Showing papers on "Isotropic etching published in 1977"

Chemical etching of silicon. iv. etching technology

Abstract: The etching of silicon in based systems proceeds by a sequential oxidation‐followed‐by‐dissolution process. In those composition regions where the solution is very low in and rich in , the rate‐limiting process is the oxidation step. Consequently, electron concentration, surface orientation, crystal defects, and catalysis by lower oxides of nitrogen play an important role. In those compositions where is in limited supply, dissolution of the formed oxide is the rate‐controlling step and diffusion of the complexing fluoride species is the important factor. Therefore, crystal orientation and conductivity type independence as well as hydrodynamic control are the consequences. In order to meaningfully select an etching composition to solve a specific processing problem, it is necessary to understand this composition‐mechanism interaction. Corollary with the mechanism understanding, sample geometry effects have been followed as a function of solution composition. The solution composition plane has been characterized into various regions where the two basic mechanisms interact and specific procesing utilization is shown. Similar results are shown for the system . In addition, a number of particular etching problems are posed, and solutions offered, that make use of these composition characterizations, and show how one can use their information to solve other practical processing problems.

Method for fabricating ultra-narrow metallic lines

Abstract: A method for fabricating very narrow superconducting metallic lines on a substrate using ion-implantation and etching techniques. The method permits lines to be produced which are much smaller than those fabricated by conventional masking and etching techniques. It makes the fabrication of very small Josephson and other superconducting devices possible. Also since lines are formed in metals, they have high conductivity, so are useful as ordinary conductors at high temperature or when the technique is utilized with non-superconducting materials. The method includes the steps of depositing a selected metal film on a substrate, applying a photoresist or other masking pattern and exposing, etching away the exposed region, ion-implanting the edge of the resulting pattern, removing the photoresist and etching away the unimplanted portion of the metal leaving an ultra-narrow line pattern.

Thin silicon devices

Abstract: This relates to a semiconductor device and method for making same. At least one semiconductor device is formed in a polished silicon slice, and the device is framed by a deep diffusion of boron. The surface of the slice is then coated with a layer of silicon nitride, and a glass ceramic body is bonded to the silicon nitride layer. The device is next isolated by isotropic etching, and the silicon from beneath the device is removed with a selective etch so that metal interconnections can be made to the underside of the device.

Etchant and process

Abstract: This invention is directed to an etchant and to a process for its use. The etchant comprises sulfuric acid activated with hydrogen peroxide or the synergistic combination of hydrogen peroxide and molybdenum. The etchant is characterized by a source of phosphate ions as an inhibitor against attack on tin, especially immersion tin, as well as several other metals such as nickel and alloys of nickel such as gold alloys. The etchant is especially useful for etching copper and its alloys in the presence of a tin etch resist, and therefore, provides a new procedure for the fabrication of printed circuit boards using immersion tin as an etch resist.

Method of etching a semiconductor substrate

Abstract: A method of etching a semiconductor substrate which comprises the steps of selectively mounting an etching mask on the semiconductor substrate and effecting selective etching by an anisotropic etchant comprising an aqueous solution containing 0.1 to 20% by weight of trihydrocarbon-substituted (hydroxyhydrocarbon-substituted) ammonium hydroxide.

Selective dry etching of substrates

Abstract: Magnesium oxide is deposited on a substrate as a mask with a pattern of openings which exposes a corresponding pattern of a surface of a substrate which is to be subjected to dry etching. In a specific application, the magnesium oxide mask is employed to delineate a conductor pattern on semiconductor substrates by dry etching.

Method of selective gas etching on a silicon nitride layer

Abstract: The process of etching a silicon nitride layer disposed upon a silicon substrate is completed in two steps by using a gas atmosphere composed of changing portions of CF 4 and O 2

Versatile double AC Hall effect system for profiling impurities in semiconductors

Abstract: A versatile system is described for measuring electrically active impurity distributions in semiconductors. The system uses an improved double AC Hall system for sensitive measurement of the Hall effect in conjunction with chemical etching for removal of successive layers. All processing is done with samples mounted on standardized discs, increasing the convenience and speed of the technique for repetitive measurements. A measured profile of Be-implanted GaAs obtained with this system is presented as an example.

Stepped Electrode Transistor: SET

Abstract: SET can achieve high performance without precise photolithography and metallization techniques. An arsenic doped polycrystalline silicon is used as a part of the emitter electrode in the SET structure. It is processed to have an inverse trapezoid shape. Procedure to make the inverse trapezoid shape uses a difference of etching rates between double layers of polycrystalline silicon. Base contact windows are opened through the ion-implantation process followed by chemical etching. The spacing between the emitter diffused layer and the base contact is as short as 0.4 µm or less. The cut off frequency of |S21e| is about 8.4 GHz. This frequency is higher than that of the conventional planar transistors with equal size emitter by 2 GHz. The rise time is 150 psec in the integrated SET.

