Showing papers on "Isotropic etching published in 1971"

A High‐Yield Photolithographic Technique for Surface Wave Devices

Abstract: In the fabrication of surface wave devices, standard photoresist‐chemical etching techniques often provide a very low yield even at moderate resolutions, frequently cause a degradation of the substrate finish, and in many cases are incompatible with substrates of interest. A photolithographic technique is described in which metalizing is done after a photoresist image is produced on the substrate, thereby circumventing most of the problems inherent in chemical etching. It is shown by means of electron micrographs of photoresist profiles that intimate mask‐substrate contact is essential. Devices with line widths of 1 µm can be produced with high yield.

Etching Studies of Impurity Precipitates in Pulled GaP Crystals

Abstract: Light‐emitting diodes prepared by p‐tipping on n‐type pulled substrates are considerably less efficient than those diodes prepared by p‐tipping on solution‐grown substrates. The present study represents an attempt to use chemical etching and optical microscopy to determine the differences between n‐type pulled crystals and crystals obtained by solution‐ and vapor‐growth techniques. Etch patterns believed to be associated with impurity precipitates were observed in large numbers in pulled crystals heavily doped (up to ) with sulfur or tellurium, and to a much lesser extent in lightly doped and undoped pulled crystals. Clusters of small etch pits attributed to isolated precipitates and short etch grooves attributed to decorated dislocations lying parallel to the surface were both observed. These etch patterns were not seen in solution‐grown or vapor‐grown crystals doped to approximately the same carrier concentrations.

Electron microscopy applied to quartz grains from a tropical environment

Abstract: The examination, with a scanning electron microscope, of 200 quartz grains from a tropical environment (Uganda) shows the nature of chemical weathering on these grains. Five main types of features occur: solution pits; solution crevasses; chemical etching along quartz structures; blocky forms probably resulting from swelling; and widespread disintegration of the grain surface. Few of these features have previously been recorded.

Silicon nitride-silicon oxide etchant

Abstract: This invention discloses a chemical to etchant and a process for chemically etching silicon nitride-silicon oxide composite structure which may be used, for example in microelectronic devices. The etching process or system utilizes a mixture of phosphoric acid and a fluoborate anion containing compound such as fluoboric acid. The etch rate of the silicon nitride relative to the etch rate of the silicon oxide can be controlled to the desired etch rate by varying the temperature of the etchant and/or adjusting the ratio mixture of the phosphoric acid and the fluoboric acid.

Epitaxial Growth of α-SiC from the Vapor Phase

Abstract: Epitaxial layers of α-SiC are grown on the (0001) and the (000) faces of α-SiC substrates front the silane-propane-hydrogen system. The structure, morphology and growth rate of the layers are studied as a function of the partial pressures of the reactants and the substrate temperature. It appears that the growth process is controlled by the combined effects of propane diffusion and the rate of thermal etching of SiC. The best layers in terms of surface smoothness and crystalline perfection are obtained under low reactant partial pressures (slow growth rate conditions) at temperatures in the vicinity of 1550°C. The epitaxial layers are structurally characterized with X-ray diffraction techniques, electron scanning microscopy, and chemical etching. As grown layers exhibited n-type conduction. p-type boron doped layers are grown by using borane gas in the reactant system. Light emitting p-n junctions are prepared and electrically characterized.

Porous bodies and method of making

Abstract: A process for making tapered holes in a solid material which contains tracks of radiation damaged material is described. One surface of the solid is contacted with an etchant while the opposite surface of the solid is contacted with an agent capable of substantially stopping the etching action of the etchant. Such an agent can be a neutralizer for the etchant or an inert medium. The etchant etches, i.e., extracts, the track-defining radiation damaged material, and upon penetrating through the solid to form a hole, it contacts the neutralizer or inert medium and its etching action is substantially stopped. The product is useful as a filter.

Passivation of photoresist materials used in selective plasma etching

Abstract: A method is disclosed for selective plasma etching of organic material by means of a low temperature plasma which reacts with the organic material through an apertured mask overlaying said material. The method has particular application to electronic circuit fabrication. A preferred organic dielectric material is a polymer of fluorinated ethylene propylene and a suitable mask for plasma etching of this material is a photoresist composition, which has been passivated to be resistant to attack by the plasma.

