Showing papers on "Isotropic etching published in 1983"

Effects of dry etching on GaAs

Abstract: A number of dry etching techniques have been developed and their ability to produce anisotropic etch profiles has been demonstrated. In addition to etch anisotropy, an important consideration for device and circuit fabrication is whether a sample suffers radiation damage by exposure to ions, electrons, or ultraviolet light during etching. In this study we evaluate the degree of radiation damage induced in GaAs by ion‐beam etching with Ar, reactive‐ion etching with CF4 and CHF3, and ion‐beam‐assisted etching with Ar and Cl2. In addition, we propose and demonstrate processing techniques which can be used after dry etching to reduce the effects of radiation damage. GaAs samples were etched under a variety of etching conditions. The degree of radiation damage caused by etching was determined by evaluating Schottky diodes fabricated on the etched surfaces and by using deep level transient spectroscopy to characterize trapping centers. It was found that the barrier heights and breakdown voltages of Schottky diodes were changed after etching. Also, an increase in the density of traps was observed. Variations in the etching conditions had a strong effect on the measured characteristics of the samples.

Etch procedure for optical fibers

Abstract: A process is described for etching a tapered point on a cylindrically symmetric body using an inert liquid layer on top of the etching solution. The process is extremely useful for etching tapered points on optical fibers prior to melt-back to form a small lens to couple light from laser to optical fiber. The process produces excellent tapered points rapidly and reproducibly with a minimum of operator attention and without etch marks above the taper.

Method and device for plasma etching

Abstract: PURPOSE:To enable precision plasma etching with good efficiency and high uniformity by interposing an insulating flat plate having many fine holes between a lower electrode to be placed thereon with an object to be treated and an upper electrode disposed oppositely thereto. CONSTITUTION:An electronic part forming material having a resist pattern is placed on a lower electrode 4 and an insulating flat plate 5 consisting of a ceramic, etc. having many fine holes is interposed, via supports 8 and 8' between an upper electrode 3 and the electrode 4, then a high frequency voltage is impressed on the electrode 3 and the plasma etching of the above-mentioned material is performed, in a plasma etching device consisting of a bell-shaped cover part 1, a bottom plate 2 attached with the electrode 4 and disposed with the electrode 3 oppositely to the electrode 4. The active seed of the above-mentioned material arriving at the object to be treated is adequately suppressed by the above-mentioned constitution, whereby precision etching having high uniformity is obtd., the damage of the resist, etc. is prevented, hence treating electric power is increased and high speed etching is made possible.

Plasma etching using hydrogen bromide addition

Abstract: The disclosure relates to a plasma etch chemistry which allows a near perfectly anisotropic etch of silicon. A Cl-containing compound such as HCl has HBr added thereto, readily allowing the anisotropic etching of silicon. This is due to the low volatility of SiBr 4 . The silicon surface facing the discharge is subjected to ion bombardment, allowing the volatilization (etching) of silicon as a Si-Cl-Br compound. The Br which adsorbs on the sidewalls of the etched silicon passivates them from the etching. This new plasma etch chemistry yields a very smooth etched surface, and the etch rate is relatively insensitive to the electrical conductivity of the silicon.

Chemical etching of deformation sub-structures in quartz

Abstract: Chemical etching of dislocations has been studied in natural and synthetic quartz single crystals, in deformed synthetic quartz and in naturally and experimentally deformed quartzites. The ability of different etchants to produce polished or preferentially etched surfaces on quartz is described. Dislocation etching was achieved on all crystal planes examined by using a saturated solution of ammonium bifluoride as the etchant. Appropriate etching times were determined for etching quartzites for grain size, subgrain boundaries, deformation lamellae, dislocations and twins. Growth and polished surfaces of synthetic single crystal quartz were similarly etched and dislocation etch pits, characteristic of various orientations were found. The use of ammonium bifluoride proved to be expecially advantageous for the basal plane, producing a polished surface with etch pits, suitable for dislocation etch pit counting. “Double” etch pits have been found on Dauphine twin boundaries on the basal plane and the first order prism, using this etchant. Slip lines and deformation bands were suitably etched on deformed synthetic crystal surfaces for identification of the slip planes. Other acidic etchants have been explored and their application to the study of deformation structures in quartz crystals is discussed.

