Showing papers on "Isotropic etching published in 1980"

Anisotropic plasma etching of polysilicon

Abstract: Plasma etching of polycrystalline silicon films for fabrication of silicon gate MOS integrated circuits has been studied with emphasis on fine‐line devices. CF4–O2 plasmas, commonly used for etching silicon, are unacceptable for very fine features because the etching is isotropic and load dependent. This results in substantial undercutting and insufficient dimensional control. Several alternative gases were investigated in a parallel–plate reactor. CF3Cl and a 70% CF3Br–30% He mixture were found to provide selectivities of 30:1 and 16:1, respectively, over thermal SiO2, freedom from loading effects and a large vertical to lateral etch rate anisotropy which minimizes undercutting. Extensive measurements of etch rate and edge profile as a function of gas composition were made for C2F6–Cl2 plasmas. Fully anisotropic etching (zero lateral etch rate) was observed at low Cl2 concentrations with a selectivity ≳6:1 over thermal SiO2 when using conventional photoresist masks. The vertical and lateral etch rates an...

Method of making a high density V-MOS memory array

Abstract: A method for providing high density dynamic memory cells which provides self-alignment of both V-MOSFET device elements and their interconnections through the use of a device-defining masking layer having a plurality of parallel thick and thin regions. Holes are etched in portions of the thin regions with the use of an etch mask defining a plurality of parallel regions aligned perpendicular to the regions in the masking layer. V-MOSFET devices having self-aligned gate electrodes are formed in the holes and device interconnecting lines are formed under the remaining portions of the thin regions. A combination of anisotropic etching and directionally dependent etching, such as reaction ion etching, may be used to extend the depth of V-grooves. A method of eliminating the overhang of a masking layer after anisotropic etching includes the oxidation of the V-groove followed by etching to remove both the grown oxide and the overhang is also disclosed.

Directional reactive ion etching at oblique angles

Abstract: Directional reactive ion etching (RIE) at oblique angles is possible using a simple grid‐covered structure (Faraday cage) in conventional parallel‐plate sputter etching equipment. Oblique‐angle etching, as is possible in any ion‐beam system, has been demonstrated using the etchant ions from CHF3 gas on a fused‐silica substrate. The first detailed measurements of the angular etch dependence of RIE show a strong similarity to those of an ion‐beam system (no chemical etching).

Plasma etching of silicon

Abstract: By utilizing a fluorine-containing gaseous compound in a plasma etching process, isotropic etching of monocrystalline silicon (48) and doped or undoped polycrystalline silicon (54) is achieved. The etching processes, which are applicable, for example, to pattern delineation in the processing of semiconductor wafers, are substantially free of any proximity effects and are characterized by a high etching rate at relatively low power levels, high selectivity (with respect to, for example, silicon dioxide) and excellent uniformity. By mixing other gases (for example, chlorine) with the fluorine-containing gas, the amount of undercutting achieved during the etching process can be selectively controlled.

Dry development of Se‐Ge inorganic photoresist

Abstract: Striking rate differences in gaseous plasma etching is found between undoped and Ag‐photodoped Se‐Ge inorganic photoresist. After the Ag photodoping, the plasma etch rate almost disappears and the etch rate ratio reaches 370:1. This leads to the ’’dry development’’ of the Se‐Ge inorganic resists. It is shown that by using the plasma etching technique, fine pattern delineation of less than 1‐μm linewidth is easily possible. Several advantages over wet chemical processing are expected in process simplification and reproducibility.

Plasma etching characteristics of chromium film and its novel etching mode

Abstract: The influences of chromium and chromium oxide films and gas compositions on plasma etching characteristics were investigated. Oxygen as well as chlorine is found to be responsible for etching. One possible etching reaction is proposed, in which a basic reaction product is assumed to be CrO2Cl2 which will be volatile in gas plasma. The impurities such as W, Fe, and Cu contained in the film become nonvolatile compounds which accumulate on the surface of the film and form a masking layer resulting in a suppression of the reaction. Anomalous etching modes called the contour and reverse etches were found with the chromium oxide films containing tungsten impurities. The mechanism of these anomalous etching modes is discussed, in which the accumulation of the tungsten compounds on the surface of the film is a basic mechanism. The reverse etch mode was applied to the fabrication of photomasks for MOS LSI.

