National Semiconductor Corporation

James L Bouknight

Ali A Iranmanesh

Rick C Jerome

George E Ganschow

Christopher S Blair

Vida Ilderem

Alan G Solheim

Frank Marazita

Ronald P Kovacs

Brian McFarlane

Madan Biswal

Rajeeva Lahri

Bamdad Bastani

Bancherd DeLong

Lawrence K Lam

Steve M Leibiger

Tad Davies

A vertical fuse structure including a lightly-doped shallow emitter 30 provides improved fusing characteristics. The structure includes a buried collector 14, an overlying base 30, and an emitter 44 above the base 30. In one preferred embodiment, the emitter 44 extends about 0.2 microns from the upper surface and has a dopant concentration of about 8.times.1019 atoms of arsenic per cubic centimeter at the surface. A lightly doped base region 30 extends for about 0.46 microns below the emitter 44 to the collector 14. The upper surface of emitter 44 includes a metal contact 60. Heating the metal 60/emitter 44 interface to its eutectic melting point using a current or voltage pulse causes the aluminum to short through the emitter 44 to the base 30. Shorting the emitter programs the fuse. A second preferred embodiment uses polysilicon as an interconnecting medium. Mass transport of aluminum atoms through the polysilicon allows aluminum to collect at an interface between the polysilicon and an underlying single crystal silicon layer. Aluminum atoms are supplied from a contact metal. A barrier metal between the contact metal and an underlying polysilicon contact to the emitter is not present. Inhibiting or replacing a TiSi.sub.2 layer over the fuse emitter contact provides better reproducible fusing action. PtSi replaces TiSi.sub.2 if formed over the fuse emitter contact. Separate fuse base implants for the vertical fuse change BJT parameters for improved fusing characteristics. In still another preferred embodiment, codiffusing N type and P type dopants from the polysilicon emitter contact drops a separate fuse mask. The P type codiffused dopants diffuse ahead of the N type emitter dopants into the single crystal to change the base parameters to provide a decreased gain.

Vertical fuse device

A high performance bipolar transistor and a method of fabrication. Base resistance is reduced by a self-aligned silicide formed in the single-crystal region of the extrinsic base, thereby eliminating the polysilicon to single-crystal contact resistance as well as shunting the resistance of the single-crystal extrinsic base region. Oxide from the sidewall of the polysilicon local interconnection is selectively removed prior to silicide formation. Therefore, selected sidewalls of the poly interconnect layer also becomes silicided. This results in significant reductions in resistance of the interconnection, particularly for sub-micron geometries. Improved techniques for forming field oxide regions and for forming base regions of bipolar transistors are also disclosed.

Reducing base resistance of a BJT by forming a self aligned silicide in

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Puyallup, WA, United States of America

James L Bouknight