Method and apparatus for plasma etching a substrate

Abstract: A method and apparatus for plasma etching a substrate, such as a semiconductor wafer, utilizing a multipole surface magnetic field confining within an etching chamber an etching plasma of substantially uniform density throughout its volume. The plasma is produced and maintained by subjecting a gas such as CF 4 to an ionizing discharge within the chamber. Only DC power sources are used for the discharge, so that there is virtually no perturbing radio frequency interference produced. The wafer is consequently easily biased relative to the plasma for controlled fine-scale etching. Low gas pressures permitted by the surface magnetic field result in substantially anisotropic etching of the substrate by dense plasma concentrations.

Plasma-Assisted Etching in Microfabrication

Abstract: It has long been recognized that a molecular gas glow discharge is a prolific source of chemically active radicals. However, it was not until the last twenty years or so that glow discharges were used to provide active radicals for the etching of solid materials. The first major application of this type was the use of oxygen glow discharges to volatilize carbonaceous materials such as photoresists (1). In the mid-1960s this approach was extended to the etching of silicon and its compounds using glow discharges of fluorineand chlorine-containing gases (2). Beginning in the mid-1970s and continuing up to the present time (mid-1982), there has been an explosive growth in the use of reactive gas glow discharges for etching of solids. The driving force behind this growth has been the need for anisotropic or directional etching processes in microfabrication technologies-most notably in the elec­ tronics industry. Many lithographic patterns now have minimum feature sizes in the 1-3-J.Lm range and isotropic etching processes, either wet or dry, cannot maintain the dimensional control necessary to replicate these small features with acceptable yield. Associated with this rapid growth has been a proliferation of etching equipment, accompanied by a sometimes confusing terminology. Early work was performed with "plasma ashing" or "plasma stripping" equip­ ment originally intended for oxidative volatilization of carbonaceous layers. In these systems, the surface to be etched is immersed in the glow discharge without an applied electrical bias (i.e. the surface resides at the floating potential in the plasma). These so-called barrel systems usually etch isotropically; and hence, are unsatisfactory for most high resolution etching tasks. Recognition of the importance of energetic ion bombardment in obtaining etching directionality led to the use of "planar systems" (3, 4) in which energetic ion bombardment of the surface to be etched can be easily

Laser induced dry etching of vias in glass with non-contact masking

Abstract: Disclosed is an apparatus and method for etching a glass substrate by laser induced dry etching. The apparatus features a housing including a vacuum chamber for receiving the substrate; a vacuum pump coupled to the chamber for evacuating the chamber; a gas source coupled to the chamber for supplying a halogen base gas which is capable of wetting the substrate surface and forming a glass etching specie when activated; a laser source for transmitting a light beam of predetermined wavelength and intensity through the gas; and a mask optically coupled to the laser source for patterning the light beam and also coupled to the chamber so that the light patterned by the mask may fall upon the substrate causing excitation thereof and activation of an etch specie for etching the substrate in conformity with the patterned light. The disclosed method comprises the steps of loading the substrate into a vacuum chamber; evacuating the chamber to a low pressure; controllably introducing a halogen base gas into the chamber to wet substrate surface layer to be etched; and introducing a patterned light beam of predetermined wavelength and intensity through the gas onto the surface layer causing excitation thereof and activation of an etch specie for etching the substrate in conformity with the patterned light. The laser light may be of the pulse type and of 10.6 microns wavelength in case of a CO2 laser or 249 nanometer or 193 nanometer wavelength in case of an eximer laser.