Selective etching of Si relative to SiO2 without undercutting by CBrF3 plasma

Abstract: Etching characteristics with selectivity similar to conventional CF4 plasma etching but without undercutting are realized by plasma‐reactive sputter etching, based on the reactivity of the incident ions combining fluorocarbons with low reactive halogens. In particular, the method with CBrF3 is practically useful for selective etching of Si, poly‐Si, and Mo relative to SiO2 in high‐accuracy pattern transfer.

Selective etching of SiO2 relative to Si by plasma reactive sputter etching

Abstract: Plasma reactive sputter etching, sputter etching using Freon (CF4, C2F6, etc.) instead of argon as the etching gas, has been investigated. It has been found that there exists an etching reaction caused by energetic ions (CFn+ etc.) different from reactions found in conventional methods. Selective etching of SiO2 and Si3N4 on Si has been realized by enhancing the etching reaction with the effects of etching table materials (Teflon, carbon) and mixing gas (C2H4, CH4, etc.). Pattern transfer from mask to underlying substance, at least in selective SiO2 etching, can be performed uniformly without undercutting and with almost no lateral shift of pattern edges, with higher accuracy than in conventional plasma and sputter etching.

Chemical Etching of InP and GaInAsP for Fabricating Laser Diodes and Integrated Optical Circuits

Abstract: Chemical etching techniques were developed for fabricating GaInAsP/InP DH lasers which aim at single (transverse and longitudinal) mode oscillations and their integrations. About fifty to sixty etching solutions were tested by examining the flatness of the etched surface. The volume ratio 1 : 2 : 1 in a combination of HCl, CH3COOH, and H2O2 was found to be most suitable for our purpose. Its etching rate for InP and GaxIn1-xAsyP1-y was in proportion to t0.6~0.8 at about 20°C, where t is the etching time, and it also etched Au/Zn or Au/Sn electrodes with an etching rate of 10-20 A/s at about 20°C.

Dry etching for pattern transfer

Abstract: Dry etching or plasma‐assisted etching (ion beam milling, plasma etching and reactive sputter etching) has become an indispensable preparation technique for high resolution pattern transfer in IC manufacturing and other areas of microfabrication. Etching can either be due to the purely physical process of momentum transfer from ions to the solid surface (e.g. inert ion etching) or due to chemical reactions of reactive species, produced in the plasma, with the solid surface resulting in a volatile reaction product (e.g. plasma etching in a barrel reactor). However, in most dry etching methods both effects play a major role and it is possible to optimize etch selectivity and the shape of the etched profile by a proper choice of parameters.

Method and apparatus for monitoring etching

Abstract: Method and apparatus for monitoring a dry etching process using gas plasma, wherein a ratio of a spectrum intensity which varies depending on the process of the etching process to a spectrum intensity which is independent of the process of the etching process is determined and a resulting signal intensity is monitored. The completion of the etching process can be exactly determined irrespective of variation of the etching conditions.

Dry etching of metal film

Abstract: A process for dry etching an aluminum film or an aluminum based film in the production of a semiconductor device, wherein a mixed gas of carbon chloride and boron chloride is used as the etchant gas.

Method of manufacturing a semiconductor device wherein first and second layers are formed

Abstract: A layer of photoresist 16 having a generally flat surface is formed on a layer of PSG 15 having a projection thereon. A non-selective dry etching process using a reaction gas is effected in which a layer 16 and layer 15 are etched at equal rates. The etching process may be plasma etching using a mixture of a flouride compound gas and oxygen gas. Reactive sputter etching or reactive ion etching can also be used. The photoresist of layer 16 could be replaced by polyimide or liquid glass. PSG layer 15 could alternatively be a layer of polycrystal line silicon or wiring conductor. In each case, the use of a reaction gas mixture which ensures equal etching rates provides a flat surface at the finish of etching.

Multilevel metallization process for integrated circuits

Abstract: A multilevel metallization process which allows fabrication of several types of high density MOS and bipolar integrated circuits. The process uses a pad located under the inter-layer contact opening. The material of the pad is poly-silicon (doped or undoped), a refractory metal, or a refractory metal silicide which is not capable of being attacked during chemical etching of the metallization layers. If poly-silicon is used, it is either doped during its deposition or during contact doping, or it is automatically silicided during ohmic and Schottky contact formations.

