Showing papers on "Isotropic etching published in 1974"

A Chemical Etchant for the Selective Removal of GaAs Through SiO2 Masks

Abstract: An etchant has been developed for etching selected regions of through windows in an mask. This etchant has been found to provide fiat etching profiles across the unmasked regions of the GaAs, and has considerably reduced undercutting commonly caused by attack of the . The chemical etching rates have been evaluated and have been found to depend strongly on the concentration of the etching solution and on the crystal orientation of the . The utility of the for device preparation has been demonstrated by its application to the fabrication of interdigitated bipolar transistors with 5 μm base‐emitter separation.

Preferential chemical etching of terrestrial And lunar olivines

Abstract: A new chemical etching technique has been developed to study defect structures in terrestrial and lunar olivine crystals. Dislocations, low-angle dislocation boundaries, dislocation arrays and pile-ups have been observed on the (010, (100), and (001) faces of both polished and cleaved naturally deformed single crystal olivine, on various orientations of crystals in dunite, and in an experimentally deformed olivine crystal. Etching of Apollo 12 igneous rocks revealed dislocations and radiation damage tracks in lunar olivine. Dislocation etching of the (001) face of olivine is reported for the first time in this paper.

Etching process for accurately making small holes in thick materials

Abstract: A sheet of metallic material having a thickness T is covered on one side by an etchant resist and on the opposite side by an etchant resist and a removable shield. Etching is first performed on the side with only the etchant resist layer. Next, the shield is removed and the material is etched from both sides to produce an opening having a minimum dimension less than the thickness T of the material.

Generation of permanent phase holograms and relief patterns in durable media by chemical etching

Abstract: A surface relief pattern, e.g. a surface relief hologram, is substantially linearly transferred to a hard durable substrate, capable of being used as a medium for permanent storage of the pattern or as a master for replicating the hologram, from a photoresist coated on the substrate, by exposing the photoresist and the substrate to a photoresist developer bath and a chemical bath capable of etching the substrate at a rate substantially proportional to the development rate of the photoresist. This technique allows the transfer of surface relief patterns with dimensions on the order of one micron or less, and is applicable to the formation of surface relief holographic patterns in permanent media for archival storage and to making master surface relief holograms.

Method of etching aluminum

Abstract: A method of uniformly etching a surface of aluminum foil, by immersing the foil in a bath of alkaline etchant, leveling a film of alkaline etchant carried by the foil as it is withdrawn from the bath, cooling the foil to retard the etching reaction, and flooding the surface to be uniformly etched with water to remove the leveled etchant film. The etched aluminum foil may then be treated with an aqueous acid solution to desmut the foil and neutralize residual etchant.

METHOD FOR SELECTIVELY ETCHING Al Ga AS MULTIPLIER STRUCTURES

Abstract: A method for selectively etching a layer of Alx Ga1-x As with a low concentration of Al in a multilayer structure while leaving adjacent layers of Alx Ga1-x As material of higher concentration Al relatively unaffected The structure is immersed in an etchant consisting essentially of an H2 O2 solution neutralized to a pH of 6-8 with a suitable hydroxide such as NH4 OH Preferably, the solution is agitated to insure that the etched surfaces are smooth This selective etching technique may be used to form a variety of structures including a passive optical waveguide of extremely small dimensions

Process for the automatic checking and control of etching machines

Abstract: Process and apparatus for automatic checking and control of etching machines which provides a signal related to the strength of the etching solution and provides means whereby the length of etching time can be varied in relation to the concentration of the etching solution. The present invention provides a system including a measuring compartment through which an etching solution from the etching machine is constantly circulated. A measuring wire is inserted into the measuring compartment and held stationary therein for a time sufficient to cause the etching solution to etch away an end portion of the wire. The time required to etch off this end portion is measured and provides an analog signal of etching solution strength which is proportional to etching time. This signal can be used to control the feed of the etching machine so that as the solution becomes less concentrated, the time of exposure of the material being etched is increased.

Manufacturing semiconductor devices in which silicon slices or germanium slices are etched and semiconductor devices thus manufactured

Abstract: Thinning plate-shaped bodies of silicon or germanium, adhered to a glass-plate by chemically etching in an etchant comprising hydrofluoric acid and at least one oxidant, in which, prior to said etching, the etchant is given a content of silicon. This silicon may be added in several forms, for instance as silicon oxide in readily accessible form or by dissolving some elemental silicon. It is further possible for a similar process to use an etchant comprising the above etchant after first use. The method may be used in the manufacture of semiconductor devices.

Etchant for removing metals from glass substrates

Abstract: Disclosed is an etchant for removing a metal, such as titanium, from a glass substrate without adversely attacking the glass. The etchant includes a relatively viscous coating agent that wets and coats and thus protects the glass but does not wet the metal thus permitting etching thereof. A nonionizing diluent can be included in the etchant to inhibit the etching rate if it is felt that the heat and turbulence that would otherwise be generated may be excessive and interfere with the action of the coating agent.

Grating masks suitable for ion-beam machining and chemical etching

Abstract: By using the simultaneous exposure and development technique, high‐resolution relief gratings with periods as small as 2400 A have been produced which have grooves cleanly developed down to the substrate surface and exposing wide surface stripes with clearly defined, sharp and narrow photoresist ridges. Such gratings are suitable for use as masks in ion‐beam machining and chemical etching. Results of chemically etched gratings into glass substrates with a 5000‐A period are presented and prospects of obtaining chemically etched gratings with shorter periods are discussed.

