International Business Machines Corporation

Wolf-Dieter Ruh

Gerhard Trippel

Arwed Brunsch

Werner Cziep

Ulrich Kuenzel

Viaholes are dry-etched into glass fiber reinforced plastic sheets according to a predetermined hole pattern, leaving the glass fiber meshing practically unaffected. The method is used, for instance, to fabricate plastic sheets with unilaterally or bilaterally applied conductor patterns and viaconnectors that are conductively linked to the conductor patterns, and to fabricate multilayer board laminates obtained by several plastic sheets carrying the conductor pattern being alternately packaged, if required, with untreated copper sheets, and by the package thus obtained being subsequently laminated. Such boards and/or plastic sheets bilaterally provided with conductor patterns may be used as connector boards for, say, multilayer ceramic modules carrying semiconductor chips.

Producing viaholes in plastic sheets and application of the method

A test sample (7) of the same material, or with the same structure as the workpiece (5) exposed to subtractive processing is simultaneously exposed to such processing and consists of a wedge (10) with the angle .alpha. covered by two covering plates (11) which are complementary to its two surfaces (14). By measuring the distance x.sub.1 between the thus formed gaps (15), and by comparing it with the original distance x.sub.O, thickness z of the respectively removed layer can be determined from the equation ##EQU1##

Method of measuring the thickness of the removed layer in subtractive

For a metallic thin film magnetic disk, a chromium undercoat and a magnetic layer, in particular of an FeCoCr alloy, are obliquely sputtered by means of a sputtering system onto a substrate at an angle of incidence of about 60.degree.. The operating pressure of the argon gas atmosphere is between 5 and 15 .mu.bar and the thickness (t.sub.Cr) of the undercoat, which also influences the coercive field strength, is between about 50 and 180 nm. By means of a sector shutter of suitable shape, the thickness distribution between the inner diameter ID and the outer diameter OD of the storage area of the magnetic disk can be influenced in the desired manner.

Method of producing a metallic thin film magnetic disk

Several tapered viaducts or through-holes of uniform size are simultaneously fabricated by etching in a dielectric plate or substrate. The viaducts, which are designed in particular for nozzles for ink jet printers, have identical orifice widths, irrespective of differences in the thickness of the substrate or dielectric plate or different etch rates in the various areas of the dielectric plate. The holes are first chemically pre-etched until the first hole is about to penetrate through the plate and subsequently sputter etching is applied until all holes have penetrated through the plate, whereby the dielectric plate provides the necessary sputter etch capacity on which a negative bias occurs.

Method of simultaneously etching multiple tapered viaducts in

This method of forming viaducts or 'through-holes' in semiconductor material for transistor and integrated circuit fabrication and especially for ink jet printing systems forms viaducts of uniform diameter without critical registration of masks. A seed layer of Cr-Au is sputtered onto a silicon-dioxide substrate. The viaducts or holes to be made are imaged by a photoresist process with a 5 .mu. thick photoresist on this seed layer. A 4 .mu. thick gold layer is now applied on the seed layer by a plating process. After the dissolution of the photoresist this layer contains the hole pattern with the holes having the required diameter. In order to make a through-hole, the substrate has to be etched. For that purpose, the bare substrate surface is covered with photoresist and exposed from the back through gold holes, and subsequently developed. Problems owing to light diffraction at the edges of the gold with respect to the great distance of the gold mask - photoresist layer are not anticipated here because of the large holes and the high tolerances in this process step. Prior to etching the substrate, the gold layer with the hole pattern is covered by photoresist so that the substrate etching can take place from one side only. Now the substrate is etched until all of the gold holes are free. In that process, the extent of the substrate sub-etching is of small importance as the viaduct or hole diameter is defined by the gold mask. The photoresist is removed and the exposed substrate surfaces are protected against chemical reactions with the ink by a vapor-deposition of a protective layer.

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Sindelfingen, Germany

Wolf-Dieter Ruh