Large area ion beam assisted etching of GaAs with high etch rates and controlled anisotropy

Abstract: Ion beam assisted etching (IBAE) is a dry etching technique in which the sputter etching component of an argon ion beam and the chemical etching component supplied by a Cl2 gas flux are independently controlled. This technique has been used to obtain anisotropic etching of GaAs with minimal surface damage over areas of a few square millimeters. The results reported here are achieved with an improved IBAE system designed to etch considerably larger areas. The system accurately and uniformly delivers reactive gas flux to the sample giving uniform etching rates over the 2‐cm‐diam area exposed to the ion beam. When the sample is exposed to high reactive gas fluxes, equivalent to a pressure of 1×10−2 Torr, and 1 to 2 keV Ar+ ions at 1 mA cm−2, etching rates of 5 to 10 μm/min are obtained making etched through‐holes in GaAs wafers realizable. Control of the ion beam collimation and the reactive gas flux allow for accurate control of undercutting making submicrometer etched structures in GaAs with aspect ratios>...

Generation of <50 nm period gratings using edge defined techniques

Abstract: A sequence of edge defined techniques has been developed which allows the successive multiplication of the number of lines in a grating pattern. Holographic lithography at 351.4 nm wavelength in a liquid medium has been used as the primary pattern generation technique for producing gratings with periods of ≊160 nm. A shadowing technique is then used to produce x‐ray masks with precisely controlled linewidth‐to‐period ratios. Reactive‐ion etching in CHF3 yields a square profile structure in SiO2 with precise linewidth. The basic edge defined technique consisting of CVD deposition, reactive‐ion etching, and selective isotropic etching can then be repeatedly applied given a proper choice of materials and etches. Each cycle of the edge defined technique doubles the number of lines in the pattern. Careful linewidth control at each step can result in gratings with one‐half of the initial period with minimum fundamental components. Gratings with ∼40 nm period have been fabricated by doubling the number of lines in a 160 nm period grating twice.

Radio frequency sputtering—the significance of power input

Abstract: Radio frequency (rf) sputtering is used for the deposition and etching of thin layers. In both cases the target etch rate must be controlled, and often power input has been used as one of the controlling parameters. An earlier paper has shown that the applied rf target voltage (V pp) was a more useful parameter, and here new data is presented which indicates that the peak‐to‐peak voltage remains the preferable parameter for both etch rate control and in transferring between machines. However, a new method is described here which obtains the discharge power by subtracting losses from the total power reading. This discharge power is shown to be related to etch rates, and can thus be used as an aid in the scaling of system sizes. In addition, this discharge power exhibits interesting behavior as the pressure is varied, at constant applied rf voltage. Three main regions are evident when etching Si with CF4: at low pressures directional ion‐induced etching is obtained; in an intermediate region the input power rises rapidly with pressure and the etching is less directional resulting in overhang profiles; and at high pressures an isotropic etching component results in undercut profiles. The two extreme regions correlate with the commonly identified regimes of: (a) low power input, low pressure reactive sputter etching, and (b) high power input, high pressure plasma etching.

Maskless chemical etching of submicrometer gratings in single-crystalline GaAs

Abstract: Submicrometer optical gratings are produced in a GaAs surface by a laser‐enhanced, wet‐etching process which permits the fabrication of different grating profiles. The etch process was investigated by in situ optical measurements of the diffracted beams and electron microscopy.

Process and apparatus for fabricating a semiconductor device

Abstract: MOlecular beam epitaxy (MBE) requires that the surface of a substrate on which a semiconductor layer is formed by MBE be clean. Physical etching damages the substrate, while usual chemical etching damages vacuum pumps and contaminates MBE apparatuses. Hydrogen plasma etching can clean a substrate without damaging a substrate and a vacuum pump and without contaminating an MBE apparatus. Further, by combining MBE with formation of a protective layer without breaking the vacuum used in MBE, diffusion of an impurity in the semiconductor layer formed by MBE can be greatly decreased during a subsequent high-temperature heat treatment.