Erratum: Liquid‐phase epitaxial growth of (AlGa)As on polished and roughened GaP substrates for transmission photocathodes

Abstract: It is shown that growth of smooth layers of (AlGa)As on GaP by liquid phase epitaxy (LPE) can be achieved if the GaP substrate surface possesses a certain degree of roughness when growth starts. This roughness can be introduced by various methods, including preferential chemical etching or in situ melt‐back, but the best surface morphology of the epitaxial layer is obtained after mechanical lapping of the substrate. This striking phenomenon is attributed to an increase of the density of nuclei which results in a more uniform distribution of the grains characteristic for this system with large lattice mismatch.

Direct observations of the growth of sputtered silver and gold films on (111) silicon substrates

Abstract: The growth of ion-beam-sputtered silver and gold films on (111) silicon substrates has been studied using the in situ electron microscope technique. The thin silicon substrates are obtained by jet chemical etching followed by ion-micromilling techniques. The substrate temperatures during growth vary from 300 to 600 °C. A two-layer phenomenon occurs in the growth of silver films. Both layers grow with a (111) orientation parallel to the substrate. Liquidlike coalescence which is observed in the second layer, however, is prohibited in the growth of first-layer islands. Gold films deposited under the same conditions result in the formation of discrete liquid islands even at substrate temperatures as low as 300 °C. Occurrence of solid polycrystalline gold films is first observed at 260 °C by lowering the substrate temperature after deposition. Deposition at lower temperatures results in the formation of polycrystalline and amorphous structures. Both cases can be attributed to the interface interaction between...

Method and apparatus for thermo-chemically slicing crystal boules

Abstract: Disclosed is a method and apparatus for thermochemically slicing wafers from a crystal boule by propelling a continuous flow of an acid etching solution against a heated wire which is adjacent the intended line of etch while providing for relative movement between the boule and the chemical etching solution to thereby effect a slicing action of the boule

An optical and electron microscope study of the growth and etching behaviour of electrolytic amorphous germanium

Abstract: Optical and electron microscopy are employed to find the best deposition conditions for the growth of electrolytic amorphous germanium films. The polishing treatment of the substrate and the electrodeposition time are found to influence the homogeneity of the films, while the method of cleaning the substrate affects their structure. Chemical etching behaviour is also studied: it is characterized by a much higher etching rate than in crystalline germanium samples and by various etching figures. A brief discussion of the causes that may produce the observed patterns is given.

Preparation of Samples for Electron Microscopy by Ion Micromilling

Abstract: Preparation of thin foils for transmission electron microscopy was initially limited to conductors that could be thinned by electropolishing. Chemical etching was used for non-conductors, but with only limited success. Uneven thinning, preferential etching of grain boundaries or second phases were a few of the problems encountered by chemical etching. This is not to say that complex, multiphase metallic alloys, could be easily thinned by electropolishing (1). These subjects are discussed in other chapters. A recently developed thinning technique applicable to both conductors and non-conductors is ion micromilling. This technique, which operates on the principle of ion bombardment, has added a wide variety of solids to the list of materials that can be studied by transmission electron microscopy.

Containerless processing of single crystals in low-G environment

Abstract: Experiments on containerless crystal growth from the melt were conducted during Skylab missions SL3 and SL4 (Skylab Experiment M-560). Six samples of InSb were processed, one of them heavily doped with selenium. The concept of the experiment is discussed and related to general crystal growth methods and their merits as techniques for containerless processing in space. The morphology of the crystals obtained is explained in terms of volume changes associated with solidification and wetting conditions during solidification. All samples exhibit extremely well developed growth facets. Analysis by X-ray topographical methods and chemical etching shows that the crystals are of high structural perfection. Average dislocation density as revealed by etching is of the order of 100 per sq cm; no dislocation clusters could be observed in the space-grown samples. A sequence of striations that is observed in the first half of the selenium-doped sample is explained as being caused by periodic surface breakdown.

Dislocation etching of CaWO4 crystals

Abstract: Single crystals of calcium tungstate grown in the laboratory have been cleaved for the first time along {011} and {100} planes. These cleavages, as revealed by multiplebeam interferometric examination, prove to be fairly perfect. The etching behaviour of the various cleavages, as well as the grown faces of the crystals, is described. It has been shown that a solution of concentrated hydrofluoric acid plus chromic acid produces etch pits at the emergence sites of screw dislocations only, whereas a solution of 2N acetic acid plus chromic acid operates on both edge and screw dislocations. The results of chemical etching have been compared with those reported earlier, and the implications are discussed.

A chemical etchant for the selective removal of gaas through sio2 masks

Abstract: An etchant has been developed for etching selected regions of through windows in an mask. This etchant has been found to provide fiat etching profiles across the unmasked regions of the GaAs, and has considerably reduced undercutting commonly caused by attack of the . The chemical etching rates have been evaluated and have been found to depend strongly on the concentration of the etching solution and on the crystal orientation of the . The utility of the for device preparation has been demonstrated by its application to the fabrication of interdigitated bipolar transistors with 5 μm base‐emitter separation.

Surface topographical effects on the structural growth of thick sputtered metal and alloy coatings

Abstract: Thick sputtered S-Monel, silver, and 304 stainless steel coatings were deposited on mica and metal substrates with various surface finishes to investigate the structural growth of the coating by scanning electron microscopy The geometry and the surface structure of the nodules are characterized Compositional changes within the coating were analyzed by X-ray dispersion microscopy Defects in the surface finish (ie, scratches, inclusions, etc) act as preferential nucleation sites and form isolated and complex nodules and various surface overgrowths in the coating The nodule boundaries are very vulnerable to chemical etching and these nodules do not disappear after full annealing Further, they have undesirable effects on mechanical properties; cracks are initiated at the nodules when the coating is stressed by mechanical forces These effects are illustrated by micrographs Nodular growth within a coating can be minimized or eliminated by reducing the surface roughness