Device for chemical dry etching of integrated circuits

Abstract: Apparatus for dry chemical etching caused by ion bombardment of a substrate placed in a vacuum chamber. The substrate is in contact with an electrode, connected to a high frequency bias voltage source having one terminal connected to a ground of the chamber. The etchants are produced in the form of plasma by an electrical discharge maintained in the chamber containing a gas or a suitable gaseous mixture. The plasma is produced by a microwave generator and the bias voltage by means of a high frequency source. The respective amplitudes and frequencies of the two sources enable the base of a groove on an electronic circuit to be etched without erosion of the groove.

Crystal Defects of Silicon Films Formed by Molecular Beam Epitaxy

Abstract: Crystal defect properties of silicon films grown by molecular beam epitaxy are examined by Wright chemical etching and scanning electron microscope, and the following results are obtained. 1) The preheat treatment of substrates with oxides can drastically reduce the stacking fault and dislocation densities in Si films. The unevaporated SiO2 is a major source of these defects. 2) These defect densities decrease with an increase in deposition temperature. 3) The dependences of the defects on the residual gas pressure and the crystal faces of the substrates suggest that oxygen from the residual gas may form SiO2 which acts as the source of the defects in the films. 4) Ion doping during Si growth reduces the stacking fault densities in the films. 5) High quality Si epitaxial films whose defect densities are less than 103 cm-2 are obtained.

Method of planarizing silicon dioxide in semiconductor devices

Abstract: The present invention provides a method for planarizing a non-uniform thickness of oxide, for example silicon dioxide as is formed over oxide-filled trenches used in deep dielectric isolation in integrated circuits. The oxide is removed by a planarizing resist-etching process so that etching in thicker resist areas proceeds at a rate slower than etching in thinner resist areas. A referred etchant is HF gas and etching is preferably at an elevated temperature.

HF vapor phase etching (HF/VPE): Production viability for semiconductor manufacturing and reaction model

Abstract: A nonplasma silicon dioxide etch process using anhydrous hydrogen fluoride at reduced pressures has been investigated. This technique involves the interaction of HF vapor with negative photoresist which catalizes subsequent etching beneath the photoresist. Etching in nonphotoresist coated areas can be eliminated by a short in situ plasma pretreatment followed by HF etching at 190 °C, 10 Torr, and 500 sccm in a commercial etch system. Experimental details as well as a proposed reaction mechanism will be presented.

Grain boundary effects on the electrical behavior of Al-poly-Si Schottky-barrier solar cells

Abstract: Schottky-barrier diodes using aluminum on p-type polycrystalline silicon have been fabricated. The contrast of the orientation of neighboring grains is observed after chemical etching of the surface. Comparing the surface morphology of the substrate with the electronic behavior of the Schottky diode, we are able to identify the influence of grain boundaries. It is found that the low-angle boundary has little effect on the I-V characteristics since near ideal Schottky I-V curves are obtained. The barrier height is calculated to be 0.83 V which is higher than that of the single-crystal substrate. The ideality factor is 1.17 for a device containing a twin and low-angle boundaries. The high-angle grain boundary, however, significantly alters both the I-V and low-frequency C-V plots. The experimental data indicate that recombination centers and traps are introduced, resulting in an increase in recombination current and a reduction of the effective mobility. The conduction mechanisms for the two types of diodes are clearly distinguishable both in the dark and under illumination. In the photovoltaic operation under a tungsten lamp, we obtain an open-circuit voltage of 0.48 V and a fill factor 0.51. It appears that the chemical etching along with Schottky-barrier fabrication will provide a useful method to study the polycrystalline substrate for low-cost solar cell applications.

Plasma etching process

Abstract: In an improved process for the etching of polysilicon substrates, a polysilicon substrate is exposed to plasmas of carbon tetrachloride, chlorinated gas, fluorinated gas or a gas capable of generating both chlorinated and fluorinated plasma species. The combination of a chlorinated and fluorinated etching species substantially reduces undercutting of polysilicon substrates. Improved uniformity of polysilicon etching is also achieved.