Growth of low dislocation density CdTe films on hydroplaned CdTe substrates by molecular beam epitaxy

Abstract: A systematic study of CdTe film growth by molecular beam epitaxy (MBE) on hydroplaned (111)A and (111)B CdTe substrates is discussed. Substrate preparation prior to growth involved chemical etching techniques, rather than sputtering in UHV, in order to maintain the integrity of the hydroplaned surface. A range of substrate temperature during growth was investigated. X‐ray diffraction, UV reflection, and transmission electron diffraction measurements were employed to evaluate the structural quality of the CdTe films. Bright and dark field transmission electron microscopy was used to determine film dislocation densities. An entirely different film growth morphology was observed on the (111)A versus (111)B substrate surfaces for the range of temperatures and growth rate employed. Growth of high quality, low dislocation density, twin‐free CdTe films was achieved on hydroplaned (111)A CdTe substrates at 250 °C.

Laser-controlled chemical etching of aluminum

Abstract: A new technique is described for high‐spatial‐resolution (<2‐μm linewidth) etching of Al thin films. The process is based upon moderate local heating by a tightly focused Ar+ laser beam to activate an etching reaction in mixtures of phosphoric acid, nitric acid, and potassium dichromate. By chemically biasing the reaction near its passive/active transition, the laser can enhance the reaction rate by more than six orders of magnitude. The etching mechanism has been studied by etch‐rate measurements, ellipsometry, and Auger spectroscopy, and is ascribed to a competition between the formation of soluble aluminum phosphates and insoluble aluminum oxides.

Polyimide inter-metal dielectric process

Abstract: A technique for employing polyimide as an inter-metal dielectric layer, while avoiding the difficulties usually associated with this material. An upper layer of silicon dioxide is employed as a hard mask over the polyimide, and is highly doped with phosphorous to prevent thermal cracking. Via holes are formed in a multi-stage etching process that includes a first dry-etching step that effects isotropic etching to form holes with desirably sloped sidewalls, and a second dry-etching step that effects anisotropic etching to extend the via holes through to a lower metal surface without significantly enlarging the holes in width. Finally, a dry-etching step is used to remove any residue of polyimide and to strip the silicon dioxide layer from over the polyimide. The bottom of the hole is then sputter-etched prior to metallization. In one preferred form of the method, a lower layer of silicon dioxide is formed between the lower metal layer and the polyimide layer, to facilitate removal of polyimide residue and to act as a barrier between the lower metal and the polyimide.

Silicon etching mechanism and anisotropy in CF4+O2 plasma

Abstract: From measurements of optical emission and silicon etch rate, we are able to separate contributions due to the chemical etching and the ion‐bombardment enhanced etching in the CF4+O2 reactive ion etching process. The chemical etching part of undoped polysilicon etch rates is linearly proportional to the ground state fluorine population and the ion bombardment part is proportional to the dc self‐bias voltage (V2.3bi). The chemical etching predominates during plasma etching, giving rise to the isotropic etch profile, while both the chemical etching and the ion‐bombardment enhanced etching mechanisms coexist during reactive ion etching. A degree of the etch anisotropy in reactive ion etching is determined by competition between the chemical etching and the ion‐bombardment enhanced etching, and can be expressed by an equation which only involves two physical quantities, etch rate and fluorine concentration, experimentally measurable in plasma etching and reactive ion etching. The silicon loading effect leads t...

Fully automatic apparatus for the determination of doping profiles in Si by electrical measurements and anodic stripping

Abstract: A completely automatic, computer‐controlled apparatus for the determination of doping profiles in silicon has been set up. Doping is determined by resistivity and Hall measurements associated with the subsequent removal of controlled thin layers of material. Anodic oxidation and subsequent oxide stripping by chemical etching has been chosen as the most controllable peeling technique. Electrical measurements are automatically detected and both carrier concentration and mobility values are plotted versus depth. A set of empirical parameters are provided to fit mobility‐concentration data for P, B, and As available in the literature, with analytical expressions. In this way, comparison with experimental values detected in the profiling operation can be readily made and information on the presence of lattice imperfections can be obtained. A new technique for sample preparation, which uses an ultrasonic drill for mesa etching the van der Pauw pattern, is also described. With this apparatus the critical and tim...