Method for producing nozzle arrays for ink jet printers

Abstract: Nozzle arrays for ink jet recording are produced by preferred chemical etching of a substrate material which frequently has a non-uniform thickness. The preferred substrate is a monocrystalline silicon wafer and the 100 plane surface of the wafer is coated with etchant masking material and the resist coated wafer is held in close physical contact with a base member. A suitable mask member which defines a nozzle array pattern is spaced a predetermined distance from the base member and is positioned parallel to the base member. The wafer is then exposed through the mask by a suitable light source arranged at a suitable angle while the wafer is simultaneously rotated about an axis perpendicular to the wafer. The wafer is then exposed to a chemical anisotropic etching agent to produce a uniform array of nozzles in the wafer wherein the lateral walls of the nozzles are substantially in the "111" plane of the wafer. The masking material is then stripped from the wafer.

A study of the basic properties of electrochemical track etching

Abstract: The basic properties of the electrochemical track etching method proposed by Tommasino were studied for PC and PET foils irradiated with fission fragments and/or alpha-particles. Etching was performed in a specially designed double-wall vessel applying electric fields of different strengths and frequencies, The variation in the diameters of the discharge spots produced around the tracks of fission fragments entering PC and PET foils at right angles was systematically studied as a function of the strength and frequency of the electric field, etching time and etchant temperature. For alpha-tracks registered in PC foils the dependence of the discharge spot diameter on particle energy was also determined. It was found that the production of discharge spots started at a threshold field strength depending on the type of particle. The temperature dependence of the growing rate of discharge spots followed the Arrhenius law, but with a reduced activation energy as compared to that obtained for the chemical etching rate of the bulk material.

Etchant and process of etching with the same

Abstract: This invention is directed to an etchant and to a process for its use. The etchant comprises a synergistic combination of hydrogen peroxide and molybdenum as oxidants in acidic solution. The combination of oxidants provides for sustained etching at an exalted rate. The etchant is useful for etching metals, especially copper and its alloys, and is particularly useful in the manufacture of printed circuit boards.

Method and apparatus for controlling the removal, by means of ion etching, of a thin layer from a substrate

Abstract: A method for controlling the removal, by means of ion etching, of a thin layer or regions of the layer as determined by masks, from a substrate of a sample which has a chemical composition different than that of the layer to be removed. During the ion etching process, an electrical signal which changes after the removal of the thin layer is derived from the substrate or from its mount, or from an electrode disposed in the vicinity of said substrate and this electrical signal is utilized to control an arrangement which influences the ion bombardment of the surface of the sample.

Etching metal, esp. polycrystalline silicon or aluminium - with definite angle of slope by ion bombardment before plasma etching

Abstract: Prodn. of a definite angle of slope in etching a substrate is achieved by preceding ion bombardment with an ion energy of 200-1000 eV and a dosage of 1015 to 1017 particles/cm.2 as structural defects favouring etching, as in DT 2554638. The novel feature is that the process is applied to a metal layer, pref. of polysilicon or Al. The process is used in the prodn. of integrated circuits and extends the applicability of the parent patent. A plasma etching process is employed. The process is used for the prodn. of a conducting path, on which there is an insulating layer with another insulting path, esp. for etching a layer on a semiconductor substrate already having a semiconductor element.

Dendritic Growth of Silicon Thin Films on Alumina Ceramic and Their Application to Solar Cells

Abstract: Polycrystalline silicon films on alumina ceramic are recrystallized under normal freezing conditions. A multi-layered structure containing borosilicate glass and titanium layers is successfully used to prevent molten silicon films from agglomeration. The films obtained are dendritic and of mm size. Chemical etching reveals tilt boundaries, linear and dot-like defects in addition to grain boundaries. The thin film solar cells fabricated on the recrystallized silicon by successive deposition of p and n+ layers show photovoltaic conversion efficiencies of up to 2.6% at a fill factor of 0.67 under an AMI simulator. From the spectral response curves of the cells, the electron diffusion length of the p-type active layers is calculated to be 1 µm and causes a low short circuit current density of 9.8 mA/cm2.

New methods for detecting structural defects in glass passivation films

Abstract: Conventional test methods to evaluate the quality of glass passivation overcoats on semiconductor devices are generally inadequate and/or destructive. We have recently devised three new methods that overcome these problems: (1) Sequential selective chemical etching of metal/dielectric structures to detect buried, latent, or partial defects as a function of dielectric layer depth. (2) Electrophoretic cell decoration with uv phosphor particles suspended in an insulating liquid, the sample forming one electrode of the cell. (3) Electrostatic corona charging to selectively deposit surface ions from a high‐voltage dc discharge on the insulating surfaces of the samples, followed by placing of the charged sample in a suspension of charged carbon black particles in an insulating liquid; depending on the polarity of the ions the particles can be deposited on the insulator surface or at the defect sites. The etching method is most suitable in process research studies, and the electrophoretic technique for demarcati...

