Zetex Plc

David Neil Casey

A bipolar transistor with a specific area resistance less than about 500 mOhms&#xb7;mmcomprises a first semiconductor region of a first conductivity type defining a collector region (). A second semiconductor region of a second conductivity type defines a base region (). A third semiconductor region of the first conductivity type defines an emitter region (). A metal layer provides contacts () to said base () and emitter regions (). The metal layer has thickness greater than about 3 &#x3bc;m.

Bipolar transistor with a low saturation voltage

A method for reducing damage to a semiconductor structure resulting from migration of constituents of a first component part ( ) of the structure into a subsequently deposited second component part ( ) of the structure which makes contact with a surface of the first component part ( ). A third component part ( ) of the structure is deposited before the second component part ( ), the third component part ( ) being positioned so as to be contacted by the second component part ( ) adjacent the said surface of the first component part ( ). The third component part ( ) has a composition such that it acts as a donor of constituents ( ) to the second component part. The donor constituents ( ) migrate into the second component part ( ) when the second component part ( ) is deposited and reduce the migration of constituents ( ) of the first component part ( ) into the second component part ( ). If the first component part ( ) is silicon, the third component part ( ) may be polysilicon. The invention enables the use of a pure material, for example pure aluminium, without exposing the first component part ( ) to damage as a result of migration of constituents of the first component part ( ) into the aluminium.

Semiconductor contact fabrication method

A guard ring structure formed around the periphery of a bipolar semiconductor device. A guard region ( ) is formed in a substrate ( ) of the device so as to extend adjacent a peripheral portion of the device. An insulating layer ( ) is formed on the substrate between the peripheral portion of the device and the guard region ( ). A polysilicon layer ( ) is formed on the insulating layer ( ) and covered with a layer of densified dielectic ( ). Electrical interconnections are provided between the polysilicon layer ( ) and the guard region ( ) at spaced apart portions of the device where the guard structure does not need to be protected by the densified dielectric.

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Lancashire, United Kingdom

David Neil Casey