Plasma etch chemistry for anisotropic etching of silicon

Abstract: A plasma etch chemistry which allows a near perfectly vertical etch of silicon is disclosed. A Cl-containing compound such as BCl3 has Br2 added to it, readily allowing anisotropic etching of silicon. This is due to the low volatility of SiBr4. The silicon surface facing the discharge is subjected to ion bombardment, allowing the volatilization (etching) of silicon as a Si-CI-Br compound. The Br which adsorbs on the sidewalls of the etched silicon protects them from the etching. This new plasma etch chemistry yields a very smooth etched surface, and the etch rate is relatively insensitive to the electrical conductivity of the silicon.

Plasma etching of III‐V compound semiconductors

Abstract: Plasma etching techniques for III‐V compound semiconductors are reviewed, emphasizing design considerations in the choice of gases, discharge parameters, and substrate temperature. Mechanisms are proposed for anisotropic, isotropic, and crystallographic chemical etching. Applications of plasma etching in device fabrication are given.

Manufacture of semiconductor device

Abstract: PURPOSE:To make the sides of any residual semiconductor layers smooth for manufacturing a semiconductor with narrow width by a method wherein multiple semiconductors are laminated and grown on a semiconductor substrate to perform selective chemical etching of the top layer for dry-etching the lower layers successively utilizing the top layer as a mask. CONSTITUTION:N type InP clad layer 11, InGaAsP active layer 12, P type clad layer 13, InGaAsP contact layer 14 and InP layer 15 later to be a mask are epitaxially grown on N type InP substrate 10 with face index of (100). Next, a mask 16 made of SiO2 corresponding to the shapes of laser pattern is provided on the layer 15 to be etched while providing the layer 15 with specified width. Then the mask 16 is removed to use the remaining layer 15 as a mask for performing reactive ion etching of the lower layers 14, 13, 12 and 11 to make the sides A of said layers smooth (anti 1, 1, 0). Through these procedures, the width of the laminated layers may be made narrow down to the limit within which a pattern can be formed to make suitable for laser and the like.

Method of forming a resist mask resistant to plasma etching

Abstract: A mask which is resistant to a plasma etching treatment is formed by providing an etch resistant skin over a lithographically patterned radiation sensitive resist film present on a substrate. The etch resistant skin is formed by providing a layer of, for example, chromium on the patterned resist and on the exposed surface of the substrate, and then, baking so that the chromium reacts chemically with the resist to form the etch resistant skin around the patterned film. This method may be used for example to manufacture a photo mask using a chromium coated glass substrate, or during the manufacture of semiconductor devices on a semiconductor wafer substrate.

Chemical etching of a semiconductive wafer by undercutting an etch stopped layer

Abstract: Three dimensional single crystalline structures, such as folded cantilever beams supported from a frame and supporting a central structure free to move relative to the frame, are fabricated by anisotropically etching through openings in etch stop layers on opposite sides of the substrate wafer. The openings are patterned and aligned so that the etch stop layers are undercut to define etch stop portions interconnected by unetched substrate material.

On the Preferential Etching of GaAs by H 2 SO 4 ‐ H 2 O 2 ‐ H 2 O

Abstract: The preferential etching of gallium arsenide in has been studied. A mechanism for the etching process is discussed drawing on observation by optical and scanning electron microscopy, published results on U H V surface analysis, and surface state models. The etch rates of the revealed planes are related to surface step densities, and the exposure of "equilibrium" step density surfaces is related to the surface migration lengths of probable reactant species.

Plasma etchant mixture

Abstract: Method and apparatus for masked etching of a polysilicon surface layer or film to expose a dielectric underlying layer or film on a semiconductor material using ion bombardment from an ionized mixture of a fluorine based gas with a chlorine or bromine containing gas. A particularly useful gas is a mixture of sulfur hexafluoride and Freon 115 gases (C2 ClF5). The mixture of gases achieves the result of highly selective etching through the polysilicon film without significantly attacking the underlying dielectric film and without significant undercutting in the polysilicon film or etching of the masking layer.

