994 John Wiley & Sons, Inc.

Smooth etching of single crystal 6H‐SiC in an electron cyclotron resonance plasma reactor

Abstract: Single‐crystal 6H‐SiC has been etched using a CF4/O2 gas mixture in an electron cyclotron resonance (ECR) plasma reactor. ECR etching results in SiC surfaces which are extremely smooth, without the problematic micromasking effects which have been reported to result from reactive ion etching in capacitively coupled radio‐frequency plasma reactors. The effects of microwave power, total pressure, substrate temperature, and substrate bias on the etch rate, surface morphology, etch profile, and etch selectivity have been evaluated. The etch rate increases with increasing power and bias, and decreasing pressure. However, high biases lead to enhanced etching in regions adjacent to sidewall features. Improved etch profiles and selectivity are obtained with lower applied substrate bias.

Plasma processing apparatus employing a textured focus ring

Abstract: The invention is directed to a focus ring for surrounding a workpiece/surface substrate during plasma processing comprising a hollow annular assembly comprised of electrically insulating material and having a texturized surface. The texturized ring is preferably in the geometry of a generally cylindrical structure. The texturizing of the ring can be effected by any means of surface abrasion including bead blasting or chemical etching.

Microprofile simulations for plasma etching with surface passivation

Abstract: A numerical algorithm and simulation results are presented for microscopic profile evolution of material surfaces subject to plasma etching (reactive‐ion etching) and surface passivation. Surface evolution is calculated by the shock‐tracking method, which accurately simulates formation and evolution of facet corners. The angle distribution for the reemission of sputtered materials is assumed to follow an arbitrary cosine law (i.e., ∝cosβ Θ, with Θ being the reemission angle and β≳0). Thickness of sidewall passivation layers and resulting etched profiles are shown to depend sensitively on both the reemission angular distribution and the sticking coefficient.

Low temperature formation of Si(111)7×7 surfaces from chemically prepared H/Si(111)‐(1×1) surfaces

Abstract: Reflection high energy and low energy electron diffraction, along with high resolution photoemission studies reveal that ideally H‐terminated Si(111) surfaces, H/Si(111)‐(1×1) prepared by wet chemical etching, transform in ultrahigh vacuum into atomically clean Si(111)7×7 surfaces upon hydrogen desorption at temperatures as low as 550 °C.

Redeposition kinetics in fluorocarbon plasma etching

Abstract: The redeposition kinetics of plasma etching products have been measured as a function of ion and free‐radical fluxes which are representative of the fluorocarbon etching environment. Silicon and SiO2 surfaces were exposed in a multibeam etching tool to energetic ions (Ar+), etchant radicals (F), and depositing carbonaceous species (CF2), the relative fractions of which were independently varied to alter the etching product distributions. The rate of product redeposition (i.e., the deposition rate on nonbombarded surfaces such as trench or via sidewalls) was measured using a quartz crystal microbalance (QCM) which could be rotated around the etching sample face. While redeposition rates of Ar+ sputtering products from Si and SiO2 were characteristically high, the addition of F suppressed redeposition by nearly an order of magnitude. The mechanisms for this reduction involve the passivation of the nonbombarded QCM surface by atomic F, the chemical etching of the redeposited material, and the production of v...

Method of chemical mechanical polishing planarization of an insulating film using an etching stop

Abstract: A method of planarizing an insuating film includes the steps of preparing a semiconductor substrate; treating an uneven surface of the substrate with an organic solvent; forming an insulating film on the thus-treated surface of the substrate by a chemical vapor deposition using an organic silicon compound as a raw material or depositing SOG, forming an etching stop film having a chemical mechanical polishing etching speed slower than that of the insulating film by depositing silicon oxide or silicon oxynitride by performing a chemical vapor deposition using an inorganic silicon compound as a raw material; and etching back at least a part of the insulating film formed on the uneven surface of the substrate by a chemical mechanical polishing process using the etching stop film.

Epitaxial Si-Ge etch stop layers with ethylene diamine pyrocatechol for bonded and etchback silicon-on-insulator

Abstract: The etch rate in ethylene diamine pyrocatechol of Si1-xGe1-x (0.2 ≤ x< - 0.3) etch stops grown by molecular beam epitaxy was determined using Rutherford backscattering spectrometry. Etch rate selectivities as high as 390 were measured. Such etch stops allow for higher bonding temperatures than those possible with currently used boron-based etch stops. Defect etching was used to determine the maximal thickness of dislocation-free layers.

Selective Etching of Hydrogenated Amorphous Silicon by Hydrogen Plasma.

Abstract: The selective etching of hydrogenated amorphous silicon (a-Si:H) with respect to crystalline Si (c-Si) by hydrogen plasma is investigated. We have revealed that a-Si:H is etched ten times faster than c-Si. With lower etching temperature, etching selectivity and etching rate of a-Si:H and c-Si increase. Under the high-pressure condition, the etch rate becomes low because the bright region of a very-high-frequency plasma moves away from the grounded electrode. The etching rate of a-Si:H is not sensitive to the structure of the a-Si:H deposited at 70–300° C. The surface morphologies of etched a-Si:H and c-Si are rougher for higher etching temperature. The mechanism of selectivity in etching is discussed.

