The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 25, 1995
Filed:
Feb. 14, 1994
Rick C Jerome, Puyallup, WA (US);
Ronald P Kovacs, Mountain View, CA (US);
George E Ganschow, Trabuco Canyon, CA (US);
Lawrence K Lam, Kent, WA (US);
James L Bouknight, Puyallup, WA (US);
Frank Marazita, San Jose, CA (US);
Brian McFarlane, Campbell, CA (US);
Ali Iranmanesh, Federal Way, WA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
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.