UV laser photopolymerization of volatile surface‐adsorbed methyl methacrylate

Abstract: The localized UV laser photopolymerization of surface‐adsorbed methyl methacrylate has been used to deposit poly(methyl methacrylate) films for direct patterning of wet and dry chemical etching processes. Using this negative resist process, submicrometer linewidths both in the polymer deposition and in pattern transfer into Si and SiO2 have been demonstrated. The chemical kinetics of simple and catalyzed photopolymerization have been studied by dynamic lensing experiments and modeled as a dynamic equilibrium between competing surface photoreactions.

High strength aluminum alloy plate for printing plate

Abstract: PURPOSE: To provide a high-strength Al alloy plate having improved performance as a lithographic printing plate by providing elliptical recesses of waveform pattern on the surface of the Al alloy contg. Mn is a specified amt. and etching chemically said surface thereby forming fine recesses. CONSTITUTION: An Al alloy plate contg. 0.5W2.5wt% Mn is passed through rolls having roughened surfaces in the final cold rolling stage by which the elliptical recesses of a waveform pattern independent from each other or superposed on each other are formed on the plate surface at ≥200 pieces/mm 2 density. Fine recessed patterns having 1W10μ average pitch are formed thereon by using a chemical etching bath. The production process is rationalized by the above-mentioned method without subjecting the plate to brushing and electrolytic etching. The Al alloy plate for a lithographic printing plate produced in such a way provides an excellent effect such as good reproductibility of dots, low reflectivity easy visibility of wetting state, etc. COPYRIGHT: (C)1985,JPO&Japio

Compositional Depth Profile of a Native Oxide LPCVD MNOS Structure Using X‐Ray Photoelectron Spectroscopy and Chemical Etching

Abstract: It is pointed out that there is no report of an unambiguous analysis of the composition and interfacial structure of MNOS (metal-nitride oxide semiconductor) systems, despite the technological importance of these systems. The present investigation is concerned with a study of an MNOS structure on the basis of a technique involving the use of X-ray photoelectron spectroscopy (XPS) with a controlled stopped-flow chemical-etching procedure. XPS is sensitive to the structure of surface layers, while stopped-flow etching permits the controlled removal of overlying material on a scale of atomic layers, to expose new surface layers as a function of thickness. Therefore, with careful analysis of observed intensities at measured depths, this combination of techniques provides depth resolution between 5 and 10 A. According to the obtained data there is intact SiO2 at the substrate interface. There appears to be a thin layer containing excess bonds to silicon on top of the SiO2.

Anisotropic plasma etching of semiconductors

Abstract: A method for dry anisotropic etching of semiconductor material by a reactive gas infused in the presence of a low-pressure plasma discharge uses a photoresist mask superposed on a semiconductive film with the slope of the photoresist edges defined within a critical angular range to allow selective formation of a protective polymer film which prevents lateral etching of the edges of the photoresist and sidewalls of the film, while not inhibiting vertical etching, thereby allowing precision definition of the etched pattern. A novel technique to determine the conditions of the photoresist sidewall geometry necessary for polymer film formation and predictable etching behavior encapsulates the film in a thick layer of photoresist, which after cleaving the structure permits selectively etching the photoresist to expose and retain the polymer film without deformation.

Centrifugal Etching: A Promising New Tool to Achieve Deep Etching Results

Abstract: This paper presents some theoretical considerations to show that by etching in an enhanced acceleration field, such ascan be obtained in a centrifuge, it is possible to circumvent many of the typical objectionable features of some of the traditional etching techniques. The theory is corroborated by a small series of experiments. These clearly indicate that centrifugal etching may yield very low undercutting, large etch rates, and, if proper care is taken, an extremely smooth surfacefinish.