Bbc Brown, Boveri & Company, Limited

Asea Brown Boveri Inc.

Brown, Boveri & Cie Ag

Helmut Keser

Horst Gruning

Arno Neidig

Georg F Wahl

Jan Voboril

Klaus Bunk

In a pressure-contacted large-area power semiconductor element, in which a substrate (1) is compressed between an anode-side (20) and a cathode-side compression plate (19), an improved contact is obtained by arranging, at least between one of the compression plates (19,20) and the associated contact (2,9), a metal foil (17) which is soldered to this contact.

Pressure-contacted semiconductor component

For the p-type doping of silicon, particularly for power semiconductor components, aluminum from an Al target is precipitated by cathode sputtering in an argon plasma on a major face (2) of a silicon wafer (1) by which means a comparatively high purity of the deposited aluminum is achieved. Before the aluminum deposition, the silicon water (1) is bombarded with argon ions for 10 min at an argon pressure of 20 .mu.bar which guarantees a uniform fusion of the aluminum with the silicon during later heating and, in particular, prevents the formation of droplets of the aluminum on the major face (2). The Al layer formed in this manner is photo-lithographically preferably structured in such a manner that several aluminum sources spaced apart from each other are allocated to one aluminum-doped zone (10). The subsequent diffusion occurs for 300 min at 1250.degree. C. in a gas mixture of nitrogen or argon (1 l/min) and oxygen (20 ml/min). During this process, the aluminum-doped zone (10) is produced. Subsequently, photoresist (13,14) is applied to the non-diffused regions. Residues (11') of the aluminum sources are then laterally etched by a silicon etchant and, as a result, removed. Following this, the photoresist (13,14) is removed.

Method for diffusing aluminum

A large-area semiconductor component (1) is joined without bubbles by means of soldering to a substrate (2) by placing a perforated metallic intermediate layer (5) between the solder (3) before the soldering and the substrate (2) and the assembly is brought to soldering temperature under pressure and perpendicular to the soldering plane. During this process, the solder (4) completely fills the cavities between the components (1, 2) and (5) after the soldering and drives gas bubbles and any impurities to the periphery of the assembly, a constant distance being maintained between the semiconductor component (1) and the substrate (2). The intermediate layer (5) is preferably constructed as structured foil or as metallic fabric.

Method for the bubble-free joining of a large-area semiconductor

Method for the direct joining of metal pieces which have a surface metal oxide layer, to oxide ceramic substrates by heating the ceramic substrates covered with the metal pieces in an oxygen-containing atmosphere to a temperature above the eutectic temperature of the metal and the metal oxide, but below the melting temperature of the metal. The heating is carried out in a continuous heating furnace in a nitrogen atmosphere with an addition of oxygen of 20 to 50 vpm. The cooling-down in the continuous heating furnace takes place after the solidification of the eutectic melt, in a nitrogen atmosphere which has an oxygen content well below the 20 vpm.

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Birr, Switzerland

Helmut Keser