Effects of Thermal and Chemical Treatments on the Composition and Structure of Electrodeposited CuInSe2 Thin Films

Abstract: Cu{sub 1{+-}x}In{sub 1{+-}z} thin films within a wide composition range have been obtained by a one-step electrodeposition method onto molybdenum substrates. These films were then submitted to different postdeposition treatments: annealing in argon atmosphere and/or chemical etching in a 0.5M KCN solution. The as-grown and treated samples were examined by X-ray diffraction for determination of crystalline quality and by chemical analysis for composition. Annealing improves the crystallinity of electrodeposited films; the effective grain size increased as the annealing temperature increased. Chemical etching produces significant changes in the film composition, the aqueous KCN solution dissolves secondary phases of copper selenides that have been detected in the samples. Depending on the sequence of annealing and chemical treatments, the resulting thin films exhibit different characteristics.

Surface chemical changes in PVD TiN layers induced by ion bombardment

Abstract: TiN layers produced by the PVD method were subjected to bombardment by different ion species applied in sequence. The relative atomic concentration and the chemical states of the elements in the surface layer were determined by means of x-ray photoelectron spectroscopy. The composition and chemical states of a reference sample after wet chemical etching were taken to be representative for the stoichiometric TiN not affected by ion sputtering. For this sample characteristic line energies of Ti 2p3/2 = 454.7 eV and N 1s = 396.7 eV were found. Alternate bombardment with Ar+, N2O+ ions (1–5 keV) results in significant compositional and chemical state changes. Ar+ bombardment leads to preferential loss of N from the outermost (1–3 nm) surface layers of the nearly stoichiometric TiNx (x = 1.0–1.1) without observable changes in the chemical state of the constituents. Bombardment with N2+ ions leads to a build-up of excess N (x ≫ 1) followed by the appearance of new N 1s and Ti 2p lines at 395.8 ± 0.3 eV and at 456.3 ± 0.3 eV, respectively. N2O+ bombardment increases the O and decreases the N concentration together with a concomitant shot out of a Ti 2p3/2 component peak at about 457.6 eV assignable to Ti2O3.

Method of beveled contact opening formation

Abstract: This invention provides a method of forming contact holes and via holes in interlevel dielectric which insure good metal stepcoverage. The contact or via holes have tapered sides and smoothed edges. The method uses isotropic etching, anisotropic etching, and argon sputter etching in vacuum and does not require high temperature contact reflow. The final argon sputter etch is a timed etch that smoothes all sharp edges, exposes the regions where electrical contact will be made, and planarizes the interlevel dielectric.

Method for vapor phase etching of silicon

Abstract: A method for etching a silicon wafer (20) by using hydrogen fluoride and water vapor combined with ozone is disclosed. The process does not require additional energy excitation or high pressure.

Maskless patterning of silicon surface based on scanning tunneling microscope tip-induced anodization and chemical etching

Abstract: A microprocessing method for silicon (Si) without photolithography is proposed. The method consists of only two processes. Hydrogen‐terminated Si surfaces (Si‐H) were first locally anodized using scanning tunneling microscopy (STM). The non‐anodized surfaces were then etched chemically in potassium hydroxide solution. The anodic oxide produced with the first process performed as an etching mask. The height of the etched pattern of approximately 50 nm was much larger than the thickness of the anodic oxide. Humidity effect on STM tip‐induced anodization of Si‐H is also shown. The area of the anodization was enlarged with increasing humidity, and the spatial resolution became worse.

Method for manufacturing a device separation region for semiconductor device

Abstract: Method for manufacturing a device separation region for semiconductor devices which separates regions electrically from each other stably, and allows realization of large scale integration with high reliability. When forming a device separation region 10 selectively on a substrate 1 by LOCOS method by controlling thermal oxidation, a device separation region 10 is formed to thickness t2 thinner than a predetermined thickness (FIG. 4C). A second silicon nitride layer 5 is formed onto the whole surface of the substrate 1 (FIG. 5A). A photo resist layer 8 is formed on the second silicon nitride layer 5, and the second silicon nitride layer 5 is partially removed by chemical etching (FIG. 5B). By carrying out thermal oxidation again after the etching, the device separation region 10 is formed to the predetermined thickness t (FIG. 5C). In that, device separation is accomplished stably. Also, the device formation region 15 can be formed larger than a conventional one since the occurrence of bird's beak is suppressed by controlling thermal oxidation when forming the device separation region 10. As a result, large scale integration can be realized with high reliability.

Anisotropic chemical pattern etching of copper foil. III: Mathematical model

Abstract: A mathematical model for wet chemical etching of copper in acid chloride solutions was developed for exploring the phenomenon of anisotropic etching reported in Parts I and II of this study. The model considered a two-dimensional rectangular cavity and accounted for laminar convection, diffusion, migration, homogeneous equilibria, and heterogeneous electrochemical reactions involving eight ionic species. Two compositions (3.5M CuCl 2 +0.5 M HCl+0.5 M KCl and 0.5 M CuCl 2 +0.5 M HCl+0.5 M KCl) and two cavity aspect ratios (width:depth=5:1 and 1:1) were considered. Calculation of the flow field demonstrated the existence of recirculating eddies which play a significant role on local transport, particularly in the interior corners