Semiconductor device fabrication using nickel to mask cathodic etching

Abstract: IN THE FABRICATION OF SEMICONDUCTOR DEVICES, PARTICULARLY INTEGRATED CIRCUIT DEVICES, USING THE MULTIPLE METAL SYSTEM OF BEAM LEAD TECHNOLOGY, THE PROPER DELINEATION OF THE METAL INTERCONNECTION PATTERN USING WET CHEMISTRY IS LIMITED BY THE INHERENT ISOTROPY OF THE ETCHING PROCESS. IN ACCORDANCE WITH THIS INVENTION THE METALLIZATION PATTERN IS DEFINED USING CATHODIC ETCHING, OR BACKSPUTTERING, TO REMOVE UNWANTED LAYERS OF METAL AS DEFINED BY AN ELECTRODEPOSITED MASK OF NICKEL. WELL-DEFINED NICKEL PATTERNS CAN BE PRECISELY FORMED BY ELECTRODEPOSITION USING PHOTORESIST TECHNIQUES FOR MASKING. THE PROCESS ELIMINATES THE UNDERCUTTING AND LACK OF DEFINITION CONTRIBUTED BY CHEMICAL ETCHING PROCESSES.

System suitable for controlling etching without the aid of an etchant resistant

Abstract: AN ETCHING SYSTEM HAVING SETS OF PREARRANGED NOZZLES FOR DISPENSING ETCHANT ONTO PREFORMED MASKS IN A PREDETERMINED PATTERN TO ALLOW AN OPERATOR TO CONTROLLABLY ENLARGE THE APERTURES IN A PREFORMED MASK WITHOUT THE AID OF AN ETCHANT RESIST.

A.C. Losses of Nb-Ti Wires

Abstract: A.C. losses of superconducting Nb-Ti alloy wires were measured by electrical method with alternating electrical current through wires. The losses were measured on various diameter of wires which were chemically or mechanically thined, and it was found that there were no size effects.The losses were measured under the external parallel D.C. magnetic field, and those of commercial fine wires were also investigated. We computed the loss of multi cores wire, form the results obtained from single core wires and compared it with the experimental resuls of fine multi cores wires.The effects of chemical etching and mechanical drawing on the losses are considered in the metallurgical points of view. The losses of Nb-Ti wires in the region of low magnetic field seem to fit Yasukochi's model.

Two-step photo-etching method for semiconductors

Abstract: A method of selectively etching a substrate to form areas of a predetermined depth by first etching through an etch resistance mask to a substantial portion of the depth to be etched, removing the etch resistant mask and, finally, etching the remaining material in the selective areas by exposing the substrate to a second etchant. The method prevents contaminants from the first etchant, the etch mask and the original surface to be etched from contacting the finally etched surface of the second etch step.

Method for etching metallic copper with chromosulfuric acid and regenerating the etching solutions as well as recovering the corroded copper

Abstract: Process for the etching of metallic copper with chromosulfuric etching solution, in which the etching and regenerating of the solution are simultaneously effected but spatially separated from each other, the etching solution being circulated between the etching vessel and the anode space of an electrolytic cell provided with a diaphragm, in the anode space of which chromium-III-ions produced in the etching operation are oxidized anodically and half of the sulfuric acid consumed in the etching is reformed, and when copper-II-ions in the circulated etching solution reaches a specified concentration, crystallizing out the copper sulfate and utilizing a solution thereof in the cathode space of the electroyltic cell to separate out metallic copper at the cathode and reproduce the second half of the sulfuric acid consumed in the etching process.

Preferential etching of silicon

Abstract: PREFERENTIAL ETCHING OF SILICON-TYPICALLY ETCHING OF AN N-TYPE SILICON MATERIAL THROUGH AN ETCH RESILIENT MATERIAL, BY ETCHING WITH ORTHOPHOSPHORIC ACID TO WHICH HAS BEEN ADDED ARESENIC TRIOXIDE. THE EFFECTIVE RANGE OF ADDITIVE IS BETWEEN 0.1 GM. AND 20 GMS. OR ARSENIC TRIOXIDE PER QUART OF ACID.

Process for producing monolithic circuits

Abstract: A technique of fabricating semiconductor devices so as to avoid mask alignment difficulties when it is required that electrical contact be made subsequent to the formation of extremely small device regions. The diffusion mask for creating the small device regions is constituted of a first film which is subject to ready etching by a first etchant but which is substantially unaffected by a second etchant. A second film covers the opening in the device region formation. This film being subject to etching by the second etchant but being substantially unaffected by the first etchant. As a result, the second film is removed from within the opening without affecting the first film since the first film will resist the second etchant. Thus, the original opening is re-established for the purpose of making contact to the device region, the first film remaining as a passivating film on the substrate.

Fast Rejuvenation of Copper-Beryllium Multipliers Used with Mass Spectrometers

Abstract: A simple procedure for restoring the signal‐to‐noise (S/N) ratio of electron multipliers is described. The method consists of removing the surface contamination on the dynodes by chemical etching and cleaning.

Ultrasonic metal etching for metallographic analysis

Abstract: Ultrasonic etching delineates microstructural features not discernible in specimens prepared for metallographic analysis by standard chemical etching procedures. Cavitation bubbles in ultrasonically excited water produce preferential damage /etching/ of metallurgical phases or grain boundaries, depending on hardness of metal specimens.