Method of epitaxial deposition of an AIII BV -semiconductor layer on a germanium substrate

Abstract: The method makes possible the manufacture of luminescence diodes on the basis of GaAsP or other ternary semiconductor layers deposited on a Ge substrate of n-type conductivity, followed by a zinc diffusion. In the method, a resist layer is deposited on the backside of the Ge substrate to passivate the backside to an extent such that it becomes thermally and chemically stable and does not release any Ge to the ambient atmosphere, and the front side of the Ge substrate is chemo-mechanically polished to microsmoothness. Immediately before the epitaxial deposition, the polished front side is subjected to a very weak chemical etching to a removal depth of 500 A units without eliminating the polish or microsmoothness and, thereupon, the substrate is heated, in a high purity hydrogen atmosphere, to a temperature between about 680° C and 720° C and a GaAs layer is deposited on the front side. The temperature is then increased and there is deposited, on the GaAs layer, a ternary A III B V compound including a third, additive component whose proportion increases in the direction away from the GaAs layer and which consists of either an A III element or a B V element. The increase in concentration of the third component is continued to a predetermined final value determined by either the band gap or the corresponding wavelength of the emitted light, and then a third relatively thick layer of the ternary component is deposited, and the composition thereof is maintained constant at the predetermined final value of the second layer.

Method of etching a1 and a1-based alloy

Abstract: PURPOSE:To accomplish a high speed, percision etching without undercutting through sputter-etching of a photoresist-masked Al-evaporated plate for circuitting on a semi-conductive substrate with a gas containing boron trichloride.

Microstructural Studies of Alloy Oxidation I. Selective Etching

Abstract: The oxide film formed at 600°c on iron-chromium alloys consists of a thin inner chromium-rich layer with a much thicker outer layer of Fe2 03. The Fe2O3 can be removed from stripped oxide films by etching with solutions of hydrochloric acid in methanol; about 90–95% of the iron is removed, but no chromium. Etching avoids the difficulties in characterising the films introduced by the Fe2O3, which confuses both electron microscopy and X-ray analysis. This technique yields information on the oxidation process which cannot be obtained by other means, and it is particularly useful with oxide features too thick to be characterised directly. Consideration of the kinetics of the etching process suggests that the main factor affecting the rate is the stoichiometry of the Fe2 03, so that etching also indicates changes in stoichiometry as oxidation proceeds. Initiation of etching shows some dependence on the chromium-rich oxide sheet, but the effects are short-lived. The mechanism is discussed with reference...

Evaluation of different polymers for fast neutron personnel dosimetry using electrochemical etching

Abstract: There is considerable optimism for the enhancement by electrochemical etching of fast neutron-induced recoil tracks in polycarbonate for the purpose of personnel dosimetry. The threshold energy, however, is rather high. A desirable improvement would be to lower this energy below 1 MeV. With this objective in mind, we have commenced an investigation of cellulose acetate, triacetate, and acetobutyrate in addition to polycarbonate. These cellulose derivatives are chemically more reactive and physically weaker than polycarbonate. It might, therefore, be possible to initiate the electrochemical amplification at the sites of shorter recoil atom damage tracks than is possible with polycarbonate. Some characteristics important for electrochemically etching in aqueous electrolytes are listed. Chemical etching is combined with treeing, an electrical breakdown process that starts when the dielectric strength is exceeded. These mechanical and electrical properties pertain to the dry plastics. The absorption of water molecules and electrolyte ions will cause these values to be reduced. Results and conclusions of the study are presented.

Support structure of quartz crystal oscillator

Abstract: PURPOSE:The quartz crystal oscillator is supported/fixed by lead wire produced through photo chemical etching. As a result, a small-size and low-cost oscillator can be obtained.

Thin silicon films made for surface barrier diodes - and mfr. of nuclear particle detectors using the diodes

Abstract: Thin, n-type Si films are made from a thick monocrystalline n+ rype Si wafer (1) covered by a thin epitaxial layer (2) of n-type Si, and then using the steps:- (a) Layer (2) and part of wafer (1) are masked, esp. by an inert jig leaving only a central zone of wafer (1) exposed for electrolytic etching with a soln. contg. fluoride ions where the wafer forms the anode with a potential lower than that at the start of electropolishing w.r.t. a reference electrode; etching is stopped when the current drops, leaving a matte surface on a zone of layer (2) exposed by removing part of the wafer. (b) Slow chemical etching in the absence of air, using a soln. contg. HF, an oxidant, and a moderator; (d) washing with de-ionised water in the absence of air. In step (a) the anode potential is pref. controlled and at least the final stage conducted in darkness. Exact control of the etching process (a) and subsequent stages in mfg. the diodes and detectors of nuclear energy, esp. the loss dE/dx, e.g. detecting alpha rays emitted by Am.