Process for patterning metal connections on a semiconductor structure by using an aluminum oxide etch resistant layer

Abstract: A process for patterning plasma etchable regions on a semiconductor structure includes the steps of forming a layer of an oxide of aluminum over the surface of the semiconductor structure, forming an overlying layer of plasma etchable material on the layer of oxide, and removing undesired portions of the overlying layer by plasma etching to thereby expose portions of the layer of oxide. In some embodiments of the invention the thereby exposed portions of the layer of oxide are then removed, together with any underlying portions of the first layer, by isotropic etching.

Jet etch apparatus for decapsulation of molded devices

Abstract: A jet etch apparatus and method for decapsulation of molded devices having an etching block through which an etchant solution is drawn. The etchant solution which flows through the etching block forms a jet spray that impinges upon a device to be decapsulated. The etchant solution is drawn through the etching block by means of suction created by a jet pump. The decapsulation process is monitored by detecting current flow between an electrode in the etchant solution and the device. The imposed current also serves to limit excessive oxidation of aluminum pads within the device, thereby preventing attack of the aluminum by the etchant.

Undercutting Phenomena in Al Plasma Etching

Abstract: Undercutting phenomena in Al plasma etching were investigated. Photoresist, SiO2 and Si3N4 were used for etching masks. PSG, Si(100), Si3N4 and Al2O3 were used for underlying layers. In various combinations of etching masks and underlying layers, only photoresist mask exhibits no undercutting. However, even in this case, undercutting occurs according to over-etching time and pattern density. An hypothesis that a film observed on an Al pattern sidewall acts as a protection against undercutting was proposed. Undercutting phenomena were easily explained by this hypothesis.

Method for forming electrical connecting lines by monitoring the etch rate during wet etching

Abstract: A method for forming a electrical interconnections, according to the invention, comprises forming number of semiconductor circuit elements on one semiconductor substrate, depositing an electrically conductive layer on substantially the entire surface of the semiconductor substrate, etching the electrically conductive layer patterned by the photolithography, for example, coating a photoresist on the electrically conductive layer, placing a mask of a pattern of electrical connecting lines on the photoresist-coated conductive layer and exposing the assembly to actinic rays to effect a development treatment, then placing one electrode composed of the electrochemically same material as that of the electrically conductive layer so that at least one point of said one electrode is brought into contact with the electrically conductive layer, dipping the assembly in an etching solution while using as the other electrode an electric conductor composed of a material electrochemically different from the material of the electrically conductive layer, performing wet chemical etching of the electrically conductive layer while measuring an electric current flowing between the two electrodes, and terminating etching of the electrically conductive layer when said current largely decreases or continuing etching for a certain time after said current largely decreases and is reduced below a timely determined level whereby electrical interconnections are formed for the respective semiconductor circuit elements on the semiconductor substrate.

Characterization of tin in the bottom surface of float glass by ellipsometry and XPS

Abstract: The composition of tin-contact surfaces of production float glass has been characterized by means of the ellipsometric refractive index and XPS measurement of cation concentrations. Successive layers under the outer surface were exposed by ion etching, mechanical polishing and chemical etching, and depths of those layers between 0.01 and 0.5 μm were determined by optical interferometry. Tin concentrations at the surface, expressed as SnO 2 , exceeded 30 weight % but decreased by an order of magnitude at about 0.01 μm. Over the range of 0.01 to 0.5 μm, SnO 2 content decreased regularly to about 2%. Over most of this same thickness, Na and Ca levels remained well below those of the bulk composition.

Process of etching glass surfaces, particularly in the manufacture of optical waveguides

Abstract: A process of treating surfaces of silica or silicate glass, especially in preparation for subsequent coating in the manufacture of optical waveguides includes introducing a gaseous medium containing at least one component which forms hydrogen fluoride when sufficiently heated to the surface to be treated, while an etching zone which covers only a portion of the surface is thus heated, so that the hydrogen fluoride etches the surface only at the etching zone. The temperature is so selected that silicon tetrafluoride formed during the etching is oxidized and the resultant silicon dioxide is deposited from the gaseous medium onto the surface outside of the etching zone to form a fused fluorine-doped vitreous layer on the previously etched portion of the surface.